Programs & Examples On #Stl

The Standard Template Library, or STL, is a C++ library of generic containers, iterators, algorithms, and function objects. When C++ was standardised, large parts of the STL were adopted into the Standard Library, and these parts in the Standard Library are also sometimes referred to collectively as "the STL".

How could I create a list in c++?

We are already in 21st century!! Don't try to implement the already existing data structures. Try to use the existing data structures.

Use STL or Boost library

How to sort an STL vector?

Overload less than operator, then sort. This is an example I found off the web...

class MyData
{
public:
  int m_iData;
  string m_strSomeOtherData;
  bool operator<(const MyData &rhs) const { return m_iData < rhs.m_iData; }
};

std::sort(myvector.begin(), myvector.end());

Source: here

I want to convert std::string into a const wchar_t *

If you have a std::wstring object, you can call c_str() on it to get a wchar_t*:

std::wstring name( L"Steve Nash" );
const wchar_t* szName = name.c_str();

Since you are operating on a narrow string, however, you would first need to widen it. There are various options here; one is to use Windows' built-in MultiByteToWideChar routine. That will give you an LPWSTR, which is equivalent to wchar_t*.

Iteration over std::vector: unsigned vs signed index variable

Obscure but important detail: if you say "for(auto it)" as follows, you get a copy of the object, not the actual element:

struct Xs{int i} x;
x.i = 0;
vector <Xs> v;
v.push_back(x);
for(auto it : v)
    it.i = 1;         // doesn't change the element v[0]

To modify the elements of the vector, you need to define the iterator as a reference:

for(auto &it : v)

maximum value of int

#include <climits>
#include <iostream>
using namespace std;

int main() {
  cout << INT_MAX << endl;
}

How to find if a given key exists in a C++ std::map

I know this question already has some good answers but I think my solution is worth of sharing.

It works for both std::map and std::vector<std::pair<T, U>> and is available from C++11.

template <typename ForwardIterator, typename Key>
bool contains_key(ForwardIterator first, ForwardIterator last, Key const key) {
    using ValueType = typename std::iterator_traits<ForwardIterator>::value_type;

    auto search_result = std::find_if(
        first, last,
        [&key](ValueType const& item) {
            return item.first == key;
        }
    );

    if (search_result == last) {
        return false;
    } else {
        return true;
    }
}

push_back vs emplace_back

In addition to what visitor said :

The function void emplace_back(Type&& _Val) provided by MSCV10 is non conforming and redundant, because as you noted it is strictly equivalent to push_back(Type&& _Val).

But the real C++0x form of emplace_back is really useful: void emplace_back(Args&&...);

Instead of taking a value_type it takes a variadic list of arguments, so that means that you can now perfectly forward the arguments and construct directly an object into a container without a temporary at all.

That's useful because no matter how much cleverness RVO and move semantic bring to the table there is still complicated cases where a push_back is likely to make unnecessary copies (or move). For example, with the traditional insert() function of a std::map, you have to create a temporary, which will then be copied into a std::pair<Key, Value>, which will then be copied into the map :

std::map<int, Complicated> m;
int anInt = 4;
double aDouble = 5.0;
std::string aString = "C++";

// cross your finger so that the optimizer is really good
m.insert(std::make_pair(4, Complicated(anInt, aDouble, aString))); 

// should be easier for the optimizer
m.emplace(4, anInt, aDouble, aString);

So why didn't they implement the right version of emplace_back in MSVC? Actually, it bugged me too a while ago, so I asked the same question on the Visual C++ blog. Here is the answer from Stephan T Lavavej, the official maintainer of the Visual C++ standard library implementation at Microsoft.

Q: Are beta 2 emplace functions just some kind of placeholder right now?

A: As you may know, variadic templates aren't implemented in VC10. We simulate them with preprocessor machinery for things like make_shared<T>(), tuple, and the new things in <functional>. This preprocessor machinery is relatively difficult to use and maintain. Also, it significantly affects compilation speed, as we have to repeatedly include subheaders. Due to a combination of our time constraints and compilation speed concerns, we haven't simulated variadic templates in our emplace functions.

When variadic templates are implemented in the compiler, you can expect that we'll take advantage of them in the libraries, including in our emplace functions. We take conformance very seriously, but unfortunately, we can't do everything all at once.

It's an understandable decision. Everyone who tried just once to emulate variadic template with preprocessor horrible tricks knows how disgusting this stuff gets.

C++ Erase vector element by value rather than by position?

You can not do that directly. You need to use std::remove algorithm to move the element to be erased to the end of the vector and then use erase function. Something like: myVector.erase(std::remove(myVector.begin(), myVector.end(), 8), myVec.end());. See this erasing elements from vector for more details.

How to check if std::map contains a key without doing insert?

Your desideratum,map.contains(key), is scheduled for the draft standard C++2a. In 2017 it was implemented by gcc 9.2. It's also in the current clang.

Remove spaces from std::string in C++

string removeSpaces(string word) {
    string newWord;
    for (int i = 0; i < word.length(); i++) {
        if (word[i] != ' ') {
            newWord += word[i];
        }
    }

    return newWord;
}

This code basically takes a string and iterates through every character in it. It then checks whether that string is a white space, if it isn't then the character is added to a new string.

How to get std::vector pointer to the raw data?

&something gives you the address of the std::vector object, not the address of the data it holds. &something.begin() gives you the address of the iterator returned by begin() (as the compiler warns, this is not technically allowed because something.begin() is an rvalue expression, so its address cannot be taken).

Assuming the container has at least one element in it, you need to get the address of the initial element of the container, which you can get via

  • &something[0] or &something.front() (the address of the element at index 0), or

  • &*something.begin() (the address of the element pointed to by the iterator returned by begin()).

In C++11, a new member function was added to std::vector: data(). This member function returns the address of the initial element in the container, just like &something.front(). The advantage of this member function is that it is okay to call it even if the container is empty.

How to use the priority queue STL for objects?

We can define user defined comparator: .The code below can be helpful for you.

Code Snippet :

#include<bits/stdc++.h>
using namespace std;

struct man
{
  string name;
  int priority; 
};

class comparator
{
 public:
   bool operator()(const man& a, const man& b)
   {
        return a.priority<b.priority;
   }
};

int main()
{
   man arr[5];
   priority_queue<man, vector<man>, comparator> pq;

   for(int i=0; i<3; i++)
   {
     cin>>arr[i].name>>arr[i].priority;
     pq.push(arr[i]);
   }

   while (!pq.empty())
   {
     cout<<pq.top().name<<" "<<pq.top().priority;
     pq.pop();
     cout<<endl;
   }
   return 0;
}

input :

batman 2
goku 9
mario 4

Output

goku 9
mario 4
batman 2

In STL maps, is it better to use map::insert than []?

The two have different semantics when it comes to the key already existing in the map. So they aren't really directly comparable.

But the operator[] version requires default constructing the value, and then assigning, so if this is more expensive then copy construction, then it will be more expensive. Sometimes default construction doesn't make sense, and then it would be impossible to use the operator[] version.

What are the complexity guarantees of the standard containers?

I'm not aware of anything like a single table that lets you compare all of them in at one glance (I'm not sure such a table would even be feasible).

Of course the ISO standard document enumerates the complexity requirements in detail, sometimes in various rather readable tables, other times in less readable bullet points for each specific method.

Also the STL library reference at http://www.cplusplus.com/reference/stl/ provides the complexity requirements where appropriate.

use std::fill to populate vector with increasing numbers

There is another option - without using iota. For_each + lambda expression can be used:

vector<int> ivec(10); // the vector of size 10
int i = 0;            // incrementor
for_each(ivec.begin(), ivec.end(), [&](int& item) { ++i; item += i;});

Two important things why it's working:

  1. Lambda captures outer scope [&] which means that i will be available inside expression
  2. item passed as a reference, therefore, it is mutable inside the vector

How do I find an element position in std::vector?

Take a look at the answers provided for this question: Invalid value for size_t?. Also you can use std::find_if with std::distance to get the index.

std::vector<type>::iterator iter = std::find_if(vec.begin(), vec.end(), comparisonFunc);
size_t index = std::distance(vec.begin(), iter);
if(index == vec.size()) 
{
    //invalid
}

vector vs. list in STL

The only hard rule where list must be used is where you need to distribute pointers to elements of the container.

Unlike with vector, you know that the memory of elements won't be reallocated. If it could be then you might have pointers to unused memory, which is at best a big no-no and at worst a SEGFAULT.

(Technically a vector of *_ptr would also work but in that case you are emulating list so that's just semantics.)

Other soft rules have to do with the possible performance issues of inserting elements into the middle of a container, whereupon list would be preferable.

Why does the C++ STL not provide any "tree" containers?

In a way, std::map is a tree (it is required to have the same performance characteristics as a balanced binary tree) but it doesn't expose other tree functionality. The likely reasoning behind not including a real tree data structure was probably just a matter of not including everything in the stl. The stl can be looked as a framework to use in implementing your own algorithms and data structures.

In general, if there's a basic library functionality that you want, that's not in the stl, the fix is to look at BOOST.

Otherwise, there's a bunch of libraries out there, depending on the needs of your tree.

what is the difference between const_iterator and iterator?

if you have a list a and then following statements

list<int>::iterator it; // declare an iterator
    list<int>::const_iterator cit; // declare an const iterator 
    it=a.begin();
    cit=a.begin();

you can change the contents of the element in the list using “it” but not “cit”, that is you can use “cit” for reading the contents not for updating the elements.

*it=*it+1;//returns no error
    *cit=*cit+1;//this will return error

Can't include C++ headers like vector in Android NDK

If you are using ndk r10c or later, simply add APP_STL=c++_static to Application.mk

Appending a vector to a vector

std::copy (b.begin(), b.end(), std::back_inserter(a));

This can be used in case the items in vector a have no assignment operator (e.g. const member).

In all other cases this solution is ineffiecent compared to the above insert solution.

How do I clear the std::queue efficiently?

You could create a class that inherits from queue and clear the underlying container directly. This is very efficient.

template<class T>
class queue_clearable : public std::queue<T>
{
public:
    void clear()
    {
        c.clear();
    }
};

Maybe your a implementation also allows your Queue object (here JobQueue) to inherit std::queue<Job> instead of having the queue as a member variable. This way you would have direct access to c.clear() in your member functions.

How to update std::map after using the find method?

std::map::find returns an iterator to the found element (or to the end() if the element was not found). So long as the map is not const, you can modify the element pointed to by the iterator:

std::map<char, int> m;
m.insert(std::make_pair('c', 0));  // c is for cookie

std::map<char, int>::iterator it = m.find('c'); 
if (it != m.end())
    it->second = 42;

How to set initial size of std::vector?

std::vector<CustomClass *> whatever(20000);

or:

std::vector<CustomClass *> whatever;
whatever.reserve(20000);

The former sets the actual size of the array -- i.e., makes it a vector of 20000 pointers. The latter leaves the vector empty, but reserves space for 20000 pointers, so you can insert (up to) that many without it having to reallocate.

At least in my experience, it's fairly unusual for either of these to make a huge difference in performance--but either can affect correctness under some circumstances. In particular, as long as no reallocation takes place, iterators into the vector are guaranteed to remain valid, and once you've set the size/reserved space, you're guaranteed there won't be any reallocations as long as you don't increase the size beyond that.

How to search for an element in an stl list?

Besides using std::find (from algorithm), you can also use std::find_if (which is, IMO, better than std::find), or other find algorithm from this list


#include <list>
#include <algorithm>
#include <iostream>

int main()
{
    std::list<int> myList{ 5, 19, 34, 3, 33 };
    

    auto it = std::find_if( std::begin( myList ),
                            std::end( myList ),
                            [&]( const int v ){ return 0 == ( v % 17 ); } );
        
    if ( myList.end() == it )
    {
        std::cout << "item not found" << std::endl;
    }
    else
    {
        const int pos = std::distance( myList.begin(), it ) + 1;
        std::cout << "item divisible by 17 found at position " << pos << std::endl;
    }
}

What is the preferred/idiomatic way to insert into a map?

First of all, operator[] and insert member functions are not functionally equivalent :

  • The operator[] will search for the key, insert a default constructed value if not found, and return a reference to which you assign a value. Obviously, this can be inefficient if the mapped_type can benefit from being directly initialized instead of default constructed and assigned. This method also makes it impossible to determine if an insertion has indeed taken place or if you have only overwritten the value for an previously inserted key
  • The insert member function will have no effect if the key is already present in the map and, although it is often forgotten, returns an std::pair<iterator, bool> which can be of interest (most notably to determine if insertion has actually been done).

From all the listed possibilities to call insert, all three are almost equivalent. As a reminder, let's have look at insert signature in the standard :

typedef pair<const Key, T> value_type;

  /* ... */

pair<iterator, bool> insert(const value_type& x);

So how are the three calls different ?

  • std::make_pair relies on template argument deduction and could (and in this case will) produce something of a different type than the actual value_type of the map, which will require an additional call to std::pair template constructor in order to convert to value_type (ie : adding const to first_type)
  • std::pair<int, int> will also require an additional call to the template constructor of std::pair in order to convert the parameter to value_type (ie : adding const to first_type)
  • std::map<int, int>::value_type leaves absolutely no place for doubt as it is directly the parameter type expected by the insert member function.

In the end, I would avoid using operator[] when the objective is to insert, unless there is no additional cost in default-constructing and assigning the mapped_type, and that I don't care about determining if a new key has effectively inserted. When using insert, constructing a value_type is probably the way to go.

How to change a particular element of a C++ STL vector

at and operator[] both return a reference to the indexed element, so you can simply use:

l.at(4) = -1;

or

l[4] = -1;

How can I create my own comparator for a map?

Specify the type of the pointer to your comparison function as the 3rd type into the map, and provide the function pointer to the map constructor:
map<keyType, valueType, typeOfPointerToFunction> mapName(pointerToComparisonFunction);

Take a look at the example below for providing a comparison function to a map, with vector iterator as key and int as value.

#include "headers.h"

bool int_vector_iter_comp(const vector<int>::iterator iter1, const vector<int>::iterator iter2) {
    return *iter1 < *iter2;
}

int main() {
    // Without providing custom comparison function
    map<vector<int>::iterator, int> default_comparison;

    // Providing custom comparison function
    // Basic version
    map<vector<int>::iterator, int,
        bool (*)(const vector<int>::iterator iter1, const vector<int>::iterator iter2)>
        basic(int_vector_iter_comp);

    // use decltype
    map<vector<int>::iterator, int, decltype(int_vector_iter_comp)*> with_decltype(&int_vector_iter_comp);

    // Use type alias or using
    typedef bool my_predicate(const vector<int>::iterator iter1, const vector<int>::iterator iter2);
    map<vector<int>::iterator, int, my_predicate*> with_typedef(&int_vector_iter_comp);

    using my_predicate_pointer_type = bool (*)(const vector<int>::iterator iter1, const vector<int>::iterator iter2);
    map<vector<int>::iterator, int, my_predicate_pointer_type> with_using(&int_vector_iter_comp);


    // Testing 
    vector<int> v = {1, 2, 3};

    default_comparison.insert(pair<vector<int>::iterator, int>({v.end(), 0}));
    default_comparison.insert(pair<vector<int>::iterator, int>({v.begin(), 0}));
    default_comparison.insert(pair<vector<int>::iterator, int>({v.begin(), 1}));
    default_comparison.insert(pair<vector<int>::iterator, int>({v.begin() + 1, 1}));

    cout << "size: " << default_comparison.size() << endl;
    for (auto& p : default_comparison) {
        cout << *(p.first) << ": " << p.second << endl;
    }

    basic.insert(pair<vector<int>::iterator, int>({v.end(), 0}));
    basic.insert(pair<vector<int>::iterator, int>({v.begin(), 0}));
    basic.insert(pair<vector<int>::iterator, int>({v.begin(), 1}));
    basic.insert(pair<vector<int>::iterator, int>({v.begin() + 1, 1}));

    cout << "size: " << basic.size() << endl;
    for (auto& p : basic) {
        cout << *(p.first) << ": " << p.second << endl;
    }

    with_decltype.insert(pair<vector<int>::iterator, int>({v.end(), 0}));
    with_decltype.insert(pair<vector<int>::iterator, int>({v.begin(), 0}));
    with_decltype.insert(pair<vector<int>::iterator, int>({v.begin(), 1}));
    with_decltype.insert(pair<vector<int>::iterator, int>({v.begin() + 1, 1}));

    cout << "size: " << with_decltype.size() << endl;
    for (auto& p : with_decltype) {
        cout << *(p.first) << ": " << p.second << endl;
    }

    with_typedef.insert(pair<vector<int>::iterator, int>({v.end(), 0}));
    with_typedef.insert(pair<vector<int>::iterator, int>({v.begin(), 0}));
    with_typedef.insert(pair<vector<int>::iterator, int>({v.begin(), 1}));
    with_typedef.insert(pair<vector<int>::iterator, int>({v.begin() + 1, 1}));

    cout << "size: " << with_typedef.size() << endl;
    for (auto& p : with_typedef) {
        cout << *(p.first) << ": " << p.second << endl;
    }
}

Concatenating two std::vectors

If you are using C++11, and wish to move the elements rather than merely copying them, you can use std::move_iterator along with insert (or copy):

#include <vector>
#include <iostream>
#include <iterator>

int main(int argc, char** argv) {
  std::vector<int> dest{1,2,3,4,5};
  std::vector<int> src{6,7,8,9,10};

  // Move elements from src to dest.
  // src is left in undefined but safe-to-destruct state.
  dest.insert(
      dest.end(),
      std::make_move_iterator(src.begin()),
      std::make_move_iterator(src.end())
    );

  // Print out concatenated vector.
  std::copy(
      dest.begin(),
      dest.end(),
      std::ostream_iterator<int>(std::cout, "\n")
    );

  return 0;
}

This will not be more efficient for the example with ints, since moving them is no more efficient than copying them, but for a data structure with optimized moves, it can avoid copying unnecessary state:

#include <vector>
#include <iostream>
#include <iterator>

int main(int argc, char** argv) {
  std::vector<std::vector<int>> dest{{1,2,3,4,5}, {3,4}};
  std::vector<std::vector<int>> src{{6,7,8,9,10}};

  // Move elements from src to dest.
  // src is left in undefined but safe-to-destruct state.
  dest.insert(
      dest.end(),
      std::make_move_iterator(src.begin()),
      std::make_move_iterator(src.end())
    );

  return 0;
}

After the move, src's element is left in an undefined but safe-to-destruct state, and its former elements were transfered directly to dest's new element at the end.

How to increment an iterator by 2?

Assuming list size may not be an even multiple of step you must guard against overflow:

static constexpr auto step = 2;

// Guard against invalid initial iterator.
if (!list.empty())
{
    for (auto it = list.begin(); /*nothing here*/; std::advance(it, step))
    {
        // do stuff...

        // Guard against advance past end of iterator.
        if (std::distance(it, list.end()) > step)
            break;
    }
}

Depending on the collection implementation, the distance computation may be very slow. Below is optimal and more readable. The closure could be changed to a utility template with the list end value passed by const reference:

const auto advance = [&](list_type::iterator& it, size_t step)
{
    for (size_t i = 0; it != list.end() && i < step; std::next(it), ++i);
};

static constexpr auto step = 2;

for (auto it = list.begin(); it != list.end(); advance(it, step))
{
    // do stuff...
}

If there is no looping:

static constexpr auto step = 2;
auto it = list.begin();

if (step <= list.size())
{
    std::advance(it, step);
}

How do I erase an element from std::vector<> by index?

It may seem obvious to some people, but to elaborate on the above answers:

If you are doing removal of std::vector elements using erase in a loop over the whole vector, you should process your vector in reverse order, that is to say using

for (int i = v.size() - 1; i >= 0; i--)

instead of (the classical)

for (int i = 0; i < v.size(); i++)

The reason is that indices are affected by erase so if you remove the 4-th element, then the former 5-th element is now the new 4-th element, and it won't be processed by your loop if you're doing i++.

Below is a simple example illustrating this where I want to remove all the odds element of an int vector;

#include <iostream>
#include <vector>

using namespace std;

void printVector(const vector<int> &v)
{
    for (size_t i = 0; i < v.size(); i++)
    {
        cout << v[i] << " ";
    }
    cout << endl;
}

int main()
{    
    vector<int> v1, v2;
    for (int i = 0; i < 10; i++)
    {
        v1.push_back(i);
        v2.push_back(i);
    }

    // print v1
    cout << "v1: " << endl;
    printVector(v1);
    
    cout << endl;
    
    // print v2
    cout << "v2: " << endl;
    printVector(v2);
    
    // Erase all odd elements
    cout << "--- Erase odd elements ---" << endl;
    
    // loop with decreasing indices
    cout << "Process v2 with decreasing indices: " << endl;
    for (int i = v2.size() - 1; i >= 0; i--)
    {
        if (v2[i] % 2 != 0)
        {
            cout << "# ";
            v2.erase(v2.begin() + i);
        }
        else
        {
            cout << v2[i] << " ";
        }
    }
    cout << endl;
    cout << endl;
    
    // loop with increasing indices
    cout << "Process v1 with increasing indices: " << endl;
    for (int i = 0; i < v1.size(); i++)
    {
        if (v1[i] % 2 != 0)
        {
            cout << "# ";
            v1.erase(v1.begin() + i);
        }
        else
        {
            cout << v1[i] << " ";
        }
    }
    
    
    return 0;
}

Output:

v1:
0 1 2 3 4 5 6 7 8 9

v2:
0 1 2 3 4 5 6 7 8 9
--- Erase odd elements ---
Process v2 with decreasing indices:
# 8 # 6 # 4 # 2 # 0

Process v1 with increasing indices:
0 # # # # #

Note that on the second version with increasing indices, even numbers are not displayed as they are skipped because of i++

Parsing a comma-delimited std::string

You could also use the following function.

void tokenize(const string& str, vector<string>& tokens, const string& delimiters = ",")
{
  // Skip delimiters at beginning.
  string::size_type lastPos = str.find_first_not_of(delimiters, 0);

  // Find first non-delimiter.
  string::size_type pos = str.find_first_of(delimiters, lastPos);

  while (string::npos != pos || string::npos != lastPos) {
    // Found a token, add it to the vector.
    tokens.push_back(str.substr(lastPos, pos - lastPos));

    // Skip delimiters.
    lastPos = str.find_first_not_of(delimiters, pos);

    // Find next non-delimiter.
    pos = str.find_first_of(delimiters, lastPos);
  }
}

Replace an element into a specific position of a vector

vec1[i] = vec2[i]

will set the value of vec1[i] to the value of vec2[i]. Nothing is inserted. Your second approach is almost correct. Instead of +i+1 you need just +i

v1.insert(v1.begin()+i, v2[i])

How can I use std::maps with user-defined types as key?

class key
{
    int m_value;
public:
    bool operator<(const key& src)const
    {
        return (this->m_value < src.m_value);
    }

};
int main()
{
    key key1;
    key key2;
    map<key,int> mymap;
    mymap.insert(pair<key,int>(key1,100));
    mymap.insert(pair<key,int>(key2,200));
    map<key,int>::iterator iter=mymap.begin();
    for(;iter!=mymap.end();++iter)
    {
        cout<<iter->second<<endl;
    }


}

Delete all items from a c++ std::vector

Is v.clear() not working for some reason?

