Programs & Examples On #Instance

In object-oriented programming an instance is an occurrence or a copy of an object, whether currently executing or not.

The difference between Classes, Objects, and Instances

Class is a template or type. An object is an instance of the class.

For example:

public class Tweet {

}

Tweet newTweet = new Tweet();

Tweet is a class and newTweet is an object of the class.

Python object deleting itself

I can't tell you how this is possible with classes, but functions can delete themselves.

def kill_self(exit_msg = 'killed'):
    global kill_self
    del kill_self
    return exit_msg

And see the output:

 >>> kill_self
<function kill_self at 0x02A2C780>
>>> kill_self()
'killed'
>>> kill_self
Traceback (most recent call last):
  File "<pyshell#28>", line 1, in <module>
    kill_self
NameError: name 'kill_self' is not defined

I don't think that deleting an individual instance of a class without knowing the name of it is possible.

NOTE: If you assign another name to the function, the other name will still reference the old one, but will cause errors once you attempt to run it:

>>> x = kill_self
>>> kill_self()
>>> kill_self
NameError: name 'kill_self' is not defined
>>> x
<function kill_self at 0x...>
>>> x()
NameError: global name 'kill_self' is not defined

What is the difference between an Instance and an Object?

I can't believe, except for one guy no one has used the code to explain this, let me give it a shot too!

// Design Class
class HumanClass {
    var name:String
    init(name:String) {
        self.name = name
    }
}

var humanClassObject1 = HumanClass(name: "Rehan") 

Now the left side i.e: "humanClassObject1" is the object and the right side i.e: HumanClass(name: "Rehan") is the instance of this object.

var humanClassObject2 = HumanClass(name: "Ahmad") // again object on left and it's instance on the right.

So basically, instance contains the specific values for that object and objects contains the memory location (at run-time).

Remember the famous statement "object reference not set to an instance of an object", this means that non-initialised objects don't have any instance. In some programming languages like swift the compiler will not allow you to even design a class that don't have any way to initialise all it's members (variable eg: name, age e.t.c), but in some language you are allowed to do this:

// Design Class
class HumanClass {
    var name:String // See we don't have any way to initialise name property.
}

And the error will only be shown at run time when you try to do something like this:

var myClass = HumanClass()
print(myClass.name) // will give, object reference not set to an instance of the object.

This error indicates that, the specific values (for variables\property) is the "INSTANCE" as i tried to explain this above! And the object i.e: "myClass" contains the memory location (at run-time).

What exactly is an instance in Java?

Computer c= new Computer()

Here an object is created from the Computer class. A reference named c allows the programmer to access the object.

How to create a list of objects?

You can create a list of objects in one line using a list comprehension.

class MyClass(object): pass

objs = [MyClass() for i in range(10)]

print(objs)

best way to create object

There's not really a best way. Both are quite the same, unless you want to do some additional processing using the parameters passed to the constructor during initialization or if you want to ensure a coherent state just after calling the constructor. If it is the case, prefer the first one.

But for readability/maintainability reasons, avoid creating constructors with too many parameters.

In this case, both will do.

__init__ and arguments in Python

Every method needs to accept one argument: The instance itself (or the class if it is a static method).

Read more about classes in Python.

Can we create an instance of an interface in Java?

Yes it is correct. you can do it with an inner class.

How to get character array from a string?

This is an old question but I came across another solution not yet listed.

You can use the Object.assign function to get the desired output:

_x000D_
_x000D_
var output = Object.assign([], "Hello, world!");_x000D_
console.log(output);_x000D_
    // [ 'H', 'e', 'l', 'l', 'o', ',', ' ', 'w', 'o', 'r', 'l', 'd', '!' ]
_x000D_
_x000D_
_x000D_

Not necessarily right or wrong, just another option.

Object.assign is described well at the MDN site.

How to read the content of a file to a string in C?

If you are reading special files like stdin or a pipe, you are not going to be able to use fstat to get the file size beforehand. Also, if you are reading a binary file fgets is going to lose the string size information because of embedded '\0' characters. Best way to read a file then is to use read and realloc:

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

int main () {
    char buf[4096];
    ssize_t n;
    char *str = NULL;
    size_t len = 0;
    while (n = read(STDIN_FILENO, buf, sizeof buf)) {
        if (n < 0) {
            if (errno == EAGAIN)
                continue;
            perror("read");
            break;
        }
        str = realloc(str, len + n + 1);
        memcpy(str + len, buf, n);
        len += n;
        str[len] = '\0';
    }
    printf("%.*s\n", len, str);
    return 0;
}

ERROR 1049 (42000): Unknown database 'mydatabasename'

If dump file contains:

CREATE DATABASE mydatabasename;
USE mydatabasename; 

You may just use in CLI:

mysql -uroot –pmypassword < mydatabase.sql

It works.

