Programs & Examples On #Pass by reference

Pass by reference is an argument marshalling strategy whereby a variable's location in memory is passed to a function, rather than a copy of the variable's value, although the function appears in the source code to receive the variable itself rather than a pointer to it.

C++ pass an array by reference

Yes, but when argument matching for a reference, the implicit array to pointer isn't automatic, so you need something like:

void foo( double (&array)[42] );


void foo( double (&array)[] );

Be aware, however, that when matching, double [42] and double [] are distinct types. If you have an array of an unknown dimension, it will match the second, but not the first, and if you have an array with 42 elements, it will match the first but not the second. (The latter is, IMHO, very counter-intuitive.)

In the second case, you'll also have to pass the dimension, since there's no way to recover it once you're inside the function.

Pass by Reference / Value in C++

I think much confusion is generated by not communicating what is meant by passed by reference. When some people say pass by reference they usually mean not the argument itself, but rather the object being referenced. Some other say that pass by reference means that the object can't be changed in the callee. Example:

struct Object {
    int i;

void sample(Object* o) { // 1

void sample(Object const& o) { // 2
    // nothing useful here :)

void sample(Object & o) { // 3

void sample1(Object o) { // 4

int main() {
    Object obj = { 10 };
    Object const obj_c = { 10 };

    sample(&obj); // calls 1
    sample(obj) // calls 3
    sample(obj_c); // calls 2
    sample1(obj); // calls 4

Some people would claim that 1 and 3 are pass by reference, while 2 would be pass by value. Another group of people say all but the last is pass by reference, because the object itself is not copied.

I would like to draw a definition of that here what i claim to be pass by reference. A general overview over it can be found here: Difference between pass by reference and pass by value. The first and last are pass by value, and the middle two are pass by reference:

       // yields a `Object*`. Passes a *pointer* to the object by value. 
       // The caller can change the pointer (the parameter), but that 
       // won't change the temporary pointer created on the call side (the argument). 

       // passes the object by *reference*. It denotes the object itself. The callee
       // has got a reference parameter.

       // also passes *by reference*. the reference parameter references the
       // same object like the argument expression. 

       // pass by value. The parameter object denotes a different object than the 
       // one passed in.

I vote for the following definition:

An argument (1.3.1) is passed by reference if and only if the corresponding parameter of the function that's called has reference type and the reference parameter binds directly to the argument expression (8.5.3/4). In all other cases, we have to do with pass by value.

That means that the following is pass by value:

void f1(Object const& o);
f1(Object()); // 1

void f2(int const& i);
f2(42); // 2

void f3(Object o);
f3(Object());     // 3
Object o1; f3(o1); // 4

void f4(Object *o);
Object o1; f4(&o1); // 5

1 is pass by value, because it's not directly bound. The implementation may copy the temporary and then bind that temporary to the reference. 2 is pass by value, because the implementation initializes a temporary of the literal and then binds to the reference. 3 is pass by value, because the parameter has not reference type. 4 is pass by value for the same reason. 5 is pass by value because the parameter has not got reference type. The following cases are pass by reference (by the rules of 8.5.3/4 and others):

void f1(Object *& op);
Object a; Object *op1 = &a; f1(op1); // 1

void f2(Object const& op);
Object b; f2(b); // 2

struct A { };
struct B { operator A&() { static A a; return a; } };
void f3(A &);
B b; f3(b); // passes the static a by reference

Why should I use the keyword "final" on a method parameter in Java?

Sometimes it's nice to be explicit (for readability) that the variable doesn't change. Here's a simple example where using final can save some possible headaches:

public void setTest(String test) {
    test = test;

If you forget the 'this' keyword on a setter, then the variable you want to set doesn't get set. However, if you used the final keyword on the parameter, then the bug would be caught at compile time.

Is it better in C++ to pass by value or pass by constant reference?

Simple difference :- In function we have input and output parameter , so if your passing input and out parameter is same then use call by reference else if input and output parameter are different then better to use call by value .

example void amount(int account , int deposit , int total )

input parameter : account , deposit output paramteter: total

input and out is different use call by vaule

  1. void amount(int total , int deposit )

input total deposit output total

Passing an integer by reference in Python

It doesn't quite work that way in Python. Python passes references to objects. Inside your function you have an object -- You're free to mutate that object (if possible). However, integers are immutable. One workaround is to pass the integer in a container which can be mutated:

def change(x):
    x[0] = 3

x = [1]
print x

This is ugly/clumsy at best, but you're not going to do any better in Python. The reason is because in Python, assignment (=) takes whatever object is the result of the right hand side and binds it to whatever is on the left hand side *(or passes it to the appropriate function).

Understanding this, we can see why there is no way to change the value of an immutable object inside a function -- you can't change any of its attributes because it's immutable, and you can't just assign the "variable" a new value because then you're actually creating a new object (which is distinct from the old one) and giving it the name that the old object had in the local namespace.

Usually the workaround is to simply return the object that you want:

def multiply_by_2(x):
    return 2*x

x = 1
x = multiply_by_2(x)

*In the first example case above, 3 actually gets passed to x.__setitem__.

What's the difference between passing by reference vs. passing by value?

A major difference between them is that value-type variables store values, so specifying a value-type variable in a method call passes a copy of that variable's value to the method. Reference-type variables store references to objects, so specifying a reference-type variable as an argument passes the method a copy of the actual reference that refers to the object. Even though the reference itself is passed by value, the method can still use the reference it receives to interact with—and possibly modify—the original object. Similarly, when returning information from a method via a return statement, the method returns a copy of the value stored in a value-type variable or a copy of the reference stored in a reference-type variable. When a reference is returned, the calling method can use that reference to interact with the referenced object. So, in effect, objects are always passed by reference.

In c#, to pass a variable by reference so the called method can modify the variable's, C# provides keywords ref and out. Applying the ref keyword to a parameter declaration allows you to pass a variable to a method by reference—the called method will be able to modify the original variable in the caller. The ref keyword is used for variables that already have been initialized in the calling method. Normally, when a method call contains an uninitialized variable as an argument, the compiler generates an error. Preceding a parameter with keyword out creates an output parameter. This indicates to the compiler that the argument will be passed into the called method by reference and that the called method will assign a value to the original variable in the caller. If the method does not assign a value to the output parameter in every possible path of execution, the compiler generates an error. This also prevents the compiler from generating an error message for an uninitialized variable that is passed as an argument to a method. A method can return only one value to its caller via a return statement, but can return many values by specifying multiple output (ref and/or out) parameters.

see c# discussion and examples here link text

Passing by reference in C

Your example works because you are passing the address of your variable to a function that manipulates its value with the dereference operator.

While C does not support reference data types, you can still simulate passing-by-reference by explicitly passing pointer values, as in your example.

The C++ reference data type is less powerful but considered safer than the pointer type inherited from C. This would be your example, adapted to use C++ references:

void f(int &j) {

int main() {
  int i = 20;
  printf("i = %d\n", i);

  return 0;

Passing an array by reference in C?

In plain C you can use a pointer/size combination in your API.

void doSomething(MyStruct* mystruct, size_t numElements)
    for (size_t i = 0; i < numElements; ++i)
        MyStruct current = mystruct[i];

Using pointers is the closest to call-by-reference available in C.

Passing properties by reference in C#

The accepted answer is good if that function is in your code and you can modify it. But sometimes you have to use an object and a function from some external library and you can't change the property and function definition. Then you can just use a temporary variable.

var phone = Client.WorkPhone;
GetString(input, ref phone);
Client.WorkPhone = phone;

Object passed as parameter to another class, by value or reference?

I found the other examples unclear, so I did my own test which confirmed that a class instance is passed by reference and as such actions done to the class will affect the source instance.

In other words, my Increment method modifies its parameter myClass everytime its called.

class Program
    static void Main(string[] args)
        MyClass myClass = new MyClass();
        Console.WriteLine(myClass.Value);  // Displays 1
        Console.WriteLine(myClass.Value);  // Displays 2
        Console.WriteLine(myClass.Value);  // Displays 3           
        Console.WriteLine(myClass.Value);  // Displays 4
        Console.WriteLine("Hit Enter to exit.");

    public static void Increment(MyClass myClassRef)

public class MyClass
    public int Value {get;set;}
    public MyClass()
        Value = 1;

Pass variables by reference in JavaScript

I know exactly what you mean. The same thing in Swift will be no problem. The bottom line is use let, not var.

The fact that primitives are passed by value, but the fact that the value of var i at the point of iteration is not copied into the anonymous function is quite surprising to say the least.

for (let i = 0; i < boxArray.length; i++) {
  boxArray[i].onclick = function() { console.log(i) }; // Correctly prints the index

Passing Objects By Reference or Value in C#

In Pass By Reference You only add "ref" in the function parameters and one more thing you should be declaring function "static" because of main is static(#public void main(String[] args))!

namespace preparation
  public  class Program
      public static void swap(ref int lhs,ref int rhs)
          int temp = lhs;
          lhs = rhs;
          rhs = temp;
          static void Main(string[] args)
            int a = 10;
            int b = 80;

  Console.WriteLine("a is before sort " + a);
            Console.WriteLine("b is before sort " + b);
            swap(ref a, ref b);
            Console.WriteLine("a is after sort " + a);
            Console.WriteLine("b is after sort " + b);  

Default value to a parameter while passing by reference in C++

virtual const ULONG Write(ULONG &State = 0, bool sequence = true);

The answer is quite simple and I am not so good on explaining but if you want to pass a default value to a non-const parameter which probably will be modified in this function is to use it like this:

virtual const ULONG Write(ULONG &State = *(ULONG*)0, bool sequence =
> true);

Are there benefits of passing by pointer over passing by reference in C++?

A pointer can receive a NULL parameter, a reference parameter can not. If there's ever a chance that you could want to pass "no object", then use a pointer instead of a reference.

Also, passing by pointer allows you to explicitly see at the call site whether the object is passed by value or by reference:

// Is mySprite passed by value or by reference?  You can't tell 
// without looking at the definition of func()

// func2 passes "by pointer" - no need to look up function definition

How to pass objects to functions in C++?

Do I need to pass pointers, references, or non-pointer and non-reference values?

This is a question that matters when writing a function and choosing the types of the parameters it takes. That choice will affect how the function is called and it depends on a few things.

The simplest option is to pass objects by value. This basically creates a copy of the object in the function, which has many advantages. But sometimes copying is costly, in which case a constant reference, const&, is usually best. And sometimes you need your object to be changed by the function. Then a non-constant reference, &, is needed.

For guidance on the choice of parameter types, see the Functions section of the C++ Core Guidelines, starting with F.15. As a general rule, try to avoid raw pointers, *.

Is Ruby pass by reference or by value?

Try this:--

#=> 3

#=> 5

a = 1
#=> 1
#=> 3

b = 2
#=> 2
#=> 5

identifier a contains object_id 3 for value object 1 and identifier b contains object_id 5 for value object 2.

Now do this:--

a.object_id = 5
#=> error

a = b
#value(object_id) at b copies itself as value(object_id) at a. value object 2 has object_id 5
#=> 2

#=> 5

Now, a and b both contain same object_id 5 which refers to value object 2. So, Ruby variable contains object_ids to refer to value objects.

Doing following also gives error:--

#=> error

but doing this won't give error:--

#=> 11

c = 5
#=> value object 5 provides return type for variable c and saves 5.object_id i.e. 11 at c
#=> 5
#=> 11 

a = c.object_id
#=> object_id of c as a value object changes value at a
#=> 11
#=> 23
a.object_id == 11.object_id
#=> true

#=> Value at a
#=> 11

Here identifier a returns value object 11 whose object id is 23 i.e. object_id 23 is at identifier a, Now we see an example by using method.

def foo(arg)
  p arg
  p arg.object_id
#=> nil
#=> 23
x = 11
#=> 11
#=> 23
#=> 11
#=> 23

arg in foo is assigned with return value of x. It clearly shows that argument is passed by value 11, and value 11 being itself an object has unique object id 23.

Now see this also:--

def foo(arg)
  p arg
  p arg.object_id
  arg = 12
  p arg
  p arg.object_id

#=> nil
#=> 23
x = 11
#=> 11
#=> 23
#=> 11
#=> 23
#=> 12
#=> 25
#=> 11
#=> 23

Here, identifier arg first contains object_id 23 to refer 11 and after internal assignment with value object 12, it contains object_id 25. But it does not change value referenced by identifier x used in calling method.

Hence, Ruby is pass by value and Ruby variables do not contain values but do contain reference to value object.

JavaScript by reference vs. by value

Yes, Javascript always passes by value, but in an array or object, the value is a reference to it, so you can 'change' the contents.

But, I think you already read it on SO; here you have the documentation you want:

How can I pass a reference to a function, with parameters?

What you are after is called partial function application.

Don't be fooled by those that don't understand the subtle difference between that and currying, they are different.

Partial function application can be used to implement, but is not currying. Here is a quote from a blog post on the difference:

Where partial application takes a function and from it builds a function which takes fewer arguments, currying builds functions which take multiple arguments by composition of functions which each take a single argument.

This has already been answered, see this question for your answer: How can I pre-set arguments in JavaScript function call?


var fr = partial(f, 1, 2, 3);

// now, when you invoke fr() it will invoke f(1,2,3)

Again, see that question for the details.

Passing a String by Reference in Java?

java.lang.String is immutable.

I hate pasting URLs but is essential for you to read and understand if you're in java-land.

Why use the 'ref' keyword when passing an object?

In .NET when you pass any parameter to a method, a copy is created. In value types means that any modification you make to the value is at the method scope, and is lost when you exit the method.

When passing a Reference Type, a copy is also made, but it is a copy of a reference, i.e. now you have TWO references in memory to the same object. So, if you use the reference to modify the object, it gets modified. But if you modify the reference itself - we must remember it is a copy - then any changes are also lost upon exiting the method.

As people have said before, an assignment is a modification of the reference, thus is lost:

public void Method1(object obj) {   
 obj = new Object(); 

public void Method2(object obj) {  
 obj = _privateObject; 

The methods above does not modifies the original object.

A little modification of your example

 using System;

    class Program
            static void Main(string[] args)
                TestRef t = new TestRef();
                t.Something = "Foo";



            static public void DoSomething(TestRef t)
                t = new TestRef();
                t.Something = "Bar";

    public class TestRef
    private string s;
        public string Something 
            get {return s;} 
            set { s = value; }

List passed by ref - help me explain this behaviour

C# just does a shallow copy when it passes by value unless the object in question executes ICloneable (which apparently the List class does not).

What this means is that it copies the List itself, but the references to the objects inside the list remain the same; that is, the pointers continue to reference the same objects as the original List.

If you change the values of the things your new List references, you change the original List also (since it is referencing the same objects). However, you then change what myList references entirely, to a new List, and now only the original List is referencing those integers.

Read the Passing Reference-Type Parameters section from this MSDN article on "Passing Parameters" for more information.

"How do I Clone a Generic List in C#" from StackOverflow talks about how to make a deep copy of a List.

Are PHP Variables passed by value or by reference?

For anyone who comes across this in the future, I want to share this gem from the PHP docs, posted by an anonymous user:

There seems to be some confusion here. The distinction between pointers and references is not particularly helpful. The behavior in some of the "comprehensive" examples already posted can be explained in simpler unifying terms. Hayley's code, for example, is doing EXACTLY what you should expect it should. (Using >= 5.3)

First principle: A pointer stores a memory address to access an object. Any time an object is assigned, a pointer is generated. (I haven't delved TOO deeply into the Zend engine yet, but as far as I can see, this applies)

2nd principle, and source of the most confusion: Passing a variable to a function is done by default as a value pass, ie, you are working with a copy. "But objects are passed by reference!" A common misconception both here and in the Java world. I never said a copy OF WHAT. The default passing is done by value. Always. WHAT is being copied and passed, however, is the pointer. When using the "->", you will of course be accessing the same internals as the original variable in the caller function. Just using "=" will only play with copies.