Iterate keys in a C++ map

You want to do this?

std::map<type,type>::iterator iter = myMap.begin();
std::map<type,type>::iterator iter = myMap.end();
for(; iter != endIter; ++iter)
{
   type key = iter->first;  
   .....
}

Use of for_each on map elements

From what I remembered, C++ map can return you an iterator of keys using map.begin(), you can use that iterator to loop over all the keys until it reach map.end(), and get the corresponding value: C++ map

Is it more efficient to copy a vector by reserving and copying, or by creating and swapping?

you should not use swap to copy vectors, it would change the "original" vector.

pass the original as a parameter to the new instead.

How do you copy the contents of an array to a std::vector in C++ without looping?

If you can construct the vector after you've gotten the array and array size, you can just say:

std::vector<ValueType> vec(a, a + n);

...assuming a is your array and n is the number of elements it contains. Otherwise, std::copy() w/resize() will do the trick.

I'd stay away from memcpy() unless you can be sure that the values are plain-old data (POD) types.

Also, worth noting that none of these really avoids the for loop--it's just a question of whether you have to see it in your code or not. O(n) runtime performance is unavoidable for copying the values.

Finally, note that C-style arrays are perfectly valid containers for most STL algorithms--the raw pointer is equivalent to begin(), and (ptr + n) is equivalent to end().

How to get a certain element in a list, given the position?

If you frequently need to access the Nth element of a sequence, std::list, which is implemented as a doubly linked list, is probably not the right choice. std::vector or std::deque would likely be better.

That said, you can get an iterator to the Nth element using std::advance:

std::list<Object> l;
// add elements to list 'l'...

unsigned N = /* index of the element you want to retrieve */;
if (l.size() > N)
{
    std::list<Object>::iterator it = l.begin();
    std::advance(it, N);
    // 'it' points to the element at index 'N'
}

For a container that doesn't provide random access, like std::list, std::advance calls operator++ on the iterator N times. Alternatively, if your Standard Library implementation provides it, you may call std::next:

if (l.size() > N)
{
    std::list<Object>::iterator it = std::next(l.begin(), N);
}

std::next is effectively wraps a call to std::advance, making it easier to advance an iterator N times with fewer lines of code and fewer mutable variables. std::next was added in C++11.

How do I remove an item from a stl vector with a certain value?

Use the global method std::remove with the begin and end iterator, and then use std::vector.erase to actually remove the elements.

Documentation links
std::remove http://www.cppreference.com/cppalgorithm/remove.html
std::vector.erase http://www.cppreference.com/cppvector/erase.html

std::vector<int> v;
v.push_back(1);
v.push_back(2);

//Vector should contain the elements 1, 2

//Find new end iterator
std::vector<int>::iterator newEnd = std::remove(v.begin(), v.end(), 1);

//Erase the "removed" elements.
v.erase(newEnd, v.end());

//Vector should now only contain 2

Thanks to Jim Buck for pointing out my error.

Is std::vector copying the objects with a push_back?

std::vector always makes a copy of whatever is being stored in the vector.

If you are keeping a vector of pointers, then it will make a copy of the pointer, but not the instance being to which the pointer is pointing. If you are dealing with large objects, you can (and probably should) always use a vector of pointers. Often, using a vector of smart pointers of an appropriate type is good for safety purposes, since handling object lifetime and memory management can be tricky otherwise.

Determine if map contains a value for a key?

You can create your getValue function with the following code:

bool getValue(const std::map<int, Bar>& input, int key, Bar& out)
{
   std::map<int, Bar>::iterator foundIter = input.find(key);
   if (foundIter != input.end())
   {
      out = foundIter->second;
      return true;
   }
   return false;
}

What does iterator->second mean?

The type of the elements of an std::map (which is also the type of an expression obtained by dereferencing an iterator of that map) whose key is K and value is V is std::pair<const K, V> - the key is const to prevent you from interfering with the internal sorting of map values.

std::pair<> has two members named first and second (see here), with quite an intuitive meaning. Thus, given an iterator i to a certain map, the expression:

i->first

Which is equivalent to:

(*i).first

Refers to the first (const) element of the pair object pointed to by the iterator - i.e. it refers to a key in the map. Instead, the expression:

i->second

Which is equivalent to:

(*i).second

Refers to the second element of the pair - i.e. to the corresponding value in the map.

How to remove all the occurrences of a char in c++ string

#include <string>
#include <algorithm>
std::string str = "YourString";
char chars[] = {'Y', 'S'};
str.erase (std::remove(str.begin(), str.end(), chars[i]), str.end());

Will remove capital Y and S from str, leaving "ourtring".

Note that remove is an algorithm and needs the header <algorithm> included.

Why is it OK to return a 'vector' from a function?

I do not agree and do not recommend to return a vector:

vector <double> vectorial(vector <double> a, vector <double> b)
{
    vector <double> c{ a[1] * b[2] - b[1] * a[2], -a[0] * b[2] + b[0] * a[2], a[0] * b[1] - b[0] * a[1] };
    return c;
}

This is much faster:

void vectorial(vector <double> a, vector <double> b, vector <double> &c)
{
    c[0] = a[1] * b[2] - b[1] * a[2]; c[1] = -a[0] * b[2] + b[0] * a[2]; c[2] = a[0] * b[1] - b[0] * a[1];
}

I tested on Visual Studio 2017 with the following results in release mode:

8.01 MOPs by reference
5.09 MOPs returning vector

In debug mode, things are much worse:

0.053 MOPS by reference
0.034 MOPs by return vector

How do I sort a vector of pairs based on the second element of the pair?

With C++0x we can use lambda functions:

using namespace std;
vector<pair<int, int>> v;
        .
        .
sort(v.begin(), v.end(),
     [](const pair<int, int>& lhs, const pair<int, int>& rhs) {
             return lhs.second < rhs.second; } );

In this example the return type bool is implicitly deduced.

Lambda return types

When a lambda-function has a single statement, and this is a return-statement, the compiler can deduce the return type. From C++11, §5.1.2/4:

...

  • If the compound-statement is of the form { return expression ; } the type of the returned expression after lvalue-to-rvalue conversion (4.1), array-to-pointer conversion (4.2), and function-to-pointer conversion (4.3);
  • otherwise, void.

To explicitly specify the return type use the form []() -> Type { }, like in:

sort(v.begin(), v.end(),
     [](const pair<int, int>& lhs, const pair<int, int>& rhs) -> bool {
             if (lhs.second == 0)
                 return true;
             return lhs.second < rhs.second; } );

Sorting a vector of custom objects

You could use functor as third argument of std::sort, or you could define operator< in your class.

struct X {
    int x;
    bool operator<( const X& val ) const { 
        return x < val.x; 
    }
};

struct Xgreater
{
    bool operator()( const X& lx, const X& rx ) const {
        return lx.x < rx.x;
    }
};

int main () {
    std::vector<X> my_vec;

    // use X::operator< by default
    std::sort( my_vec.begin(), my_vec.end() );

    // use functor
    std::sort( my_vec.begin(), my_vec.end(), Xgreater() );
}

Initialize a vector array of strings

 const char* args[] = {"01", "02", "03", "04"};
 std::vector<std::string> v(args, args + 4);

And in C++0x, you can take advantage of std::initializer_list<>:

http://en.wikipedia.org/wiki/C%2B%2B0x#Initializer_lists

How to convert wstring into string?

Here is a worked-out solution based on the other suggestions:

#include <string>
#include <iostream>
#include <clocale>
#include <locale>
#include <vector>

int main() {
  std::setlocale(LC_ALL, "");
  const std::wstring ws = L"hëllö";
  const std::locale locale("");
  typedef std::codecvt<wchar_t, char, std::mbstate_t> converter_type;
  const converter_type& converter = std::use_facet<converter_type>(locale);
  std::vector<char> to(ws.length() * converter.max_length());
  std::mbstate_t state;
  const wchar_t* from_next;
  char* to_next;
  const converter_type::result result = converter.out(state, ws.data(), ws.data() + ws.length(), from_next, &to[0], &to[0] + to.size(), to_next);
  if (result == converter_type::ok or result == converter_type::noconv) {
    const std::string s(&to[0], to_next);
    std::cout <<"std::string =     "<<s<<std::endl;
  }
}

This will usually work for Linux, but will create problems on Windows.

C++ sorting and keeping track of indexes

I wrote generic version of index sort.

template <class RAIter, class Compare>
void argsort(RAIter iterBegin, RAIter iterEnd, Compare comp, 
    std::vector<size_t>& indexes) {

    std::vector< std::pair<size_t,RAIter> > pv ;
    pv.reserve(iterEnd - iterBegin) ;

    RAIter iter ;
    size_t k ;
    for (iter = iterBegin, k = 0 ; iter != iterEnd ; iter++, k++) {
        pv.push_back( std::pair<int,RAIter>(k,iter) ) ;
    }

    std::sort(pv.begin(), pv.end(), 
        [&comp](const std::pair<size_t,RAIter>& a, const std::pair<size_t,RAIter>& b) -> bool 
        { return comp(*a.second, *b.second) ; }) ;

    indexes.resize(pv.size()) ;
    std::transform(pv.begin(), pv.end(), indexes.begin(), 
        [](const std::pair<size_t,RAIter>& a) -> size_t { return a.first ; }) ;
}

Usage is the same as that of std::sort except for an index container to receive sorted indexes. testing:

int a[] = { 3, 1, 0, 4 } ;
std::vector<size_t> indexes ;
argsort(a, a + sizeof(a) / sizeof(a[0]), std::less<int>(), indexes) ;
for (size_t i : indexes) printf("%d\n", int(i)) ;

you should get 2 1 0 3. for the compilers without c++0x support, replace the lamba expression as a class template:

template <class RAIter, class Compare> 
class PairComp {
public:
  Compare comp ;
  PairComp(Compare comp_) : comp(comp_) {}
  bool operator() (const std::pair<size_t,RAIter>& a, 
    const std::pair<size_t,RAIter>& b) const { return comp(*a.second, *b.second) ; }        
} ;

and rewrite std::sort as

std::sort(pv.begin(), pv.end(), PairComp(comp)()) ;

How can I create Min stl priority_queue?

We can do this using several ways.

Using template comparator parameter

    int main() 
    {
      priority_queue<int, vector<int>, greater<int> > pq;

      pq.push(40);
      pq.push(320);
      pq.push(42);
      pq.push(65);
      pq.push(12);

      cout<<pq.top()<<endl;
      return 0;
    }

Using used defined compartor class

     struct comp
     {
        bool operator () (int lhs, int rhs)
        {
           return lhs > rhs;
        }
     };

    int main()
    {
       priority_queue<int, vector<int>, comp> pq;

       pq.push(40);
       pq.push(320);
       pq.push(42);
       pq.push(65);
       pq.push(12);

       cout<<pq.top()<<endl;

       return 0;
    }

C++ STL Vectors: Get iterator from index?

Try this:

vector<Type>::iterator nth = v.begin() + index;

How do I reverse a C++ vector?

Often the reason you want to reverse the vector is because you fill it by pushing all the items on at the end but were actually receiving them in reverse order. In that case you can reverse the container as you go by using a deque instead and pushing them directly on the front. (Or you could insert the items at the front with vector::insert() instead, but that would be slow when there are lots of items because it has to shuffle all the other items along for every insertion.) So as opposed to:

std::vector<int> foo;
int nextItem;
while (getNext(nextItem)) {
    foo.push_back(nextItem);
}
std::reverse(foo.begin(), foo.end());

You can instead do:

std::deque<int> foo;
int nextItem;
while (getNext(nextItem)) {
    foo.push_front(nextItem);
}
// No reverse needed - already in correct order

Recommended way to insert elements into map

Use insert if you want to insert a new element. insert will not overwrite an existing element, and you can verify that there was no previously exising element:

if ( !myMap.insert( std::make_pair( key, value ) ).second ) {
    //  Element already present...
}

Use [] if you want to overwrite a possibly existing element:

myMap[ key ] = value;
assert( myMap.find( key )->second == value ); // post-condition

This form will overwrite any existing entry.

How to initialize std::vector from C-style array?

Don't forget that you can treat pointers as iterators:

w_.assign(w, w + len);

Best way to extract a subvector from a vector?

You didn't mention what type std::vector<...> myVec is, but if it's a simple type or struct/class that doesn't include pointers, and you want the best efficiency, then you can do a direct memory copy (which I think will be faster than the other answers provided). Here is a general example for std::vector<type> myVec where type in this case is int:

typedef int type; //choose your custom type/struct/class
int iFirst = 100000; //first index to copy
int iLast = 101000; //last index + 1
int iLen = iLast - iFirst;
std::vector<type> newVec;
newVec.resize(iLen); //pre-allocate the space needed to write the data directly
memcpy(&newVec[0], &myVec[iFirst], iLen*sizeof(type)); //write directly to destination buffer from source buffer

How to retrieve all keys (or values) from a std::map and put them into a vector?

I found the following three lines of code as the easiest way:

// save keys in vector

vector<string> keys;
for (auto & it : m) {
    keys.push_back(it.first);
}

It is a shorten version of the first way of this answer.

std::string length() and size() member functions

length of string ==how many bits that string having, size==size of those bits, In strings both are same if the editor allocates size of character is 1 byte

What is the easiest way to initialize a std::vector with hardcoded elements?

Before C++ 11 :

Method 1=>

vector<int> v(arr, arr + sizeof(arr)/sizeof(arr[0]));
vector<int>v;

Method 2 =>

 v.push_back(SomeValue);

C++ 11 onward below is also possible

vector<int>v = {1, 3, 5, 7};

Erasing elements from a vector

Use the remove/erase idiom:

std::vector<int>& vec = myNumbers; // use shorter name
vec.erase(std::remove(vec.begin(), vec.end(), number_in), vec.end());

What happens is that remove compacts the elements that differ from the value to be removed (number_in) in the beginning of the vector and returns the iterator to the first element after that range. Then erase removes these elements (whose value is unspecified).

What's the most efficient way to erase duplicates and sort a vector?

void EraseVectorRepeats(vector <int> & v){ 
TOP:for(int y=0; y<v.size();++y){
        for(int z=0; z<v.size();++z){
            if(y==z){ //This if statement makes sure the number that it is on is not erased-just skipped-in order to keep only one copy of a repeated number
                continue;}
            if(v[y]==v[z]){
                v.erase(v.begin()+z); //whenever a number is erased the function goes back to start of the first loop because the size of the vector changes
            goto TOP;}}}}

This is a function that I created that you can use to delete repeats. The header files needed are just <iostream> and <vector>.

Case insensitive std::string.find()

If you want “real” comparison according to Unicode and locale rules, use ICU’s Collator class.

Why can I not push_back a unique_ptr into a vector?

std::unique_ptr has no copy constructor. You create an instance and then ask the std::vector to copy that instance during initialisation.

error: deleted function 'std::unique_ptr<_Tp, _Tp_Deleter>::uniqu
e_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = int, _Tp_D
eleter = std::default_delete<int>, std::unique_ptr<_Tp, _Tp_Deleter> =
 std::unique_ptr<int>]'

The class satisfies the requirements of MoveConstructible and MoveAssignable, but not the requirements of either CopyConstructible or CopyAssignable.

The following works with the new emplace calls.

std::vector< std::unique_ptr< int > > vec;
vec.emplace_back( new int( 1984 ) );

See using unique_ptr with standard library containers for further reading.

Why can't I make a vector of references?

As the other comments suggest, you are confined to using pointers. But if it helps, here is one technique to avoid facing directly with pointers.

You can do something like the following:

vector<int*> iarray;
int default_item = 0; // for handling out-of-range exception

int& get_item_as_ref(unsigned int idx) {
   // handling out-of-range exception
   if(idx >= iarray.size()) 
      return default_item;
   return reinterpret_cast<int&>(*iarray[idx]);
}

Copy map values to vector in STL

If you are using the boost libraries, you can use boost::bind to access the second value of the pair as follows:

#include <string>
#include <map>
#include <vector>
#include <algorithm>
#include <boost/bind.hpp>

int main()
{
   typedef std::map<std::string, int> MapT;
   typedef std::vector<int> VecT;
   MapT map;
   VecT vec;

   map["one"] = 1;
   map["two"] = 2;
   map["three"] = 3;
   map["four"] = 4;
   map["five"] = 5;

   std::transform( map.begin(), map.end(),
                   std::back_inserter(vec),
                   boost::bind(&MapT::value_type::second,_1) );
}

This solution is based on a post from Michael Goldshteyn on the boost mailing list.

How to sum up elements of a C++ vector?

The easiest way is to use std:accumulate of a vector<int> A:

#include <numeric>
cout << accumulate(A.begin(), A.end(), 0);

C++ Double Address Operator? (&&)

As other answers have mentioned, the && token in this context is new to C++0x (the next C++ standard) and represent an "rvalue reference".

Rvalue references are one of the more important new things in the upcoming standard; they enable support for 'move' semantics on objects and permit perfect forwarding of function calls.

It's a rather complex topic - one of the best introductions (that's not merely cursory) is an article by Stephan T. Lavavej, "Rvalue References: C++0x Features in VC10, Part 2"

Note that the article is still quite heavy reading, but well worthwhile. And even though it's on a Microsoft VC++ Blog, all (or nearly all) the information is applicable to any C++0x compiler.

Using custom std::set comparator

1. Modern C++20 solution

auto cmp = [](int a, int b) { return ... };
std::set<int, decltype(cmp)> s;

We use lambda function as comparator. As usual, comparator should return boolean value, indicating whether the element passed as first argument is considered to go before the second in the specific strict weak ordering it defines.

Online demo

2. Modern C++11 solution

auto cmp = [](int a, int b) { return ... };
std::set<int, decltype(cmp)> s(cmp);

Before C++20 we need to pass lambda as argument to set constructor

Online demo

3. Similar to first solution, but with function instead of lambda

Make comparator as usual boolean function

bool cmp(int a, int b) {
    return ...;
}

Then use it, either this way:

std::set<int, decltype(cmp)*> s(cmp);

Online demo

or this way:

std::set<int, decltype(&cmp)> s(&cmp);

Online demo

4. Old solution using struct with () operator

struct cmp {
    bool operator() (int a, int b) const {
        return ...
    }
};

// ...
// later
std::set<int, cmp> s;

Online demo

5. Alternative solution: create struct from boolean function

Take boolean function

bool cmp(int a, int b) {
    return ...;
}

And make struct from it using std::integral_constant

#include <type_traits>
using Cmp = std::integral_constant<decltype(&cmp), &cmp>;

Finally, use the struct as comparator

std::set<X, Cmp> set;

Online demo

c++ exception : throwing std::string

A few principles:

  1. you have a std::exception base class, you should have your exceptions derive from it. That way general exception handler still have some information.

  2. Don't throw pointers but object, that way memory is handled for you.

Example:

struct MyException : public std::exception
{
   std::string s;
   MyException(std::string ss) : s(ss) {}
   ~MyException() throw () {} // Updated
   const char* what() const throw() { return s.c_str(); }
};

And then use it in your code:

void Foo::Bar(){
  if(!QueryPerformanceTimer(&m_baz)){
    throw MyException("it's the end of the world!");
  }
}

void Foo::Caller(){
  try{
    this->Bar();// should throw
  }catch(MyException& caught){
    std::cout<<"Got "<<caught.what()<<std::endl;
  }
}

Initializing a static std::map<int, int> in C++

I would wrap the map inside a static object, and put the map initialisation code in the constructor of this object, this way you are sure the map is created before the initialisation code is executed.

C++ equivalent of StringBuffer/StringBuilder?

std::string is the C++ equivalent: It's mutable.

Use the auto keyword in C++ STL

It's additional information, and isn't an answer.

In C++11 you can write:

for (auto& it : s) {
    cout << it << endl;
}

instead of

for (auto it = s.begin(); it != s.end(); it++) {
    cout << *it << endl;
}

It has the same meaning.

Update: See the @Alnitak's comment also.