How to find a string inside a entire database?

create procedure usp_find_string(@string as varchar(1000))
as
begin
declare @mincounter as int
declare @maxcounter as int
declare @stmtquery as varchar(1000)
set @stmtquery=''
create table #tmp(tablename varchar(128),columnname varchar(128),rowid int identity)
create table #tablelist(tablename varchar(128),columnname varchar(128))
declare @tmp table(name varchar(128))
declare @tablename as varchar(128)
declare @columnname as varchar(128)

insert into #tmp(tablename,columnname)
select a.name,b.name as columnname from sysobjects a
inner join syscolumns b on a.name=object_name(b.id)
where a.type='u'
and b.xtype in(select xtype from systypes
    where name='text' or name='ntext' or name='varchar' or name='nvarchar' or name='char' or name='nchar')
order by a.name

select @maxcounter=max(rowid),@mincounter=min(rowid) from #tmp 
while(@mincounter <= @maxcounter )
begin
 select @tablename=tablename, @columnname=columnname from #tmp where rowid=@mincounter
 set @stmtquery ='select top 1  ' + '[' +@columnname+']' + ' from ' + '['+@tablename+']' + ' where ' + '['+@columnname+']' + ' like ' + '''%' + @string + '%'''
 insert into @tmp(name) exec(@stmtquery)
 if @@rowcount >0
 insert into #tablelist values(@tablename,@columnname)
 set @mincounter=@mincounter +1
end
select * from #tablelist
end

Automatic date update in a cell when another cell's value changes (as calculated by a formula)

You could fill the dependend cell (D2) by a User Defined Function (VBA Macro Function) that takes the value of the C2-Cell as input parameter, returning the current date as ouput.

Having C2 as input parameter for the UDF in D2 tells Excel that it needs to reevaluate D2 everytime C2 changes (that is if auto-calculation of formulas is turned on for the workbook).

EDIT:

Here is some code:

For the UDF:

    Public Function UDF_Date(ByVal data) As Date

        UDF_Date = Now()

    End Function

As Formula in D2:

=UDF_Date(C2)

You will have to give the D2-Cell a Date-Time Format, or it will show a numeric representation of the date-value.

And you can expand the formula over the desired range by draging it if you keep the C2 reference in the D2-formula relative.

Note: This still might not be the ideal solution because every time Excel recalculates the workbook the date in D2 will be reset to the current value. To make D2 only reflect the last time C2 was changed there would have to be some kind of tracking of the past value(s) of C2. This could for example be implemented in the UDF by providing also the address alonside the value of the input parameter, storing the input parameters in a hidden sheet, and comparing them with the previous values everytime the UDF gets called.

Addendum:

Here is a sample implementation of an UDF that tracks the changes of the cell values and returns the date-time when the last changes was detected. When using it, please be aware that:

  • The usage of the UDF is the same as described above.

  • The UDF works only for single cell input ranges.

  • The cell values are tracked by storing the last value of cell and the date-time when the change was detected in the document properties of the workbook. If the formula is used over large datasets the size of the file might increase considerably as for every cell that is tracked by the formula the storage requirements increase (last value of cell + date of last change.) Also, maybe Excel is not capable of handling very large amounts of document properties and the code might brake at a certain point.

  • If the name of a worksheet is changed all the tracking information of the therein contained cells is lost.

  • The code might brake for cell-values for which conversion to string is non-deterministic.

  • The code below is not tested and should be regarded only as proof of concept. Use it at your own risk.

    Public Function UDF_Date(ByVal inData As Range) As Date
    
        Dim wb As Workbook
        Dim dProps As DocumentProperties
        Dim pValue As DocumentProperty
        Dim pDate As DocumentProperty
        Dim sName As String
        Dim sNameDate As String
    
        Dim bDate As Boolean
        Dim bValue As Boolean
        Dim bChanged As Boolean
    
        bDate = True
        bValue = True
    
        bChanged = False
    
    
        Dim sVal As String
        Dim dDate As Date
    
        sName = inData.Address & "_" & inData.Worksheet.Name
        sNameDate = sName & "_dat"
    
        sVal = CStr(inData.Value)
        dDate = Now()
    
        Set wb = inData.Worksheet.Parent
    
        Set dProps = wb.CustomDocumentProperties
    
    On Error Resume Next
    
        Set pValue = dProps.Item(sName)
    
        If Err.Number <> 0 Then
            bValue = False
            Err.Clear
        End If
    
    On Error GoTo 0
    
        If Not bValue Then
            bChanged = True
            Set pValue = dProps.Add(sName, False, msoPropertyTypeString, sVal)
        Else
            bChanged = pValue.Value <> sVal
            If bChanged Then
                pValue.Value = sVal
            End If
        End If
    
    On Error Resume Next
    
        Set pDate = dProps.Item(sNameDate)
    
        If Err.Number <> 0 Then
            bDate = False
            Err.Clear
        End If
    
    On Error GoTo 0
    
        If Not bDate Then
            Set pDate = dProps.Add(sNameDate, False, msoPropertyTypeDate, dDate)
        End If
    
        If bChanged Then
            pDate.Value = dDate
        Else
            dDate = pDate.Value
        End If
    
    
        UDF_Date = dDate
     End Function
    

Make the insertion of the date conditional upon the range.