3rd principle: "&" automatically and permanently sets another variable name/pointer to the same memory address as something else until you decouple them. It is correct to use the term "alias" here. Think of it as joining two pointers at the hip until forcibly separated with "unset()". This functionality exists both in the same scope and when an argument is passed to a function. Often the passed argument is called a "reference," due to certain distinctions between "passing by value" and "passing by reference" that were clearer in C and C++.

Just remember: pointers to objects, not objects themselves, are passed to functions. These pointers are COPIES of the original unless you use "&" in your parameter list to actually pass the originals. Only when you dig into the internals of an object will the originals change.

And here's the example they provide:


//The two are meant to be the same
$a = "Clark Kent"; //a==Clark Kent
$b = &$a; //The two will now share the same fate.

$b="Superman"; // $a=="Superman" too.
echo $a;
echo $a="Clark Kent"; // $b=="Clark Kent" too.
unset($b); // $b divorced from $a
echo $a; // $a=="Clark Kent" still, since $b is a free agent pointer now.

//The two are NOT meant to be the same.
$d="Pretender to the Throne";
echo $c."\n"; // $c=="King"
echo $d."\n"; // $d=="Pretender to the Throne"
swapByValue($c, $d);
echo $c."\n"; // $c=="King"
echo $d."\n"; // $d=="Pretender to the Throne"
swapByRef($c, $d);
echo $c."\n"; // $c=="Pretender to the Throne"
echo $d."\n"; // $d=="King"

function swapByValue($x, $y){
//All this beautiful work will disappear
//because it was done on COPIES of pointers.
//The originals pointers still point as they did.

function swapByRef(&$x, &$y){
//Note the parameter list: now we switched 'em REAL good.


I wrote an extensive, detailed blog post on this subject for JavaScript, but I believe it applies equally well to PHP, C++, and any other language where people seem to be confused about pass by value vs. pass by reference.

Clearly, PHP, like C++, is a language that does support pass by reference. By default, objects are passed by value. When working with variables that store objects, it helps to see those variables as pointers (because that is fundamentally what they are, at the assembly level). If you pass a pointer by value, you can still "trace" the pointer and modify the properties of the object being pointed to. What you cannot do is have it point to a different object. Only if you explicitly declare a parameter as being passed by reference will you be able to do that.

Is Java "pass-by-reference" or "pass-by-value"?

Basically, reassigning Object parameters doesn't affect the argument, e.g.,

private void foo(Object bar) {
    bar = null;

public static void main(String[] args) {
    String baz = "Hah!";

will print out "Hah!" instead of null. The reason this works is because bar is a copy of the value of baz, which is just a reference to "Hah!". If it were the actual reference itself, then foo would have redefined baz to null.

Does JavaScript pass by reference?

JavaScript is pass by value.

For primitives, primitive's value is passed. For Objects, Object's reference "value" is passed.

Example with Object:

var f1 = function(inputObject){
    inputObject.a = 2;

var f2 = function(){
    var inputObject = {"a": 1};

Calling f2 results in printing out "a" value as 2 instead of 1, as the reference is passed and the "a" value in reference is updated.

Example with primitive:

var f1 = function(a){
    a = 2;
var f2 = function(){
    var a = 1;

Calling f2 results in printing out "a" value as 1.

Is JavaScript a pass-by-reference or pass-by-value language?

It's always pass by value, but for objects the value of the variable is a reference. Because of this, when you pass an object and change its members, those changes persist outside of the function. This makes it look like pass by reference. But if you actually change the value of the object variable you will see that the change does not persist, proving it's really pass by value.


function changeObject(x) {_x000D_
  x = { member: "bar" };_x000D_
  console.log("in changeObject: " + x.member);_x000D_
function changeMember(x) {_x000D_
  x.member = "bar";_x000D_
  console.log("in changeMember: " + x.member);_x000D_
var x = { member: "foo" };_x000D_
console.log("before changeObject: " + x.member);_x000D_
console.log("after changeObject: " + x.member); /* change did not persist */_x000D_
console.log("before changeMember: " + x.member);_x000D_
console.log("after changeMember: " + x.member); /* change persists */


before changeObject: foo
in changeObject: bar
after changeObject: foo

before changeMember: foo
in changeMember: bar
after changeMember: bar

Are arrays in PHP copied as value or as reference to new variables, and when passed to functions?

By default

  1. Primitives are passed by value. Unlikely to Java, string is primitive in PHP
  2. Arrays of primitives are passed by value
  3. Objects are passed by reference
  4. Arrays of objects are passed by value (the array) but each object is passed by reference.

    $obj=new stdClass();
    function example($hello) {
        $hello[0]->field='mundo'; // change will be applied in $original
        $hello[1]=new stdClass(); // change will not be applied in $original
    // array(1) { [0]=> object(stdClass)#1 (1) { ["field"]=> string(5) "mundo" } } 

Note: As an optimization, every single value is passed as reference until its modified inside the function. If it's modified and the value was passed by reference then, it's copied and the copy is modified.

How can I pass an Integer class correctly by reference?

There are two problems:

  1. Integer is pass by value, not by reference. Changing the reference inside a method won't be reflected into the passed-in reference in the calling method.
  2. Integer is immutable. There's no such method like Integer#set(i). You could otherwise just make use of it.

To get it to work, you need to reassign the return value of the inc() method.

integer = inc(integer);

To learn a bit more about passing by value, here's another example:

public static void main(String... args) {
    String[] strings = new String[] { "foo", "bar" };
    System.out.println(Arrays.toString(strings)); // still [foo, bar]
    System.out.println(Arrays.toString(strings)); // [foo, foo]
public static void changeReference(String[] strings) {
    strings = new String[] { "foo", "foo" };
public static void changeValue(String[] strings) {
    strings[1] = "foo";

How to do the equivalent of pass by reference for primitives in Java

public static void main(String[] args) {
    int[] toyNumber = new int[] {5};
    NewClass temp = new NewClass();;
    System.out.println("Toy number in main " + toyNumber[0]);

void play(int[] toyNumber){
    System.out.println("Toy number in play " + toyNumber[0]);
    System.out.println("Toy number in play after increement " + toyNumber[0]);

change values in array when doing foreach

The callback is passed the element, the index, and the array itself.

arr.forEach(function(part, index, theArray) {
  theArray[index] = "hello world";

edit — as noted in a comment, the .forEach() function can take a second argument, which will be used as the value of this in each call to the callback:

arr.forEach(function(part, index) {
  this[index] = "hello world";
}, arr); // use arr as this

That second example shows arr itself being set up as this in the callback.One might think that the array involved in the .forEach() call might be the default value of this, but for whatever reason it's not; this will be undefined if that second argument is not provided.

(Note: the above stuff about this does not apply if the callback is a => function, because this is never bound to anything when such functions are invoked.)

Also it's important to remember that there is a whole family of similar utilities provided on the Array prototype, and many questions pop up on Stackoverflow about one function or another such that the best solution is to simply pick a different tool. You've got:

  • forEach for doing a thing with or to every entry in an array;
  • filter for producing a new array containing only qualifying entries;
  • map for making a one-to-one new array by transforming an existing array;
  • some to check whether at least one element in an array fits some description;
  • every to check whether all entries in an array match a description;
  • find to look for a value in an array

and so on. MDN link

How do I pass a variable by reference?

alternatively you could use ctypes witch would look something like this

import ctypes

def f(a):
    a.value=2398 ## resign the value in a function

a = ctypes.c_int(0)
print("pre f", a)
print("post f", a)

as a is a c int and not a python integer and apperently passed by reference. however you have to be carefull as strange things could happen and is therefor not advised

Call-time pass-by-reference has been removed

Only call time pass-by-reference is removed. So change:

call_user_func($func, &$this, &$client ...

To this:

call_user_func($func, $this, $client ...

&$this should never be needed after PHP4 anyway period.

If you absolutely need $client to be passed by reference, update the function ($func) signature instead (function func(&$client) {)

Is there an alternative to string.Replace that is case-insensitive?

Let me make my case and then you can tear me to shreds if you like.

Regex is not the answer for this problem - too slow and memory hungry, relatively speaking.

StringBuilder is much better than string mangling.

Since this will be an extension method to supplement string.Replace, I believe it important to match how that works - therefore throwing exceptions for the same argument issues is important as is returning the original string if a replacement was not made.

I believe that having a StringComparison parameter is not a good idea. I did try it but the test case originally mentioned by michael-liu showed a problem:-

[TestCase("œ", "oe", "", StringComparison.InvariantCultureIgnoreCase, Result = "")]

Whilst IndexOf will match, there is a mismatch between the length of the match in the source string (1) and oldValue.Length (2). This manifested itself by causing IndexOutOfRange in some other solutions when oldValue.Length was added to the current match position and I could not find a way around this. Regex fails to match the case anyway, so I took the pragmatic solution of only using StringComparison.OrdinalIgnoreCase for my solution.

My code is similar to other answers but my twist is that I look for a match before going to the trouble of creating a StringBuilder. If none is found then a potentially large allocation is avoided. The code then becomes a do{...}while rather than a while{...}

I have done some extensive testing against other Answers and this came out fractionally faster and used slightly less memory.

    public static string ReplaceCaseInsensitive(this string str, string oldValue, string newValue)
        if (str == null) throw new ArgumentNullException(nameof(str));
        if (oldValue == null) throw new ArgumentNullException(nameof(oldValue));
        if (oldValue.Length == 0) throw new ArgumentException("String cannot be of zero length.", nameof(oldValue));

        var position = str.IndexOf(oldValue, 0, StringComparison.OrdinalIgnoreCase);
        if (position == -1) return str;

        var sb = new StringBuilder(str.Length);

        var lastPosition = 0;

            sb.Append(str, lastPosition, position - lastPosition);


        } while ((position = str.IndexOf(oldValue, lastPosition = position + oldValue.Length, StringComparison.OrdinalIgnoreCase)) != -1);

        sb.Append(str, lastPosition, str.Length - lastPosition);

        return sb.ToString();

How to create an empty DataFrame with a specified schema?

Lets assume you want a data frame with the following schema:

 |-- k: string (nullable = true)
 |-- v: integer (nullable = false)

You simply define schema for a data frame and use empty RDD[Row]:

import org.apache.spark.sql.types.{
    StructType, StructField, StringType, IntegerType}
import org.apache.spark.sql.Row

val schema = StructType(
    StructField("k", StringType, true) ::
    StructField("v", IntegerType, false) :: Nil)

// Spark < 2.0
// sqlContext.createDataFrame(sc.emptyRDD[Row], schema) 
spark.createDataFrame(sc.emptyRDD[Row], schema)

PySpark equivalent is almost identical:

from pyspark.sql.types import StructType, StructField, IntegerType, StringType

schema = StructType([
    StructField("k", StringType(), True), StructField("v", IntegerType(), False)

# or df = sc.parallelize([]).toDF(schema)

# Spark < 2.0 
# sqlContext.createDataFrame([], schema)
df = spark.createDataFrame([], schema)

Using implicit encoders (Scala only) with Product types like Tuple:

import spark.implicits._

Seq.empty[(String, Int)].toDF("k", "v")

or case class:

case class KV(k: String, v: Int)




Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0

It work for me in this issue in a project of react-native:

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.

244 actionable tasks: 2 executed, 242 up-to-date D8: Cannot fit requested classes in a single dex file (# fields: 67296 > 65536) Error while merging dex archives: The number of method references in a .dex file cannot exceed 64K. Learn how to resolve this issue at ....

I Did this:

File upload progress bar with jQuery

I have used the following in my project. you can try too.

ajax = new XMLHttpRequest();
ajax.onreadystatechange = function () {

    if (ajax.status) {

        if (ajax.status == 200 && (ajax.readyState == 4)){
            //To do tasks if any, when upload is completed
ajax.upload.addEventListener("progress", function (event) {

    var percent = (event.loaded / * 100;
    //**percent** variable can be used for modifying the length of your progress bar.

});"POST", 'your file upload link', true);
//ajax.send is for uploading form data.

Dynamically set value of a file input

I had similar problem, then I tried writing this from JavaScript and it works! : referenceToYourInputFile.value = "" ;

How to find all links / pages on a website

function getalllinks($url) {
    $links = array();
    if ($fp = fopen($url, 'r')) {
        $content = '';
        while ($line = fread($fp, 1024)) {
            $content. = $line;
    $textLen = strlen($content);
    if ($textLen > 10) {
        $startPos = 0;
        $valid = true;
        while ($valid) {
            $spos = strpos($content, '<a ', $startPos);
            if ($spos < $startPos) $valid = false;
            $spos = strpos($content, 'href', $spos);
            $spos = strpos($content, '"', $spos) + 1;
            $epos = strpos($content, '"', $spos);
            $startPos = $epos;
            $link = substr($content, $spos, $epos - $spos);
            if (strpos($link, 'http://') !== false) $links[] = $link;
    return $links;

try this code....

Comparing mongoose _id and strings

Mongoose uses the mongodb-native driver, which uses the custom ObjectID type. You can compare ObjectIDs with the .equals() method. With your example, results.userId.equals(AnotherMongoDocument._id). The ObjectID type also has a toString() method, if you wish to store a stringified version of the ObjectID in JSON format, or a cookie.

If you use ObjectID = require("mongodb").ObjectID (requires the mongodb-native library) you can check if results.userId is a valid identifier with results.userId instanceof ObjectID.


How to change folder with git bash?

I wanted to add that if you are using a shared drive, enclose the path in double quotes and keep the backslashes. This is what worked for me:

$cd /path/to/"\\\share\users\username\My Documents\mydirectory\"

I ran into a merge conflict. How can I abort the merge?

I found the following worked for me (revert a single file to pre-merge state):

git reset *currentBranchIntoWhichYouMerged* -- *fileToBeReset*

How to calculate number of days between two given dates?

everyone has answered excellently using the date, let me try to answer it using pandas

dt = pd.to_datetime('2008/08/18', format='%Y/%m/%d')
dt1 = pd.to_datetime('2008/09/26', format='%Y/%m/%d')


This will give the answer. In case one of the input is dataframe column. simply use dt.days in place of days


Wait 5 seconds before executing next line

using angularjs:


Regular expression that doesn't contain certain string

All you need is a reluctant quantifier:

regex: /aa.*?aa/

aabbabcaabda   => aabbabcaa

aaaaaabda      => aaaa

aabbabcaabda   => aabbabcaa

aababaaaabdaa  => aababaa, aabdaa

You could use negative lookahead, too, but in this case it's just a more verbose way accomplish the same thing. Also, it's a little trickier than gpojd made it out to be. The lookahead has to be applied at each position before the dot is allowed to consume the next character.


As for the approach suggested by Claudiu and finnw, it'll work okay when the sentinel string is only two characters long, but (as Claudiu acknowledged) it's too unwieldy for longer strings.

What are major differences between C# and Java?

C# has automatic properties which are incredibly convenient and they also help to keep your code cleaner, at least when you don't have custom logic in your getters and setters.