How do I print the elements of a C++ vector in GDB?

put the following in ~/.gdbinit

define print_vector
    if $argc == 2
        set $elem = $arg0.size()
        if $arg1 >= $arg0.size()
            printf "Error, %s.size() = %d, printing last element:\n", "$arg0", $arg0.size()
            set $elem = $arg1 -1
        end
        print *($arg0._M_impl._M_start + $elem)@1
    else
        print *($arg0._M_impl._M_start)@$arg0.size()
    end
end

document print_vector
Display vector contents
Usage: print_vector VECTOR_NAME INDEX
VECTOR_NAME is the name of the vector
INDEX is an optional argument specifying the element to display
end

After restarting gdb (or sourcing ~/.gdbinit), show the associated help like this

gdb) help print_vector
Display vector contents
Usage: print_vector VECTOR_NAME INDEX
VECTOR_NAME is the name of the vector
INDEX is an optional argument specifying the element to display

Example usage:

(gdb) print_vector videoconfig_.entries 0
$32 = {{subChannelId = 177 '\261', sourceId = 0 '\000', hasH264PayloadInfo = false, bitrate = 0,     payloadType = 68 'D', maxFs = 0, maxMbps = 0, maxFps = 134, encoder = 0 '\000', temporalLayers = 0 '\000'}}

Sorting a vector in descending order

According to my machine, sorting a long long vector of [1..3000000] using the first method takes around 4 seconds, while using the second takes about twice the time. That says something, obviously, but I don't understand why either. Just think this would be helpful.

Same thing reported here.

As said by Xeo, with -O3 they use about the same time to finish.

How to check that an element is in a std::set?

If you were going to add a contains function, it might look like this:

#include <algorithm>
#include <iterator>

template<class TInputIterator, class T> inline
bool contains(TInputIterator first, TInputIterator last, const T& value)
{
    return std::find(first, last, value) != last;
}

template<class TContainer, class T> inline
bool contains(const TContainer& container, const T& value)
{
    // This works with more containers but requires std::begin and std::end
    // from C++0x, which you can get either:
    //  1. By using a C++0x compiler or
    //  2. Including the utility functions below.
    return contains(std::begin(container), std::end(container), value);

    // This works pre-C++0x (and without the utility functions below, but doesn't
    // work for fixed-length arrays.
    //return contains(container.begin(), container.end(), value);
}

template<class T> inline
bool contains(const std::set<T>& container, const T& value)
{
    return container.find(value) != container.end();
}

This works with std::set, other STL containers, and even fixed-length arrays:

void test()
{
    std::set<int> set;
    set.insert(1);
    set.insert(4);
    assert(!contains(set, 3));

    int set2[] = { 1, 2, 3 };
    assert(contains(set2, 3));
}

Edit:

As pointed out in the comments, I unintentionally used a function new to C++0x (std::begin and std::end). Here is the near-trivial implementation from VS2010:

namespace std {

template<class _Container> inline
    typename _Container::iterator begin(_Container& _Cont)
    { // get beginning of sequence
    return (_Cont.begin());
    }

template<class _Container> inline
    typename _Container::const_iterator begin(const _Container& _Cont)
    { // get beginning of sequence
    return (_Cont.begin());
    }

template<class _Container> inline
    typename _Container::iterator end(_Container& _Cont)
    { // get end of sequence
    return (_Cont.end());
    }

template<class _Container> inline
    typename _Container::const_iterator end(const _Container& _Cont)
    { // get end of sequence
    return (_Cont.end());
    }

template<class _Ty,
    size_t _Size> inline
    _Ty *begin(_Ty (&_Array)[_Size])
    { // get beginning of array
    return (&_Array[0]);
    }

template<class _Ty,
    size_t _Size> inline
    _Ty *end(_Ty (&_Array)[_Size])
    { // get end of array
    return (&_Array[0] + _Size);
    }

}

Convert iterator to pointer?

I haven't tested this but could you use a set of pairs of iterators instead? Each iterator pair would represent the begin and end iterator of the sequence vector. E.g.:

typedef std::vector<int> Seq;
typedef std::pair<Seq::const_iterator, Seq::const_iterator> SeqRange;

bool operator< (const SeqRange& lhs, const SeqRange& rhs)
{
    Seq::const_iterator lhsNext = lhs.first;
    Seq::const_iterator rhsNext = rhs.first;

    while (lhsNext != lhs.second && rhsNext != rhs.second)
        if (*lhsNext < *rhsNext)
            return true;
        else if (*lhsNext > *rhsNext)
            return false;

    return false;
}

typedef std::set<SeqRange, std::less<SeqRange> > SeqSet;

Seq sequences;

void test (const SeqSet& seqSet, const SeqRange& seq)
{
    bool find = seqSet.find (seq) != seqSet.end ();
    bool find2 = seqSet.find (SeqRange (seq.first + 1, seq.second)) != seqSet.end ();
}

Obviously the vectors have to be held elsewhere as before. Also if a sequence vector is modified then its entry in the set would have to be removed and re-added as the iterators may have changed.

Jon

Advantages of std::for_each over for loop

The for_each loop is meant to hide the iterators (detail of how a loop is implemented) from the user code and define clear semantics on the operation: each element will be iterated exactly once.

The problem with readability in the current standard is that it requires a functor as the last argument instead of a block of code, so in many cases you must write specific functor type for it. That turns into less readable code as functor objects cannot be defined in-place (local classes defined within a function cannot be used as template arguments) and the implementation of the loop must be moved away from the actual loop.

struct myfunctor {
   void operator()( int arg1 ) { code }
};
void apply( std::vector<int> const & v ) {
   // code
   std::for_each( v.begin(), v.end(), myfunctor() );
   // more code
}

Note that if you want to perform an specific operation on each object, you can use std::mem_fn, or boost::bind (std::bind in the next standard), or boost::lambda (lambdas in the next standard) to make it simpler:

void function( int value );
void apply( std::vector<X> const & v ) {
   // code
   std::for_each( v.begin(), v.end(), boost::bind( function, _1 ) );
   // code
}

Which is not less readable and more compact than the hand rolled version if you do have function/method to call in place. The implementation could provide other implementations of the for_each loop (think parallel processing).

The upcoming standard takes care of some of the shortcomings in different ways, it will allow for locally defined classes as arguments to templates:

void apply( std::vector<int> const & v ) {
   // code
   struct myfunctor {
      void operator()( int ) { code }
   };
   std::for_each( v.begin(), v.end(), myfunctor() );
   // code
}

Improving the locality of code: when you browse you see what it is doing right there. As a matter of fact, you don't even need to use the class syntax to define the functor, but use a lambda right there:

void apply( std::vector<int> const & v ) {
   // code
   std::for_each( v.begin(), v.end(), 
      []( int ) { // code } );
   // code
}

Even if for the case of for_each there will be an specific construct that will make it more natural:

void apply( std::vector<int> const & v ) {
   // code
   for ( int i : v ) {
      // code
   }
   // code
}

I tend to mix the for_each construct with hand rolled loops. When only a call to an existing function or method is what I need (for_each( v.begin(), v.end(), boost::bind( &Type::update, _1 ) )) I go for the for_each construct that takes away from the code a lot of boiler plate iterator stuff. When I need something more complex and I cannot implement a functor just a couple of lines above the actual use, I roll my own loop (keeps the operation in place). In non-critical sections of code I might go with BOOST_FOREACH (a co-worker got me into it)

Command line for looking at specific port

In RHEL 7, I use this command to filter several ports in LISTEN State:

sudo netstat -tulpn | grep LISTEN | egrep '(8080 |8082 |8083 | etc )'

Is it still valid to use IE=edge,chrome=1?

<head>
<meta http-equiv='X-UA-Compatible' content='IE=edge'>

worked for me, to force IE to "snap out of compatibility mode" (so to speak), BUT that meta statement must appear IMMEDIATELY after the <head>, or it won't work!

How do I evenly add space between a label and the input field regardless of length of text?

You can also used below code

<html>
<head>
    <style>
        .labelClass{
            float: left;
            width: 113px;
        }
    </style>
</head>
<body>
  <form action="yourclassName.jsp">
    <span class="labelClass">First name: </span><input type="text" name="fname"><br>
    <span class="labelClass">Last name: </span><input type="text" name="lname"><br>
    <input type="submit" value="Submit">
  </form>
</body>
</html>

Is it better to return null or empty collection?

Depends on the situation. If it is a special case, then return null. If the function just happens to return an empty collection, then obviously returning that is ok. However, returning an empty collection as a special case because of invalid parameters or other reasons is NOT a good idea, because it is masking a special case condition.

Actually, in this case I usually prefer to throw an exception to make sure it is REALLY not ignored :)

Saying that it makes the code more robust (by returning an empty collection) as they do not have to handle the null condition is bad, as it is simply masking a problem that should be handled by the calling code.

How to develop Android app completely using python?

To answer your first question: yes it is feasible to develop an android application in pure python, in order to achieve this I suggest you use BeeWare, which is just a suite of python tools, that work together very well and they enable you to develop platform native applications in python.

checkout this video by the creator of BeeWare that perfectly explains and demonstrates it's application

How it works

Android's preferred language of implementation is Java - so if you want to write an Android application in Python, you need to have a way to run your Python code on a Java Virtual Machine. This is what VOC does. VOC is a transpiler - it takes Python source code, compiles it to CPython Bytecode, and then transpiles that bytecode into Java-compatible bytecode. The end result is that your Python source code files are compiled directly to a Java .class file, which can be packaged into an Android application.

VOC also allows you to access native Java objects as if they were Python objects, implement Java interfaces with Python classes, and subclass Java classes with Python classes. Using this, you can write an Android application directly against the native Android APIs.

Once you've written your native Android application, you can use Briefcase to package your Python code as an Android application.

Briefcase is a tool for converting a Python project into a standalone native application. You can package projects for:

  • Mac
  • Windows
  • Linux
  • iPhone/iPad
  • Android
  • AppleTV
  • tvOS.

You can check This native Android Tic Tac Toe app written in Python, using the BeeWare suite. on GitHub

in addition to the BeeWare tools, you'll need to have a JDK and Android SDK installed to test run your application.

and to answer your second question: a good environment can be anything you are comfortable with be it a text editor and a command line, or an IDE, if you're looking for a good python IDE I would suggest you try Pycharm, it has a community edition which is free, and it has a similar environment as android studio, due to to the fact that were made by the same company.

I hope this has been helpful

IntelliJ: Working on multiple projects

Since macOS Big Sur and IntelliJ IDEA 2020.3.2 you can use "open projects in tabs on macOS Big Sur" feature. To use it, you have to enable this feature in your system settings:

System Preferences -> General -> Prefer tabs [always] when opening documents

enter image description here

After this step, when you will try to open second project in IntelliJ, choose New Window (yes, New Window, not This Window).

enter image description here

It should result with opening new project in same window, but in the new card:

enter image description here

Ignore Duplicates and Create New List of Unique Values in Excel

Find here mentioned above formula with error control

=IFERROR(INDEX($B$2:$B$9, MATCH(0,COUNTIF($D$1:D1, $B$2:$B$9), 0)),"") 

where: (B2:B9 is the column data which you want to extract the unique values, D1 is the above cell where your formula is located)

Allow Access-Control-Allow-Origin header using HTML5 fetch API

Solution to resolve issue in Local env's

I had my front-end code running in http://localhost:3000 and my API(Backend code) running at http://localhost:5000

Was using fetch API to call the API. Initially, it was throwing "cors" error. Then added this below code in my Backend API code, allowing origin and header from anywhere.

let allowCrossDomain = function(req, res, next) {
  res.header('Access-Control-Allow-Origin', "*");
  res.header('Access-Control-Allow-Headers', "*");
  next();
}
app.use(allowCrossDomain);

However you must restrict origins in case of other environments like stage, prod.

Strictly NO for higher environments.

Get a list of dates between two dates using a function

Try something like this:

CREATE FUNCTION dbo.ExplodeDates(@startdate datetime, @enddate datetime)
returns table as
return (
with 
 N0 as (SELECT 1 as n UNION ALL SELECT 1)
,N1 as (SELECT 1 as n FROM N0 t1, N0 t2)
,N2 as (SELECT 1 as n FROM N1 t1, N1 t2)
,N3 as (SELECT 1 as n FROM N2 t1, N2 t2)
,N4 as (SELECT 1 as n FROM N3 t1, N3 t2)
,N5 as (SELECT 1 as n FROM N4 t1, N4 t2)
,N6 as (SELECT 1 as n FROM N5 t1, N5 t2)
,nums as (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 1)) as num FROM N6)
SELECT DATEADD(day,num-1,@startdate) as thedate
FROM nums
WHERE num <= DATEDIFF(day,@startdate,@enddate) + 1
);

You then use:

SELECT *
FROM dbo.ExplodeDates('20090401','20090531') as d;

Edited (after the acceptance):

Please note... if you already have a sufficiently large nums table then you should use:

CREATE FUNCTION dbo.ExplodeDates(@startdate datetime, @enddate datetime)
returns table as
return (
SELECT DATEADD(day,num-1,@startdate) as thedate
FROM nums
WHERE num <= DATEDIFF(day,@startdate,@enddate) + 1
);

And you can create such a table using:

CREATE TABLE dbo.nums (num int PRIMARY KEY);
INSERT dbo.nums values (1);
GO
INSERT dbo.nums SELECT num + (SELECT COUNT(*) FROM nums) FROM nums
GO 20

These lines will create a table of numbers containing 1M rows... and far quicker than inserting them one by one.

You should NOT create your ExplodeDates function using a function that involves BEGIN and END, as the Query Optimizer becomes unable to simplify the query at all.

Difference between window.location.href=window.location.href and window.location.reload()

Came across this question researching some aberrant behavior in IE, specifically IE9, didn't check older versions. It seems

window.location.reload();

results in a refresh that blanks out the entire screen for a second, where as

 window.location = document.URL;

refreshes the page much more quickly, almost imperceptibly.

Doing a bit more research, and some experimentation with fiddler, it seems that window.location.reload() will bypass the cache and reload from the server regardless if you pass the boolean with it or not, this includes getting all of your assets (images, scripts, style sheets, etc) again. So if you just want the page to refresh the HTML, the window.location = document.URL will return much quicker and with less traffic.

A difference in behavior between browsers is that when IE9 uses the reload method it clears the visible page and seemingly rebuilds it from scratch, where FF and chrome wait till they get the new assets and rebuild them if they are different.

Detect URLs in text with JavaScript

Here is what I ended up using as my regex:

var urlRegex =/(\b(https?|ftp|file):\/\/[-A-Z0-9+&@#\/%?=~_|!:,.;]*[-A-Z0-9+&@#\/%=~_|])/ig;

This doesn't include trailing punctuation in the URL. Crescent's function works like a charm :) so:

function linkify(text) {
    var urlRegex =/(\b(https?|ftp|file):\/\/[-A-Z0-9+&@#\/%?=~_|!:,.;]*[-A-Z0-9+&@#\/%=~_|])/ig;
    return text.replace(urlRegex, function(url) {
        return '<a href="' + url + '">' + url + '</a>';
    });
}

How do I remove the last comma from a string using PHP?

Use the rtrim function:

rtrim($my_string, ',');

The Second parameter indicates the character to be deleted.

Class file has wrong version 52.0, should be 50.0

It means your Java runtime version is 1.8, but your compiler version (javac) is 1.6. To simply solve it, just retreat the Java version from 1.8 to 1.6.

But if you don't want to change the Java runtime version, then do the following steps:

  1. JAVA_HOME= "your jdk v1.8 folder path", to make sure jdk is also v1.8 and use java -version and javac -version again to ensure it
  2. Make sure IntelliJ 's compiler mode is set to compliant with v1.6 But i have tried that. it didn't solve my problem.

How can I run Tensorboard on a remote server?

You have to create a ssh connection using port forwarding:

ssh -L 16006:127.0.0.1:6006 user@host

Then you run the tensorboard command:

tensorboard --logdir=/path/to/logs

Then you can easily access the tensorboard in your browser under:

localhost:16006/

Select multiple rows with the same value(s)

You need to understand that when you include GROUP BY in your query you are telling SQL to combine rows. you will get one row per unique Locus value. The Having then filters those groups. Usually you specify an aggergate function in the select list like:

--show how many of each Locus there is
SELECT COUNT(*),Locus FROM Genes GROUP BY Locus

--only show the groups that have more than one row in them
SELECT COUNT(*),Locus FROM Genes GROUP BY Locus HAVING COUNT(*)>1

--to just display all the rows for your condition, don't use GROUP BY or HAVING
SELECT * FROM Genes WHERE Locus = '3' AND Chromosome = '10'

How to "grep" out specific line ranges of a file

If you want lines instead of line ranges, you can do it with perl: eg. if you want to get line 1, 3 and 5 from a file, say /etc/passwd:

perl -e 'while(<>){if(++$l~~[1,3,5]){print}}' < /etc/passwd

Right way to write JSON deserializer in Spring or extend it

I've searched a lot and the best way I've found so far is on this article:

Class to serialize

package net.sghill.example;

import net.sghill.example.UserDeserializer
import net.sghill.example.UserSerializer
import org.codehaus.jackson.map.annotate.JsonDeserialize;
import org.codehaus.jackson.map.annotate.JsonSerialize;

@JsonDeserialize(using = UserDeserializer.class)
public class User {
    private ObjectId id;
    private String   username;
    private String   password;

    public User(ObjectId id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public ObjectId getId()       { return id; }
    public String   getUsername() { return username; }
    public String   getPassword() { return password; }
}

Deserializer class

package net.sghill.example;

import net.sghill.example.User;
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.ObjectCodec;
import org.codehaus.jackson.map.DeserializationContext;
import org.codehaus.jackson.map.JsonDeserializer;

import java.io.IOException;

public class UserDeserializer extends JsonDeserializer<User> {

    @Override
    public User deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
        ObjectCodec oc = jsonParser.getCodec();
        JsonNode node = oc.readTree(jsonParser);
        return new User(null, node.get("username").getTextValue(), node.get("password").getTextValue());
    }
}

Edit: Alternatively you can look at this article which uses new versions of com.fasterxml.jackson.databind.JsonDeserializer.

How to center a window on the screen in Tkinter?

You can try to use the methods winfo_screenwidth and winfo_screenheight, which return respectively the width and height (in pixels) of your Tk instance (window), and with some basic math you can center your window:

import tkinter as tk
from PyQt4 import QtGui    # or PySide

def center(toplevel):
    toplevel.update_idletasks()

    # Tkinter way to find the screen resolution
    # screen_width = toplevel.winfo_screenwidth()
    # screen_height = toplevel.winfo_screenheight()

    # PyQt way to find the screen resolution
    app = QtGui.QApplication([])
    screen_width = app.desktop().screenGeometry().width()
    screen_height = app.desktop().screenGeometry().height()

    size = tuple(int(_) for _ in toplevel.geometry().split('+')[0].split('x'))
    x = screen_width/2 - size[0]/2
    y = screen_height/2 - size[1]/2

    toplevel.geometry("+%d+%d" % (x, y))
    toplevel.title("Centered!")    

if __name__ == '__main__':
    root = tk.Tk()
    root.title("Not centered")

    win = tk.Toplevel(root)
    center(win)

    root.mainloop()

I am calling update_idletasks method before retrieving the width and the height of the window in order to ensure that the values returned are accurate.

Tkinter doesn't see if there are 2 or more monitors extended horizontal or vertical. So, you 'll get the total resolution of all screens together and your window will end-up somewhere in the middle of the screens.

PyQt from the other hand, doesn't see multi-monitors environment either, but it will get only the resolution of the Top-Left monitor (Imagine 4 monitors, 2 up and 2 down making a square). So, it does the work by putting the window on center of that screen. If you don't want to use both, PyQt and Tkinter, maybe it would be better to go with PyQt from start.

How do you revert to a specific tag in Git?

Git tags are just pointers to the commit. So you use them the same way as you do HEAD, branch names or commit sha hashes. You can use tags with any git command that accepts commit/revision arguments. You can try it with git rev-parse tagname to display the commit it points to.

In your case you have at least these two alternatives:

  1. Reset the current branch to specific tag:

    git reset --hard tagname
    
  2. Generate revert commit on top to get you to the state of the tag:

    git revert tag
    

This might introduce some conflicts if you have merge commits though.

How to parse string into date?

CONVERT(datetime, '24.04.2012', 104)

Should do the trick. See here for more info: CAST and CONVERT (Transact-SQL)

The declared package does not match the expected package ""

You need to have the class inside a folder Devices.

How to make a Generic Type Cast function

While probably not as clean looking as the IConvertible approach, you could always use the straightforward checking typeof(T) to return a T:

public static T ReturnType<T>(string stringValue)
{
    if (typeof(T) == typeof(int))
        return (T)(object)1;
    else if (typeof(T) == typeof(FooBar))
        return (T)(object)new FooBar(stringValue);
    else
        return default(T);
}

public class FooBar
{
    public FooBar(string something)
    {}
}

How do I navigate to a parent route from a child route?

constructor(private router: Router) {}

navigateOnParent() {
  this.router.navigate(['../some-path-on-parent']);
}

The router supports

  • absolute paths /xxx - started on the router of the root component
  • relative paths xxx - started on the router of the current component
  • relative paths ../xxx - started on the parent router of the current component

Negative regex for Perl string pattern match

What's wrong with using two regexs (or three)? This makes your intentions more clear and may even improve your performance:

if ($string =~ /^(Clinton|Reagan)/i && $string !~ /Bush/i) { ... }

if (($string =~ /^Clinton/i || $string =~ /^Reagan/i)
        && $string !~ /Bush/i) {
    print "$string\n"
}

Using union and order by clause in mysql

(select add_date,col2 from table_name) 
  union 
(select add_date,col2 from table_name) 
  union 
(select add_date,col2 from table_name) 

order by add_date

How do I pass a list as a parameter in a stored procedure?

Maybe you could use:

select last_name+', '+first_name 
from user_mstr
where ',' + @user_id_list + ',' like '%,' + convert(nvarchar, user_id) + ',%'

c# foreach (property in object)... Is there a simple way of doing this?