This has an advantage of not changing the dates unless the content of the cell is changed, and it is in the range C2:C2, even if the sheet is closed and saved, it doesn't recalculate unless the adjacent cell changes.

Adapted from this tip and @Paul S answer

Private Sub Worksheet_Change(ByVal Target As Range)
 Dim R1 As Range
 Dim R2 As Range
 Dim InRange As Boolean
    Set R1 = Range(Target.Address)
    Set R2 = Range("C2:C20")
    Set InterSectRange = Application.Intersect(R1, R2)

  InRange = Not InterSectRange Is Nothing
     Set InterSectRange = Nothing
   If InRange = True Then
     R1.Offset(0, 1).Value = Now()
   End If
     Set R1 = Nothing
     Set R2 = Nothing
 End Sub

jQuery - multiple $(document).ready ...?

$(document).ready(); is the same as any other function. it fires once the document is ready - ie loaded. the question is about what happens when multiple $(document).ready()'s are fired not when you fire the same function within multiple $(document).ready()'s

//this
<div id="target"></div>

$(document).ready(function(){
   jQuery('#target').append('target edit 1<br>');
});
$(document).ready(function(){
   jQuery('#target').append('target edit 2<br>');
});
$(document).ready(function(){
   jQuery('#target').append('target edit 3<br>');
});

//is the same as
<div id="target"></div>

$(document).ready(function(){

    jQuery('#target').append('target edit 1<br>');

    jQuery('#target').append('target edit 2<br>');

    jQuery('#target').append('target edit 3<br>');

});

both will behave exactly the same. the only difference is that although the former will achieve the same results. the latter will run a fraction of a second faster and requires less typing. :)

in conclusion where ever possible only use 1 $(document).ready();

//old answer

They will both get called in order. Best practice would be to combine them. but dont worry if its not possible. the page will not explode.

Fill formula down till last row in column

Alternatively, you may use FillDown

Range("M3") = "=G3&"",""&L3": Range("M3:M" & LastRow).FillDown

How to find rows that have a value that contains a lowercase letter

SELECT * FROM my_table WHERE my_column = 'my string'
COLLATE Latin1_General_CS_AS

This would make a case sensitive search.


EDIT

As stated in kouton's comment here and tormuto's comment here whosoever faces problem with the below collation

COLLATE Latin1_General_CS_AS

should first check the default collation for their SQL server, their respective database and the column in question; and pass in the default collation with the query expression. List of collations can be found here.

Android button onClickListener

easy:

launching activity (onclick handler)

 Intent myIntent = new Intent(CurrentActivity.this, NextActivity.class);
 myIntent.putExtra("key", value); //Optional parameters
 CurrentActivity.this.startActivity(myIntent);

on the new activity:

@Override
protected void onCreate(Bundle savedInstanceState) {
Intent intent = getIntent();
String value = intent.getStringExtra("key"); //if it's a string you stored.

and add your new activity in the AndroidManifest.xml:

<activity android:label="@string/app_name" android:name="NextActivity"/>

Java string split with "." (dot)

This is because . is a reserved character in regular expression, representing any character. Instead, we should use the following statement:

String extensionRemoved = filename.split("\\.")[0];

Facebook page automatic "like" URL (for QR Code)

Have you tried using the fb:// protocol?

To have them like your page when they scan the qr code, it goes like this:

fb://page/(pageID)/addfan

If you need to get the pageID, replace "www" with "graph" in the Facebook url when you visit your page in a desktop browser and it will display the ID and other data.

Not only does this add them automatically, but it opens up the page in the FB app instead of the mobile browser.

As far as legality, I would assume as long as you put something like "Scan to like our page", you're in the clear. They know what they're getting into.

Docker for Windows error: "Hardware assisted virtualization and data execution protection must be enabled in the BIOS"

I have tried many suggestions above but docker keeps complaining about hardware assisted virtualization error. Virtualization is enabled in BIOS, and also Hyper-V is installed and enabled. After a few try and errors, I eventually downloaded coreinfo tool and found out that Hypervisor was not actually enabled. Using ISE (64 bit) as admin and run command from above Solution B and that enables Hypervisor successfully (checked via coreinfo -v again). After restart, docker is now running successfully.