How to format a DateTime in PowerShell

I needed the time and a slight variation on format. This works great for my purposes:

$((get-date).ToLocalTime()).ToString("yyyy-MM-dd HHmmss")

2019-08-16 215757

According to @mklement0 in comments, this should yield the same result:

(get-date).ToString("yyyy-MM-dd HHmmss")

How to re-sync the Mysql DB if Master and slave have different database incase of Mysql replication?

Here is a complete answer that will hopefully help others...

I want to setup mysql replication using master and slave, and since the only thing I knew was that it uses log file(s) to synchronize, if the slave goes offline and gets out of sync, in theory it should only need to connect back to its master and keep reading the log file from where it left off, as user malonso mentioned.

So here are the test result after configuring the master and slave as mentioned by: ...

Provided you use the recommended master/slave configuration and don't write to the slave, he and I where right (as far as mysql-server 5.x is concerned). I didn't even need to use "START SLAVE;", it just caught up to its master. But there is a default 88000 something retries every 60 second so I guess if you exhaust that you might have to start or restart the slave. Anyways, for those like me who wanted to know if having a slave going offline and back up again requires manual intervention.. no, it doesn't.

Maybe the original poster had corruption in the log-file(s)? But most probably not just a server going off-line for a day.

pulled from /usr/share/doc/mysql-server-5.1/README.Debian.gz which probably makes sense to non debian servers as well:

If the MySQL server is acting as a replication slave, you should not
set --tmpdir to point to a directory on a memory-based filesystem or to
a directory that is cleared when the server host restarts. A replication
slave needs some of its temporary files to survive a machine restart so
that it can replicate temporary tables or LOAD DATA INFILE operations. If
files in the temporary file directory are lost when the server restarts,
replication fails.

you can use something sql like: show variables like 'tmpdir'; to find out.

Animate scroll to ID on page load

Pure javascript solution with scrollIntoView() function:

document.getElementById('title1').scrollIntoView({block: 'start', behavior: 'smooth'});
<h2 id="title1">Some title</h2>

P.S. 'smooth' parameter now works from Chrome 61 as julien_c mentioned in the comments.

How do I convert from BLOB to TEXT in MySQL?

You can do it very easily.

ALTER TABLE `table_name` CHANGE COLUMN `column_name` `column_name` LONGTEXT NULL DEFAULT NULL ;

The above query worked for me. I hope it helps you too.

Open youtube video in Fancybox jquery

This has a regular expression so it's easier to just copy and paste the youtube url. Is great for when you use a CMS for clients.

/*fancybox yt video*/
$(".fancybox-video").click(function() {

    padding: 0,
        'autoScale'     : false,
        'transitionIn'  : 'none',
        'transitionOut' : 'none',
        'title'         : this.title,
        'width'         : 795,
        'height'        : 447,
        'href'          : this.href.replace(new RegExp("watch.*v=","i"), "v/"),
        'type'          : 'swf',
        'swf'           : {
        'wmode'             : 'transparent',
        'allowfullscreen'   : 'true'

    return false;

Find the 2nd largest element in an array with minimum number of comparisons

Suppose provided array is inPutArray = [1,2,5,8,7,3] expected O/P -> 7 (second largest)

 take temp array 
      temp = [0,0], int dummmy=0;
    for (no in inPutArray) {
     temp[1] = no
    dummmy = temp[0]
    temp[0] = temp[1]
    temp[1] = temp

    print("Second largest no is %d",temp[1])

"Invalid form control" only in Google Chrome

I was getting this error, and determined it was actually on a field that was not hidden.

In this case, it was a type="number" field, that is required. When no value has ever been entered into this field, the error message is shown in the console, and the form is not submitted. Entering a value, and then removing it means that the validation error is shown as expected.

I believe this is a bug in Chrome: my workaround for now was to come up with an initial/default value.

How to debug Google Apps Script (aka where does Logger.log log to?)

Currently you are confined to the container bound nature of using scripts within docs. If you create a new script inside outside of docs then you will be able to export information to a google spreadsheet and use it like a logging tool.

For example in your first code block

function setCheckboxes() {

    // Add your spreadsheet data
    var errorSheet = SpreadsheetApp.openById('EnterSpreadSheetIDHere').getSheetByName('EnterSheetNameHere');
    var cell = errorSheet.getRange('A1').offset(errorSheet.getLastRow(),0);

    // existing code
    var checklist = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("checklist");
    var checklist_data_range = checklist.getDataRange();
    var checklist_num_rows = checklist_data_range.getNumRows();

    // existing logger
    Logger.log("checklist num rows: " + checklist_num_rows);

   //We can pass the information to the sheet using cell.setValue()
    cell.setValue(new Date() + "Checklist num rows: " + checklist_num_rows);

When I'm working with GAS I have two monitors ( you can use two windows ) set up with one containing the GAS environment and the other containing the SS so I can write information to and log.

Receiver not registered exception error?

For anybody who will come upon this problem and they tried all that was suggested and nothing still works, this is how I sorted my problem, instead of doing LocalBroadcastManager.getInstance(this).registerReceiver(...) I first created a local variable of type LocalBroadcastManager,

private LocalBroadcastManager lbman;

And used this variable to carry out the registering and unregistering on the broadcastreceiver, that is




Integrating Dropzone.js into existing HTML form with other fields

This is just another example of how you can use Dropzone.js in an existing form.

dropzone.js :

 init: function() {

   this.on("success", function(file, responseText) {
     //alert("HELLO ?" + responseText); 

   return noop;

Then, later in the file I put

function mylittlefix(responseText) {
  $('#botofform').append('<input type="hidden" name="files[]" value="'+ responseText +'">');

This assumes you have a div with id #botofform that way when uploading you can use the uploaded files' names.

Note: my upload script returned theuploadedfilename.jpeg dubblenote you also would need to make a cleanup script that checks the upload directory for files not in use and deletes them ..if in a front end non authenticated form :)

Checking if a variable is initialized

There is no way of checking of the contents of a variable are undefined or not. The best thing you can do is to assign a signal/sentinel value (for example in the constructor) to indicate that further initialization will need to be carried out.

Decimal separator comma (',') with numberDecimal inputType in EditText

to get localize your input use:

char sep = DecimalFormatSymbols.getInstance().getDecimalSeparator();

and then add:

textEdit.setKeyListener(DigitsKeyListener.getInstance("0123456789" + sep));

than don't forget to replace "," with "." so Float or Double can parse it without errors.

PHP Get Highest Value from Array

You need to use by ksort(array("a"=>1,"b"=>2,"c"=>4,"d"=>5)); for more info:

Singleton design pattern vs Singleton beans in Spring container

Singleton beans in Spring and classes based on Singleton design pattern are quite different.

Singleton pattern ensures that one and only one instance of a particular class will ever be created per classloader where as the scope of a Spring singleton bean is described as 'per container per bean'. Singleton scope in Spring means that this bean will be instantiated only once by Spring. Spring container merely returns the same instance again and again for subsequent calls to get the bean.

Insert picture/table in R Markdown

When it comes to inserting a picture, r2evans's suggestion of ![Caption for the picture.](/path/to/image.png) can be problematic if PDF output is required.

The knitr function include_graphics knitr::include_graphics('/path/to/image.png') is a more portable alternative that will generate, on your behalf, the markdown that is most appropriate to the output format that you are generating.

data.frame Group By column

This is a common question. In base, the option you're looking for is aggregate. Assuming your data.frame is called "mydf", you can use the following.

> aggregate(B ~ A, mydf, sum)
  A  B
1 1  5
2 2  3
3 3 11

I would also recommend looking into the "data.table" package.

> library(data.table)
> DT <- data.table(mydf)
> DT[, sum(B), by = A]
   A V1
1: 1  5
2: 2  3
3: 3 11

How do I add python3 kernel to jupyter (IPython)

Shortest and best solution from my side

conda create --name py3-ml python=3.6
conda install ipykernel

source activate py3-ml # or conda activate py3-ml
python -m ipykernel install --user --name py3-ml

Android : How to set onClick event for Button in List item of ListView

Try This,

public View getView(final int position, View convertView,ViewGroup parent) 
   if(convertView == null)
        LayoutInflater inflater = getLayoutInflater();
        convertView  = (LinearLayout)inflater.inflate(R.layout.YOUR_LAYOUT, null);

   Button Button1= (Button)  convertView  .findViewById(;

   Button1.setOnClickListener(new OnClickListener() 
       public void onClick(View v) 
           // Your code that you want to execute on this button click


   return convertView ;

It may help you....

Node.js heap out of memory

I just want to add that in some systems, even increasing the node memory limit with --max-old-space-size, it's not enough and there is an OS error like this:

terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc
Aborted (core dumped)

In this case, probably is because you reached the max mmap per process.

You can check the max_map_count by running

sysctl vm.max_map_count

and increas it by running

sysctl -w vm.max_map_count=655300

and fix it to not be reset after a reboot by adding this line


in /etc/sysctl.conf file.

Check here for more info.

A good method to analyse the error is by run the process with strace

strace node --max-old-space-size=128000 my_memory_consuming_process.js

How to find substring from string?

As user1511510 has identified, there's an unusual case when abc is at the end of the file name. We need to look for either /abc/ or /abc followed by a string-terminator '\0'. A naive way to do this would be to check if either /abc/ or /abc\0 are substrings:

#include <stdio.h>
#include <string.h>

int main() {
    const char *str = "/user/desktop/abc";
    const int exists = strstr(str, "/abc/") || strstr(str, "/abc\0");
    return 0;

but exists will be 1 even if abc is not followed by a null-terminator. This is because the string literal "/abc\0" is equivalent to "/abc". A better approach is to test if /abc is a substring, and then see if the character after this substring (indexed using the pointer returned by strstr()) is either a / or a '\0':

#include <stdio.h>
#include <string.h>

int main() {
    const char *str = "/user/desktop/abc", *substr;
    const int exists = (substr = strstr(str, "/abc")) && (substr[4] == '\0' || substr[4] == '/');
    return 0;

This should work in all cases.

How to create a list of objects?

if my_list is the list that you want to store your objects in it and my_object is your object wanted to be stored, use this structure:


Adding a collaborator to my free GitHub account?

Go to Manage Access page under settings ( and add the collaborators as needed.


enter image description here

angularjs getting previous route path

This is how I currently store a reference to the previous path in the $rootScope:

run(['$rootScope', function($rootScope) {
        $rootScope.$on('$locationChangeStart', function() {
            $rootScope.previousPage = location.pathname;

What is the use of reads from the standard input.

The standard input can be used to get input from user in a console environment but, as such user interface has no editing facilities, the interactive use of standard input is restricted to courses that teach programming.

Most production use of standard input is in programs designed to work inside Unix command-line pipelines. In such programs the payload that the program is processing is coming from the standard input and the program's result gets written to the standard output. In that case the standard input is never written directly by the user, it is the redirected output of another program or the contents of a file.

A typical pipeline looks like this:

# list files and directories ordered by increasing size
du -s * | sort -n

sort reads its data from the standard input, which is in fact the output of the du command. The sorted data is written to the standard output of sort, which ends up on the console by default, and can be easily redirected to a file or to another command.

As such, the standard input is comparatively rarely used in Java.

Excel formula to reference 'CELL TO THE LEFT'


How to install ia32-libs in Ubuntu 14.04 LTS (Trusty Tahr)

The problem is that in many cases the packages are multiarch already so the i386 package is not available, but other packages still depend on the i386 package only. This is a problem in the repository, and the managers of the repos should fix it

trying to align html button at the center of the my page

There are multiple ways to fix the same. PFB two of them -

1st Way using position: fixed - position: fixed; positions relative to the viewport, which means it always stays in the same place even if the page is scrolled. Adding the left and top value to 50% will place it into the middle of the screen.

 button {
   position: fixed;
   left: 50%;

2nd Way using margin: auto -margin: 0 auto; for horizontal centering, but margin: auto; has refused to work for vertical centering… until now! But actually absolute centering only requires a declared height and these styles:

button {
  margin: auto;
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  height: 40px;

Best way to reset an Oracle sequence to the next value in an existing column?

These two procedures let me reset the sequence and reset the sequence based on data in a table (apologies for the coding conventions used by this client):

   l_num   NUMBER;
   EXECUTE IMMEDIATE 'select ' || p_name || '.nextval from dual' INTO l_num;

   -- Added check for 0 to avoid "ORA-04002: INCREMENT must be a non-zero integer"
   IF (p_val - l_num - 1) != 0
      EXECUTE IMMEDIATE 'alter sequence ' || p_name || ' increment by ' || (p_val - l_num - 1) || ' minvalue 0';
   END IF;

   EXECUTE IMMEDIATE 'select ' || p_name || '.nextval from dual' INTO l_num;

   EXECUTE IMMEDIATE 'alter sequence ' || p_name || ' increment by 1 ';

   DBMS_OUTPUT.put_line('Sequence ' || p_name || ' is now at ' || p_val);

   nextnum   NUMBER;
   EXECUTE IMMEDIATE 'SELECT MAX(' || col_name || ') + 1 AS n FROM ' || table_name INTO nextnum;

   SET_SEQ_TO(seq_name, nextnum);

How to run code after some delay in Flutter?

Figured it out

class AnimatedFlutterLogo extends StatefulWidget {
  State<StatefulWidget> createState() => new _AnimatedFlutterLogoState();

class _AnimatedFlutterLogoState extends State<AnimatedFlutterLogo> {
  Timer _timer;
  FlutterLogoStyle _logoStyle = FlutterLogoStyle.markOnly;

  _AnimatedFlutterLogoState() {
    _timer = new Timer(const Duration(milliseconds: 400), () {
      setState(() {
        _logoStyle = FlutterLogoStyle.horizontal;

  void dispose() {

  Widget build(BuildContext context) {
    return new FlutterLogo(
      size: 200.0,
      textColor: Palette.white,
      style: _logoStyle,

Looping through a hash, or using an array in PowerShell

About looping through a hash:

$Q = @{"ONE"="1";"TWO"="2";"THREE"="3"}

$Q.GETENUMERATOR() | % { $_.key }

The type or namespace name 'Entity' does not exist in the namespace 'System.Data'

I had the same errors.

I added System.Data.Entity.Repository from Nuget Packages and the errors disappears.

Hope it wil help!

Twig ternary operator, Shorthand if-then-else

{{ ( in company_abilities) ? 'selected' : '' }}

The ternary operator is documented under 'other operators'

Angularjs - simple form submit

WARNING This is for Angular 1.x

If you are looking for Angular (v2+, currently version 8), try this answer or the official guide.


I have rewritten your JS fiddle here:

<div ng-app="myApp">

    <form name="saveTemplateData" action="#" ng-controller="FormCtrl" ng-submit="submitForm()">

        First name:    <br/><input type="text" name="form.firstname">    

        Email Address: <br/><input type="text" ng-model="form.emailaddress"> 

        <textarea rows="3" cols="25">
          Describe your reason for submitting this form ... 

        <input type="radio" ng-model="form.gender" value="female" />Female
        <input type="radio" ng-model="form.gender" value="male" />Male 

        <input type="checkbox" ng-model="form.member" value="true"/> Already a member
        <input type="checkbox" ng-model="form.member" value="false"/> Not a member

        <input type="file" ng-model="form.file_profile" id="file_profile">

        <input type="file" ng-model="form.file_avatar" id="file_avatar">

        <input type="submit">

Here I'm using lots of angular directives(ng-controller, ng-model, ng-submit) where you were using basic html form submission. Normally all alternatives to "The angular way" work, but form submission is intercepted and cancelled by Angular to allow you to manipulate the data before submission

BUT the JSFiddle won't work properly as it doesn't allow any type of ajax/http post/get so you will have to run it locally.