I looked for the answer to a similar question on this page, I wrote the answers to several similar questions that may help people who enter this page.

Class List

List < T > class represents the list of objects which can be accessed by index. It comes under the System.Collection.Generic namespace. List class can be used to create a collection of different types like integers, strings etc. List class also provides the methods to search, sort, and manipulate lists.

Class with property:

class TestClss
{
    public string id { set; get; }
    public string cell1 { set; get; }
    public string cell2 { set; get; }
}
var MyArray = new List<TestClss> {
    new TestClss() { id = "1", cell1 = "cell 1 row 1 Data", cell2 = "cell 2 row 1 Data" },
    new TestClss() { id = "2", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 2 Data" },
    new TestClss() { id = "3", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 3 Data" }
};
foreach (object Item in MyArray)
{
    Console.WriteLine("Row Start");
    foreach (PropertyInfo property in Item.GetType().GetProperties())
    {
        var Key = property.Name;
        var Value = property.GetValue(Item, null);
        Console.WriteLine("{0}={1}", Key, Value);
    }
}

OR, Class with field:

class TestClss
{
    public string id = "";
    public string cell1 = "";
    public string cell2 = "";
}
var MyArray = new List<TestClss> {
    new TestClss() { id = "1", cell1 = "cell 1 row 1 Data", cell2 = "cell 2 row 1 Data" },
    new TestClss() { id = "2", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 2 Data" },
    new TestClss() { id = "3", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 3 Data" }
};
foreach (object Item in MyArray)
{
    Console.WriteLine("Row Start");
    foreach (var fieldInfo in Item.GetType().GetFields())
    {
        var Key = fieldInfo.Name;
        var Value = fieldInfo.GetValue(Item);
    }

}

OR, List of objects (without same cells):

var MyArray = new List<object> {
    new { id = "1", cell1 = "cell 1 row 1 Data", cell2 = "cell 2 row 1 Data" },
    new { id = "2", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 2 Data" },
    new { id = "3", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 3 Data", anotherCell = "" }
};
foreach (object Item in MyArray)
{
    Console.WriteLine("Row Start");
    foreach (var props in Item.GetType().GetProperties())
    {
        var Key = props.Name;
        var Value = props.GetMethod.Invoke(Item, null).ToString();
        Console.WriteLine("{0}={1}", Key, Value);
    }
}

OR, List of objects (It must have the same cells):

var MyArray = new[] {
    new { id = "1", cell1 = "cell 1 row 1 Data", cell2 = "cell 2 row 1 Data" },
    new { id = "2", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 2 Data" },
    new { id = "3", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 3 Data" }
};
foreach (object Item in MyArray)
{
    Console.WriteLine("Row Start");
    foreach (var props in Item.GetType().GetProperties())
    {
        var Key = props.Name;
        var Value = props.GetMethod.Invoke(Item, null).ToString();
        Console.WriteLine("{0}={1}", Key, Value);
    }
}

OR, List of objects (with key):

var MyArray = new {
    row1 = new { id = "1", cell1 = "cell 1 row 1 Data", cell2 = "cell 2 row 1 Data" },
    row2 = new { id = "2", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 2 Data" },
    row3 = new { id = "3", cell1 = "cell 1 row 2 Data", cell2 = "cell 2 row 3 Data" }
};
// using System.ComponentModel;  for TypeDescriptor
foreach (PropertyDescriptor Item in TypeDescriptor.GetProperties(MyArray))
{
    string Rowkey = Item.Name;
    object RowValue = Item.GetValue(MyArray);
    Console.WriteLine("Row key is: {0}", Rowkey);
    foreach (var props in RowValue.GetType().GetProperties())
    {
        var Key = props.Name;
        var Value = props.GetMethod.Invoke(RowValue, null).ToString();
        Console.WriteLine("{0}={1}", Key, Value);
    }
}

OR, List of Dictionary

var MyArray = new List<Dictionary<string, string>>() {
    new Dictionary<string, string>() { { "id", "1" }, { "cell1", "cell 1 row 1 Data" }, { "cell2", "cell 2 row 1 Data" } },
    new Dictionary<string, string>() { { "id", "2" }, { "cell1", "cell 1 row 2 Data" }, { "cell2", "cell 2 row 2 Data" } },
    new Dictionary<string, string>() { { "id", "3" }, { "cell1", "cell 1 row 3 Data" }, { "cell2", "cell 2 row 3 Data" } }
};
foreach (Dictionary<string, string> Item in MyArray)
{
    Console.WriteLine("Row Start");
    foreach (KeyValuePair<string, string> props in Item)
    {
        var Key = props.Key;
        var Value = props.Value;
        Console.WriteLine("{0}={1}", Key, Value);
    }
}

Good luck..

Generate Controller and Model

For generate Model , controller with resources and migration best command is:

php artisan make:model ModelName -m -cr 

Remove multiple items from a Python list in just one statement

I'm reposting my answer from here because I saw it also fits in here. It allows removing multiple values or removing only duplicates of these values and returns either a new list or modifies the given list in place.


def removed(items, original_list, only_duplicates=False, inplace=False):
    """By default removes given items from original_list and returns
    a new list. Optionally only removes duplicates of `items` or modifies
    given list in place.
    """
    if not hasattr(items, '__iter__') or isinstance(items, str):
        items = [items]

    if only_duplicates:
        result = []
        for item in original_list:
            if item not in items or item not in result:
                result.append(item)
    else:
        result = [item for item in original_list if item not in items]

    if inplace:
        original_list[:] = result
    else:
        return result

Docstring extension:

"""
Examples:
---------

    >>>li1 = [1, 2, 3, 4, 4, 5, 5]
    >>>removed(4, li1)
       [1, 2, 3, 5, 5]
    >>>removed((4,5), li1)
       [1, 2, 3]
    >>>removed((4,5), li1, only_duplicates=True)
       [1, 2, 3, 4, 5]

    # remove all duplicates by passing original_list also to `items`.:
    >>>removed(li1, li1, only_duplicates=True)
      [1, 2, 3, 4, 5]

    # inplace:
    >>>removed((4,5), li1, only_duplicates=True, inplace=True)
    >>>li1
        [1, 2, 3, 4, 5]

    >>>li2 =['abc', 'def', 'def', 'ghi', 'ghi']
    >>>removed(('def', 'ghi'), li2, only_duplicates=True, inplace=True)
    >>>li2
        ['abc', 'def', 'ghi']
"""

You should be clear about what you really want to do, modify an existing list, or make a new list with the specific items missing. It's important to make that distinction in case you have a second reference pointing to the existing list. If you have, for example...

li1 = [1, 2, 3, 4, 4, 5, 5]
li2 = li1
# then rebind li1 to the new list without the value 4
li1 = removed(4, li1)
# you end up with two separate lists where li2 is still pointing to the 
# original
li2
# [1, 2, 3, 4, 4, 5, 5]
li1
# [1, 2, 3, 5, 5]

This may or may not be the behaviour you want.

String to Dictionary in Python

Use ast.literal_eval to evaluate Python literals. However, what you have is JSON (note "true" for example), so use a JSON deserializer.

>>> import json
>>> s = """{"id":"123456789","name":"John Doe","first_name":"John","last_name":"Doe","link":"http:\/\/www.facebook.com\/jdoe","gender":"male","email":"jdoe\u0040gmail.com","timezone":-7,"locale":"en_US","verified":true,"updated_time":"2011-01-12T02:43:35+0000"}"""
>>> json.loads(s)
{u'first_name': u'John', u'last_name': u'Doe', u'verified': True, u'name': u'John Doe', u'locale': u'en_US', u'gender': u'male', u'email': u'[email protected]', u'link': u'http://www.facebook.com/jdoe', u'timezone': -7, u'updated_time': u'2011-01-12T02:43:35+0000', u'id': u'123456789'}

Matplotlib 2 Subplots, 1 Colorbar

As pointed out in other answers, the idea is usually to define an axes for the colorbar to reside in. There are various ways of doing so; one that hasn't been mentionned yet would be to directly specify the colorbar axes at subplot creation with plt.subplots(). The advantage is that the axes position does not need to be manually set and in all cases with automatic aspect the colorbar will be exactly the same height as the subplots. Even in many cases where images are used the result will be satisfying as shown below.

When using plt.subplots(), the use of gridspec_kw argument allows to make the colorbar axes much smaller than the other axes.

fig, (ax, ax2, cax) = plt.subplots(ncols=3,figsize=(5.5,3), 
                  gridspec_kw={"width_ratios":[1,1, 0.05]})

Example:

import matplotlib.pyplot as plt
import numpy as np; np.random.seed(1)

fig, (ax, ax2, cax) = plt.subplots(ncols=3,figsize=(5.5,3), 
                  gridspec_kw={"width_ratios":[1,1, 0.05]})
fig.subplots_adjust(wspace=0.3)
im  = ax.imshow(np.random.rand(11,8), vmin=0, vmax=1)
im2 = ax2.imshow(np.random.rand(11,8), vmin=0, vmax=1)
ax.set_ylabel("y label")

fig.colorbar(im, cax=cax)

plt.show()

enter image description here

This works well, if the plots' aspect is autoscaled or the images are shrunk due to their aspect in the width direction (as in the above). If, however, the images are wider then high, the result would look as follows, which might be undesired.

enter image description here

A solution to fix the colorbar height to the subplot height would be to use mpl_toolkits.axes_grid1.inset_locator.InsetPosition to set the colorbar axes relative to the image subplot axes.

import matplotlib.pyplot as plt
import numpy as np; np.random.seed(1)
from mpl_toolkits.axes_grid1.inset_locator import InsetPosition

fig, (ax, ax2, cax) = plt.subplots(ncols=3,figsize=(7,3), 
                  gridspec_kw={"width_ratios":[1,1, 0.05]})
fig.subplots_adjust(wspace=0.3)
im  = ax.imshow(np.random.rand(11,16), vmin=0, vmax=1)
im2 = ax2.imshow(np.random.rand(11,16), vmin=0, vmax=1)
ax.set_ylabel("y label")

ip = InsetPosition(ax2, [1.05,0,0.05,1]) 
cax.set_axes_locator(ip)

fig.colorbar(im, cax=cax, ax=[ax,ax2])

plt.show()

enter image description here

What is a serialVersionUID and why should I use it?

I can't pass up this opportunity to plug Josh Bloch's book Effective Java (2nd Edition). Chapter 11 is an indispensible resource on Java serialization.

Per Josh, the automatically-generated UID is generated based on a class name, implemented interfaces, and all public and protected members. Changing any of these in any way will change the serialVersionUID. So you don't need to mess with them only if you are certain that no more than one version of the class will ever be serialized (either across processes or retrieved from storage at a later time).

If you ignore them for now, and find later that you need to change the class in some way but maintain compatibility w/ old version of the class, you can use the JDK tool serialver to generate the serialVersionUID on the old class, and explicitly set that on the new class. (Depending on your changes you may need to also implement custom serialization by adding writeObject and readObject methods - see Serializable javadoc or aforementioned chapter 11.)

LINUX: Link all files from one to another directory

The posted solutions will not link any hidden files. To include them, try this:

cd /usr/lib
find /mnt/usr/lib -maxdepth 1 -print "%P\n" | while read file; do ln -s "/mnt/usr/lib/$file" "$file"; done

If you should happen to want to recursively create the directories and only link files (so that if you create a file within a directory, it really is in /usr/lib not /mnt/usr/lib), you could do this:

cd /usr/lib
find /mnt/usr/lib -mindepth 1 -depth -type d -printf "%P\n" | while read dir; do mkdir -p "$dir"; done
find /mnt/usr/lib -type f -printf "%P\n" | while read file; do ln -s "/mnt/usr/lib/$file" "$file"; done

PHP get dropdown value and text

You will have to save the relationship on the server side. The value is the only part that is transmitted when the form is posted. You could do something nasty like...

<option value="2|Dog">Dog</option>

Then split the result apart if you really wanted to, but that is an ugly hack and a waste of bandwidth assuming the numbers are truly unique and have a one to one relationship with the text.

The best way would be to create an array, and loop over the array to create the HTML. Once the form is posted you can use the value to look up the text in that same array.

Get class name using jQuery

If your <div> has an id:

?<div id="test" class="my-custom-class"></div>????????????????????????????????????????????????????????????????????????

...you can try:

var yourClass = $("#test").prop("class");

If your <div> has only a class, you can try:

var yourClass = $(".my-custom-class").prop("class");

Python IndentationError unindent does not match any outer indentation level

You are mixing tabs and spaces. Don't do that. Specifically, the __init__ function body is indented with tabs while your on_data method is not.

Here is a screenshot of your code in my text editor; I set the tab stop to 8 spaces (which is what Python uses) and selected the text, which causes the editor to display tabs with continuous horizontal lines:

highlighted code with tabs shown as lines

You have your editor set to expanding tabs to every fourth column instead, so the methods appear to line up.

Run your code with:

python -tt scriptname.py

and fix all errors that finds. Then configure your editor to use spaces only for indentation; a good editor will insert 4 spaces every time you use the TAB key.

How to import a .cer certificate into a java keystore?

An open source GUI tool is available at keystore-explorer.org

KeyStore Explorer

KeyStore Explorer is an open source GUI replacement for the Java command-line utilities keytool and jarsigner. KeyStore Explorer presents their functionality, and more, via an intuitive graphical user interface.

Following screens will help (they are from the official site)

Default screen that you get by running the command:

shantha@shantha:~$./Downloads/kse-521/kse.sh

enter image description here

And go to Examine and Examine a URL option and then give the web URL that you want to import.

The result window will be like below if you give google site link. enter image description here

This is one of Use case and rest is up-to the user(all credits go to the keystore-explorer.org)

Get selected value in dropdown list using JavaScript

Just do: document.getElementById('idselect').options.selectedIndex

Then you i'll get select index value, starting in 0.

PHP write file from input to txt

If you use file_put_contents you don't need to do a fopen -> fwrite -> fclose, the file_put_contents does all that for you. You should also check if the webserver has write rights in the directory where you are trying to write your "data.txt" file.

Depending on your PHP version (if it's old) you might not have the file_get/put_contents functions. Check your webserver log to see if any error appeared when you executed the script.

Text in a flex container doesn't wrap in IE11

As Tyler has suggested in one of the comments here, using

max-width: 100%;

on the child may work (worked for me). Using align-self: stretch only works if you aren't using align-items: center (which I did). width: 100% only works if you haven't multiple childs inside your flexbox which you want to show side by side.

How to keep a git branch in sync with master

Run the following commands:

$ git checkout mobiledevice
$ git pull origin master 

This would merge all the latest commits to your branch. If the merge results in some conflicts, you'll need to fix them.

I don't know if this is the best practice but works for me.

How might I find the largest number contained in a JavaScript array?

Find the largest number in a multidimensional array

var max = [];

for(var i=0; arr.length>i; i++ ) {

   var arra = arr[i];
   var largest = Math.max.apply(Math, arra);
   max.push(largest);
}
return max;

How do you find what version of libstdc++ library is installed on your linux machine?

What exactly do you want to know?

The shared library soname? That's part of the filename, libstdc++.so.6, or shown by readelf -d /usr/lib64/libstdc++.so.6 | grep soname.

The minor revision number? You should be able to get that by simply checking what the symlink points to:

$ ls -l  /usr/lib/libstdc++.so.6
lrwxrwxrwx. 1 root root 19 Mar 23 09:43 /usr/lib/libstdc++.so.6 -> libstdc++.so.6.0.16

That tells you it's 6.0.16, which is the 16th revision of the libstdc++.so.6 version, which corresponds to the GLIBCXX_3.4.16 symbol versions.

Or do you mean the release it comes from? It's part of GCC so it's the same version as GCC, so unless you've screwed up your system by installing unmatched versions of g++ and libstdc++.so you can get that from:

$ g++ -dumpversion
4.6.3

Or, on most distros, you can just ask the package manager. On my Fedora host that's

$ rpm -q libstdc++
libstdc++-4.6.3-2.fc16.x86_64
libstdc++-4.6.3-2.fc16.i686

As other answers have said, you can map releases to library versions by checking the ABI docs

How to save a git commit message from windows cmd?

You are inside vim. To save changes and quit, type:

<esc> :wq <enter>

That means:

  • Press Escape. This should make sure you are in command mode
  • type in :wq
  • Press Return

An alternative that stdcall in the comments mentions is:

  • Press Escape
  • Press shift+Z shift+Z (capital Z twice).

No process is on the other end of the pipe (SQL Server 2012)

If you are trying to login with SQL credentials, you can also try changing the LoginMode for SQL Server in the registry to allow both SQL Server and Windows Authentication.

  1. Open regedit
  2. Go to the SQL instance key (may vary depending on your instance name): Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL14.SQLEXPRESS\MSSQLServer\
  3. Set LoginMode to 2

enter image description here

  1. Restart SQL service and SQL Server Management Studio and try again.

Exiting out of a FOR loop in a batch file?

Based on Tim's second edit and this page you could do this:

@echo off
if "%1"=="loop" (
  for /l %%f in (1,1,1000000) do (
    echo %%f
    if exist %%f exit
  )
  goto :eof
)
cmd /v:on /q /d /c "%0 loop"
echo done

This page suggests a way to use a goto inside a loop, it seems it does work, but it takes some time in a large loop. So internally it finishes the loop before the goto is executed.

GET parameters in the URL with CodeIgniter

You can Try this

$this->uri->segment('');

.htaccess 301 redirect of single page

RedirectMatch uses a regular expression that is matched against the URL path. And your regular expression /contact.php just means any URL path that contains /contact.php but not just any URL path that is exactly /contact.php. So use the anchors for the start and end of the string (^ and $):

RedirectMatch 301 ^/contact\.php$ /contact-us.php

Visual Studio can't 'see' my included header files

I encountered this issue, but the solutions provided didn't directly help me, so I'm sharing how I got myself into a similar situation and temporarily resolved it.

I created a new project within an existing solution and copy & pasted the Header and CPP file from another project within that solution that I needed to include in my new project through the IDE. Intellisense displayed an error suggesting it could not resolve the reference to the header file and compiling the code failed with the same error too.

After reading the posts here, I checked the project folder with Windows File Explorer and only the main.cpp file was found. For some reason, my copy and paste of the header file and CPP file were just a reference? (I assume) and did not physically copy the file into the new project file.

I deleted the files from the Project view within Visual Studio and I used File Explorer to copy the files that I needed to the project folder/directory. I then referenced the other solutions posted here to "include files in project" by showing all files and this resolved the problem.

It boiled down to the files not being physically in the Project folder/directory even though they were shown correctly within the IDE.

Please Note I understand duplicating code is not best practice and my situation is purely a learning/hobby project. It's probably in my best interest and anyone else who ended up in a similar situation to use the IDE/project/Solution setup correctly when reusing code from other projects - I'm still learning and I'll figure this out one day!

SQL Server equivalent to Oracle's CREATE OR REPLACE VIEW

I typically use something like this:

if exists (select * from dbo.sysobjects
  where id = object_id(N'dbo.MyView') and
  OBJECTPROPERTY(id, N'IsView') = 1)
drop view dbo.MyView
go
create view dbo.MyView [...]

Label encoding across multiple columns in scikit-learn

I checked the source code (https://github.com/scikit-learn/scikit-learn/blob/master/sklearn/preprocessing/label.py) of LabelEncoder. It was based on a set of numpy transformation, which one of those is np.unique(). And this function only takes 1-d array input. (correct me if I am wrong).

Very Rough ideas... first, identify which columns needed LabelEncoder, then loop through each column.

def cat_var(df): 
    """Identify categorical features. 

    Parameters
    ----------
    df: original df after missing operations 

    Returns
    -------
    cat_var_df: summary df with col index and col name for all categorical vars
    """
    col_type = df.dtypes
    col_names = list(df)

    cat_var_index = [i for i, x in enumerate(col_type) if x=='object']
    cat_var_name = [x for i, x in enumerate(col_names) if i in cat_var_index]

    cat_var_df = pd.DataFrame({'cat_ind': cat_var_index, 
                               'cat_name': cat_var_name})

    return cat_var_df



from sklearn.preprocessing import LabelEncoder 

def column_encoder(df, cat_var_list):
    """Encoding categorical feature in the dataframe

    Parameters
    ----------
    df: input dataframe 
    cat_var_list: categorical feature index and name, from cat_var function

    Return
    ------
    df: new dataframe where categorical features are encoded
    label_list: classes_ attribute for all encoded features 
    """

    label_list = []
    cat_var_df = cat_var(df)
    cat_list = cat_var_df.loc[:, 'cat_name']

    for index, cat_feature in enumerate(cat_list): 

        le = LabelEncoder()

        le.fit(df.loc[:, cat_feature])    
        label_list.append(list(le.classes_))

        df.loc[:, cat_feature] = le.transform(df.loc[:, cat_feature])

    return df, label_list

The returned df would be the one after encoding, and label_list will show you what all those values means in the corresponding column. This is a snippet from a data process script I wrote for work. Let me know if you think there could be any further improvement.

EDIT: Just want to mention here that the methods above work with data frame with no missing the best. Not sure how it is working toward data frame contains missing data. (I had a deal with missing procedure before execute above methods)

How to set timeout for a line of c# code

You can use the Task Parallel Library. To be more exact, you can use Task.Wait(TimeSpan):

using System.Threading.Tasks;

var task = Task.Run(() => SomeMethod(input));
if (task.Wait(TimeSpan.FromSeconds(10)))
    return task.Result;
else
    throw new Exception("Timed out");

How to open a URL in a new Tab using JavaScript or jQuery?

 var url = "http://www.example.com";
 window.open(url, '_blank');

Copy file from source directory to binary directory using CMake

If you want to put the content of example into install folder after build:

code/
  src/
  example/
  CMakeLists.txt

try add the following to your CMakeLists.txt:

install(DIRECTORY example/ DESTINATION example)

What does 'stale file handle' in Linux mean?