How to import functions from different js file in a Vue+webpack+vue-loader project

I like the answer of Anacrust, though, by the fact "console.log" is executed twice, I would like to do a small update for src/mylib.js:

let test = {
  foo () { return 'foo' },
  bar () { return 'bar' },
  baz () { return 'baz' }
}

export default test

All other code remains the same...

d3 add text to circle

Here is an example showing some text in circles with data from a json file: http://bl.ocks.org/4474971. Which gives the following:

enter image description here

The main idea behind this is to encapsulate the text and the circle in the same "div" as you would do in html to have the logo and the name of the company in the same div in a page header.

The main code is:

var width = 960,
    height = 500;

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height)

d3.json("data.json", function(json) {
    /* Define the data for the circles */
    var elem = svg.selectAll("g")
        .data(json.nodes)

    /*Create and place the "blocks" containing the circle and the text */  
    var elemEnter = elem.enter()
        .append("g")
        .attr("transform", function(d){return "translate("+d.x+",80)"})

    /*Create the circle for each block */
    var circle = elemEnter.append("circle")
        .attr("r", function(d){return d.r} )
        .attr("stroke","black")
        .attr("fill", "white")

    /* Create the text for each block */
    elemEnter.append("text")
        .attr("dx", function(d){return -20})
        .text(function(d){return d.label})
})

and the json file is:

{"nodes":[
  {"x":80, "r":40, "label":"Node 1"}, 
  {"x":200, "r":60, "label":"Node 2"}, 
  {"x":380, "r":80, "label":"Node 3"}
]}

The resulting html code shows the encapsulation you want:

<svg width="960" height="500">
    <g transform="translate(80,80)">
        <circle r="40" stroke="black" fill="white"></circle>
        <text dx="-20">Node 1</text>
    </g>
    <g transform="translate(200,80)">
        <circle r="60" stroke="black" fill="white"></circle>
        <text dx="-20">Node 2</text>
    </g>
    <g transform="translate(380,80)">
        <circle r="80" stroke="black" fill="white"></circle>
        <text dx="-20">Node 3</text>
    </g>
</svg>

Search and replace a line in a file in Python

Create a new file, copy lines from the old to the new, and do the replacing before you write the lines to the new file.

Alter a SQL server function to accept new optional parameter

From CREATE FUNCTION:

When a parameter of the function has a default value, the keyword DEFAULT must be specified when the function is called to retrieve the default value. This behavior is different from using parameters with default values in stored procedures in which omitting the parameter also implies the default value.

So you need to do:

SELECT dbo.fCalculateEstimateDate(647,DEFAULT)

Experimental decorators warning in TypeScript compilation

have to add typescript.tsdk to my .vscode/settings.json:

"typescript.tsdk": "node_modules/typescript/lib"

Heap vs Binary Search Tree (BST)

Summary

          Type      BST (*)   Heap
Insert    average   log(n)    1
Insert    worst     log(n)    log(n) or n (***)
Find any  worst     log(n)    n
Find max  worst     1 (**)    1
Create    worst     n log(n)  n
Delete    worst     log(n)    log(n)

All average times on this table are the same as their worst times except for Insert.

  • *: everywhere in this answer, BST == Balanced BST, since unbalanced sucks asymptotically
  • **: using a trivial modification explained in this answer
  • ***: log(n) for pointer tree heap, n for dynamic array heap

Advantages of binary heap over a BST

  • average time insertion into a binary heap is O(1), for BST is O(log(n)). This is the killer feature of heaps.

    There are also other heaps which reach O(1) amortized (stronger) like the Fibonacci Heap, and even worst case, like the Brodal queue, although they may not be practical because of non-asymptotic performance: Are Fibonacci heaps or Brodal queues used in practice anywhere?

  • binary heaps can be efficiently implemented on top of either dynamic arrays or pointer-based trees, BST only pointer-based trees. So for the heap we can choose the more space efficient array implementation, if we can afford occasional resize latencies.

  • binary heap creation is O(n) worst case, O(n log(n)) for BST.

Advantage of BST over binary heap

  • search for arbitrary elements is O(log(n)). This is the killer feature of BSTs.

    For heap, it is O(n) in general, except for the largest element which is O(1).

"False" advantage of heap over BST

  • heap is O(1) to find max, BST O(log(n)).

    This is a common misconception, because it is trivial to modify a BST to keep track of the largest element, and update it whenever that element could be changed: on insertion of a larger one swap, on removal find the second largest. Can we use binary search tree to simulate heap operation? (mentioned by Yeo).

    Actually, this is a limitation of heaps compared to BSTs: the only efficient search is that for the largest element.