For general advice on angular form submission see the cookbook examples

UPDATE The cookbook is gone. Instead have a look at the 1.x guide for for form submission

The cookbook for angular has lots of sample code which will help as the docs aren't very user friendly.

Angularjs changes your entire web development process, don't try doing things the way you are used to with JQuery or regular html/js, but for everything you do take a look around for some sample code, as there is almost always an angular alternative.

Simple JavaScript problem: onClick confirm not preventing default action

I use this, works like a charm. No need to have any functions, just inline with your link(s)

onclick="javascript:return confirm('Are you sure you want to delete this comment?')"

How to save an image locally using Python whose URL address I already know?

A solution which works with Python 2 and Python 3:

    from urllib.request import urlretrieve  # Python 3
except ImportError:
    from urllib import urlretrieve  # Python 2

url = ""
urlretrieve(url, "local-filename.jpg")

or, if the additional requirement of requests is acceptable and if it is a http(s) URL:

def load_requests(source_url, sink_path):
    Load a file from an URL (e.g. http).

    source_url : str
        Where to load the file from.
    sink_path : str
        Where the loaded file is stored.
    import requests
    r = requests.get(source_url, stream=True)
    if r.status_code == 200:
        with open(sink_path, 'wb') as f:
            for chunk in r:

count (non-blank) lines-of-code in bash

rgrep . | wc -l

gives the count of non blank lines in the current working directory.

How to serve up images in Angular2?

In angular only one page is requested from server, that is index.html. And index.html and assets folder are on same directory. while putting image in any component give src value like assets\image.png. This will work fine because browser will make request to server for that image and webpack will be able serve that image.

Lodash remove duplicates from array

You could use lodash method _.uniqWith, it is available in the current version of lodash 4.17.2.


var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.uniqWith(objects, _.isEqual);
// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }]

More info:

DateTimePicker: pick both date and time

It is best to use two DateTimePickers for the Job One will be the default for the date section and the second DateTimePicker is for the time portion. Format the second DateTimePicker as follows.

      timePortionDateTimePicker.Format = DateTimePickerFormat.Time;
      timePortionDateTimePicker.ShowUpDown = true;

The Two should look like this after you capture them

Two Date Time Pickers

To get the DateTime from both these controls use the following code

DateTime myDate = datePortionDateTimePicker.Value.Date + 

To assign the DateTime to both these controls use the following code

datePortionDateTimePicker.Value  = myDate.Date;  
timePortionDateTimePicker.Value  = myDate.TimeOfDay; 

Undefined class constant 'MYSQL_ATTR_INIT_COMMAND' with pdo

I just tried with PHP 5.2, and that constant seems to exists :


Gives me :

int 1002

But it seems there is a bug in PHP 5.3, that causes this constant to not exists anymore -- or, at least, not when the mysqlnd driver is used (and it's the one that's configured by default)

I suppose a temporary solution, as suggested on this bug report, could be to directly use the integer 1002 value, instead of the contant...

But note that you should go back to using the constant as soon as possible -- as this makes the code easier to understand.

Get Date Object In UTC format in Java

In java 8 , It's really easy to get timestamp in UTC by using java 8 java.time.Instant library :;

That few word of code will return the UTC Timestamp.

MySQL Nested Select Query?

You just need to write the first query as a subquery (derived table), inside parentheses, pick an alias for it (t below) and alias the columns as well.

The DISTINCT can also be safely removed as the internal GROUP BY makes it redundant:

SELECT DATE(`date`) AS `date` , COUNT(`player_name`) AS `player_count`
    SELECT MIN(`date`) AS `date`, `player_name`
    FROM `player_playtime`
    GROUP BY `player_name`
) AS t

Since the COUNT is now obvious that is only counting rows of the derived table, you can replace it with COUNT(*) and further simplify the query:

SELECT , COUNT(*) AS player_count
    SELECT DATE(MIN(`date`)) AS date
    FROM player_playtime
    GROUP BY player_name
) AS t

Detect when input has a 'readonly' attribute

Try a simple way:


Merge data frames based on rownames in R

See ?merge:

the name "row.names" or the number 0 specifies the row names.


R> de <- merge(d, e, by=0, all=TRUE)  # merge by row names (by=0 or by="row.names")
R> de[] <- 0                 # replace NA values
R> de
  Row.names   a   b   c   d   e   f   g   h   i  j  k  l  m  n  o  p  q  r  s
1         1 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 11 12 13 14 15 16 17 18 19
2         2 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9  1  0  0  0  0  0  0  0  0  0
3         3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  0 21 22 23 24 25 26 27 28 29
1 20
2  0
3 30

ModelState.AddModelError - How can I add an error that isn't for a property?

You can add the model error on any property of your model, I suggest if there is nothing related to create a new property.

As an exemple we check if the email is already in use in DB and add the error to the Email property in the action so when I return the view, they know that there's an error and how to show it up by using

<%: Html.ValidationSummary(true)%>
<%: Html.ValidationMessageFor(model => model.Email) %>


ModelState.AddModelError("Email", Resources.EmailInUse);

sed command with -i option failing on Mac, but works on Linux

Had the same problem in Mac and solved it with brew:

brew install gnu-sed

and use as


you can set as well set sed as alias to gsed (if you want):

alias sed=gsed

Regex doesn't work in String.matches()

I have faced the same problem once:

Pattern ptr = Pattern.compile("^[a-zA-Z][\\']?[a-zA-Z\\s]+$");

The above failed!

Pattern ptr = Pattern.compile("(^[a-zA-Z][\\']?[a-zA-Z\\s]+$)");

The above worked with pattern within ( and ).

Scrolling an iframe with JavaScript?

A jQuery solution:

$("#frame1").ready( function() {

  $("#frame1").contents().scrollTop( $("#frame1").contents().scrollTop() + 10 );


How to use "like" and "not like" in SQL MSAccess for the same field?

Not sure if this is still extant but I'm guessing you need something like

((field Like "AA*") AND (field Not Like "BB*"))

Changing image sizes proportionally using CSS?

This help me to make the image 150% with ease.

.img-popup img {
  transform: scale(1.5);

How to use setArguments() and getArguments() methods in Fragments?

You have a method called getArguments() that belongs to Fragment class.

What is CMake equivalent of 'configure --prefix=DIR && make all install '?

Regarding Bruce Adams answer:

Your answer creates dangerous confusion. DESTDIR is intended for installs out of the root tree. It allows one to see what would be installed in the root tree if one did not specify DESTDIR. PREFIX is the base directory upon which the real installation is based.

For example, PREFIX=/usr/local indicates that the final destination of a package is /usr/local. Using DESTDIR=$HOME will install the files as if $HOME was the root (/). If, say DESTDIR, was /tmp/destdir, one could see what 'make install' would affect. In that spirit, DESTDIR should never affect the built objects.

A makefile segment to explain it:

    cp program $DESTDIR$PREFIX/bin/program

Programs must assume that PREFIX is the base directory of the final (i.e. production) directory. The possibility of symlinking a program installed in DESTDIR=/something only means that the program does not access files based upon PREFIX as it would simply not work. cat(1) is a program that (in its simplest form) can run from anywhere. Here is an example that won't:

    sed -e "s/@prefix@/$PREFIX/" > prog.pseudo
    compile prog.pseudo

    cp prog $DESTDIR$PREFIX/bin/prog
    cp prog.db $DESTDIR$PREFIX/share/prog.db

If you tried to run prog from elsewhere than $PREFIX/bin/prog, prog.db would never be found as it is not in its expected location.

Finally, /etc/alternatives really does not work this way. There are symlinks to programs installed in the root tree (e.g. vi -> /usr/bin/nvi, vi -> /usr/bin/vim, etc.).

No increment operator (++) in Ruby?

Ruby has no pre/post increment/decrement operator. For instance, x++ or x-- will fail to parse. More importantly, ++x or --x will do nothing! In fact, they behave as multiple unary prefix operators: -x == ---x == -----x == ...... To increment a number, simply write x += 1.

Taken from "Things That Newcomers to Ruby Should Know " (archive, mirror)

That explains it better than I ever could.

EDIT: and the reason from the language author himself (source):

  1. ++ and -- are NOT reserved operator in Ruby.
  2. C's increment/decrement operators are in fact hidden assignment. They affect variables, not objects. You cannot accomplish assignment via method. Ruby uses +=/-= operator instead.
  3. self cannot be a target of assignment. In addition, altering the value of integer 1 might cause severe confusion throughout the program.

How to make this Header/Content/Footer layout using CSS?

Try this


    height: 100%; 
    overflow: auto;
    padding-top: 10px;
    padding-bottom: 40px;
    position: relative;
    margin-top: -30px; /* negative value of footer height */
    height: 30px;


    <div class="Header">Header</div>
    <div class="Content">Content</div>
    <div class="Footer">Footer</div>

How can I configure Logback to log different levels for a logger to different destinations?

I believe this would be the simplest solution:

    <!-- Logging configuration -->  
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <pattern>[%d{yyyy-MM-dd HH:mm:ss.SSS}] [%level] %msg%n</pattern>
    <appender name="STDERR" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <pattern>[%d{yyyy-MM-dd HH:mm:ss.SSS}] [%level] [%thread] %logger{10} [%file:%line] %msg%n</pattern> 
    <root level="INFO">
        <appender-ref ref="STDOUT"/>
        <appender-ref ref="STDERR" />

Reading column names alone in a csv file

I am just mentioning how to get all the column names from a csv file. I am using pandas library.

First we read the file.

import pandas as pd
file = pd.read_csv('details.csv')

Then, in order to just get all the column names as a list from input file use:-

columns = list(file.head(0))

Angular.js ng-repeat filter by property having one of multiple values (OR of values)

After not able to find a good universal solution I made something of my own. I have not tested it for a very large list.

It takes care of nested keys,arrays or just about anything.

Here is the github and demo

app.filter('xf', function() {
    function keyfind(f, obj) {
        if (obj === undefined)
            return -1;
        else {
            var sf = f.split(".");
            if (sf.length <= 1) {
                return obj[sf[0]];
            } else {
                var newobj = obj[sf[0]];
                sf.splice(0, 1);
                return keyfind(sf.join("."), newobj)

    return function(input, clause, fields) {
        var out = [];
        if (clause && clause.query && clause.query.length > 0) {
            clause.query = String(clause.query).toLowerCase();
            angular.forEach(input, function(cp) {
                for (var i = 0; i < fields.length; i++) {
                    var haystack = String(keyfind(fields[i], cp)).toLowerCase();
                    if (haystack.indexOf(clause.query) > -1) {
        } else {
            angular.forEach(input, function(cp) {
        return out;



<input ng-model="search.query" type="text" placeholder="search by any property">
<div ng-repeat="product in products |  xf:search:['color','name']">

How to debug Apache mod_rewrite

Based on Ben's answer you you could do the following when running apache on Linux (Debian in my case).

First create the file rewrite-log.load


RewriteLog "/var/log/apache2/rewrite.log"
RewriteLogLevel 3

Then enter

$ a2enmod rewrite-log

followed by

$ service apache2 restart

And when you finished with debuging your rewrite rules

$ a2dismod rewrite-log && service apache2 restart

Does a "Find in project..." feature exist in Eclipse IDE?

There is no way to do pure text search in whole work workspace/project via a shortcut that I know of (and it is a PITA), but this will find references in the workspace:

  1. Put your cursor on what you want to lookup
  2. Press Ctrl + Shift + g

Compress images on client side before uploading

If you are looking for a library to carry out client-side image compression, you can check this out:compress.js. This will basically help you compress multiple images purely with JavaScript and convert them to base64 string. You can optionally set the maximum size in MB and also the preferred image quality.

How to use background thread in swift?

in Swift 4.2 this works.

import Foundation

class myThread: Thread
    override func main() {
        while(true) {
            print("Running in the Thread");
            Thread.sleep(forTimeInterval: 4);

let t = myThread();

while(true) {
    print("Main Loop");

What is an unsigned char?

In terms of direct values a regular char is used when the values are known to be between CHAR_MIN and CHAR_MAX while an unsigned char provides double the range on the positive end. For example, if CHAR_BIT is 8, the range of regular char is only guaranteed to be [0, 127] (because it can be signed or unsigned) while unsigned char will be [0, 255] and signed char will be [-127, 127].

In terms of what it's used for, the standards allow objects of POD (plain old data) to be directly converted to an array of unsigned char. This allows you to examine the representation and bit patterns of the object. The same guarantee of safe type punning doesn't exist for char or signed char.

Ruby String to Date Conversion

What is wrong with Date.parse method?

str = "Tue, 10 Aug 2010 01:20:19 -0400 (EDT)"
date = Date.parse str
=> #<Date: 4910837/2,0,2299161>
puts date

It seems to work.

The only problem here is time zone. If you want date in UTC time zone, then it is better to use Time object, suppose we have string:

str = "Tue, 10 Aug 2010 01:20:19 +0400"
puts Date.parse str
puts Date.parse(Time.parse(str).utc.to_s)

I couldn't find simpler method to convert Time to Date.

Why should text files end with a newline?

Some tools expect this. For example, wc expects this:

$ echo -n "Line not ending in a new line" | wc -l
$ echo "Line ending with a new line" | wc -l

How to make a submit out of a <a href...>...</a> link?

We replace the submit button with this all the time on forms:

<form method="post" action="whatever.asp">
<input type=...n

<input type="image" name="Submit" src="/graphics/continue.gif" align="middle" border="0" alt="Continue">

Clicking the image submits the form. Hope that helps!

How to retrieve available RAM from Windows command line?

This cannot be done in pure java. But you can run external programs using java and get the result.

Process p=Runtime.getRuntime().exec("systeminfo");
Scanner scan=new Scanner(p.getInputStream());
    String temp=scan.nextLine();
    if(temp.equals("Available Physical Memmory")){
       System.out.println("RAM :"temp.split(":")[1]);

How to find where javaw.exe is installed?

Open a cmd shell,

cd \\
dir javaw.exe /s

How to check is Apache2 is stopped in Ubuntu?

You can also type "top" and look at the list of running processes.

How can I print a circular structure in a JSON-like format?

Based on the other answers I end up with the following code. It works pretty well with circular references, objects with custom constructors.

From the given object to be serialized,

  • Cache all the object you come across while traversing the object and assign each of them a unique hashID (an auto-incrementing number also works)
  • Once a circular reference is found mark that field in the new object as circular and store the hashID of the original object as an attribute.