When the directory is deleted, the inode for that directory (and the inodes for its contents) are recycled. The pointer your shell has to that directory's inode (and its contents's inodes) are now no longer valid. When the directory is restored from backup, the old inodes are not (necessarily) reused; the directory and its contents are stored on random inodes. The only thing that stays the same is that the parent directory reuses the same name for the restored directory (because you told it to).

Now if you attempt to access the contents of the directory that your original shell is still pointing to, it communicates that request to the file system as a request for the original inode, which has since been recycled (and may even be in use for something entirely different now). So you get a stale file handle message because you asked for some nonexistent data.

When you perform a cd operation, the shell reevaluates the inode location of whatever destination you give it. Now that your shell knows the new inode for the directory (and the new inodes for its contents), future requests for its contents will be valid.

Automatically deleting related rows in Laravel (Eloquent ORM)

Or you can do this if you wanted, just another option:

try {
    DB::connection()->pdo->beginTransaction();

    $photos = Photo::where('user_id', '=', $user_id)->delete(); // Delete all photos for user
    $user = Geofence::where('id', '=', $user_id)->delete(); // Delete users

    DB::connection()->pdo->commit();

}catch(\Laravel\Database\Exception $e) {
    DB::connection()->pdo->rollBack();
    Log::exception($e);
}

Note if you are not using the default laravel db connection then you need to do the following:

DB::connection('connection_name')->pdo->beginTransaction();
DB::connection('connection_name')->pdo->commit();
DB::connection('connection_name')->pdo->rollBack();

How can I check the extension of a file?

or perhaps:

from glob import glob
...
for files in glob('path/*.mp3'): 
  do something
for files in glob('path/*.flac'): 
  do something else

Grouping switch statement cases together?

No, unless you want to break compatibility and your compiler supports it.

git clone through ssh

Disclaimer: This is just a copy of a comment by bobbaluba made more visible for future visitors. It helped me more than any other answer.


You have to drop the ssh:// prefix when using git clone as an example

git clone [email protected]:owner/repo.git

JQuery/Javascript: check if var exists

For your case, and 99.9% of all others elclanrs answer is correct.

But because undefined is a valid value, if someone were to test for an uninitialized variable

var pagetype; //== undefined
if (typeof pagetype === 'undefined') //true

the only 100% reliable way to determine if a var exists is to catch the exception;

var exists = false;
try { pagetype; exists = true;} catch(e) {}
if (exists && ...) {}

But I would never write it this way

How to get the previous page URL using JavaScript?

<script type="text/javascript">
    document.write(document.referrer);
</script>

document.referrer serves your purpose, but it doesn't work for Internet Explorer versions earlier than IE9.

It will work for other popular browsers, like Chrome, Mozilla, Opera, Safari etc.

Cannot convert lambda expression to type 'string' because it is not a delegate type

My case it solved i was using

@Html.DropDownList(model => model.TypeId ...)  

using

@Html.DropDownListFor(model => model.TypeId ...) 

will solve it

End of File (EOF) in C

EOF indicates "end of file". A newline (which is what happens when you press enter) isn't the end of a file, it's the end of a line, so a newline doesn't terminate this loop.

The code isn't wrong[*], it just doesn't do what you seem to expect. It reads to the end of the input, but you seem to want to read only to the end of a line.

The value of EOF is -1 because it has to be different from any return value from getchar that is an actual character. So getchar returns any character value as an unsigned char, converted to int, which will therefore be non-negative.

If you're typing at the terminal and you want to provoke an end-of-file, use CTRL-D (unix-style systems) or CTRL-Z (Windows). Then after all the input has been read, getchar() will return EOF, and hence getchar() != EOF will be false, and the loop will terminate.

[*] well, it has undefined behavior if the input is more than LONG_MAX characters due to integer overflow, but we can probably forgive that in a simple example.

Getting the location from an IP address

I wrote a bot using an API from ipapi.co, here's how you can get location for an IP address (e.g. 1.2.3.4) in php :

Set header :

$opts = array('http'=>array('method'=>"GET", 'header'=>"User-Agent: mybot.v0.7.1"));
$context = stream_context_create($opts);

Get JSON response

echo file_get_contents('https://ipapi.co/1.2.3.4/json/', false, $context);

of get a specific field (country, timezone etc.)

echo file_get_contents('https://ipapi.co/1.2.3.4/country/', false, $context);

Understanding __get__ and __set__ and Python descriptors

Why do I need the descriptor class?

It gives you extra control over how attributes work. If you're used to getters and setters in Java, for example, then it's Python's way of doing that. One advantage is that it looks to users just like an attribute (there's no change in syntax). So you can start with an ordinary attribute and then, when you need to do something fancy, switch to a descriptor.

An attribute is just a mutable value. A descriptor lets you execute arbitrary code when reading or setting (or deleting) a value. So you could imagine using it to map an attribute to a field in a database, for example – a kind of ORM.

Another use might be refusing to accept a new value by throwing an exception in __set__ – effectively making the "attribute" read only.

What is instance and owner here? (in __get__). What is the purpose of these parameters?

This is pretty subtle (and the reason I am writing a new answer here - I found this question while wondering the same thing and didn't find the existing answer that great).

A descriptor is defined on a class, but is typically called from an instance. When it's called from an instance both instance and owner are set (and you can work out owner from instance so it seems kinda pointless). But when called from a class, only owner is set – which is why it's there.

This is only needed for __get__ because it's the only one that can be called on a class. If you set the class value you set the descriptor itself. Similarly for deletion. Which is why the owner isn't needed there.

How would I call/use this example?

Well, here's a cool trick using similar classes:

class Celsius:

    def __get__(self, instance, owner):
        return 5 * (instance.fahrenheit - 32) / 9

    def __set__(self, instance, value):
        instance.fahrenheit = 32 + 9 * value / 5


class Temperature:

    celsius = Celsius()

    def __init__(self, initial_f):
        self.fahrenheit = initial_f


t = Temperature(212)
print(t.celsius)
t.celsius = 0
print(t.fahrenheit)

(I'm using Python 3; for python 2 you need to make sure those divisions are / 5.0 and / 9.0). That gives:

100.0
32.0

Now there are other, arguably better ways to achieve the same effect in python (e.g. if celsius were a property, which is the same basic mechanism but places all the source inside the Temperature class), but that shows what can be done...

Clear text from textarea with selenium

Option a)

If you want to ensure keyboard events are fired, consider using sendKeys(CharSequence).

Example 1:

 from selenium.webdriver.common.keys import Keys
 # ...
 webElement.sendKeys(Keys.CONTROL + "a");
 webElement.sendKeys(Keys.DELETE);

Example 2:

 from selenium.webdriver.common.keys import Keys
 # ...
 webElement.sendKeys(Keys.BACK_SPACE); //do repeatedly, e.g. in while loop

WebElement

There are many ways to get the required WebElement, e.g.:

  • driver.find_element_by_id
  • driver.find_element_by_xpath
  • driver.find_element

Option b)

 webElement.clear();

If this element is a text entry element, this will clear the value.

Note that the events fired by this event may not be as you'd expect. In particular, we don't fire any keyboard or mouse events.

How can I generate an HTML report for Junit results?

Alternatively for those using Maven build tool, there is a plugin called Surefire Report.

The report looks like this : Sample

ssh_exchange_identification: Connection closed by remote host under Git bash

I experienced this today and I just do a:

12345@123456 MINGW64 ~/development/workspace/test (develop)
$ git status
Refresh index: 100% (1204/1204), done.
On branch develop
Your branch is up to date with 'origin/develop'.

nothing to commit, working tree clean

12345@123456 MINGW64 ~/development/workspace/test (develop)
$ git fetch

Then all worked again.

What is the difference between a symbolic link and a hard link?

I just found an easy way to understand hard links in a common scenario, software install.

One day I downloaded a software to folder Downloads for install. After I did sudo make install, some executables were cped to local bin folder. Here, cp creates hard link. I was happy with the software but soon realized that Downloads isn't a good place in the long run. So I mved the software folder to source directory. Well, I can still run the software as before without worrying about any target link things, like in Windows. This means hard link finds inode directly and other files around.

How can I export the schema of a database in PostgreSQL?

If you only want the create tables, then you can do pg_dump -s databasename | awk 'RS="";/CREATE TABLE[^;]*;/'

How to set a cell to NaN in a pandas dataframe

just use replace:

In [106]:
df.replace('N/A',np.NaN)

Out[106]:
    x    y
0  10   12
1  50   11
2  18  NaN
3  32   13
4  47   15
5  20  NaN

What you're trying is called chain indexing: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy

You can use loc to ensure you operate on the original dF:

In [108]:
df.loc[df['y'] == 'N/A','y'] = np.nan
df

Out[108]:
    x    y
0  10   12
1  50   11
2  18  NaN
3  32   13
4  47   15
5  20  NaN

Can I do Android Programming in C++, C?

You can take a look also at C++ Builder XE6, and XE7 supports android in c++ code, and with Firemonkey library.

http://www.embarcadero.com/products/cbuilder

Pretty easy way to start, and native code. But the binaries have a big size.

Maintain/Save/Restore scroll position when returning to a ListView

For some looking for a solution to this problem, the root of the issue may be where you are setting your list views adapter. After you set the adapter on the listview, it resets the scroll position. Just something to consider. I moved setting the adapter into my onCreateView after we grab the reference to the listview, and it solved the problem for me. =)

How to set time to midnight for current day?

I believe you are looking for DateTime.Today. The documentation states:

An object that is set to today's date, with the time component set to 00:00:00.

http://msdn.microsoft.com/en-us/library/system.datetime.today.aspx

Your code would be

DateTime _Begin = DateTime.Today;

Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)

I have faced the same issue. Here is how I have fixed it.

Step 1: Remove mysql using command:

brew uninstall --force mysql

Step 2: Run command brew doctor which will give you some hint related to your brew packages.

Step 3: Cleanup brew packages using command:

brew cleanup

Step 4: Move/delete previously installed mysql data using command:

mv /usr/local/var/mysql/ /usr/local/var/old_mysql

Step 5: Finally install mysql again using command:

brew install mysql

LIKE operator in LINQ

@adobrzyc had this great custom LIKE function - I just wanted to share the IEnumerable version of it.

public static class LinqEx
{
    private static readonly MethodInfo ContainsMethod = typeof(string).GetMethod("Contains");
    private static readonly MethodInfo StartsWithMethod = typeof(string).GetMethod("StartsWith", new[] { typeof(string) });
    private static readonly MethodInfo EndsWithMethod = typeof(string).GetMethod("EndsWith", new[] { typeof(string) });

    private static Func<TSource, bool> LikeExpression<TSource, TMember>(Expression<Func<TSource, TMember>> property, string value)
    {
        var param = Expression.Parameter(typeof(TSource), "t");
        var propertyInfo = GetPropertyInfo(property);
        var member = Expression.Property(param, propertyInfo.Name);

        var startWith = value.StartsWith("%");
        var endsWith = value.EndsWith("%");

        if (startWith)
            value = value.Remove(0, 1);

        if (endsWith)
            value = value.Remove(value.Length - 1, 1);

        var constant = Expression.Constant(value);
        Expression exp;

        if (endsWith && startWith)
        {
            exp = Expression.Call(member, ContainsMethod, constant);
        }
        else if (startWith)
        {
            exp = Expression.Call(member, EndsWithMethod, constant);
        }
        else if (endsWith)
        {
            exp = Expression.Call(member, StartsWithMethod, constant);
        }
        else
        {
            exp = Expression.Equal(member, constant);
        }

        return Expression.Lambda<Func<TSource, bool>>(exp, param).Compile();
    }

    public static IEnumerable<TSource> Like<TSource, TMember>(this IEnumerable<TSource> source, Expression<Func<TSource, TMember>> parameter, string value)
    {
        return source.Where(LikeExpression(parameter, value));
    }


    private static PropertyInfo GetPropertyInfo(Expression expression)
    {
        var lambda = expression as LambdaExpression;
        if (lambda == null)
            throw new ArgumentNullException("expression");

        MemberExpression memberExpr = null;

        switch (lambda.Body.NodeType)
        {
            case ExpressionType.Convert:
                memberExpr = ((UnaryExpression)lambda.Body).Operand as MemberExpression;
                break;
            case ExpressionType.MemberAccess:
                memberExpr = lambda.Body as MemberExpression;
                break;
        }

        if (memberExpr == null)
            throw new InvalidOperationException("Specified expression is invalid. Unable to determine property info from expression.");


        var output = memberExpr.Member as PropertyInfo;

        if (output == null)
            throw new InvalidOperationException("Specified expression is invalid. Unable to determine property info from expression.");

        return output;
    }
}

JavaScript blob filename without link

I just wanted to expand on the accepted answer with support for Internet Explorer (most modern versions, anyways), and to tidy up the code using jQuery:

$(document).ready(function() {
    saveFile("Example.txt", "data:attachment/text", "Hello, world.");
});

function saveFile (name, type, data) {
    if (data !== null && navigator.msSaveBlob)
        return navigator.msSaveBlob(new Blob([data], { type: type }), name);
    var a = $("<a style='display: none;'/>");
    var url = window.URL.createObjectURL(new Blob([data], {type: type}));
    a.attr("href", url);
    a.attr("download", name);
    $("body").append(a);
    a[0].click();
    window.URL.revokeObjectURL(url);
    a.remove();
}

Here is an example Fiddle. Godspeed.

creating array without declaring the size - java

I think what you really want is an ArrayList or Vector. Arrays in Java are not like those in Javascript.

Rest-assured. Is it possible to extract value from request json?

There are several ways. I personally use the following ones:

extracting single value:

String user_Id =
given().
when().
then().
extract().
        path("user_id");

work with the entire response when you need more than one:

Response response =
given().
when().
then().
extract().
        response();

String userId = response.path("user_id");

extract one using the JsonPath to get the right type:

long userId =
given().
when().
then().
extract().
        jsonPath().getLong("user_id");

Last one is really useful when you want to match against the value and the type i.e.

assertThat(
    when().
    then().
    extract().
            jsonPath().getLong("user_id"), equalTo(USER_ID)
);

The rest-assured documentation is quite descriptive and full. There are many ways to achieve what you are asking: https://github.com/jayway/rest-assured/wiki/Usage

Bootstrap 3 unable to display glyphicon properly

I had the same problem using a local apache server. This solved my problem:

http://www.ifusio.com/blog/firefox-issue-with-twitter-bootstrap-glyphicons

For Amazon s3 you need to edit your CORS configuration:

<CORSConfiguration>
    <CORSRule>
        <AllowedOrigin>*</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Authorization</AllowedHeader>
    </CORSRule>
</CORSConfiguration>

Remove First and Last Character C++

My BASIC interpreter chops beginning and ending quotes with

str->pop_back();
str->erase(str->begin());

Of course, I always expect well-formed BASIC style strings, so I will abort with failed assert if not:

assert(str->front() == '"' && str->back() == '"');

Just my two cents.

Laravel 5 - How to access image uploaded in storage within View?

If you are like me and you somehow have full file paths (I did some glob() pattern matching on required photos so I do pretty much end up with full file paths), and your storage setup is well linked (i.e. such that your paths have the string storage/app/public/), then you can use my little dirty hack below :p)

 public static function hackoutFileFromStorageFolder($fullfilePath) {
        if (strpos($fullfilePath, 'storage/app/public/')) {
           $fileParts = explode('storage/app/public/', $fullfilePath);
           if( count($fileParts) > 1){
               return $fileParts[1];
           }
        }

        return '';
    }

Android how to convert int to String?

You called an incorrect method of String class, try:

int tmpInt = 10;
String tmpStr10 = String.valueOf(tmpInt);

You can also do:

int tmpInt = 10;
String tmpStr10 = Integer.toString(tmpInt);

Most efficient way to concatenate strings?

From this MSDN article:

There is some overhead associated with creating a StringBuilder object, both in time and memory. On a machine with fast memory, a StringBuilder becomes worthwhile if you're doing about five operations. As a rule of thumb, I would say 10 or more string operations is a justification for the overhead on any machine, even a slower one.

So if you trust MSDN go with StringBuilder if you have to do more than 10 strings operations/concatenations - otherwise simple string concat with '+' is fine.

How to show/hide if variable is null

In this case, myvar should be a boolean value. If this variable is true, it will show the div, if it's false.. It will hide.

Check this out.

How to create unit tests easily in eclipse

You can use my plug-in to create tests easily:

  1. highlight the method
  2. press Ctrl+Alt+Shift+U
  3. it will create the unit test for it.

The plug-in is available here. Hope this helps.

'namespace' but is used like a 'type'

I had this problem as I created a class "Response.cs" inside a folder named "Response". So VS was catching the new Response () as Folder/namespace.

So I changed the class name to StatusResponse.cs and called new StatusResponse().This solved the issue.

Print debugging info from stored procedure in MySQL

I usually create log table with a stored procedure to log to it. The call the logging procedure wherever needed from the procedure under development.

Looking at other posts on this same question, it seems like a common practice, although there are some alternatives.

Web API optional parameters

I figured it out. I was using a bad example I found in the past of how to map query string to the method parameters.

In case anyone else needs it, in order to have optional parameters in a query string such as:

  • ~/api/products/filter?apc=AA&xpc=BB
  • ~/api/products/filter?sku=7199123

you would use:

[Route("products/filter/{apc?}/{xpc?}/{sku?}")]
public IHttpActionResult Get(string apc = null, string xpc = null, int? sku = null)
{ ... }

It seems odd to have to define default values for the method parameters when these types already have a default.

json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

I had similar error: "Expecting value: line 1 column 1 (char 0)"

It helped for me to add "myfile.seek(0)", move the pointer to the 0 character

with open(storage_path, 'r') as myfile:
if len(myfile.readlines()) != 0:
    myfile.seek(0)
    Bank_0 = json.load(myfile)

What are some ways of accessing Microsoft SQL Server from Linux?

I'd like to recommend Sqlectron. Besides being open source under MIT license it's multiplatform boosted by Electron. Its own definition is:

A simple and lightweight SQL client desktop with cross database and platform support

It currently supports PostgreSQL, MySQL, MS SQL Server, Cassandra and SQLite.

How to check all versions of python installed on osx and centos

Here is a cleaner way to show them (technically without symbolic links):

ls -1 /usr/bin/python* | grep '[2-3].[0-9]$'

Where grep filters the output of ls that that has that numeric pattern at the end ($).

Or using find:

find /usr/bin/python* ! -type l

Which shows all the different (!) of symbolic link type (-type l).

How to make a script wait for a pressed key?

os.system seems to always invoke sh, which does not recognize the s and n options for read. However the read command can be passed to bash:

 os.system("""bash -c 'read -s -n 1 -p "Press any key to continue..."'""")

How to expand 'select' option width after the user wants to select an option

I fixed my problem with the following code:

_x000D_
_x000D_
<div style="width: 180px; overflow: hidden;">_x000D_
   <select style="width: auto;" name="abc" id="10">_x000D_
     <option value="-1">AAAAAAAAAAA</option>_x000D_
     <option value="123">123</option>_x000D_
   </select>_x000D_
</div>
_x000D_
_x000D_
_x000D_

Hope it helps!

How to have Ellipsis effect on Text

<View 
   style={{
        flexDirection: 'row',
        padding: 10,
    }}
>
  <Text numberOfLines={5} style={{flex:1}}>
       This is a very long text that will overflow on a small device This is a very 
       long text that will overflow on a small deviceThis is a very long text that 
       will overflow on a small deviceThis is a very long text that will overflow 
       on a small device
  </Text>
</View>

DataTable: Hide the Show Entries dropdown but keep the Search box

To disable the "Show Entries" label, add the code dom: 'Bfrtip' or you can add "bInfo": false

$('#example').DataTable({
    dom: 'Bfrtip'
})

UnicodeEncodeError: 'charmap' codec can't encode characters

While saving the response of get request, same error was thrown on Python 3.7 on window 10. The response received from the URL, encoding was UTF-8 so it is always recommended to check the encoding so same can be passed to avoid such trivial issue as it really kills lots of time in production

import requests
resp = requests.get('https://en.wikipedia.org/wiki/NIFTY_50')
print(resp.encoding)
with open ('NiftyList.txt', 'w') as f:
    f.write(resp.text)

When I added encoding="utf-8" with the open command it saved the file with the correct response

with open ('NiftyList.txt', 'w', encoding="utf-8") as f:
    f.write(resp.text)

Else clause on Python while statement

The else clause is executed if you exit a block normally, by hitting the loop condition or falling off the bottom of a try block. It is not executed if you break or return out of a block, or raise an exception. It works for not only while and for loops, but also try blocks.

You typically find it in places where normally you would exit a loop early, and running off the end of the loop is an unexpected/unusual occasion. For example, if you're looping through a list looking for a value:

for value in values:
    if value == 5:
        print "Found it!"
        break
else:
    print "Nowhere to be found. :-("

AngularJS sorting rows by table header

I'm just getting my feet wet with angular, but I found this great tutorial.
Here's a working plunk I put together with credit to Scott Allen and the above tutorial. Click search to display the sortable table.

For each column header you need to make it clickable - ng-click on a link will work. This will set the sortName of the column to sort.