Average binary heap insert is O(1)

Sources:

Intuitive argument:

  • bottom tree levels have exponentially more elements than top levels, so new elements are almost certain to go at the bottom
  • heap insertion starts from the bottom, BST must start from the top

In a binary heap, increasing the value at a given index is also O(1) for the same reason. But if you want to do that, it is likely that you will want to keep an extra index up-to-date on heap operations How to implement O(logn) decrease-key operation for min-heap based Priority Queue? e.g. for Dijkstra. Possible at no extra time cost.

GCC C++ standard library insert benchmark on real hardware

I benchmarked the C++ std::set (Red-black tree BST) and std::priority_queue (dynamic array heap) insert to see if I was right about the insert times, and this is what I got:

enter image description here

  • benchmark code
  • plot script
  • plot data
  • tested on Ubuntu 19.04, GCC 8.3.0 in a Lenovo ThinkPad P51 laptop with CPU: Intel Core i7-7820HQ CPU (4 cores / 8 threads, 2.90 GHz base, 8 MB cache), RAM: 2x Samsung M471A2K43BB1-CRC (2x 16GiB, 2400 Mbps), SSD: Samsung MZVLB512HAJQ-000L7 (512GB, 3,000 MB/s)

So clearly:

  • heap insert time is basically constant.

    We can clearly see dynamic array resize points. Since we are averaging every 10k inserts to be able to see anything at all above system noise, those peaks are in fact about 10k times larger than shown!

    The zoomed graph excludes essentially only the array resize points, and shows that almost all inserts fall under 25 nanoseconds.

  • BST is logarithmic. All inserts are much slower than the average heap insert.

  • BST vs hashmap detailed analysis at: What data structure is inside std::map in C++?

GCC C++ standard library insert benchmark on gem5

gem5 is a full system simulator, and therefore provides an infinitely accurate clock with with m5 dumpstats. So I tried to use it to estimate timings for individual inserts.

enter image description here

Interpretation:

  • heap is still constant, but now we see in more detail that there are a few lines, and each higher line is more sparse.

    This must correspond to memory access latencies are done for higher and higher inserts.

  • TODO I can't really interpret the BST fully one as it does not look so logarithmic and somewhat more constant.

    With this greater detail however we can see can also see a few distinct lines, but I'm not sure what they represent: I would expect the bottom line to be thinner, since we insert top bottom?

Benchmarked with this Buildroot setup on an aarch64 HPI CPU.

BST cannot be efficiently implemented on an array

Heap operations only need to bubble up or down a single tree branch, so O(log(n)) worst case swaps, O(1) average.

Keeping a BST balanced requires tree rotations, which can change the top element for another one, and would require moving the entire array around (O(n)).

Heaps can be efficiently implemented on an array

Parent and children indexes can be computed from the current index as shown here.

There are no balancing operations like BST.

Delete min is the most worrying operation as it has to be top down. But it can always be done by "percolating down" a single branch of the heap as explained here. This leads to an O(log(n)) worst case, since the heap is always well balanced.

If you are inserting a single node for every one you remove, then you lose the advantage of the asymptotic O(1) average insert that heaps provide as the delete would dominate, and you might as well use a BST. Dijkstra however updates nodes several times for each removal, so we are fine.

Dynamic array heaps vs pointer tree heaps

Heaps can be efficiently implemented on top of pointer heaps: Is it possible to make efficient pointer-based binary heap implementations?

The dynamic array implementation is more space efficient. Suppose that each heap element contains just a pointer to a struct:

  • the tree implementation must store three pointers for each element: parent, left child and right child. So the memory usage is always 4n (3 tree pointers + 1 struct pointer).

    Tree BSTs would also need further balancing information, e.g. black-red-ness.

  • the dynamic array implementation can be of size 2n just after a doubling. So on average it is going to be 1.5n.

On the other hand, the tree heap has better worst case insert, because copying the backing dynamic array to double its size takes O(n) worst case, while the tree heap just does new small allocations for each node.

Still, the backing array doubling is O(1) amortized, so it comes down to a maximum latency consideration. Mentioned here.

Philosophy

  • BSTs maintain a global property between a parent and all descendants (left smaller, right bigger).

    The top node of a BST is the middle element, which requires global knowledge to maintain (knowing how many smaller and larger elements are there).

    This global property is more expensive to maintain (log n insert), but gives more powerful searches (log n search).

  • Heaps maintain a local property between parent and direct children (parent > children).

    The top node of a heap is the big element, which only requires local knowledge to maintain (knowing your parent).