Github Link - DecycledJSON

DJSHelper = {};
DJSHelper.Cache = [];
DJSHelper.currentHashID = 0;
DJSHelper.ReviveCache = [];

function DJSNode(name, object, isRoot){ = name;
    // [ATTRIBUTES] contains the primitive fields of the Node
    this.attributes = {};

    // [CHILDREN] contains the Object/Typed fields of the Node
    // All [CHILDREN] must be of type [DJSNode]
    this.children = []; //Array of DJSNodes only

    // If [IS-ROOT] is true reset the Cache and currentHashId
    // before encoding
    isRoot = typeof isRoot === 'undefined'? true:isRoot;
    this.isRoot = isRoot;
        DJSHelper.Cache = [];
        DJSHelper.currentHashID = 0;

        // CACHE THE ROOT
        object.hashID = DJSHelper.currentHashID++;

    for(var a in object){
            var val = object[a];

            if (typeof val === 'object') {
                // IF OBJECT OR NULL REF.

                if(val !== null) {
                    if (DJSHelper.Cache.indexOf(val) === -1) {
                        // VAL NOT IN CACHE
                        val.hashID = DJSHelper.currentHashID++;
                        //console.log("Assigned", val.hashID, "to", a);

                        if (!(val instanceof Array)) {
                            // VAL NOT AN [ARRAY]
                            try {
                                this.children.push(new DJSNode(a, val, false));
                            } catch (err) {
                                console.log(err.message, a);
                                throw err;
                        } else {
                            // VAL IS AN [ARRAY]
                            var node = new DJSNode(a, {
                                array: true,
                                hashID: val.hashID // HashID of array
                            }, false);
                            val.forEach(function (elem, index) {
                                node.children.push(new DJSNode("elem", {val: elem}, false));
                    } else {
                        // VAL IN CACHE
                        // ADD A CYCLIC NODE WITH HASH-ID
                        this.children.push(new DJSNode(a, {
                            cyclic: true,
                            hashID: val.hashID
                        }, false));
                    // PUT NULL AS AN ATTRIBUTE
                    this.attributes[a] = 'null';
            } else if (typeof val !== 'function') {
                // MUST BE A PRIMITIVE
                // ADD IT AS AN ATTRIBUTE
                this.attributes[a] = val;

        DJSHelper.Cache = null;
    this.constructorName =;
DJSNode.Revive = function (xmlNode, isRoot) {
    // Default value of [isRoot] is True
    isRoot = typeof isRoot === 'undefined'?true: isRoot;
    var root;
        DJSHelper.ReviveCache = []; //Garbage Collect
    if(window[xmlNode.constructorName].toString().indexOf('[native code]') > -1 ) {
        // yep, native in the browser
        if(xmlNode.constructorName == 'Object'){
            root = {};
            return null;
    }else {
        eval('root = new ' + xmlNode.constructorName + "()");

    DJSHelper.ReviveCache[xmlNode.attributes.hashID] = root;

    for(var k in xmlNode.attributes){
        if(xmlNode.attributes.hasOwnProperty(k)) {
            var a = xmlNode.attributes[k];
            if(a == 'null'){
                root[k] = null;
            }else {
                root[k] = a;

    xmlNode.children.forEach(function (value) {
        // Each children is an [DJSNode]
        // [Array]s are stored as [DJSNode] with an positive Array attribute
        // So is value

            // ITS AN [ARRAY]
            root[] = [];
            value.children.forEach(function (elem) {
            //console.log("Caching", value.attributes.hashID);
            DJSHelper.ReviveCache[value.attributes.hashID] = root[];
        }else if(!value.attributes.cyclic){
            // ITS AN [OBJECT]
            root[] = DJSNode.Revive(value, false);
            //console.log("Caching", value.attributes.hashID);
            DJSHelper.ReviveCache[value.attributes.hashID] = root[];

    xmlNode.children.forEach(function (value) {
        // Each children is an [DJSNode]
        // [Array]s are stored as [DJSNode] with an positive Array attribute
        // So is value

            root[] = DJSHelper.ReviveCache[value.attributes.hashID];

        DJSHelper.ReviveCache = null; //Garbage Collect
    return root;

DecycledJSON = {};
DecycledJSON.stringify = function (obj) {
    return JSON.stringify(new DJSNode("root", obj));
DecycledJSON.parse = function (json, replacerObject) {
    // use the replacerObject to get the null values
    return DJSNode.Revive(JSON.parse(json));
DJS = DecycledJSON;

Example Usage 1:

var obj = {
    box: {
        owner: null,
        key: 'storm'

console.log(obj); // ORIGINAL

var jsonObj = DJS.stringify(obj);

Example Usage 2:


function Person() { = null;
    this.child = null; = null; = null;
var Dad = new Person(); = 'John';
var Mom = new Person(); = 'Sarah';
var Child = new Person(); = 'Kiddo';

Dad.child = Mom.child = Child; = Dad; = Mom;

console.log(Child); // ORIGINAL

var jsonChild = DJS.stringify(Child);

align 3 images in same row with equal spaces?

  • Option 1:

    • Instead of putting the images inside div put each one of them inside a span.
    • Float 1st and 2nd image to left.
    • Give some left padding to the 2nd image.
    • Float the right image to right.

Always remember to add overflow:hidden to the parent (if you have one) of all the images because using floats with images have some side effects.

  • Option 2 (Preferred):

    • Put all the images inside a table with border="0".
    • Make the width of the table 100%.

This will be the best way to make sure the 2nd image is alligned to the center always without worrying for the exact width of the table.

Something like below:

<table width="100%" border="0">
  <td><img src="@Url.Content("~/images/image1.bmp")" alt="" align="left" /></td>
  <td><img src="@Url.Content("~/images/image2.bmp")" alt="" align="center" /></td>
  <td><img src="@Url.Content("~/images/image3.bmp")" alt="" align="right"/></td>

Quicker way to get all unique values of a column in VBA?

Loading the values in an array would be much faster:

Dim data(), dict As Object, r As Long
Set dict = CreateObject("Scripting.Dictionary")

data = ActiveSheet.UsedRange.Columns(1).Value

For r = 1 To UBound(data)
    dict(data(r, some_column_number)) = Empty

data = WorksheetFunction.Transpose(dict.keys())

You should also consider early binding for the Scripting.Dictionary:

Dim dict As New Scripting.Dictionary  ' requires `Microsoft Scripting Runtime` '

Note that using a dictionary is way faster than Range.AdvancedFilter on large data sets.

As a bonus, here's a procedure similare to Range.RemoveDuplicates to remove duplicates from a 2D array:

Public Sub RemoveDuplicates(data, ParamArray columns())
    Dim ret(), indexes(), ids(), r As Long, c As Long
    Dim dict As New Scripting.Dictionary  ' requires `Microsoft Scripting Runtime` '

    If VarType(data) And vbArray Then Else Err.Raise 5, , "Argument data is not an array"

    ReDim ids(LBound(columns) To UBound(columns))

    For r = LBound(data) To UBound(data)         ' each row '
        For c = LBound(columns) To UBound(columns)   ' each column '
            ids(c) = data(r, columns(c))                ' build id for the row
        dict(Join$(ids, ChrW(-1))) = r  ' associate the row index to the id '

    indexes = dict.Items()
    ReDim ret(LBound(data) To LBound(data) + dict.Count - 1, LBound(data, 2) To UBound(data, 2))

    For c = LBound(ret, 2) To UBound(ret, 2)  ' each column '
        For r = LBound(ret) To UBound(ret)      ' each row / unique id '
            ret(r, c) = data(indexes(r - 1), c)   ' copy the value at index '

    data = ret
End Sub

Fill formula down till last row in column

Wonderful answer! I needed to fill in the empty cells in a column where there were titles in cells that applied to the empty cells below until the next title cell.

I used your code above to develop the code that is below my example sheet here. I applied this code as a macro ctl/shft/D to rapidly run down the column copying the titles.

--- Example Spreadsheet ------------ Title1 is copied to rows 2 and 3; Title2 is copied to cells below it in rows 5 and 6. After the second run of the Macro the active cell is the Title3 cell.

 ' **row** **Column1**        **Column2**
 '    1     Title1         Data 1 for title 1
 '    2                    Data 2 for title 1
 '    3                    Data 3 for title 1
 '    4     Title2         Data 1 for title 2
 '    5                    Data 2 for title 2
 '    6                    Data 3 for title 2
 '    7   Title 3          Data 1 for title 3

----- CopyDown code ----------

Sub CopyDown()
Dim Lastrow As String, FirstRow As String, strtCell As Range
' CopyDown Macro
' Copies the current cell to any empty cells below it.   
' Keyboard Shortcut: Ctrl+Shift+D
    Set strtCell = ActiveCell
    FirstRow = strtCell.Address
' Lastrow is address of the *list* of empty cells
    Lastrow = Range(Selection, Selection.End(xlDown).Offset(-1, 0)).Address
'   MsgBox Lastrow
    Range(Lastrow).Formula = strtCell.Formula

 End Sub

Sql Server string to date conversion

If you want SQL Server to try and figure it out, just use CAST CAST('whatever' AS datetime) However that is a bad idea in general. There are issues with international dates that would come up. So as you've found, to avoid those issues, you want to use the ODBC canonical format of the date. That is format number 120, 20 is the format for just two digit years. I don't think SQL Server has a built-in function that allows you to provide a user given format. You can write your own and might even find one if you search online.

How to handle-escape both single and double quotes in an SQL-Update statement

You can escape the quotes with a backslash:

"I asked my son's teacher, \"How is my son doing now?\""

How to set up Spark on Windows?

You can download spark from here:

I recommend you this version: Hadoop 2 (HDP2, CDH5)

Since version 1.0.0 there are .cmd scripts to run spark in windows.

Unpack it using 7zip or similar.

To start you can execute /bin/spark-shell.cmd --master local[2]

To configure your instance, you can follow this link:

How to get english language word database?

You didn't say what you needed this list for. If something used as a blacklist for password checks is enough cracklib might be good for you. It contains over 1.5M words.

Magento: get a static block as html in a phtml file

Following code will work when you Call CMS-Static Block in Magento.

<?php echo 



YYYY-MM-DD format date in shell script

You can do something like this:

$ date +'%Y-%m-%d'

How do I edit an incorrect commit message in git ( that I've pushed )?

At our shop, I introduced the convention of adding recognizably named annotated tags to commits with incorrect messages, and using the annotation as the replacement.

Even though this doesn't help folks who run casual "git log" commands, it does provide us with a way to fix incorrect bug tracker references in the comments, and all my build and release tools understand the convention.

This is obviously not a generic answer, but it might be something folks can adopt within specific communities. I'm sure if this is used on a larger scale, some sort of porcelain support for it may crop up, eventually...

JQuery / JavaScript - trigger button click from another button click event

   return false;

What's the best way to do a backwards loop in C/C#/C++?

I'd use the code in the original question, but if you really wanted to use foreach and have an integer index in C#:

foreach (int i in Enumerable.Range(0, myArray.Length).Reverse())
    myArray[i] = 42; 

Illegal mix of collations MySQL Error

You should set both your table encoding and connection encoding to UTF-8:

ALTER TABLE keywords CHARACTER SET UTF8; -- run once



RegEx pattern any two letters followed by six numbers

Everything you need here can be found in this quickstart guide. A straightforward solution would be [A-Za-z][A-Za-z]\d\d\d\d\d\d or [A-Za-z]{2}\d{6}.

If you want to accept only capital letters then replace [A-Za-z] with [A-Z].

How to add Drop-Down list (<select>) programmatically?

it's very simple yet tricky but here is what you wanted, hope it's helpful : this function generates a select list from 1990 to 2018 i think this example can help ya, if you want to add any other value just change value of x and y ;)

function dropDown(){
    var start = 1990;
    var today = 2019;
    for (var i = start ; i <= today; i++)
    document.write("<option>" + i + "</option>");


"Could not find or load main class" Error while running java program using cmd prompt

When the Main class is inside a package then you need to run it as follows :

java <packageName>.<MainClassName>

In your case you should run the program as follows :

java org.tij.exercises.HelloWorld 

Calculating distance between two points, using latitude longitude?

This wikipedia article provides the formulae and an example. The text is in german, but the calculations speak for themselves.

What's the difference between lists enclosed by square brackets and parentheses in Python?

One interesting difference :

print lst          // prints [1]
print type(lst)    // prints <type 'list'>

print notATuple        // prints 1
print type(notATuple)  // prints <type 'int'>
                                         ^^ instead of tuple(expected)

A comma must be included in a tuple even if it contains only a single value. e.g. (1,) instead of (1).

How to convert FormData (HTML5 object) to JSON

Here's a way to do it in a more functional style, without the use of a library.

Array.from(formData.entries()).reduce((memo, pair) => ({
  [pair[0]]: pair[1],
}), {});


document.getElementById('foobar').addEventListener('submit', (e) => {_x000D_
  const formData = new FormData(;_x000D_
  const data = Array.from(formData.entries()).reduce((memo, pair) => ({_x000D_
    [pair[0]]: pair[1],_x000D_
  }), {});_x000D_
  document.getElementById('output').innerHTML = JSON.stringify(data);_x000D_
<form id='foobar'>_x000D_
  <input name='baz' />_x000D_
  <input type='submit' />_x000D_
<pre id='output'>Input some value and submit</pre>

When to use Common Table Expression (CTE)

Today we are going to learn about Common table expression that is a new feature which was introduced in SQL server 2005 and available in later versions as well.

Common table Expression :- Common table expression can be defined as a temporary result set or in other words its a substitute of views in SQL Server. Common table expression is only valid in the batch of statement where it was defined and cannot be used in other sessions.

Syntax of declaring CTE(Common table expression) :-

with [Name of CTE]
Body of common table expression

Lets take an example :-

CREATE TABLE Employee([EID] [int] IDENTITY(10,5) NOT NULL,[Name] [varchar](50) NULL)

insert into Employee(Name) values('Neeraj')
insert into Employee(Name) values('dheeraj')
insert into Employee(Name) values('shayam')
insert into Employee(Name) values('vikas')
insert into Employee(Name) values('raj')

insert into dept values(10,'IT')
insert into dept values(15,'Finance')
insert into dept values(20,'Admin')
insert into dept values(25,'HR')
insert into dept values(10,'Payroll')

I have created two tables employee and Dept and inserted 5 rows in each table. Now I would like to join these tables and create a temporary result set to use it further.

With CTE_Example(EID,Name,DeptName)
select Employee.EID,Name,DeptName from Employee 
inner join DEPT on Employee.EID =DEPT.EID
select * from CTE_Example

Lets take each line of the statement one by one and understand.

To define CTE we write "with" clause, then we give a name to the table expression, here I have given name as "CTE_Example"

Then we write "As" and enclose our code in two brackets (---), we can join multiple tables in the enclosed brackets.

In the last line, I have used "Select * from CTE_Example" , we are referring the Common table expression in the last line of code, So we can say that Its like a view, where we are defining and using the view in a single batch and CTE is not stored in the database as an permanent object. But it behaves like a view. we can perform delete and update statement on CTE and that will have direct impact on the referenced table those are being used in CTE. Lets take an example to understand this fact.

With CTE_Example(EID,DeptName)
select EID,DeptName from DEPT 
delete from CTE_Example where EID=10 and DeptName ='Payroll'

In the above statement we are deleting a row from CTE_Example and it will delete the data from the referenced table "DEPT" that is being used in the CTE.

ORDER BY items must appear in the select list if SELECT DISTINCT is specified

While they are not the same thing, in one sense DISTINCT implies a GROUP BY, because every DISTINCT could be re-written using GROUP BY instead. With that in mind, it doesn't make sense to order by something that's not in the aggregate group.

For example, if you have a table like this:

col1  col2
----  ----
 1     1
 1     2
 2     1
 2     2
 2     3
 3     1

and then try to query it like this:

SELECT DISTINCT col1 FROM [table] WHERE col2 > 2 ORDER BY col1, col2

That would make no sense, because there could end up being multiple col2 values per row. Which one should it use for the order? Of course, in this query you know the results wouldn't be that way, but the database server can't know that in advance.

Now, your case is a little different. You included all the columns from the order by clause in the select clause, and therefore it would seem at first glance that they were all grouped. However, some of those columns were included in a calculated field. When you do that in combination with distinct, the distinct directive can only be applied to the final results of the calculation: it doesn't know anything about the source of the calculation any more.