<th>
     <a href="#" ng-click="sortName='name'; sortReverse = !sortReverse">
          <span ng-show="sortName == 'name' && sortReverse" class="glyphicon glyphicon-triangle-bottom"></span>
          <span ng-show="sortName == 'name' && !sortReverse" class="glyphicon glyphicon-triangle-top"></span>
           Name
     </a>
</th>

Then, in the table body you can pipe in that sortName in the orderBy filter orderBy:sortName:sortReverse

<tr ng-repeat="repo in repos | orderBy:sortName:sortReverse | filter:searchRepos">
     <td>{{repo.name}}</td>
     <td class="tag tag-primary">{{repo.stargazers_count | number}}</td>
     <td>{{repo.language}}</td>
</tr>

Styling a disabled input with css only

Use this CSS (jsFiddle example):

input:disabled.btn:hover,
input:disabled.btn:active,
input:disabled.btn:focus {
  color: green
}

You have to write the most outer element on the left and the most inner element on the right.

.btn:hover input:disabled would select any disabled input elements contained in an element with a class btn which is currently hovered by the user.

I would prefer :disabled over [disabled], see this question for a discussion: Should I use CSS :disabled pseudo-class or [disabled] attribute selector or is it a matter of opinion?


By the way, Laravel (PHP) generates the HTML - not the browser.

NSURLConnection Using iOS Swift

Check Below Codes :

1. SynchronousRequest

Swift 1.2

    let urlPath: String = "YOUR_URL_HERE"
    var url: NSURL = NSURL(string: urlPath)!
    var request1: NSURLRequest = NSURLRequest(URL: url)
    var response: AutoreleasingUnsafeMutablePointer<NSURLResponse?>=nil
    var dataVal: NSData =  NSURLConnection.sendSynchronousRequest(request1, returningResponse: response, error:nil)!
    var err: NSError
    println(response)
    var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataVal, options: NSJSONReadingOptions.MutableContainers, error: &err) as? NSDictionary
    println("Synchronous\(jsonResult)")

Swift 2.0 +

let urlPath: String = "YOUR_URL_HERE"
    let url: NSURL = NSURL(string: urlPath)!
    let request1: NSURLRequest = NSURLRequest(URL: url)
    let response: AutoreleasingUnsafeMutablePointer<NSURLResponse?>=nil


    do{

        let dataVal = try NSURLConnection.sendSynchronousRequest(request1, returningResponse: response)

            print(response)
            do {
                if let jsonResult = try NSJSONSerialization.JSONObjectWithData(dataVal, options: []) as? NSDictionary {
                    print("Synchronous\(jsonResult)")
                }
            } catch let error as NSError {
                print(error.localizedDescription)
            }



    }catch let error as NSError
    {
         print(error.localizedDescription)
    }

2. AsynchonousRequest

Swift 1.2

let urlPath: String = "YOUR_URL_HERE"
    var url: NSURL = NSURL(string: urlPath)!
    var request1: NSURLRequest = NSURLRequest(URL: url)
    let queue:NSOperationQueue = NSOperationQueue()
    NSURLConnection.sendAsynchronousRequest(request1, queue: queue, completionHandler:{ (response: NSURLResponse!, data: NSData!, error: NSError!) -> Void in
        var err: NSError
        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        println("Asynchronous\(jsonResult)")
       })

Swift 2.0 +

let urlPath: String = "YOUR_URL_HERE"
    let url: NSURL = NSURL(string: urlPath)!
    let request1: NSURLRequest = NSURLRequest(URL: url)
    let queue:NSOperationQueue = NSOperationQueue()

    NSURLConnection.sendAsynchronousRequest(request1, queue: queue, completionHandler:{ (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in

        do {
            if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary {
                print("ASynchronous\(jsonResult)")
            }
        } catch let error as NSError {
            print(error.localizedDescription)
        }


    })

3. As usual URL connection

Swift 1.2

    var dataVal = NSMutableData()
    let urlPath: String = "YOUR URL HERE"
    var url: NSURL = NSURL(string: urlPath)!
    var request: NSURLRequest = NSURLRequest(URL: url)
    var connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: true)!
    connection.start()

Then

 func connection(connection: NSURLConnection!, didReceiveData data: NSData!){
    self.dataVal?.appendData(data)
}


func connectionDidFinishLoading(connection: NSURLConnection!)
{
    var error: NSErrorPointer=nil

    var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataVal!, options: NSJSONReadingOptions.MutableContainers, error: error) as NSDictionary

    println(jsonResult)



}

Swift 2.0 +

   var dataVal = NSMutableData()
    let urlPath: String = "YOUR URL HERE"
    var url: NSURL = NSURL(string: urlPath)!
    var request: NSURLRequest = NSURLRequest(URL: url)
    var connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: true)!
    connection.start()

Then

func connection(connection: NSURLConnection!, didReceiveData data: NSData!){
    dataVal.appendData(data)
}


func connectionDidFinishLoading(connection: NSURLConnection!)
{

    do {
        if let jsonResult = try NSJSONSerialization.JSONObjectWithData(dataVal, options: []) as? NSDictionary {
            print(jsonResult)
        }
    } catch let error as NSError {
        print(error.localizedDescription)
    }

}

4. Asynchronous POST Request

Swift 1.2

    let urlPath: String = "YOUR URL HERE"
    var url: NSURL = NSURL(string: urlPath)!
    var request1: NSMutableURLRequest = NSMutableURLRequest(URL: url)

    request1.HTTPMethod = "POST"
     var stringPost="deviceToken=123456" // Key and Value

    let data = stringPost.dataUsingEncoding(NSUTF8StringEncoding)

    request1.timeoutInterval = 60
    request1.HTTPBody=data
    request1.HTTPShouldHandleCookies=false

    let queue:NSOperationQueue = NSOperationQueue()

     NSURLConnection.sendAsynchronousRequest(request1, queue: queue, completionHandler:{ (response: NSURLResponse!, data: NSData!, error: NSError!) -> Void in


        var err: NSError

        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        println("AsSynchronous\(jsonResult)")


        })

Swift 2.0 +

let urlPath: String = "YOUR URL HERE"
    let url: NSURL = NSURL(string: urlPath)!
    let request1: NSMutableURLRequest = NSMutableURLRequest(URL: url)

    request1.HTTPMethod = "POST"
    let stringPost="deviceToken=123456" // Key and Value

    let data = stringPost.dataUsingEncoding(NSUTF8StringEncoding)

    request1.timeoutInterval = 60
    request1.HTTPBody=data
    request1.HTTPShouldHandleCookies=false

    let queue:NSOperationQueue = NSOperationQueue()

    NSURLConnection.sendAsynchronousRequest(request1, queue: queue, completionHandler:{ (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in

        do {
            if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary {
                print("ASynchronous\(jsonResult)")
            }
        } catch let error as NSError {
            print(error.localizedDescription)
        }


    })

5. Asynchronous GET Request

Swift 1.2

    let urlPath: String = "YOUR URL HERE"
    var url: NSURL = NSURL(string: urlPath)!
    var request1: NSMutableURLRequest = NSMutableURLRequest(URL: url)

    request1.HTTPMethod = "GET"
    request1.timeoutInterval = 60
    let queue:NSOperationQueue = NSOperationQueue()

     NSURLConnection.sendAsynchronousRequest(request1, queue: queue, completionHandler:{ (response: NSURLResponse!, data: NSData!, error: NSError!) -> Void in


        var err: NSError

        var jsonResult: NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
        println("AsSynchronous\(jsonResult)")


        })

Swift 2.0 +

let urlPath: String = "YOUR URL HERE"
    let url: NSURL = NSURL(string: urlPath)!
    let request1: NSMutableURLRequest = NSMutableURLRequest(URL: url)

    request1.HTTPMethod = "GET"
    let queue:NSOperationQueue = NSOperationQueue()

    NSURLConnection.sendAsynchronousRequest(request1, queue: queue, completionHandler:{ (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in

        do {
            if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary {
                print("ASynchronous\(jsonResult)")
            }
        } catch let error as NSError {
            print(error.localizedDescription)
        }


    })

6. Image(File) Upload

Swift 2.0 +

  let mainURL = "YOUR_URL_HERE"

    let url = NSURL(string: mainURL)
    let request = NSMutableURLRequest(URL: url!)
    let boundary = "78876565564454554547676"
    request.addValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")


    request.HTTPMethod = "POST" // POST OR PUT What you want
    let session = NSURLSession(configuration:NSURLSessionConfiguration.defaultSessionConfiguration(), delegate: nil, delegateQueue: nil)

    let imageData = UIImageJPEGRepresentation(UIImage(named: "Test.jpeg")!, 1)





    var body = NSMutableData()

    body.appendData("--\(boundary)\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)

    // Append your parameters

    body.appendData("Content-Disposition: form-data; name=\"name\"\r\n\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
    body.appendData("PREMKUMAR\r\n".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!)
    body.appendData("--\(boundary)\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)

    body.appendData("Content-Disposition: form-data; name=\"description\"\r\n\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
    body.appendData("IOS_DEVELOPER\r\n".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!)
    body.appendData("--\(boundary)\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)


    // Append your Image/File Data

    var imageNameval = "HELLO.jpg"

    body.appendData("--\(boundary)\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
    body.appendData("Content-Disposition: form-data; name=\"profile_photo\"; filename=\"\(imageNameval)\"\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
    body.appendData("Content-Type: image/jpeg\r\n\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)
    body.appendData(imageData!)
    body.appendData("\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)

    body.appendData("--\(boundary)--\r\n".dataUsingEncoding(NSUTF8StringEncoding)!)

    request.HTTPBody = body




    let dataTask = session.dataTaskWithRequest(request) { (data, response, error) -> Void in

        if error != nil {

            //handle error


        }
        else {




            let outputString : NSString = NSString(data:data!, encoding:NSUTF8StringEncoding)!
            print("Response:\(outputString)")


        }
    }
    dataTask.resume()

7. GET,POST,Etc Swift 3.0 +

let request = NSMutableURLRequest(url: URL(string: "YOUR_URL_HERE" ,param: param))!,
    cachePolicy: .useProtocolCachePolicy,
    timeoutInterval:60)
request.httpMethod = "POST" // POST ,GET, PUT What you want 

let session = URLSession.shared



  let dataTask = session.dataTask(with: request as URLRequest) {data,response,error in

do {
            if let jsonResult = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary {
                print("ASynchronous\(jsonResult)")
            }
        } catch let error as NSError {
            print(error.localizedDescription)
        }

    }
    dataTask.resume()

urlencoded Forward slash is breaking URL

I had the same problem with slash in url get param, in my case following php code works:

$value = "hello/world"
$value = str_replace('/', '&#47;', $value;?>
$value = urlencode($value);?>
# $value is now hello%26%2347%3Bworld

I first replace the slash by html entity and then I do the url encoding.

JUnit: how to avoid "no runnable methods" in test utils classes

In your test class if wrote import org.junit.jupiter.api.Test; delete it and write import org.junit.Test; In this case it worked me as well.

input checkbox true or checked or yes

Only checked and checked="checked" are valid. Your other options depend on error recovery in browsers.

checked="yes" and checked="true" are particularly bad as they imply that checked="no" and checked="false" will set the default state to be unchecked … which they will not.

How to create enum like type in TypeScript?

This is now part of the language. See TypeScriptLang.org > Basic Types > enum for the documentation on this. An excerpt from the documentation on how to use these enums:

enum Color {Red, Green, Blue};
var c: Color = Color.Green;

Or with manual backing numbers:

enum Color {Red = 1, Green = 2, Blue = 4};
var c: Color = Color.Green;

You can also go back to the enum name by using for example Color[2].

Here's an example of how this all goes together:

module myModule {
    export enum Color {Red, Green, Blue};

    export class MyClass {
        myColor: Color;

        constructor() {
            console.log(this.myColor);
            this.myColor = Color.Blue;
            console.log(this.myColor);
            console.log(Color[this.myColor]);
        }
    }
}

var foo = new myModule.MyClass();

This will log:

undefined  
2  
Blue

Because, at the time of writing this, the Typescript Playground will generate this code:

var myModule;
(function (myModule) {
    (function (Color) {
        Color[Color["Red"] = 0] = "Red";
        Color[Color["Green"] = 1] = "Green";
        Color[Color["Blue"] = 2] = "Blue";
    })(myModule.Color || (myModule.Color = {}));
    var Color = myModule.Color;
    ;
    var MyClass = (function () {
        function MyClass() {
            console.log(this.myColor);
            this.myColor = Color.Blue;
            console.log(this.myColor);
            console.log(Color[this.myColor]);
        }
        return MyClass;
    })();
    myModule.MyClass = MyClass;
})(myModule || (myModule = {}));
var foo = new myModule.MyClass();

Get CPU Usage from Windows Command Prompt

For anyone that stumbles upon this page, none of the solutions here worked for me. I found this is the way to do it (in a batch file):

@for /f "skip=1" %%p in ('wmic cpu get loadpercentage /VALUE') do (
   for /F "tokens=2 delims==" %%J in ("%%p") do echo %%J
)

What are your favorite extension methods for C#? (codeplex.com/extensionoverflow)

Didn't check the whole thread, so it may already be here, but:

public static class FluentOrderingExtensions
    public class FluentOrderer<T> : IEnumerable<T>
    {
        internal List<Comparison<T>> Comparers = new List<Comparison<T>>();

        internal IEnumerable<T> Source;

        public FluentOrderer(IEnumerable<T> source)
        {
            Source = source;
        }

        #region Implementation of IEnumerable

        public IEnumerator<T> GetEnumerator()
        {
            var workingArray = Source.ToArray();
            Array.Sort(workingArray, IterativeComparison);

            foreach(var element in workingArray) yield return element;
        }

        private int IterativeComparison(T a, T b)
        {
            foreach (var comparer in Comparers)
            {
                var result = comparer(a,b);
                if(result != 0) return result;
            }
            return 0;
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        #endregion
    }

    public static FluentOrderer<T> OrderFluentlyBy<T,TResult>(this IEnumerable<T> source, Func<T,TResult> predicate) 
        where TResult : IComparable<TResult>
    {
        var result = new FluentOrderer<T>(source);
        result.Comparers.Add((a,b)=>predicate(a).CompareTo(predicate(b)));
        return result;
    }

    public static FluentOrderer<T> OrderFluentlyByDescending<T,TResult>(this IEnumerable<T> source, Func<T,TResult> predicate) 
        where TResult : IComparable<TResult>
    {
        var result = new FluentOrderer<T>(source);
        result.Comparers.Add((a,b)=>predicate(a).CompareTo(predicate(b)) * -1);
        return result;
    }

    public static FluentOrderer<T> ThenBy<T, TResult>(this FluentOrderer<T> source, Func<T, TResult> predicate)
        where TResult : IComparable<TResult>
    {
        source.Comparers.Add((a, b) => predicate(a).CompareTo(predicate(b)));
        return source;
    }

    public static FluentOrderer<T> ThenByDescending<T, TResult>(this FluentOrderer<T> source, Func<T, TResult> predicate)
        where TResult : IComparable<TResult>
    {
        source.Comparers.Add((a, b) => predicate(a).CompareTo(predicate(b)) * -1);
        return source;
    }
}

Usage:

var myFluentlyOrderedList = GetABunchOfComplexObjects()
    .OrderFluentlyBy(x=>x.PropertyA)
    .ThenByDescending(x=>x.PropertyB)
    .ThenBy(x=>x.SomeMethod())
    .ThenBy(x=>SomeOtherMethodAppliedTo(x))
    .ToList();

... assuming of course that all the predicates return types that are IComparable to themselves. It would work better with a stable sort like a MergeSort instead of .NET's built-in QuickSort, but it provides you with readable multi-field ordering ability similar to SQL (as close as a method chain can get, anyway). You can extend this to accomodate members that aren't IComparable, by defining overloads that take a comparison lambda instead of creating it based on a predicate.

EDIT: A little explanation, since the commenter got some upticks: this set of methods improves upon the basic OrderBy() functionality by allowing you to sort based on multiple fields in descending order of importance. A real-world example would be sorting a list of invoices by customer, then by invoice number (or invoice date). Other methods of getting the data in this order either wouldn't work (OrderBy() uses an unstable sort, so it cannot be chained) or would be inefficient and not look like it does what you're trying to do.

Missing Microsoft RDLC Report Designer in Visual Studio

In addition to previous answers, here is a link to the latest SQL Server Data Tools. Note that the download link for Visual Studio 2015 is broken. ISO is available from here, links at the bottom of the page:

https://msdn.microsoft.com/en-us/library/mt204009.aspx

MSDN Subscriber Downloads do not list the VS 2015 compatible version at the time of writing.

However, even with the latest tools (February 2015), I can't open previous version of .rptproj files.

How to pass data in the ajax DELETE request other than headers

I was able to successfully pass through the data attribute in the ajax method. Here is my code

$.ajax({
     url: "/api/Gigs/Cancel",
     type: "DELETE",
     data: {
             "GigId": link.attr('data-gig-id')
           }

  })

The link.attr method simply returned the value of 'data-gig-id' .

jQuery DataTable overflow and text-wrapping issues

You can just use render and wrap your own div or span around it. TD`s are hard to style when it comes to max-width, max-height, etc. Div and span is easy..

See: https://datatables.net/examples/advanced_init/column_render.html

I think a nicer solution then working with CSS hacks which are not supported cross browser.

Using Server.MapPath() inside a static field in ASP.NET MVC

Try HostingEnvironment.MapPath, which is static.

See this SO question for confirmation that HostingEnvironment.MapPath returns the same value as Server.MapPath: What is the difference between Server.MapPath and HostingEnvironment.MapPath?

How to change the new TabLayout indicator color and height

With the design support library you can now change them in the xml:

To change the color of the TabLayout indicator:

app:tabIndicatorColor="@color/color"

To change the height of the TabLayout indicator:

app:tabIndicatorHeight="4dp"

How do I give ASP.NET permission to write to a folder in Windows 7?

I know this is an old thread but to further expand the answer here, by default IIS 7.5 creates application pool identity accounts to run the worker process under. You can't search for these accounts like normal user accounts when adding file permissions. To add them into NTFS permission ACL you can type the entire name of the application pool identity and it will work.

It is just a slight difference in the way the application pool identity accounts are handle as they are seen to be virtual accounts.

Also the username of the application pool identity is "IIS AppPool\application pool name" so if it was the application pool DefaultAppPool the user account would be "IIS AppPool\DefaultAppPool".

These can be seen if you open computer management and look at the members of the local group IIS_IUSRS. The SID appended to the end of them is not need when adding the account into an NTFS permission ACL.

Hope that helps

How to check if multiple array keys exists

try this

$required=['a','b'];$data=['a'=>1,'b'=>2];
if(count(array_intersect($required,array_keys($data))>0){
    //a key or all keys in required exist in data
 }else{
    //no keys found
  }

Show MySQL host via SQL Command

To get current host name :-

select @@hostname;
show variables where Variable_name like '%host%';

To get hosts for all incoming requests :-

select host from information_schema.processlist;

Based on your last comment,
I don't think you can resolve IP for the hostname using pure mysql function,
as it require a network lookup, which could be taking long time.

However, mysql document mention this :-

resolveip google.com.sg

docs :- http://dev.mysql.com/doc/refman/5.0/en/resolveip.html

Download history stock prices automatically from yahoo finance in python

Short answer: Yes. Use Python's urllib to pull the historical data pages for the stocks you want. Go with Yahoo! Finance; Google is both less reliable, has less data coverage, and is more restrictive in how you can use it once you have it. Also, I believe Google specifically prohibits you from scraping the data in their ToS.

Longer answer: This is the script I use to pull all the historical data on a particular company. It pulls the historical data page for a particular ticker symbol, then saves it to a csv file named by that symbol. You'll have to provide your own list of ticker symbols that you want to pull.

import urllib

base_url = "http://ichart.finance.yahoo.com/table.csv?s="
def make_url(ticker_symbol):
    return base_url + ticker_symbol

output_path = "C:/path/to/output/directory"
def make_filename(ticker_symbol, directory="S&P"):
    return output_path + "/" + directory + "/" + ticker_symbol + ".csv"

def pull_historical_data(ticker_symbol, directory="S&P"):
    try:
        urllib.urlretrieve(make_url(ticker_symbol), make_filename(ticker_symbol, directory))
    except urllib.ContentTooShortError as e:
        outfile = open(make_filename(ticker_symbol, directory), "w")
        outfile.write(e.content)
        outfile.close()

Get parent directory of running script

As of PHP 5.3.0 you can use __DIR__ for this purpose.

The directory of the file. If used inside an include, the directory of the included file is returned. This is equivalent to dirname(__ FILE__).

See PHP Magic constants.

C:\www>php --version
PHP 5.5.6 (cli) (built: Nov 12 2013 11:33:44)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies

C:\www>php -r "echo __DIR__;"
C:\www

Maven Out of Memory Build Failure

What type of OS are you running on?

In order to assign more than 2GB of ram it needs to be at least a 64bit OS.

Then there is another problem. Even if your OS has Unlimited RAM, but that is fragmented in a way that not a single free block of 2GB is available, you'll get out of memory exceptions too. And keep in mind that the normal Heap memory is only part of the memory the VM process is using. So on a 32bit machine you will probably never be able to set Xmx to 2048MB.

I would also suggest to set min an max memory to the same value, because in this case as soon as the VM runs out of memory the frist time 1GB is allocated from the start, the VM then allocates a new block (assuming it increases with 500MB blocks) of 1,5GB after that is allocated, it would copy all the stuff from block one to the new one and free Memory after that. If it runs out of Memory again the 2GB are allocated and the 1,5 GB are then copied, temporarily allocating 3,5GB of memory.

onKeyDown event not working on divs in React

You need to write it this way

<div 
    className="player"
    style={{ position: "absolute" }}
    onKeyDown={this.onKeyPressed}
    tabIndex="0"
  >

If onKeyPressed is not bound to this, then try to rewrite it using arrow function or bind it in the component constructor.

relative path in require_once doesn't work

for php version 5.2.17 __DIR__ will not work it will only works with php 5.3

But for older version of php dirname(__FILE__) perfectly

For example write like this

require_once dirname(__FILE__) . '/db_config.php';

add to array if it isn't there already

Try this code, I got it from here

$input = Array(1,2,3,1,2,3,4,5,6);
$input = array_map("unserialize", array_unique(array_map("serialize", $input)));

PRINT statement in T-SQL

Query Analyzer buffers messages. The PRINT and RAISERROR statements both use this buffer, but the RAISERROR statement has a WITH NOWAIT option. To print a message immediately use the following:

RAISERROR ('Your message', 0, 1) WITH NOWAIT

RAISERROR will only display 400 characters of your message and uses a syntax similar to the C printf function for formatting text.