Comparing BST vs Heap vs Hashmap:

  • BST: can either be either a reasonable:

    • unordered set (a structure that determines if an element was previously inserted or not). But hashmap tends to be better due to O(1) amortized insert.
    • sorting machine. But heap is generally better at that, which is why heapsort is much more widely known than tree sort
  • heap: is just a sorting machine. Cannot be an efficient unordered set, because you can only check for the smallest/largest element fast.

  • hash map: can only be an unordered set, not an efficient sorting machine, because the hashing mixes up any ordering.

Doubly-linked list

A doubly linked list can be seen as subset of the heap where first item has greatest priority, so let's compare them here as well:

  • insertion:
    • position:
      • doubly linked list: the inserted item must be either the first or last, as we only have pointers to those elements.
      • binary heap: the inserted item can end up in any position. Less restrictive than linked list.
    • time:
      • doubly linked list: O(1) worst case since we have pointers to the items, and the update is really simple
      • binary heap: O(1) average, thus worse than linked list. Tradeoff for having more general insertion position.
  • search: O(n) for both

An use case for this is when the key of the heap is the current timestamp: in that case, new entries will always go to the beginning of the list. So we can even forget the exact timestamp altogether, and just keep the position in the list as the priority.

This can be used to implement an LRU cache. Just like for heap applications like Dijkstra, you will want to keep an additional hashmap from the key to the corresponding node of the list, to find which node to update quickly.

Comparison of different Balanced BST

Although the asymptotic insert and find times for all data structures that are commonly classified as "Balanced BSTs" that I've seen so far is the same, different BBSTs do have different trade-offs. I haven't fully studied this yet, but it would be good to summarize these trade-offs here:

  • Red-black tree. Appears to be the most commonly used BBST as of 2019, e.g. it is the one used by the GCC 8.3.0 C++ implementation
  • AVL tree. Appears to be a bit more balanced than BST, so it could be better for find latency, at the cost of slightly more expensive finds. Wiki summarizes: "AVL trees are often compared with red–black trees because both support the same set of operations and take [the same] time for the basic operations. For lookup-intensive applications, AVL trees are faster than red–black trees because they are more strictly balanced. Similar to red–black trees, AVL trees are height-balanced. Both are, in general, neither weight-balanced nor mu-balanced for any mu < 1/2; that is, sibling nodes can have hugely differing numbers of descendants."
  • WAVL. The original paper mentions advantages of that version in terms of bounds on rebalancing and rotation operations.

See also

Similar question on CS: https://cs.stackexchange.com/questions/27860/whats-the-difference-between-a-binary-search-tree-and-a-binary-heap

How to format a java.sql.Timestamp(yyyy-MM-dd HH:mm:ss.S) to a date(yyyy-MM-dd HH:mm:ss)

You do not need to use substring at all since your format doesn't hold that info.

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String fechaStr = "2013-10-10 10:49:29.10000";  
Date fechaNueva = format.parse(fechaStr);

System.out.println(format.format(fechaNueva)); // Prints 2013-10-10 10:49:29

How do I use the Tensorboard callback of Keras?

Create the Tensorboard callback:

from keras.callbacks import TensorBoard
from datetime import datetime
logDir = "./Graph/" + datetime.now().strftime("%Y%m%d-%H%M%S") + "/"
tb = TensorBoard(log_dir=logDir, histogram_freq=2, write_graph=True, write_images=True, write_grads=True)

Pass the Tensorboard callback to the fit call:

history = model.fit(X_train, y_train, epochs=200, callbacks=[tb])

When running the model, if you get a Keras error of

"You must feed a value for placeholder tensor"

try reseting the Keras session before the model creation by doing:

import keras.backend as K
K.clear_session()

What does LayoutInflater in Android do?

Here is another example similar to the previous one, but extended to further demonstrate inflate parameters and dynamic behavior it can provide.

Suppose your ListView row layout can have variable number of TextViews. So first you inflate the base item View (just like the previous example), and then loop dynamically adding TextViews at run-time. Using android:layout_weight additionally aligns everything perfectly.

Here are the Layouts resources:

list_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" >
    <TextView 
        android:id="@+id/field1"
        android:layout_width="0dp"  
        android:layout_height="wrap_content" 
        android:layout_weight="2"/>
    <TextView 
        android:id="@+id/field2"
        android:layout_width="0dp"  
        android:layout_height="wrap_content" 
        android:layout_weight="1"
/>
</LinearLayout>

schedule_layout.xml

<?xml version="1.0" encoding="utf-8"?>
   <TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="0dp"  
    android:layout_height="wrap_content" 
    android:layout_weight="1"/>

Override getView method in extension of BaseAdapter class

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = activity.getLayoutInflater();
    View lst_item_view = inflater.inflate(R.layout.list_layout, null);
    TextView t1 = (TextView) lst_item_view.findViewById(R.id.field1);
    TextView t2 = (TextView) lst_item_view.findViewById(R.id.field2);
    t1.setText("some value");
    t2.setText("another value");