This means the server doesn't really know it can count on those columns any more. It knows that they were used, but it doesn't know if the calculation operation might cause an effect similar to my first simple example above.

So now you need to do something else to tell the server that the columns are okay to use for ordering. There are several ways to do that, but this approach should work okay:

SELECT rsc.RadioServiceCodeId,
            rsc.RadioServiceCode + ' - ' + rsc.RadioService as RadioService
FROM sbi_l_radioservicecodes rsc
INNER JOIN sbi_l_radioservicecodegroups rscg 
    ON rsc.radioservicecodeid = rscg.radioservicecodeid
WHERE rscg.radioservicegroupid IN 
    (SELECT val FROM dbo.fnParseArray(@RadioServiceGroup,','))
    OR @RadioServiceGroup IS NULL  
GROUP BY rsc.RadioServiceCode,rsc.RadioServiceCodeId,rsc.RadioService
ORDER BY rsc.RadioServiceCode,rsc.RadioServiceCodeId,rsc.RadioService

How to use QTimer

  1. It's good practice to give a parent to your QTimer to use Qt's memory management system.

  2. update() is a QWidget function - is that what you are trying to call or not?

  3. If number 2 does not apply, make sure that the function you are trying to trigger is declared as a slot in the header.

  4. Finally if none of these are your issue, it would be helpful to know if you are getting any run-time connect errors.

iterating quickly through list of tuples

The question is dead but still knowing one more way doesn't hurt:

my_list = [ (old1, new1), (old2, new2), (old3, new3), ... (oldN, newN)]

for first,*args in my_list:
    if first == Value:
        PAIR_FOUND = True
        MATCHING_VALUE = args

How to make an HTTP get request with parameters

You can also pass value directly via URL.

If you want to call method public static void calling(string name){....}

then you should call usingHttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create("http://localhost:****/Report/calling?name=Priya); webrequest.Method = "GET"; webrequest.ContentType = "application/text";

Just make sure you are using ?Object = value in URL

Using Excel OleDb to get sheet names IN SHEET ORDER

Can't find this in actual MSDN documentation, but a moderator in the forums said

I am afraid that OLEDB does not preserve the sheet order as they were in Excel

Excel Sheet Names in Sheet Order

Seems like this would be a common enough requirement that there would be a decent workaround.

How do I convert the date from one format to another date object in another format without using any deprecated classes?

Hope this will help someone.

 public static String getDate(
        String date, String currentFormat, String expectedFormat)
throws ParseException {
    // Validating if the supplied parameters is null 
    if (date == null || currentFormat == null || expectedFormat == null ) {
        return null;
    // Create SimpleDateFormat object with source string date format
    SimpleDateFormat sourceDateFormat = new SimpleDateFormat(currentFormat);
    // Parse the string into Date object
    Date dateObj = sourceDateFormat.parse(date);
    // Create SimpleDateFormat object with desired date format
    SimpleDateFormat desiredDateFormat = new SimpleDateFormat(expectedFormat);
    // Parse the date into another format
    return desiredDateFormat.format(dateObj).toString();

Dynamic Height Issue for UITableView Cells (Swift)

To make autoresizing of UITableViewCell to work make sure you are doing these changes :

  • In Storyboard your UITableView should only contain Dynamic Prototype Cells (It shouldn't use static cells) otherwise autoresizing won't work.
  • In Storyboard your UITableViewCell's UILabel has configured for all 4 constraints that is top, bottom, leading and trailing constraints.
  • In Storyboard your UITableViewCell's UILabel's number of lines should be 0
  • In your UIViewController's viewDidLoad function set below UITableView Properties :

    self.tableView.estimatedRowHeight = <minimum cell height> 
    self.tableView.rowHeight = UITableViewAutomaticDimension

WinForms DataGridView font size

The straight forward approach:

this.dataGridView1.DefaultCellStyle.Font = new Font("Tahoma", 15);

What is the difference between require_relative and require in Ruby?

require_relative is a convenient subset of require



require(File.expand_path('path', File.dirname(__FILE__)))

if __FILE__ is defined, or it raises LoadError otherwise.

This implies that:

  • require_relative 'a' and require_relative './a' require relative to the current file (__FILE__).

    This is what you want to use when requiring inside your library, since you don't want the result to depend on the current directory of the caller.

  • eval('require_relative("a.rb")') raises LoadError because __FILE__ is not defined inside eval.

    This is why you can't use require_relative in RSpec tests, which get evaled.

The following operations are only possible with require:

  • require './a.rb' requires relative to the current directory

  • require 'a.rb' uses the search path ($LOAD_PATH) to require. It does not find files relative to current directory or path.

    This is not possible with require_relative because the docs say that path search only happens when "the filename does not resolve to an absolute path" (i.e. starts with / or ./ or ../), which is always the case for File.expand_path.

The following operation is possible with both, but you will want to use require as it is shorter and more efficient:

  • require '/a.rb' and require_relative '/a.rb' both require the absolute path.

Reading the source

When the docs are not clear, I recommend that you take a look at the sources (toggle source in the docs). In some cases, it helps to understand what is going on.


VALUE rb_f_require(VALUE obj, VALUE fname) {
  return rb_require_safe(fname, rb_safe_level());


VALUE rb_f_require_relative(VALUE obj, VALUE fname) {
    VALUE base = rb_current_realfilepath();
    if (NIL_P(base)) {
        rb_loaderror("cannot infer basepath");
    base = rb_file_dirname(base);
    return rb_require_safe(rb_file_absolute_path(fname, base), rb_safe_level());

This allows us to conclude that


is the same as:

require(File.expand_path('path', File.dirname(__FILE__)))


rb_file_absolute_path   =~ File.expand_path
rb_file_dirname1        =~ File.dirname
rb_current_realfilepath =~ __FILE__

Passing parameters in Javascript onClick event

link.onclick = function() { onClickLink(i+''); };

Is a closure and stores a reference to the variable i, not the value that i holds when the function is created. One solution would be to wrap the contents of the for loop in a function do this:

for (var i = 0; i < 10; i++) (function(i) {
    var link = document.createElement('a');
    link.setAttribute('href', '#');
    link.innerHTML = i + '';
    link.onclick=  function() { onClickLink(i+'');};

Can I disable a CSS :hover effect via JavaScript?

You can manipulate the stylesheets and stylesheet rules themselves with javascript

var sheetCount = document.styleSheets.length;
var lastSheet = document.styleSheets[sheetCount-1];
var ruleCount;
if (lastSheet.cssRules) { // Firefox uses 'cssRules'
    ruleCount = lastSheet.cssRules.length;
else if (lastSheet.rules) { / /IE uses 'rules'
    ruleCount = lastSheet.rules.length;
var newRule = "a:hover { text-decoration: none !important; color: #000 !important; }";
// insert as the last rule in the last sheet so it
// overrides (not overwrites) previous definitions
lastSheet.insertRule(newRule, ruleCount);

Making the attributes !important and making this the very last CSS definition should override any previous definition, unless one is more specifically targeted. You may have to insert more rules in that case.

What is the difference between origin and upstream on GitHub?

In a nutshell answer.

  • origin: the fork
  • upstream: the forked

The response content cannot be parsed because the Internet Explorer engine is not available, or

In your invoke web request just use the parameter -UseBasicParsing

e.g. in your script (line 2) you should use:

$rss = Invoke-WebRequest -UseBasicParsing

According to the documentation, this parameter is necessary on systems where IE isn't installed or configured.

Uses the response object for HTML content without Document Object Model (DOM) parsing. This parameter is required when Internet Explorer is not installed on the computers, such as on a Server Core installation of a Windows Server operating system.

Sample random rows in dataframe

You could do this:


cols <- paste0("a", 1:10)
tab <- matrix(1:1000, nrow = 100) %>% as.tibble() %>% set_names(cols)
# A tibble: 100 x 10
      a1    a2    a3    a4    a5    a6    a7    a8    a9   a10
   <int> <int> <int> <int> <int> <int> <int> <int> <int> <int>
 1     1   101   201   301   401   501   601   701   801   901
 2     2   102   202   302   402   502   602   702   802   902
 3     3   103   203   303   403   503   603   703   803   903
 4     4   104   204   304   404   504   604   704   804   904
 5     5   105   205   305   405   505   605   705   805   905
 6     6   106   206   306   406   506   606   706   806   906
 7     7   107   207   307   407   507   607   707   807   907
 8     8   108   208   308   408   508   608   708   808   908
 9     9   109   209   309   409   509   609   709   809   909
10    10   110   210   310   410   510   610   710   810   910
# ... with 90 more rows

Above I just made a dataframe with 10 columns and 100 rows, ok?

Now you can sample it with sample_n:

sample_n(tab, size = 800, replace = T)
# A tibble: 800 x 10
      a1    a2    a3    a4    a5    a6    a7    a8    a9   a10
   <int> <int> <int> <int> <int> <int> <int> <int> <int> <int>
 1    53   153   253   353   453   553   653   753   853   953
 2    14   114   214   314   414   514   614   714   814   914
 3    10   110   210   310   410   510   610   710   810   910
 4    70   170   270   370   470   570   670   770   870   970
 5    36   136   236   336   436   536   636   736   836   936
 6    77   177   277   377   477   577   677   777   877   977
 7    13   113   213   313   413   513   613   713   813   913
 8    58   158   258   358   458   558   658   758   858   958
 9    29   129   229   329   429   529   629   729   829   929
10     3   103   203   303   403   503   603   703   803   903
# ... with 790 more rows

How to increase maximum execution time in php

use below statement if safe_mode is off


Git, fatal: The remote end hung up unexpectedly

I was able to get around this issue using Git Shell.

Each repository within gives you HTTPS/SSH/Subversion URL's that you can use to download using Shell, see here:
Based on GitHub's recent changes, SSH seems to be the best method.

Command to use in Shell:

git clone "URL of repo goes here w/ no quotes"

jQuery ui datepicker with Angularjs

I finally was able to run datepicker directive in angular js , here are pointers

include following JS in order

  1. jquery.js
  2. jquery-ui.js
  3. angular-min.js

I added the following

<script src=""></script>
<script src=""></script> 
<script src=""> </script>      

in html code

<body ng-app="myApp" ng-controller="myController">
// some other html code 
<input type="text" ng-model="date" mydatepicker />
 {{ date }}
 //some other html code

in the js , make sure you code for the directive first and after that add the code for controller , else it will cause issues.

date picker directive :

var app = angular.module('myApp',[]);
app.directive('mydatepicker', function () {
return {
    restrict: 'A',
    require: 'ngModel',
     link: function (scope, element, attrs, ngModelCtrl) {
            dateFormat: 'DD, d  MM, yy',
            onSelect: function (date) {
       = date;

directive code referred from above answers.

After this directive , write the controller

//controller code

TRY THIS INSTEAD in angular js

  <script src=""></script>  

along with jquery.js and jquery-ui.js

we can implement angular js datepicker as

<input type="date" ng-model="date" name="DOB">

This gives the built in datepicker and date is set in ng-model and can be used for further processing and validation.

Found this after lot of successful headbanging with previous approach. :)

Syntax for an If statement using a boolean

You can change the value of a bool all you want. As for an if:

if randombool == True:

works, but you can also use:

if randombool:

If you want to test whether something is false you can use:

if randombool == False

but you can also use:

if not randombool:

What are naming conventions for MongoDB?

Even if no convention is specified about this, manual references are consistently named after the referenced collection in the Mongo documentation, for one-to-one relations. The name always follows the structure <document>_id.

For example, in a dogs collection, a document would have manual references to external documents named like this:

  name: 'fido',
  owner_id: '5358e4249611f4a65e3068ab',
  race_id: '5358ee549611f4a65e3068ac',
  colour: 'yellow'

This follows the Mongo convention of naming _id the identifier for every document.

Complex nesting of partials and templates

I too was struggling with nested views in Angular.

Once I got a hold of ui-router I knew I was never going back to angular default routing functionality.

Here is an example application that uses multiple levels of views nesting

app.config(function ($stateProvider, $urlRouterProvider,$httpProvider) {
// navigate to view1 view by default

    .state('view1', {
        url: '/view1',
        templateUrl: 'partials/view1.html',
        controller: 'view1.MainController'
    .state('view1.nestedViews', {
        url: '/view1',
        views: {
            'childView1': { templateUrl: 'partials/view1.childView1.html' , controller: 'childView1Ctrl'},
            'childView2': { templateUrl: 'partials/view1.childView2.html', controller: 'childView2Ctrl' },
            'childView3': { templateUrl: 'partials/view1.childView3.html', controller: 'childView3Ctrl' }

    .state('view2', {
        url: '/view2',

    .state('view3', {
        url: '/view3',

    .state('view4', {
        url: '/view4',

As it can be seen there are 4 main views (view1,view2,view3,view4) and view1 has 3 child views.

T-SQL: How to Select Values in Value List that are NOT IN the Table?

Use this : -- SQL Server 2008 or later

Inner Join (
    EMail, [Status]
        ('email1', 'Exist'),
        ('email2', 'Exist'),
        ('email3', 'Not Exist'),
        ('email4', 'Exist')
    )AS TempTableName (EMail, [Status])
  Where TempTableName.EMail IN ('email1','email2','email3')
) As TMP ON U.EMail = TMP.EMail

positional argument follows keyword argument

The grammar of the language specifies that positional arguments appear before keyword or starred arguments in calls:

argument_list        ::=  positional_arguments ["," starred_and_keywords]
                            ["," keywords_arguments]
                          | starred_and_keywords ["," keywords_arguments]
                          | keywords_arguments

Specifically, a keyword argument looks like this: tag='insider trading!' while a positional argument looks like this: ..., exchange, .... The problem lies in that you appear to have copy/pasted the parameter list, and left some of the default values in place, which makes them look like keyword arguments rather than positional ones. This is fine, except that you then go back to using positional arguments, which is a syntax error.

Also, when an argument has a default value, such as price=None, that means you don't have to provide it. If you don't provide it, it will use the default value instead.

To resolve this error, convert your later positional arguments into keyword arguments, or, if they have default values and you don't need to use them, simply don't specify them at all:

order_id = kite.order_place(self, exchange, tradingsymbol,
    transaction_type, quantity)

# Fully positional:
order_id = kite.order_place(self, exchange, tradingsymbol, transaction_type, quantity, price, product, order_type, validity, disclosed_quantity, trigger_price, squareoff_value, stoploss_value, trailing_stoploss, variety, tag)

# Some positional, some keyword (all keywords at end):

order_id = kite.order_place(self, exchange, tradingsymbol,
    transaction_type, quantity, tag='insider trading!')

Select NOT IN multiple columns

I use a way that may look stupid but it works for me. I simply concat the columns I want to compare and use NOT IN:

FROM table1 t1
WHERE CONCAT(t1.first_name,t1.last_name) NOT IN (SELECT CONCAT(t2.first_name,t2.last_name) FROM table2 t2)

LINQ orderby on date field in descending order

I don't believe that Distinct() is guaranteed to maintain the order of the set.