Please note that the use of RAISERROR with the WITH NOWAIT option will flush the message buffer, so all previously buffered information will be output also.

What's the equivalent of Java's Thread.sleep() in JavaScript?

Try with this code. I hope it's useful for you.

function sleep(seconds) 
{
  var e = new Date().getTime() + (seconds * 1000);
  while (new Date().getTime() <= e) {}
}

How to take the nth digit of a number in python

I was curious about the relative speed of the two popular approaches - casting to string and using modular arithmetic - so I profiled them and was surprised to see how close they were in terms of performance.

(My use-case was slightly different, I wanted to get all digits in the number.)

The string approach gave:

         10000002 function calls in 1.113 seconds

   Ordered by: cumulative time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
 10000000    1.113    0.000    1.113    0.000 sandbox.py:1(get_digits_str)
        1    0.000    0.000    0.000    0.000 cProfile.py:133(__exit__)
        1    0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}

While the modular arithmetic approach gave:


         10000002 function calls in 1.102 seconds

   Ordered by: cumulative time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
 10000000    1.102    0.000    1.102    0.000 sandbox.py:6(get_digits_mod)
        1    0.000    0.000    0.000    0.000 cProfile.py:133(__exit__)
        1    0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}

There were 10^7 tests run with a max number size less than 10^28.

Code used for reference:

def get_digits_str(num):
    for n_str in str(num):
        yield int(n_str)


def get_digits_mod(num, radix=10):

    remaining = num
    yield remaining % radix

    while remaining := remaining // radix:
        yield remaining % radix


if __name__ == '__main__':

    import cProfile
    import random

    random_inputs = [random.randrange(0, 10000000000000000000000000000) for _ in range(10000000)]

    with cProfile.Profile() as str_profiler:
        for rand_num in random_inputs:
            get_digits_str(rand_num)

    str_profiler.print_stats(sort='cumtime')

    with cProfile.Profile() as mod_profiler:
        for rand_num in random_inputs:
            get_digits_mod(rand_num)

    mod_profiler.print_stats(sort='cumtime')

Is it possible to hide the cursor in a webpage using CSS or Javascript?

Pointer Lock API

While the cursor: none CSS solution is definitely a solid and easy workaround, if your actual goal is to remove the default cursor while your web application is being used, or implement your own interpretation of raw mouse movement (for FPS games, for example), you might want to consider using the Pointer Lock API instead.

You can use requestPointerLock on an element to remove the cursor, and redirect all mousemove events to that element (which you may or may not handle):

document.body.requestPointerLock();

To release the lock, you can use exitPointerLock:

document.exitPointerLock();

Additional notes

No cursor, for real

This is a very powerful API call. It not only renders your cursor invisible, but it actually removes your operating system's native cursor. You won't be able to select text, or do anything with your mouse (except listening to some mouse events in your code) until the pointer lock is released (either by using exitPointerLock or pressing ESC in some browsers).

That is, you cannot leave the window with your cursor for it to show again, as there is no cursor.

Restrictions

As mentioned above, this is a very powerful API call, and is thus only allowed to be made in response to some direct user-interaction on the web, such as a click; for example:

document.addEventListener("click", function () {
    document.body.requestPointerLock();
});

Also, requestPointerLock won't work from a sandboxed iframe unless the allow-pointer-lock permission is set.

User-notifications

Some browsers will prompt the user for a confirmation before the lock is engaged, some will simply display a message. This means pointer lock might not activate right away after the call. However, the actual activation of pointer locking can be listened to by listening to the pointerchange event on the element on which requestPointerLock was called:

document.body.addEventListener("pointerlockchange", function () {
    if (document.pointerLockElement === document.body) {
        // Pointer is now locked to <body>.
    }
});

Most browsers will only display the message once, but Firefox will occasionally spam the message on every single call. AFAIK, this can only be worked around by user-settings, see Disable pointer-lock notification in Firefox.

Listening to raw mouse movement

The Pointer Lock API not only removes the mouse, but instead redirects raw mouse movement data to the element requestPointerLock was called on. This can be listened to simply by using the mousemove event, then accessing the movementX and movementY properties on the event object:

document.body.addEventListener("mousemove", function (e) {
    console.log("Moved by " + e.movementX + ", " + e.movementY);
});

javax.el.PropertyNotFoundException: Property 'foo' not found on type com.example.Bean

javax.el.PropertyNotFoundException: Property 'foo' not found on type com.example.Bean

This literally means that the mentioned class com.example.Bean doesn't have a public (non-static!) getter method for the mentioned property foo. Note that the field itself is irrelevant here!

The public getter method name must start with get, followed by the property name which is capitalized at only the first letter of the property name as in Foo.

public Foo getFoo() {
    return foo;
}

You thus need to make sure that there is a getter method matching exactly the property name, and that the method is public (non-static) and that the method does not take any arguments and that it returns non-void. If you have one and it still doesn't work, then chances are that you were busy editing code forth and back without firmly cleaning the build, rebuilding the code and redeploying/restarting the application. You need to make sure that you have done so.

For boolean (not Boolean!) properties, the getter method name must start with is instead of get.

public boolean isFoo() {
    return foo;
}

Regardless of the type, the presence of the foo field itself is thus not relevant. It can have a different name, or be completely absent, or even be static. All of below should still be accessible by ${bean.foo}.

public Foo getFoo() {
    return bar;
}
public Foo getFoo() {
    return new Foo("foo");
}
public Foo getFoo() {
    return FOO_CONSTANT;
}

You see, the field is not what counts, but the getter method itself. Note that the property name itself should not be capitalized in EL. In other words, ${bean.Foo} won't ever work, it should be ${bean.foo}.

See also:

Run a single test method with maven

As of surefire plugin version 2.22.1 (possibly earlier) you can run single test using testnames property when using testng.xml

Given a following testng.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite name="Suite">
    <test name="all-tests">
        <classes>
            <class name="server.Atest"/>
            <class name="server.Btest"/>
            <class name="server.Ctest"/>
        </classes>
    </test>
    <test name="run-A-test">
        <classes>
            <class name="server.Atest"/>
        </classes>
    </test>
    <test name="run-B-test">
        <classes>
            <class name="server.Btest"/>
        </classes>
    </test>
    <test name="run-C-test">
        <classes>
            <class name="server.Ctest"/>
        </classes>
    </test>
</suite> 

with the pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    [...]
    <properties>
        <selectedTests>all-tests</selectedTests>
    </properties>
    [...]
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.22.1</version>
            <configuration>
                <suiteXmlFiles>
                    <file>src/test/resources/testng.xml</file>
                </suiteXmlFiles>
                <properties>
                    <property>
                        <name>testnames</name>
                        <value>${selectedTests}</value>
                    </property>
                </properties>
            </configuration>
        </plugin>
    </plugins>
    [...]
</project>

From command line

mvn clean test -DselectedTests=run-B-test

Further reading - Maven surefire plugin using testng

Why are my PowerShell scripts not running?

It could be PowerShell's default security level, which (IIRC) will only run signed scripts.

Try typing this:

set-executionpolicy remotesigned

That will tell PowerShell to allow local (that is, on a local drive) unsigned scripts to run.

Then try executing your script again.

How to get first/top row of the table in Sqlite via Sql Query

Use the following query:

SELECT * FROM SAMPLE_TABLE ORDER BY ROWID ASC LIMIT 1

Note: Sqlite's row id references are detailed here.

Given an array of numbers, return array of products of all other numbers (no division)

C++, O(n):

long long prod = accumulate(in.begin(), in.end(), 1LL, multiplies<int>());
transform(in.begin(), in.end(), back_inserter(res),
          bind1st(divides<long long>(), prod));

Copy Paste in Bash on Ubuntu on Windows

That turned out to be pretty simple. I've got it occasionally. To paste a text you simply need to right mouse button click anywhere in terminal window.

HTML.ActionLink method

You might want to look at the RouteLink() method.That one lets you specify everything (except the link text and route name) via a dictionary.

Why do I get permission denied when I try use "make" to install something?

Giving us the whole error message would be much more useful. If it's for make install then you're probably trying to install something to a system directory and you're not root. If you have root access then you can run

sudo make install

or log in as root and do the whole process as root.

Skip to next iteration in loop vba

The present solution produces the same flow as your OP. It does not use Labels, but this was not a requirement of the OP. You only asked for "a simple conditional loop that will go to the next iteration if a condition is true", and since this is cleaner to read, it is likely a better option than that using a Label.

What you want inside your for loop follows the pattern

If (your condition) Then
    'Do something
End If

In this case, your condition is Not(Return = 0 And Level = 0), so you would use

For i = 2 To 24
    Level = Cells(i, 4)
    Return = Cells(i, 5)

    If (Not(Return = 0 And Level = 0)) Then
        'Do something
    End If
Next i

PS: the condition is equivalent to (Return <> 0 Or Level <> 0)

How to insert Records in Database using C# language?

You should change your code to make use of SqlParameters and adapt your insert statement to the following

string connetionString = "Data Source=UMAIR;Initial Catalog=Air; Trusted_Connection=True;" ;
// [ ] required as your fields contain spaces!!
string insStmt = "insert into Main ([First Name], [Last Name]) values (@firstName,@lastName)";

using (SqlConnection cnn = new SqlConnection(connetionString))
{
    cnn.Open();
    SqlCommand insCmd = new SqlCommand(insStmt, cnn);
    // use sqlParameters to prevent sql injection!
    insCmd.Parameters.AddWithValue("@firstName", textbox2.Text);
    insCmd.Parameters.AddWithValue("@lastName", textbox3.Text);
    int affectedRows = insCmd.ExecuteNonQuery();
    MessageBox.Show (affectedRows + " rows inserted!");
}

md-table - How to update the column width

Check this: https://github.com/angular/material2/issues/5808

Since material2 is using flex layout, you can just set fxFlex="40" (or the value you want for fxFlex) to md-cell and md-header-cell.

How to uninstall Golang?

Update August 2019

Found the official uninstall docs worked as expected (on Mac OSX).

$ which go
/usr/local/go/bin/go

In summary, to uninstall:

$ sudo rm -rf /usr/local/go
$ sudo rm /etc/paths.d/go

Then, did a fresh install with homebrew using brew install go. Now, i have:

 $ which go
/usr/local/bin/go

height style property doesn't work in div elements

Also, make sure you add ";" to each style. Your excluding them from width and height and while it might not be causing your specific problem, it's important to close it.

<div style="height:20px; width: 70px;">My Text Here</div>

Mysql command not found in OS X 10.7

You have to set PATH for mysql in your .bashrc file using following:

  export PATH=$PATH:/usr/local/mysql/bin

But If you are using oh my zsh then you have to add path inside .zshrc file.

How to use getJSON, sending data with post method?

The $.getJSON() method does an HTTP GET and not POST. You need to use $.post()

$.post(url, dataToBeSent, function(data, textStatus) {
  //data contains the JSON object
  //textStatus contains the status: success, error, etc
}, "json");

In that call, dataToBeSent could be anything you want, although if are sending the contents of a an html form, you can use the serialize method to create the data for the POST from your form.

var dataToBeSent = $("form").serialize();

Copying and pasting data using VBA code

Use the PasteSpecial method:

sht.Columns("A:G").Copy
Range("A1").PasteSpecial Paste:=xlPasteValues

BUT your big problem is that you're changing your ActiveSheet to "Data" and not changing it back. You don't need to do the Activate and Select, as per my code (this assumes your button is on the sheet you want to copy to).

How can I clear the NuGet package cache using the command line?

The nuget.exe utility doesn't have this feature, but seeing that the NuGet cache is simply a folder on your computer, you can delete the files manually. Just add this to your batch file:

del %LOCALAPPDATA%\NuGet\Cache\*.nupkg /q

Creating a "logical exclusive or" operator in Java

That's because operator overloading is something they specifically left out of the language deliberately. They "cheated" a bit with string concatenation, but beyond that, such functionality doesn't exist.

(disclaimer: I haven't worked with the last 2 major releases of java, so if it's in now, I'll be very surprised)

Compare two objects in Java with possible null values

For those on android, who can't use API 19's Objects.equals(str1, str2), there is this:

android.text.TextUtils.equals(str1, str2);

It is null safe. It rarely has to use the more expensive string.equals() method because identical strings on android almost always compare true with the "==" operand thanks to Android's String Pooling, and length checks are a fast way to filter out most mismatches.

Source Code:

/**
 * Returns true if a and b are equal, including if they are both null.
 * <p><i>Note: In platform versions 1.1 and earlier, this method only worked  well if
 * both the arguments were instances of String.</i></p>
 * @param a first CharSequence to check
 * @param b second CharSequence to check
 * @return true if a and b are equal
 */
public static boolean equals(CharSequence a, CharSequence b) {
    if (a == b) return true;
    int length;
    if (a != null && b != null && (length = a.length()) == b.length()) {
        if (a instanceof String && b instanceof String) {
            return a.equals(b);
        } else {
            for (int i = 0; i < length; i++) {
                if (a.charAt(i) != b.charAt(i)) return false;
            }
            return true;
        }
    }
    return false;
}

Call to getLayoutInflater() in places not in activity

Using context object you can get LayoutInflater from following code

LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

Rails 3 check if attribute changed

This is how I solved the problem of checking for changes in multiple attributes.

attrs = ["street1", "street2", "city", "state", "zipcode"]

if (@user.changed & attrs).any?
  then do something....
end

The changed method returns an array of the attributes changed for that object.

Both @user.changed and attrs are arrays so I can get the intersection (see ary & other ary method). The result of the intersection is an array. By calling any? on the array, I get true if there is at least one intersection.

Also very useful, the changed_attributes method returns a hash of the attributes with their original values and the changes returns a hash of the attributes with their original and new values (in an array).

You can check APIDock for which versions supported these methods.

http://apidock.com/rails/ActiveModel/Dirty

How to implement authenticated routes in React Router 4?

Here is the simple clean protected route

const ProtectedRoute 
  = ({ isAllowed, ...props }) => 
     isAllowed 
     ? <Route {...props}/> 
     : <Redirect to="/authentificate"/>;
const _App = ({ lastTab, isTokenVerified })=> 
    <Switch>
      <Route exact path="/authentificate" component={Login}/>
      <ProtectedRoute 
         isAllowed={isTokenVerified} 
         exact 
         path="/secrets" 
         component={Secrets}/>
      <ProtectedRoute 
         isAllowed={isTokenVerified} 
         exact 
         path="/polices" 
         component={Polices}/>
      <ProtectedRoute 
         isAllowed={isTokenVerified} 
         exact 
         path="/grants" component={Grants}/>
      <Redirect from="/" to={lastTab}/>
    </Switch>

isTokenVerified is a method call to check the authorization token basically it returns boolean.

Iterating over arrays in Python 3

When you loop in an array like you did, your for variable(in this example i) is current element of your array.

For example if your ar is [1,5,10], the i value in each iteration is 1, 5, and 10. And because your array length is 3, the maximum index you can use is 2. so when i = 5 you get IndexError. You should change your code into something like this:

for i in ar:
    theSum = theSum + i

Or if you want to use indexes, you should create a range from 0 ro array length - 1.

for i in range(len(ar)):
    theSum = theSum + ar[i]

How to check postgres user and password?

You will not be able to find out the password he chose. However, you may create a new user or set a new password to the existing user.

Usually, you can login as the postgres user:

Open a Terminal and do sudo su postgres. Now, after entering your admin password, you are able to launch psql and do

CREATE USER yourname WITH SUPERUSER PASSWORD 'yourpassword';

This creates a new admin user. If you want to list the existing users, you could also do

\du

to list all users and then

ALTER USER yourusername WITH PASSWORD 'yournewpass';

Remove an item from an IEnumerable<T> collection

The IEnumerable interface is just that, enumerable - it doesn't provide any methods to Add or Remove or modify the list at all.

The interface just provides a way to iterate over some items - most implementations that require enumeration will implement IEnumerable such as List<T>

Why don't you just use your code without the implicit cast to IEnumerable

// Treat this like a list, not an enumerable
List<User> modifiedUsers = new List<User>();

foreach(var u in users)
{
   if(u.userId != 1233)
   {
        // Use List<T>.Add
        modifiedUsers.Add(u);
   }
}

Processing Symbol Files in Xcode

Annoying error. I solved it by plugging the cable directly into the iPad. For some reason the process would never finish if I had the iPad in Apple's pass-through stand.

How can I disable a button in a jQuery dialog from a function?

I created a jQuery function in order to make this task a bit easier. Just add this to your JavaScript file:

$.fn.dialogButtons = function(name, state){
var buttons = $(this).next('div').find('button');
if(!name)return buttons;
return buttons.each(function(){
    var text = $(this).text();
    if(text==name && state=='disabled') {$(this).attr('disabled',true).addClass('ui-state-disabled');return this;}
    if(text==name && state=='enabled') {$(this).attr('disabled',false).removeClass('ui-state-disabled');return this;}
    if(text==name){return this;}
    if(name=='disabled'){$(this).attr('disabled',true).addClass('ui-state-disabled');return buttons;}
    if(name=='enabled'){$(this).attr('disabled',false).removeClass('ui-state-disabled');return buttons;}
});};

Disable button 'OK' on dialog with class 'dialog':

$('.dialog').dialogButtons('Ok', 'disabled');

Enable all buttons:

$('.dialog').dialogButtons('enabled');

Enable 'Close' button and change color:

$('.dialog').dialogButtons('Close', 'enabled').css('color','red');

I hope this helps.

Please run `npm cache clean`

As of npm@5, the npm cache self-heals from corruption issues and data extracted from the cache is guaranteed to be valid. If you want to make sure everything is consistent, use npm cache verify instead. On the other hand, if you're debugging an issue with the installer, you can use npm install --cache /tmp/empty-cache to use a temporary cache instead of nuking the actual one.

If you're sure you want to delete the entire cache, rerun:

npm cache clean --force

A complete log of this run can be found in /Users/USERNAME/.npm/_logs/2019-01-08T21_29_30_811Z-debug.log.

Visual Studio Code - Target of URI doesn't exist 'package:flutter/material.dart'

Open the command palette (ctrl+shift+p), type flutter: get packages (should autocomplete); after it resolves open the command palette again and type reload window and execute the command. This should resolve the issue as quickly as possible.

Scroll event listener javascript

I was looking a lot to find a solution for sticy menue with old school JS (without JQuery). So I build small test to play with it. I think it can be helpfull to those looking for solution in js. It needs improvments of unsticking the menue back, and making it more smooth. Also I find a nice solution with JQuery that clones the original div instead of position fixed, its better since the rest of page element dont need to be replaced after fixing. Anyone know how to that with JS ? Please remark, correct and improve.

<!DOCTYPE html>
<html>

<head>
<script>

// addEvent function by John Resig:
// http://ejohn.org/projects/flexible-javascript-events/

function addEvent( obj, type, fn ) {

    if ( obj.attachEvent ) {

        obj['e'+type+fn] = fn;
        obj[type+fn] = function(){obj['e'+type+fn]( window.event );};
        obj.attachEvent( 'on'+type, obj[type+fn] );
    } else {
        obj.addEventListener( type, fn, false );
    }
}
function getScrollY() {
    var  scrOfY = 0;
    if( typeof( window.pageYOffset ) == 'number' ) {
        //Netscape compliant
        scrOfY = window.pageYOffset;

    } else if( document.body && document.body.scrollTop )  {
        //DOM compliant
        scrOfY = document.body.scrollTop;
    } 
    return scrOfY;
}
</script>
<style>
#mydiv {
    height:100px;
    width:100%;
}
#fdiv {
    height:100px;
    width:100%;
}
</style>
</head>

<body>

<!-- HTML for example event goes here -->

<div id="fdiv" style="background-color:red;position:fix">
</div>
<div id="mydiv" style="background-color:yellow">
</div>
<div id="fdiv" style="background-color:green">
</div>

<script>

// Script for example event goes here

addEvent(window, 'scroll', function(event) {

    var x = document.getElementById("mydiv");

    var y = getScrollY();      
    if (y >= 100) {
        x.style.position = "fixed"; 
        x.style.top= "0";
    } 
});

</script>
</body>
</html>

How to resolve a Java Rounding Double issue

Another example:

double d = 0;
for (int i = 1; i <= 10; i++) {
    d += 0.1;
}
System.out.println(d);    // prints 0.9999999999999999 not 1.0

Use BigDecimal instead.

EDIT:

Also, just to point out this isn't a 'Java' rounding issue. Other languages exhibit similar (though not necessarily consistent) behaviour. Java at least guarantees consistent behaviour in this regard.

What's the best way to set a single pixel in an HTML5 canvas?

Draw a rectangle like sdleihssirhc said!

ctx.fillRect (10, 10, 1, 1);

^-- should draw a 1x1 rectangle at x:10, y:10

Do the parentheses after the type name make a difference with new?

new Thing(); is explicit that you want a constructor called whereas new Thing; is taken to imply you don't mind if the constructor isn't called.

If used on a struct/class with a user-defined constructor, there is no difference. If called on a trivial struct/class (e.g. struct Thing { int i; };) then new Thing; is like malloc(sizeof(Thing)); whereas new Thing(); is like calloc(sizeof(Thing)); - it gets zero initialized.