    // dinamically add TextViews for each item in ArrayList list_schedule
    for(int i = 0; i < list_schedule.size(); i++){
        View schedule_view = inflater.inflate(R.layout.schedule_layout, (ViewGroup) lst_item_view, false);
        ((TextView)schedule_view).setText(list_schedule.get(i));
        ((ViewGroup) lst_item_view).addView(schedule_view);
    }
    return lst_item_view;
}

Note different inflate method calls:

inflater.inflate(R.layout.list_layout, null); // no parent
inflater.inflate(R.layout.schedule_layout, (ViewGroup) lst_item_view, false); // with parent preserving LayoutParams

What does ellipsize mean in android?

for my experience, Ellipsis works only if below two attributes are set.

android:ellipsize="end"
android:singleLine="true"

for the width of textview, wrap_content or match_parent should both be good.

sending mail from Batch file

We use blat to do this all the time in our environment. I use it as well to connect to Gmail with Stunnel. Here's the params to send a file

blat -to [email protected] -server smtp.example.com -f [email protected] -subject "subject" -body "body" -attach c:\temp\file.txt

Or you can put that file in as the body

blat c:\temp\file.txt -to [email protected] -server smtp.example.com -f [email protected] -subject "subject"

Input size vs width

I suggest, probably best way is to set style's width in em unit :) So for input size of 20 characters just set style='width:20em' :)

PHP/regex: How to get the string value of HTML tag?

try $pattern = "<($tagname)\b.*?>(.*?)</\1>" and return $matches[2]

multiple where condition codeigniter

you can use both use array like :

$array = array('tlb_account.crid' =>$value , 'tlb_request.sign'=> 'FALSE' );

and direct assign like:

$this->db->where('tlb_account.crid' =>$value , 'tlb_request.sign'=> 'FALSE');

I wish help you.

How to perform a fade animation on Activity transition?

You could create your own .xml animation files to fade in a new Activity and fade out the current Activity:

fade_in.xml

<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
           android:interpolator="@android:anim/accelerate_interpolator"
           android:fromAlpha="0.0" android:toAlpha="1.0"
           android:duration="500" />

fade_out.xml

<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
           android:interpolator="@android:anim/accelerate_interpolator"
           android:fromAlpha="1.0" android:toAlpha="0.0"
           android:fillAfter="true"
           android:duration="500" />

Use it in code like that: (Inside your Activity)

Intent i = new Intent(this, NewlyStartedActivity.class);
startActivity(i);
overridePendingTransition(R.anim.fade_in, R.anim.fade_out);

The above code will fade out the currently active Activity and fade in the newly started Activity resulting in a smooth transition.

UPDATE: @Dan J pointed out that using the built in Android animations improves performance, which I indeed found to be the case after doing some testing. If you prefer working with the built in animations, use:

overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);

Notice me referencing android.R instead of R to access the resource id.

UPDATE: It is now common practice to perform transitions using the Transition class introduced in API level 19.

How to get HQ youtube thumbnails?

YouTube resolutions and images

http://img.youtube.com/vi/<video-id>/<resolution><image>.jpg

Resolution
- lowest resolution
sd - Standard Definition
mq - Medium Quality
hq - High Quality
maxres - MAXimum RESolution

Image
default - Default image (1, 2, 3 shot from video, or custom uploaded)
1 - First shot from video
2 - Second shot from video
3 - Third shot from video

Python regex to match dates

I use something like this

>>> import datetime
>>> regex = datetime.datetime.strptime
>>>
>>> # TEST
>>> assert regex('2020-08-03', '%Y-%m-%d')
>>>

>>> assert regex('2020-08', '%Y-%m-%d')
ValueError: time data '2020-08' does not match format '%Y-%m-%d'

>>> assert regex('08/03/20', '%m/%d/%y')
>>>

>>> assert regex('08-03-2020', '%m/%d/%y')
ValueError: time data '08-03-2020' does not match format '%m/%d/%y'

SSRS Field Expression to change the background color of the Cell

The problem with IIF(Fields!column.Value = "Approved", "Green") is that you are missing the third parameter. The correct syntax is IIF( [some boolean expression], [result if boolean expression is true], [result if boolean is false])

Try this

=IIF(Fields!Column.Value = "Approved", "Green", "No Color")

Here is a list of expression examples Expression Examples in Reporting Services

IIF in SSRS report

Connect to sqlplus in a shell script and run SQL scripts

This should handle issue:

  1. WHENEVER SQLERROR EXIT SQL.SQLCODE
  2. SPOOL ${SPOOL_FILE}
  3. $RC returns oracle's exit code
  4. cat from $SPOOL_FILE explains error
SPOOL_FILE=${LOG_DIR}/${LOG_FILE_NAME}.spool 