Try pulling out an anonymous type first and distinct/sort on that before you convert to string:

var ud = env.Select(d => new 
                             FormattedDate = d.ReportDate.ToString("yyyy-MMM")
            .OrderByDescending(d => d.Year)
            .ThenByDescending(d => d.Month)
            .Select(d => d.FormattedDate);

Checking to see if a DateTime variable has had a value assigned

put this somewhere:

public static class DateTimeUtil //or whatever name
    public static bool IsEmpty(this DateTime dateTime)
        return dateTime == default(DateTime);


DateTime datetime = ...;

if (datetime.IsEmpty())

Install python 2.6 in CentOS

rpm -Uvh
rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-CHL
rpm -Uvh
yum install python26

for dos that just dont know :=)

Capture iOS Simulator video for App Preview

The best tool I have found is Appshow. Visit (I do not work for them)

How to grep a string in a directory and all its subdirectories?

grep -r -e string directory

-r is for recursive; -e is optional but its argument specifies the regex to search for. Interestingly, POSIX grep is not required to support -r (or -R), but I'm practically certain that System V grep did, so in practice they (almost) all do. Some versions of grep support -R as well as (or conceivably instead of) -r; AFAICT, it means the same thing.

What is the difference between char * const and const char *?

const * char is invalid C code and is meaningless. Perhaps you meant to ask the difference between a const char * and a char const *, or possibly the difference between a const char * and a char * const?

See also:

Keeping ASP.NET Session Open / Alive

Here JQuery plugin version of Maryan solution with handle optimization. Only with JQuery 1.7+!

(function ($) {
    $.fn.heartbeat = function (options) {
        var settings = $.extend({
            // These are the defaults.
            events: 'mousemove keydown'
            , url: '/Home/KeepSessionAlive'
            , every: 5*60*1000
        }, options);

        var keepSessionAlive = false
         , $container = $(this)
         , handler = function () {
             keepSessionAlive = true;
             $, handler)
         }, reset = function () {
             keepSessionAlive = false;
             $container.on(, handler);
             setTimeout(sessionAlive, settings.every);
         }, sessionAlive = function () {
             keepSessionAlive && $.ajax({
                 type: "POST"
                 , url: settings.url
                 ,success: reset

        return this;

and how it does import in your *.cshtml

$('body').heartbeat(); // Simple
$('body').heartbeat({url:'@Url.Action("Home", "heartbeat")'}); // different url
$('body').heartbeat({every:6*60*1000}); // different timeout

error LNK2038: mismatch detected for '_MSC_VER': value '1600' doesn't match value '1700' in CppFile1.obj

I upgraded from 2010 to 2013 and after changing all the projects' Platform Toolset, I need to right-click on the Solution and choose Retarget... to make it work.

Logging framework incompatibility

Just to help those in a similar situation to myself...

This can be caused when a dependent library has accidentally bundled an old version of slf4j. In my case, it was tika-0.8. See

The workaround is exclude the component and then manually depends on the correct, or patched version.


            <!-- NOTE: Version 4.2 has bundled slf4j -->
    <!-- Patched version 4.2-min does not bundle slf4j -->

scrollable div inside container

I created an enhanced version, based on Trey Copland's fiddle, that I think is more like what you wanted. Added here for future reference to those who come here later. Fiddle example

.modal {
  height: 390px;
  border: 5px solid green;
.heading {
  padding: 10px;
.content {
  height: 300px;
  border: 5px solid red;
.scrollable {
  height: 1200px;
  border: 5px solid yellow;

.footer {
  height: 2em;
  padding: .5em;
      <div class="modal">
          <div class="heading">
          <div class="content">
              <div class="scrollable" >hello</div>
          <div class="footer">

How To Raise Property Changed events on a Dependency Property?

  1. Implement INotifyPropertyChanged in your class.

  2. Specify a callback in the property metadata when you register the dependency property.

  3. In the callback, raise the PropertyChanged event.

Adding the callback:

public static DependencyProperty FirstProperty = DependencyProperty.Register(
  new FrameworkPropertyMetadata(
     new PropertyChangedCallback(OnFirstPropertyChanged)));

Raising PropertyChanged in the callback:

private static void OnFirstPropertyChanged(
   DependencyObject sender, DependencyPropertyChangedEventArgs e)
   PropertyChangedEventHandler h = PropertyChanged;
   if (h != null)
      h(sender, new PropertyChangedEventArgs("Second"));

How to convert UTF8 string to byte array?

JavaScript Strings are stored in UTF-16. To get UTF-8, you'll have to convert the String yourself.

One way is to mix encodeURIComponent(), which will output UTF-8 bytes URL-encoded, with unescape, as mentioned on ecmanaut.

var utf8 = unescape(encodeURIComponent(str));

var arr = [];
for (var i = 0; i < utf8.length; i++) {

Angular ui-grid dynamically calculate height of the grid

I use ui-grid - v3.0.0-rc.20 because a scrolling issue is fixed when you go full height of container. Use the ui.grid.autoResize module will dynamically auto resize the grid to fit your data. To calculate the height of your grid use the function below. The ui-if is optional to wait until your data is set before rendering.

angular.module('app',['ui.grid','ui.grid.autoResize']).controller('AppController', ['uiGridConstants', function(uiGridConstants) {_x000D_
    $scope.gridData = {_x000D_
      rowHeight: 30, // set row height, this is default size_x000D_
    $scope.getTableHeight = function() {_x000D_
       var rowHeight = 30; // your row height_x000D_
       var headerHeight = 30; // your header height_x000D_
       return {_x000D_
          height: ($ * rowHeight + headerHeight) + "px"_x000D_
<div ui-if=">0" id="grid1" ui-grid="gridData" class="grid" ui-grid-auto-resize ng-style="getTableHeight()"></div>

How to get POSTed JSON in Flask?

Assuming that you have posted valid JSON,

@app.route('/api/add_message/<uuid>', methods=['GET', 'POST'])
def add_message(uuid):
    content = request.json
    print content['uuid']
    # Return data as JSON
    return jsonify(content)

Android: Difference between onInterceptTouchEvent and dispatchTouchEvent?

ViewGroup's onInterceptTouchEvent() is always the entry point for ACTION_DOWN event which is first event to occur.

If you want ViewGroup to process this gesture, return true from onInterceptTouchEvent(). On returning true, ViewGroup's onTouchEvent() will receive all subsequent events till next ACTION_UP or ACTION_CANCEL, and in most cases, the touch events between ACTION_DOWN and ACTION_UP or ACTION_CANCEL are ACTION_MOVE, which will normally be recognized as scrolling/fling gestures.

If you return false from onInterceptTouchEvent(), the target view's onTouchEvent() will be called. It will be repeated for subsequent messages till you return true from onInterceptTouchEvent().


how to set width for PdfPCell in ItextSharp

Try something like this

PdfPCell cell;
PdfPTable tableHeader;
PdfPTable tmpTable;
PdfPTable table = new PdfPTable(10) { WidthPercentage = 100, RunDirection = PdfWriter.RUN_DIRECTION_LTR, ExtendLastRow = false };

// row 1 / cell 1 (merge)
PdfPCell _c = new PdfPCell(new Phrase("SER. No")) { Rotation = -90, VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER, BorderWidth = 1 };
_c.Rowspan = 2;


// row 1 / cell 2
_c = new PdfPCell(new Phrase("TYPE OF SHIPPING")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 1 / cell 3
_c = new PdfPCell(new Phrase("ORDER NO.")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 1 / cell 4
_c = new PdfPCell(new Phrase("QTY.")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 1 / cell 5
_c = new PdfPCell(new Phrase("DISCHARGE PPORT")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 1 / cell 6 (merge)
_c = new PdfPCell(new Phrase("DESCRIPTION OF GOODS")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };
_c.Rowspan = 2;

// row 1 / cell 7
_c = new PdfPCell(new Phrase("LINE DOC. RECI. DATE")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 1 / cell 8 (merge)
_c = new PdfPCell(new Phrase("OWNER DOC. RECI. DATE")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };
_c.Rowspan = 2;

// row 1 / cell 9 (merge)
_c = new PdfPCell(new Phrase("CLEARANCE DATE")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };
_c.Rowspan = 2;

// row 1 / cell 10 (merge)
_c = new PdfPCell(new Phrase("CUSTOM PERMIT NO.")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };
_c.Rowspan = 2;

// row 2 / cell 2
_c = new PdfPCell(new Phrase("AWB / BL NO.")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 2 / cell 3
_c = new PdfPCell(new Phrase("COMPLEX NAME")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 2 / cell 4
_c = new PdfPCell(new Phrase("G.W Kgs.")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 2 / cell 5
_c = new PdfPCell(new Phrase("DESTINATON")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };

// row 2 / cell 7
_c = new PdfPCell(new Phrase("OWNER DOC. RECI. DATE")) { VerticalAlignment = Element.ALIGN_MIDDLE, HorizontalAlignment = Element.ALIGN_CENTER };


You might need to re-adjust slightly on the widths and borders but that is a one shot to do.

Is there any way to delete local commits in Mercurial?

If you are familiar with git you'll be happy to use histedit that works like git rebase -i.

Best way to check for null values in Java?

For java 11+ you can use Objects.nonNull(Object obj)


Best way to check if a URL is valid

Another way to check if given URL is valid is to try to access it, below function will fetch the headers from given URL, this will ensure that URL is valid AND web server is alive:

function is_url($url){
        $response = array();
        //Check if URL is empty
        if(!empty($url)) {
            $response = get_headers($url);
        return (bool)in_array("HTTP/1.1 200 OK", $response, true);
    [0] => HTTP/1.1 200 OK 
    [Date] => Sat, 29 May 2004 12:28:14 GMT
    [Server] => Apache/1.3.27 (Unix)  (Red-Hat/Linux)
    [Last-Modified] => Wed, 08 Jan 2003 23:11:55 GMT
    [ETag] => "3f80f-1b6-3e1cb03b"
    [Accept-Ranges] => bytes
    [Content-Length] => 438
    [Connection] => close
    [Content-Type] => text/html

Array to Collection: Optimized code

Have you checked Arrays.asList(); see API

Custom HTTP headers : naming conventions

Modifying, or more correctly, adding additional HTTP headers is a great code debugging tool if nothing else.

When a URL request returns a redirect or an image there is no html "page" to temporarily write the results of debug code to - at least not one that is visible in a browser.

One approach is to write the data to a local log file and view that file later. Another is to temporarily add HTTP headers reflecting the data and variables being debugged.

I regularly add extra HTTP headers like X-fubar-somevar: or X-testing-someresult: to test things out - and have found a lot of bugs that would have otherwise been very difficult to trace.

Creating Threads in python

Did you override the run() method? If you overrided __init__, did you make sure to call the base threading.Thread.__init__()?

After starting the two threads, does the main thread continue to do work indefinitely/block/join on the child threads so that main thread execution does not end before the child threads complete their tasks?

And finally, are you getting any unhandled exceptions?

Capturing image from webcam in java?

Java usually doesn't like accessing hardware, so you will need a driver program of some sort, as goldenmean said. I've done this on my laptop by finding a command line program that snaps a picture. Then it's the same as goldenmean explained; you run the command line program from your java program in the takepicture() routine, and the rest of your code runs the same.

Except for the part about reading pixel values into an array, you might be better served by saving the file to BMP, which is nearly that format already, then using the standard java image libraries on it.

Using a command line program adds a dependency to your program and makes it less portable, but so was the webcam, right?

What is the best free SQL GUI for Linux for various DBMS systems

I use SQLite Database Browser for SQLite3 currently and it's pretty useful. Works across Windows/OS X/Linux and is lightweight and fast. Slightly unstable with executing SQL on the DB if it's incorrectly formatted.

Edit: I have recently discovered SQLite Manager, a plugin for Firefox. Obviously you need to run Firefox, but you can close all windows and just run it "standalone". It's very feature complete, amazingly stable and it remembers your databases! It has tonnes of features so I've moved away from SQLite Database Browser as the instability and lack of features is too much to bear.

Asynchronous method call in Python?

My solution is:

import threading

class TimeoutError(RuntimeError):

class AsyncCall(object):
    def __init__(self, fnc, callback = None):
        self.Callable = fnc
        self.Callback = callback

    def __call__(self, *args, **kwargs):
        self.Thread = threading.Thread(target =, name = self.Callable.__name__, args = args, kwargs = kwargs)
        return self

    def wait(self, timeout = None):
        if self.Thread.isAlive():
            raise TimeoutError()
            return self.Result

    def run(self, *args, **kwargs):
        self.Result = self.Callable(*args, **kwargs)
        if self.Callback:

class AsyncMethod(object):
    def __init__(self, fnc, callback=None):
        self.Callable = fnc
        self.Callback = callback

    def __call__(self, *args, **kwargs):
        return AsyncCall(self.Callable, self.Callback)(*args, **kwargs)

def Async(fnc = None, callback = None):
    if fnc == None:
        def AddAsyncCallback(fnc):
            return AsyncMethod(fnc, callback)
        return AddAsyncCallback
        return AsyncMethod(fnc, callback)

And works exactly as requested:

def fnc():

Find and Replace text in the entire table using a MySQL query

I believe "swapnesh" answer to be the best ! Unfortunately I couldn't execute it in phpMyAdmin ( who although illogical (and tried several things) it kept saying that a new statement was found and that no delimiter was found…

Thus I came with the following solution that might be usefull if you exeprience the same issue and have no other access to the database than PMA…

UPDATE `wp_posts` AS `toUpdate`,
(SELECT `ID`,REPLACE(`guid`,'http://old.tld','http://new.tld') AS `guid` 
 FROM `wp_posts` WHERE `guid` LIKE 'http://old.tld%') AS `updated`
SET `toUpdate`.`guid`=`updated`.`guid`
WHERE `toUpdate`.`ID`=`updated`.`ID`;

To test the expected result you may want to use :

SELECT `toUpdate`.`guid` AS `old guid`,`updated`.`guid` AS `new guid`
FROM `wp_posts` AS `toUpdate`,
(SELECT `ID`,REPLACE(`guid`,'http://old.tld','http://new.tld') AS `guid`
 FROM `wp_posts` WHERE `guid` LIKE 'http://old.tld%') AS `updated`
WHERE `toUpdate`.`ID`=`updated`.`ID`;

Python read JSON file and modify

Set item using data['id'] = ....

import json

with open('data.json', 'r+') as f:
    data = json.load(f)
    data['id'] = 134 # <--- add `id` value.        # <--- should reset file position to the beginning.
    json.dump(data, f, indent=4)
    f.truncate()     # remove remaining part

How can I commit a single file using SVN over a network?

strange that your command works, i thougth it would need a target directory. but it looks like it assumes current pwd as default.

cd myapp
svn ci page1.html

you can also just do svn ci in or on that folder and it will detect all changes automatically and give you a list of what will be checked in

man svn tells you the rest

Comparing arrays in C#

SequenceEqual can be faster. Namely in the case where almost all of the time, both arrays have indeed the same length and are not the same object.

It's still not the same functionality as the OP's function, as it won't silently compare null values.

if else statement in AngularJS templates

Angular itself doesn't provide if/else functionality, but you can get it by including this module:

In its own words, it's just "a simple collection of control flow directives: ng-if, ng-else-if, and ng-else." It's easy and intuitive to use.


<div ng-if="someCondition">
<div ng-else-if="someOtherCondition">
<div ng-else>

How to fix Cannot find module 'typescript' in Angular 4?

I had the same problem. If you have installed first nodejs by apt and then you use the tar.gz from, you have to delete the folder located in /usr/lib/node_modules.

Python - abs vs fabs

math.fabs() always returns float, while abs() may return integer.

javax vs java package

Javax used to be only for extensions. Yet later sun added it to the java libary forgetting to remove the x. Developers started making code with javax. Yet later on in time suns decided to change it to java. Developers didn't like the idea because they're code would be ruined... so javax was kept.