The gotcha lies in-between:

struct Thingy {
  ~Thingy(); // No-longer a trivial class
  virtual WaxOn();
  int i;
};

The behavior of new Thingy; vs new Thingy(); in this case changed between C++98 and C++2003. See Michael Burr's explanation for how and why.

Could not create SSL/TLS secure channel, despite setting ServerCertificateValidationCallback

I came across this thread because I also had the error Could not create SSL/TLS secure channel. In my case, I was attempting to access a Siebel configuration REST API from PowerShell using Invoke-RestMethod, and none of the suggestions above helped.

Eventually I stumbled across the cause of my problem: the server I was contacting required client certificate authentication.

To make the calls work, I had to provide the client certificate (including the private key) with the -Certificate parameter:

$Pwd = 'certificatepassword'
$Pfx = New-Object -TypeName 'System.Security.Cryptography.X509Certificates.X509Certificate2'
$Pfx.Import('clientcert.p12', $Pwd, 'Exportable,PersistKeySet')
Invoke-RestMethod -Uri 'https://your.rest.host/api/' -Certificate $Pfx -OtherParam ...

Hopefully my experience might help someone else who has my particular flavour of this problem.

How to line-break from css, without using <br />?

Impossible with the same HTML structure, you must have something to distinguish between Hello and How are you.

I suggest using spans that you will then display as blocks (just like a <div> actually).

_x000D_
_x000D_
p span {_x000D_
  display: block;_x000D_
}
_x000D_
<p><span>hello</span><span>How are you</span></p>
_x000D_
_x000D_
_x000D_

How to conclude your merge of a file?

I had the same error and i did followed article found on google solves my issue. You have not concluded your merge

How do I set a conditional breakpoint in gdb, when char* x points to a string whose value equals "hello"?

You can use strcmp:

break x:20 if strcmp(y, "hello") == 0

20 is line number, x can be any filename and y can be any variable.

Convert a String representation of a Dictionary to a dictionary?

To OP's example:

s = "{'muffin' : 'lolz', 'foo' : 'kitty'}"

We can use Yaml to deal with this kind of non-standard json in string:

>>> import yaml
>>> s = "{'muffin' : 'lolz', 'foo' : 'kitty'}"
>>> s
"{'muffin' : 'lolz', 'foo' : 'kitty'}"
>>> yaml.load(s)
{'muffin': 'lolz', 'foo': 'kitty'}

Curl setting Content-Type incorrectly

I think you want to specify

-H "Content-Type:text/xml"

with a colon, not an equals.

java build path problems

Go for the second option, Edit the project to agree with the latest JDK

  • Right click "JRE System Library [J2SE 1.5] in your project"
  • Choose "Properties"
  • Select "Workspace default JRE (jdk1.6)

enter image description here

Better way to call javascript function in a tag

Modern browsers support a Content Security Policy or CSP. This is the highest level of web security and strongly recommended if you can apply it because it completely blocks all XSS attacks.

Both of your suggestions break with CSP enabled because they allow inline Javascript (which could be injected by a hacker) to execute in your page.

The best practice is to subscribe to the event in Javascript, as in Konrad Rudolph's answer.

How do I find an array item with TypeScript? (a modern, easier way)

If you need some es6 improvements not supported by Typescript, you can target es6 in your tsconfig and use Babel to convert your files in es5.

Vuex - passing multiple parameters to mutation

In simple terms you need to build your payload into a key array

payload = {'key1': 'value1', 'key2': 'value2'}

Then send the payload directly to the action

this.$store.dispatch('yourAction', payload)

No change in your action

yourAction: ({commit}, payload) => {
  commit('YOUR_MUTATION',  payload )
},

In your mutation call the values with the key

'YOUR_MUTATION' (state,  payload ){
  state.state1 = payload.key1
  state.state2 =  payload.key2
},

Zooming MKMapView to fit annotation pins?

Based on answers above you can use universal method to zoom map to fit all annotations and overlays at the same time.

-(MKMapRect)getZoomingRectOnMap:(MKMapView*)map toFitAllOverlays:(BOOL)overlays andAnnotations:(BOOL)annotations includeUserLocation:(BOOL)userLocation {
    if (!map) {
        return MKMapRectNull;
    }

    NSMutableArray* overlaysAndAnnotationsCoordinateArray = [[NSMutableArray alloc]init];        
    if (overlays) {
        for (id <MKOverlay> overlay in map.overlays) {
            MKMapPoint overlayPoint = MKMapPointForCoordinate(overlay.coordinate);
            NSArray* coordinate = @[[NSNumber numberWithDouble:overlayPoint.x], [NSNumber numberWithDouble:overlayPoint.y]];
            [overlaysAndAnnotationsCoordinateArray addObject:coordinate];
        }
    }

    if (annotations) {
        for (id <MKAnnotation> annotation in map.annotations) {
            MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);
            NSArray* coordinate = @[[NSNumber numberWithDouble:annotationPoint.x], [NSNumber numberWithDouble:annotationPoint.y]];
            [overlaysAndAnnotationsCoordinateArray addObject:coordinate];
        }
    }

    MKMapRect zoomRect = MKMapRectNull;
    if (userLocation) {
        MKMapPoint annotationPoint = MKMapPointForCoordinate(map.userLocation.coordinate);
        zoomRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0.1, 0.1);
    }

    for (NSArray* coordinate in overlaysAndAnnotationsCoordinateArray) {
        MKMapRect pointRect = MKMapRectMake([coordinate[0] doubleValue], [coordinate[1] doubleValue], 0.1, 0.1);
        zoomRect = MKMapRectUnion(zoomRect, pointRect);
    }

    return zoomRect;
}

And then:

MKMapRect mapRect = [self getZoomingRectOnMap:mapView toFitAllOverlays:YES andAnnotations:YES includeUserLocation:NO];
[mapView setVisibleMapRect:mapRect edgePadding:UIEdgeInsetsMake(10.0, 10.0, 10.0, 10.0) animated:YES];

How to find encoding of a file via script on Linux?

Sounds like you're looking for enca. It can guess and even convert between encodings. Just look at the man page.

Or, failing that, use file -i (linux) or file -I (osx). That will output MIME-type information for the file, which will also include the character-set encoding. I found a man-page for it, too :)

How to move columns in a MySQL table?

Change column position:

ALTER TABLE Employees 
   CHANGE empName empName VARCHAR(50) NOT NULL AFTER department;

If you need to move it to the first position you have to use term FIRST at the end of ALTER TABLE CHANGE [COLUMN] query:

ALTER TABLE UserOrder 
   CHANGE order_id order_id INT(11) NOT NULL FIRST;

Batch files: How to read a file?

A code that displays the contents of the myfile.txt file on the screen

set %filecontent%=0
type %filename% >> %filecontent%
echo %filecontent%

Running interactive commands in Paramiko

You can use this method to send whatever confirmation message you want like "OK" or the password. This is my solution with an example:

def SpecialConfirmation(command, message, reply):
    net_connect.config_mode()    # To enter config mode
    net_connect.remote_conn.sendall(str(command)+'\n' )
    time.sleep(3)
    output = net_connect.remote_conn.recv(65535).decode('utf-8')
    ReplyAppend=''
    if str(message) in output:
        for i in range(0,(len(reply))):
            ReplyAppend+=str(reply[i])+'\n'
        net_connect.remote_conn.sendall(ReplyAppend)
        output = net_connect.remote_conn.recv(65535).decode('utf-8') 
    print (output)
    return output

CryptoPkiEnroll=['','','no','no','yes']

output=SpecialConfirmation ('crypto pki enroll TCA','Password' , CryptoPkiEnroll )
print (output)

Makefile, header dependencies

Martin's solution above works great, but does not handle .o files that reside in subdirectories. Godric points out that the -MT flag takes care of that problem, but it simultaneously prevents the .o file from being written correctly. The following will take care of both of those problems:

DEPS := $(OBJS:.o=.d)

-include $(DEPS)

%.o: %.c
    $(CC) $(CFLAGS) -MM -MT $@ -MF $(patsubst %.o,%.d,$@) $<
    $(CC) $(CFLAGS) -o $@ $<

Java: method to get position of a match in a String?

    String match = "hello";
    String text = "0123456789hello0123456789hello";

    int j = 0;
    String indxOfmatch = "";

    for (int i = -1; i < text.length()+1; i++) {
        j =  text.indexOf("hello", i);
        if (i>=j && j > -1) {
            indxOfmatch += text.indexOf("hello", i)+" ";
        }
    }
    System.out.println(indxOfmatch);

Using C++ base class constructors?

No, that's not how it is done. Normal way to initialize the base class is in the initialization list :

class A
{
public: 
    A(int val) {}
};

class B : public A
{
public:
  B( int v) : A( v )
  {
  }
};


void main()
{
    B b(10);
}

How to write into a file in PHP?

$fp = fopen('lidn.txt', 'w');
fwrite($fp, 'Cats chase');
fwrite($fp, 'mice');
fclose($fp);

http://php.net/manual/en/function.fwrite.php

Access blocked by CORS policy: Response to preflight request doesn't pass access control check

You can just create the required CORS configuration as a bean. As per the code below this will allow all requests coming from any origin. This is good for development but insecure. Spring Docs

@Bean
WebMvcConfigurer corsConfigurer() {
    return new WebMvcConfigurer() {
        @Override
        void addCorsMappings(CorsRegistry registry) {
            registry.addMapping("/**")
                    .allowedOrigins("*")
        }
    }
}

Sending websocket ping/pong frame from browser

There is no Javascript API to send ping frames or receive pong frames. This is either supported by your browser, or not. There is also no API to enable, configure or detect whether the browser supports and is using ping/pong frames. There was discussion about creating a Javascript ping/pong API for this. There is a possibility that pings may be configurable/detectable in the future, but it is unlikely that Javascript will be able to directly send and receive ping/pong frames.

However, if you control both the client and server code, then you can easily add ping/pong support at a higher level. You will need some sort of message type header/metadata in your message if you don't have that already, but that's pretty simple. Unless you are planning on sending pings hundreds of times per second or have thousands of simultaneous clients, the overhead is going to be pretty minimal to do it yourself.

Is it possible to make abstract classes in Python?

also this works and is simple:

class A_abstract(object):

    def __init__(self):
        # quite simple, old-school way.
        if self.__class__.__name__ == "A_abstract": 
            raise NotImplementedError("You can't instantiate this abstract class. Derive it, please.")

class B(A_abstract):

        pass

b = B()

# here an exception is raised:
a = A_abstract()

Using any() and all() to check if a list contains one set of values or another

Generally speaking:

all and any are functions that take some iterable and return True, if

  • in the case of all(), no values in the iterable are falsy;
  • in the case of any(), at least one value is truthy.

A value x is falsy iff bool(x) == False. A value x is truthy iff bool(x) == True.

Any non-booleans in the iterable will be fine — bool(x) will coerce any x according to these rules: 0, 0.0, None, [], (), [], set(), and other empty collections will yield False, anything else True. The docstring for bool uses the terms 'true'/'false' for 'truthy'/'falsy', and True/False for the concrete boolean values.


In your specific code samples:

You misunderstood a little bit how these functions work. Hence, the following does something completely not what you thought:

if any(foobars) == big_foobar:

...because any(foobars) would first be evaluated to either True or False, and then that boolean value would be compared to big_foobar, which generally always gives you False (unless big_foobar coincidentally happened to be the same boolean value).

Note: the iterable can be a list, but it can also be a generator/generator expression (˜ lazily evaluated/generated list) or any other iterator.

What you want instead is:

if any(x == big_foobar for x in foobars):

which basically first constructs an iterable that yields a sequence of booleans—for each item in foobars, it compares the item to big_foobar and emits the resulting boolean into the resulting sequence:

tmp = (x == big_foobar for x in foobars)

then any walks over all items in tmp and returns True as soon as it finds the first truthy element. It's as if you did the following:

In [1]: foobars = ['big', 'small', 'medium', 'nice', 'ugly']                                        

In [2]: big_foobar = 'big'                                                                          

In [3]: any(['big' == big_foobar, 'small' == big_foobar, 'medium' == big_foobar, 'nice' == big_foobar, 'ugly' == big_foobar])        
Out[3]: True

Note: As DSM pointed out, any(x == y for x in xs) is equivalent to y in xs but the latter is more readable, quicker to write and runs faster.

Some examples:

In [1]: any(x > 5 for x in range(4))
Out[1]: False

In [2]: all(isinstance(x, int) for x in range(10))
Out[2]: True

In [3]: any(x == 'Erik' for x in ['Erik', 'John', 'Jane', 'Jim'])
Out[3]: True

In [4]: all([True, True, True, False, True])
Out[4]: False

See also: http://docs.python.org/2/library/functions.html#all

How do I set GIT_SSL_NO_VERIFY for specific repos only?

Like what Thirumalai said, but inside of the cloned repository and without --global. I.e.,

  1. GIT_SSL_NO_VERIFY=true git clone https://url
  2. cd <directory-of-the-clone>
  3. git config http.sslVerify false

Why is there an unexplainable gap between these inline-block div elements?

Found a solution not involving Flex, because Flex doesn't work in older Browsers. Example:

.container {
    display:block;
    position:relative;
    height:150px;
    width:1024px;
    margin:0 auto;
    padding:0px;
    border:0px;
    background:#ececec;
    margin-bottom:10px;
    text-align:justify;
    box-sizing:border-box;
    white-space:nowrap;
    font-size:0pt;
    letter-spacing:-1em;
}

.cols {
    display:inline-block;
    position:relative;
    width:32%;
    height:100%;
    margin:0 auto;
    margin-right:2%;
    border:0px;
    background:lightgreen;  
    box-sizing:border-box;
    padding:10px;
    font-size:10pt;
    letter-spacing:normal;
}

.cols:last-child {
    margin-right:0;
}

Python Save to file

You can use this function:

def saveListToFile(listname, pathtosave):
    file1 = open(pathtosave,"w") 
    for i in listname:
        file1.writelines("{}\n".format(i))    
    file1.close() 

# to save:
saveListToFile(list, path)

How can I make a checkbox readonly? not disabled?

I use JQuery so I can use the readonly attribute on checkboxes.

//This will make all read-only check boxes truly read-only
$('input[type="checkbox"][readonly]').on("click.readonly", function(event){event.preventDefault();}).css("opacity", "0.5");

If you want the checkbox to be editable again then you need to do the following for the specific checkbox.

$('specific checkbox').off('.readonly').removeAttr("readonly").css("opacity", "1")

Display exact matches only with grep

^ marks the beginning of the line and $ marks the end of the line. This will return exact matches of "OK" only:

(This also works with double quotes if that's your preference.)

grep '^OK$'

If there are other characters before the OK / NOTOK (like the job name), you can exclude the "NOT" prefix by allowing any characters .* and then excluding "NOT" [^NOT] just before the "OK":

grep '^.*[^NOT]OK$'

Intellij reformat on file save

If it's about Prettier, just use a File Watcher :

references => Tools => File Watchers => click + to add a new watcher => Prettier

https://prettier.io/docs/en/webstorm.html#running-prettier-on-save-using-file-watcher

How to enable support of CPU virtualization on Macbook Pro?

CPU Virtualization is enabled by default on all MacBooks with compatible CPUs (i7 is compatible). You can try to reset PRAM if you think it was disabled somehow, but I doubt it.

I think the issue might be in the old version of OS. If your MacBook is i7, then you better upgrade OS to something newer.

CSS width of a <span> tag

You can't specify the width of an element with display inline. You could put something in it like a non-breaking space ( ) and then set the padding to give it some more width but you can't control it directly.

You could use display inline-block but that isn't widely supported.

A real hack would be to put an image inside and then set the width of that. Something like a transparent 1 pixel GIF. Not the recommended approach however.

If input field is empty, disable submit button

An easy way to do:

function toggleButton(ref,bttnID){
    document.getElementById(bttnID).disabled= ((ref.value !== ref.defaultValue) ? false : true);
}


<input ... onkeyup="toggleButton(this,'bttnsubmit');">
<input ... disabled='disabled' id='bttnsubmit' ... >

JSON.parse unexpected token s

valid json string must have double quote.

JSON.parse({"u1":1000,"u2":1100})       // will be ok

no quote cause error

JSON.parse({u1:1000,u2:1100})    
// error Uncaught SyntaxError: Unexpected token u in JSON at position 2

single quote cause error

JSON.parse({'u1':1000,'u2':1100})    
// error Uncaught SyntaxError: Unexpected token u in JSON at position 2

You must valid json string at https://jsonlint.com

[INSTALL_FAILED_NO_MATCHING_ABIS: Failed to extract native libraries, res=-113]

Make the splits depend on the same list of abis as the external build. Single source of truth.

android {
// ...
defaultConfig {
// ...
    externalNativeBuild {
        cmake {
            cppFlags "-std=c++17"
            abiFilters 'x86', 'armeabi-v7a', 'x86_64'
        }
    }
} //defaultConfig

splits {
    abi {
        enable true
        reset()
        include defaultConfig.externalNativeBuild.getCmake().getAbiFilters().toListString()
        universalApk true
    }
}
} //android

Mean Squared Error in Numpy?

Even more numpy

np.square(np.subtract(A, B)).mean()

MongoDB: Is it possible to make a case-insensitive query?

Starting with MongoDB 3.4, the recommended way to perform fast case-insensitive searches is to use a Case Insensitive Index.

I personally emailed one of the founders to please get this working, and he made it happen! It was an issue on JIRA since 2009, and many have requested the feature. Here's how it works:

A case-insensitive index is made by specifying a collation with a strength of either 1 or 2. You can create a case-insensitive index like this:

db.cities.createIndex(
  { city: 1 },
  { 
    collation: {
      locale: 'en',
      strength: 2
    }
  }
);

You can also specify a default collation per collection when you create them:

db.createCollection('cities', { collation: { locale: 'en', strength: 2 } } );

In either case, in order to use the case-insensitive index, you need to specify the same collation in the find operation that was used when creating the index or the collection:

db.cities.find(
  { city: 'new york' }
).collation(
  { locale: 'en', strength: 2 }
);

This will return "New York", "new york", "New york" etc.

Other notes

  • The answers suggesting to use full-text search are wrong in this case (and potentially dangerous). The question was about making a case-insensitive query, e.g. username: 'bill' matching BILL or Bill, not a full-text search query, which would also match stemmed words of bill, such as Bills, billed etc.

  • The answers suggesting to use regular expressions are slow, because even with indexes, the documentation states:

    "Case insensitive regular expression queries generally cannot use indexes effectively. The $regex implementation is not collation-aware and is unable to utilize case-insensitive indexes."

    $regex answers also run the risk of user input injection.

How do I change the select box arrow

Working with just one selector:

select {
    width: 268px;
    padding: 5px;
    font-size: 16px;
    line-height: 1;
    border: 0;
    border-radius: 5px;
    height: 34px;
    background: url(http://cdn1.iconfinder.com/data/icons/cc_mono_icon_set/blacks/16x16/br_down.png) no-repeat right #ddd;
    -webkit-appearance: none;
    background-position-x: 244px;
}

fiddler

Check/Uncheck all the checkboxes in a table

This will select and deselect all checkboxes:

function checkAll()
{
     var checkboxes = document.getElementsByTagName('input'), val = null;    
     for (var i = 0; i < checkboxes.length; i++)
     {
         if (checkboxes[i].type == 'checkbox')
         {
             if (val === null) val = checkboxes[i].checked;
             checkboxes[i].checked = val;
         }
     }
 }

Demo

Update:

You can use querySelectAll directly on the table to get the list of checkboxes instead of searching the whole document, but It might not be compatible with old browsers so you need to check that first:

 function checkAll()
 {
     var table = document.getElementById ('dataTable');
     var checkboxes = table.querySelectorAll ('input[type=checkbox]');
     var val = checkboxes[0].checked;
     for (var i = 0; i < checkboxes.length; i++) checkboxes[i].checked = val;
 }

Or to be more specific for the provided html structure in the OP question, this would be more efficient when selecting the checkboxes as it will access them directly instead of searching for them:

function checkAll (tableID)
{
    var table = document.getElementById (tableID);
    var val = table.rows[0].cells[0].children[0].checked;
    for (var i = 1; i < table.rows.length; i++)
    {
        table.rows[i].cells[0].children[0].checked = val;
    }
}

Demo

Pass PDO prepared statement to variables

Instead of using ->bindParam() you can pass the data only at the time of ->execute():

$data = [   ':item_name' => $_POST['item_name'],   ':item_type' => $_POST['item_type'],   ':item_price' => $_POST['item_price'],   ':item_description' => $_POST['item_description'],   ':image_location' => 'images/'.$_FILES['file']['name'],   ':status' => 0,   ':id' => 0, ];  $stmt->execute($data); 

In this way you would know exactly what values are going to be sent.

Centering brand logo in Bootstrap Navbar

Updated 2018

Bootstrap 3

See if this example helps: http://bootply.com/mQh8DyRfWY

The brand is centered using..

.navbar-brand
{
    position: absolute;
    width: 100%;
    left: 0;
    top: 0;
    text-align: center;
    margin: auto;
}

Your markup is for Bootstrap 2, not 3. There is no longer a navbar-inner.

EDIT - Another approach is using transform: translateX(-50%);

.navbar-brand {
  transform: translateX(-50%);
  left: 50%;
  position: absolute;
}

http://www.bootply.com/V7vKDfk46G

Bootstrap 4

In Bootstrap 4, mx-auto or flexbox can be used to center the brand and other elements. See How to position navbar contents in Bootstrap 4 for an explanation.

Also see:

Bootstrap NavBar with left, center or right aligned items

How do I get my page title to have an icon?

They're called favicons, and are quite easy to make/use. Have a read of http://www.favicon.com/ for help.