Could not find a version that satisfies the requirement tensorflow

As of October 2020:

  • Tensorflow only supports the 64-bit version of Python

  • Tensorflow only supports Python 3.5 to 3.8

So, if you're using an out-of-range version of Python (older or newer) or a 32-bit version, then you'll need to use a different version.

Ajax LARAVEL 419 POST error

You may also get that error when CSRF "token" for the active user session is out of date, even if the token was specified in ajax request.

Efficient way to determine number of digits in an integer

Perhaps I misunderstood the question but doesn't this do it?

int NumDigits(int x)  
    x = abs(x);  
    return (x < 10 ? 1 :   
        (x < 100 ? 2 :   
        (x < 1000 ? 3 :   
        (x < 10000 ? 4 :   
        (x < 100000 ? 5 :   
        (x < 1000000 ? 6 :   
        (x < 10000000 ? 7 :  
        (x < 100000000 ? 8 :  
        (x < 1000000000 ? 9 :  

jQuery Ajax PUT with parameters

You can use the PUT method and pass data that will be included in the body of the request:

let data = {"key":"value"}

    type: 'PUT',
    url: '',
    contentType: 'application/json',
    data: JSON.stringify(data), // access in body
}).done(function () {
}).fail(function (msg) {
}).always(function (msg) {

Check if something is (not) in a list in Python

The bug is probably somewhere else in your code, because it should work fine:

>>> 3 not in [2, 3, 4]
>>> 3 not in [4, 5, 6]

Or with tuples:

>>> (2, 3) not in [(2, 3), (5, 6), (9, 1)]
>>> (2, 3) not in [(2, 7), (7, 3), "hi"]

Mongoose limit/offset and count query

I suggest you to use 2 queries:

  1. db.collection.count() will return total number of items. This value is stored somewhere in Mongo and it is not calculated.

  2. db.collection.find().skip(20).limit(10) here I assume you could use a sort by some field, so do not forget to add an index on this field. This query will be fast too.

I think that you shouldn't query all items and than perform skip and take, cause later when you have big data you will have problems with data transferring and processing.

SQL - Query to get server's IP address

It's in the @@SERVERNAME variable;


Jquery, set value of td in a table?

Try the code below :

$('#detailInfo').html('your value')

In nodeJs is there a way to loop through an array without using array size?

To print 'item1' , 'item2', this code would work.

var myarray = ['hello', ' hello again'];

for (var item in myarray) {

Parsing a JSON array using Json.Net

Use Manatee.Json

And you can convert the entire object to a string, filename.json is expected to be located in documents folder.

        var text = File.ReadAllText("filename.json");
        var json = JsonValue.Parse(text);

        while (JsonValue.Null != null)


What is the significance of #pragma marks? Why do we need #pragma marks?

#pragma mark is used to tag the group of methods so you may easily find and detect methods from the Jump Bar. It may help you when your code files reach about 1000 lines and you want to find methods quickly through the category from Jump box.

In a long program it becomes difficult to remember and find a method name. So pragma mark allows you to categorize methods according to the work they do. For example, you tagged some tag for Table View Protocol Methods, AlertView Methods, Init Methods, Declaration etc.

#pragma mark is the facility for XCode but it has no impact on your code. It merely helps to make it easier to find methods while coding.

Difference between the System.Array.CopyTo() and System.Array.Clone()

The Clone() method don't give reference to the target instance just give you a copy. the CopyTo() method copies the elements into an existing instance.

Both don't give the reference of the target instance and as many members says they give shallow copy (illusion copy) without reference this is the key.

Preventing form resubmission

Well I found nobody mentioned this trick.

Without redirection, you can still prevent the form confirmation when refresh.

By default, form code is like this:

<form method="post" action="test.php">

now, change it to <form method="post" action="test.php?nonsense=1">

You will see the magic.

I guess its because browsers won't trigger the confirmation alert popup if it gets a GET method (query string) in the url.

cd into directory without having permission

chmod +x openfire worked for me. It adds execution permission to the openfire folder.

Using client certificate in Curl command

TLS client certificates are not sent in HTTP headers. They are transmitted by the client as part of the TLS handshake, and the server will typically check the validity of the certificate during the handshake as well.

If the certificate is accepted, most web servers can be configured to add headers for transmitting the certificate or information contained on the certificate to the application. Environment variables are populated with certificate information in Apache and Nginx which can be used in other directives for setting headers.

As an example of this approach, the following Nginx config snippet will validate a client certificate, and then set the SSL_CLIENT_CERT header to pass the entire certificate to the application. This will only be set when then certificate was successfully validated, so the application can then parse the certificate and rely on the information it bears.

server {
    listen 443 ssl;
    ssl_certificate /path/to/chainedcert.pem;  # server certificate
    ssl_certificate_key /path/to/key;          # server key

    ssl_client_certificate /path/to/ca.pem;    # client CA
    ssl_verify_client on;
    proxy_set_header SSL_CLIENT_CERT $ssl_client_cert;

    location / {
        proxy_pass http://localhost:3000;

How to remove all namespaces from XML with C#?

This is a solution based on Peter Stegnar's accepted answer.

I used it, but (as andygjp and John Saunders remarked) his code ignores attributes.

I needed to take care of attributes too, so I adapted his code. Andy's version was Visual Basic, this is still c#.

I know it's been a while, but perhaps it'll save somebody some time one day.

    private static XElement RemoveAllNamespaces(XElement xmlDocument)
        XElement xmlDocumentWithoutNs = removeAllNamespaces(xmlDocument);
        return xmlDocumentWithoutNs;

    private static XElement removeAllNamespaces(XElement xmlDocument)
        var stripped = new XElement(xmlDocument.Name.LocalName);            
        foreach (var attribute in
                attribute =>
                    !attribute.IsNamespaceDeclaration &&
            stripped.Add(new XAttribute(attribute.Name.LocalName, attribute.Value));
        if (!xmlDocument.HasElements)
            stripped.Value = xmlDocument.Value;
            return stripped;
            el =>
        return stripped;

What do column flags mean in MySQL Workbench?

PK - Primary Key

NN - Not Null

BIN - Binary (stores data as binary strings. There is no character set so sorting and comparison is based on the numeric values of the bytes in the values.)

UN - Unsigned (non-negative numbers only. so if the range is -500 to 500, instead its 0 - 1000, the range is the same but it starts at 0)

UQ - Create/remove Unique Key

ZF - Zero-Filled (if the length is 5 like INT(5) then every field is filled with 0’s to the 5th digit. 12 = 00012, 400 = 00400, etc. )

AI - Auto Increment

G - Generated column. i.e. value generated by a formula based on the other columns

Java Map equivalent in C#

Dictionary<,> is the equivalent. While it doesn't have a Get(...) method, it does have an indexed property called Item which you can access in C# directly using index notation:

class Test {
  Dictionary<int,String> entities;

  public String getEntity(int code) {
    return this.entities[code];

If you want to use a custom key type then you should consider implementing IEquatable<> and overriding Equals(object) and GetHashCode() unless the default (reference or struct) equality is sufficient for determining equality of keys. You should also make your key type immutable to prevent weird things happening if a key is mutated after it has been inserted into a dictionary (e.g. because the mutation caused its hash code to change).

Getting the 'external' IP address in Java


Xcode 4 - "Valid signing identity not found" error on provisioning profiles on a new Macintosh install

With Xcode 4.2 and later versions, including Xcode 4.6, there is a better way to migrate your entire developer profile to a new machine. On your existing machine, launch Xcode and do this:

  1. Open the Organizer (Shift-Command-2).
  2. Select the Devices tab.
  3. Choose Developer Profile in the upper-left corner under LIBRARY, which may be under the heading library or under a heading called TEAMS.
  4. Choose Export near the bottom left side of the window. Xcode asks you to choose a file name and password.

Edit for Xcode 4.4:

With Xcode 4.4, at step 3 choose Provisioning Profiles under LIBRARY. Then select your provisioning profiles either with the mouse or Command-A.

Also, Apple is making improvements in the way they manage this aspect of Xcode, and some users have reported that the Refresh button in the lower-right corner does the trick. So try clicking Refresh first, and if that doesn't help, do the export/import sequence.

Picture for Xcode 4.6 added by WP

screenshot of enter password to secure developer profile

Edit for Xcode 5.0 or newer:

  1. Open Xcode -> Preferences ('Command' + ',')
  2. Select the Apple ID from the list.
  3. Click on the SETTING icon near the bottom-left corner of window, and choose EXPORT ACCOUNTS... Xcode asks you to choose a file name and password.

On your new machine, launch Xcode and import the profile you exported above. Works like a charm.

Picture for Xcode 5.0 added by Ankur

For Xcode 5 or newer versions

AppStore - App status is ready for sale, but not in app store

You have to go to the "Pricing" menu. Even if the availability date is in the past, sometimes you have to set it again for today's date. Apple doesn't tell you to do this, but I found that the app goes live after resetting the dates again, especially if there's been app rejections in the past. I guess it messes up with the dates. Looks like sometimes if you do nothing and just follow the instructions, the app will never go live.

Change type of varchar field to integer: "cannot be cast automatically to type integer"

Try this, it will work for sure.

When writing Rails migrations to convert a string column to an integer you'd usually say:

change_column :table_name, :column_name, :integer

However, PostgreSQL will complain:

PG::DatatypeMismatch: ERROR:  column "column_name" cannot be cast automatically to type integer
HINT:  Specify a USING expression to perform the conversion.

The "hint" basically tells you that you need to confirm you want this to happen, and how data shall be converted. Just say this in your migration:

change_column :table_name, :column_name, 'integer USING CAST(column_name AS integer)'

The above will mimic what you know from other database adapters. If you have non-numeric data, results may be unexpected (but you're converting to an integer, after all).

JavaScript listener, "keypress" doesn't detect backspace?

Use one of keyup / keydown / beforeinput events instead.

based on this reference, keypress is deprecated and no longer recommended.

The keypress event is fired when a key that produces a character value is pressed down. Examples of keys that produce a character value are alphabetic, numeric, and punctuation keys. Examples of keys that don't produce a character value are modifier keys such as Alt, Shift, Ctrl, or Meta.

if you use "beforeinput" be careful about it's Browser compatibility. the difference between "beforeinput" and the other two is that "beforeinput" is fired when input value is about to changed, so with characters that can't change the input value, it is not fired (e.g shift, ctr ,alt).

I had the same problem and by using keyup it was solved.

How to count items in JSON object using command line?

You can also use jq to track down the array within the returned json and then pipe that in to a second jq call to get its length. Suppose it was in a property called records, like {"records":[...]}.

$ curl | jq -r '.records' | jq length

What is the T-SQL syntax to connect to another SQL Server?

In SQL Server Management Studio, turn on SQLCMD mode from the Query menu. Then at the top of your script, type in the command below

:Connect server_name[\instance_name] [-l timeout] [-U user_name [-P password]

If you are connecting to multiple servers, be sure to insert GO between connections; otherwise your T-SQL won't execute on the server you're thinking it will.

Hide Twitter Bootstrap nav collapse on click

I just replicate the 2 attributes of the btn-navbar (data-toggle="collapse" data-target="") on each link like this:

<div class="nav-collapse">
  <ul class="nav" >
    <li class="active"><a href="#home" data-toggle="collapse" data-target="">Home</a></li>
    <li><a href="#about" data-toggle="collapse" data-target="">About</a></li>
    <li><a href="#portfolio" data-toggle="collapse" data-target="">Portfolio</a></li>
    <li><a href="#services" data-toggle="collapse" data-target="">Services</a></li>
    <li><a href="#contact" data-toggle="collapse" data-target="">Contact</a></li>

In the Bootstrap 4 Navbar, in has changed to show so the syntax would be:

data-toggle="collapse" data-target=""

How to undo last commit

Warning: Don't do this if you've already pushed

You want to do:

git reset HEAD~

If you don't want the changes and blow everything away:

git reset --hard HEAD~

Add to integers in a list

fooList = [1,3,348,2]
print(fooList) # [1,3,348,2,3,2734]

Why I can't access remote Jupyter Notebook server?

From your command line, we can see your jupyter server is running normally.The reason you can't access your remote jupyter server is that your remote centos6.5 server's firewall rules block the incoming request from your local browser,i.e. block your tcp:8045 port.
sudo ufw allow 80 # enable http server
sudo ufw allow 443 # enable https server
sudo ufw allow 8045 # enable your tcp:8045 port
then try to access your jupyter again.

Maybe you also need to uncomment and edit that place in your file:

c.NotebookApp.allow_remote_access = True

and even shut down your VPN if you have one.

Any way to make a WPF textblock selectable?

I've implemented SelectableTextBlock in my opensource controls library. You can use it like this:

<jc:SelectableTextBlock Text="Some text" />

Remove innerHTML from div

To remove all child elements from your div:


.removeData() and the corresponding .data() function are used to attach data behind an element, say if you wanted to note that a specific list element referred to user ID 25 in your database:

var $li = $('<li>Joe</li>').data('id', 25);

Given a URL to a text file, what is the simplest way to read the contents of the text file?

Just updating here solution suggested by @ken-kinder for Python 2 to work for Python 3:

import urllib

Can we set a Git default to fetch all tags during a remote pull?

I use this with magit on

[remote "upstream"]
    url = <redacted>
    fetch = +refs/heads/*:refs/remotes/upstream/*
    tagOpt = --tags

Finding duplicate values in MySQL

    (SELECT COUNT(*) FROM city AS tt WHERE AS count 
FROM `city` AS t 
    (SELECT count(*) FROM city AS tt WHERE > 1 ORDER BY count DESC

How do I activate C++ 11 in CMake?

What works for me is to set the following line in your CMakeLists.txt:

set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

Setting this command activates the C++11 features for the compiler and after executing the cmake .. command, you should be able to use range based for loops in your code and compile it without any errors.

What's the proper way to compare a String to an enum value?

This seems to be clean.

public enum Plane{

 * BOEING_747 plane.

 * AIRBUS_A380 Plane.


private final String plane;       

private Plane(final String plane) {
    this.plane= plane;


 * toString method.
 * @return Value of this Enum as String.
public String toString(){
   return plane;

 * This method add support to compare Strings with the equalsIgnoreCase String method.
 * Replicated functionality of the equalsIgnorecase of the java.lang.String.class
 * @param value String to test.
 * @return True if equal otherwise false.
public boolean equalsIgnoreCase(final String value){
    return plane.equalsIgnoreCase(value);

And then in main code:

String airplane="BOEING_747";


Python function attributes - uses and abuses

I typically use function attributes as storage for annotations. Suppose I want to write, in the style of C# (indicating that a certain method should be part of the web service interface)

class Foo(WebService):
    def bar(self, arg1, arg2):

then I can define

def webmethod(func):
    func.is_webmethod = True
    return func

Then, when a webservice call arrives, I look up the method, check whether the underlying function has the is_webmethod attribute (the actual value is irrelevant), and refuse the service if the method is absent or not meant to be called over the web.

How to use underscore.js as a template engine?

with express it's so easy. all what you need is to use the consolidate module on node so you need to install it :

npm install consolidate --save

then you should change the default engine to html template by this:

app.set('view engine', 'html');

register the underscore template engine for the html extension:

app.engine('html', require('consolidate').underscore);

it's done !

Now for load for example an template called 'index.html':

res.render('index', { title : 'my first page'});

maybe you will need to install the underscore module.

npm install underscore --save

I hope this helped you!

CodeIgniter removing index.php from url

Besides these answers, one can just, add index.php or edit it (if it is already there) - for security you want to disable index.php anyway, from listing the files in your website directory - then change the content into