SQLPLUS_OUTPUT=`sqlplus -s  "$SFDC_WE_CORE" <<EOF 
        SET HEAD OFF
        SET AUTOPRINT OFF
        SET TERMOUT OFF
        SET SERVEROUTPUT ON

        SPOOL  ${SPOOL_FILE} 

        WHENEVER SQLERROR EXIT SQL.SQLCODE
        DECLARE 

        BEGIN
           foooo 
        --rollback; 
        END;
    /
    EOF` 

RC=$?

if [[ $RC != 0 ]] ; then

    echo " RDBMS exit code : $RC  "     | tee -a ${LOG_FILE}
    cat ${SPOOL_FILE}                   | tee -a ${LOG_FILE}

    cat ${LOG_FILE} | mail -s "Script ${INIT_EXE} failed on $SFDC_ENV" $SUPPORT_LIST

    exit 3

fi

Append data to a POST NSURLRequest

Any one looking for a swift solution

let url = NSURL(string: "http://www.apple.com/")
let request = NSMutableURLRequest(URL: url!)
request.HTTPBody = "company=Locassa&quality=AWESOME!".dataUsingEncoding(NSUTF8StringEncoding)

How to Remove Line Break in String

Try with the following line:

CleanString = Application.WorksheetFunction.Clean(MyString)

How to convert BigDecimal to Double in Java?

You can convert BigDecimal to double using .doubleValue(). But believe me, don't use it if you have currency manipulations. It should always be performed on BigDecimal objects directly. Precision loss in these calculations are big time problems in currency related calculations.

initializing a Guava ImmutableMap

Notice that your error message only contains five K, V pairs, 10 arguments total. This is by design; the ImmutableMap class provides six different of() methods, accepting between zero and five key-value pairings. There is not an of(...) overload accepting a varags parameter because K and V can be different types.

You want an ImmutableMap.Builder:

ImmutableMap<String,String> myMap = ImmutableMap.<String, String>builder()
    .put("key1", "value1") 
    .put("key2", "value2") 
    .put("key3", "value3") 
    .put("key4", "value4") 
    .put("key5", "value5") 
    .put("key6", "value6") 
    .put("key7", "value7") 
    .put("key8", "value8") 
    .put("key9", "value9")
    .build();

Gradle finds wrong JAVA_HOME even though it's correctly set

For me an explicit set on the arguments section of the external tools configuration in Eclipse was the problem.

enter image description here

How to retrieve inserted id after inserting row in SQLite using Python?

You could use cursor.lastrowid (see "Optional DB API Extensions"):

connection=sqlite3.connect(':memory:')
cursor=connection.cursor()
cursor.execute('''CREATE TABLE foo (id integer primary key autoincrement ,
                                    username varchar(50),
                                    password varchar(50))''')
cursor.execute('INSERT INTO foo (username,password) VALUES (?,?)',
               ('test','test'))
print(cursor.lastrowid)
# 1

If two people are inserting at the same time, as long as they are using different cursors, cursor.lastrowid will return the id for the last row that cursor inserted:

cursor.execute('INSERT INTO foo (username,password) VALUES (?,?)',
               ('blah','blah'))

cursor2=connection.cursor()
cursor2.execute('INSERT INTO foo (username,password) VALUES (?,?)',
               ('blah','blah'))

print(cursor2.lastrowid)        
# 3
print(cursor.lastrowid)
# 2

cursor.execute('INSERT INTO foo (id,username,password) VALUES (?,?,?)',
               (100,'blah','blah'))
print(cursor.lastrowid)
# 100

Note that lastrowid returns None when you insert more than one row at a time with executemany:

cursor.executemany('INSERT INTO foo (username,password) VALUES (?,?)',
               (('baz','bar'),('bing','bop')))
print(cursor.lastrowid)
# None

How to set headers in http get request?

Go's net/http package has many functions that deal with headers. Among them are Add, Del, Get and Set methods. The way to use Set is:

func yourHandler(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("header_name", "header_value")
}

Only one expression can be specified in the select list when the subquery is not introduced with EXISTS

You can't return two (or multiple) columns in your subquery to do the comparison in the WHERE A_ID IN (subquery) clause - which column is it supposed to compare A_ID to? Your subquery must only return the one column needed for the comparison to the column on the other side of the IN. So the query needs to be of the form:

SELECT * From ThisTable WHERE ThisColumn IN (SELECT ThatColumn FROM ThatTable)

You also want to add sorting so you can select just from the top rows, but you don't need to return the COUNT as a column in order to do your sort; sorting in the ORDER clause is independent of the columns returned by the query.

Try something like this:

select count(distinct dNum) 
from myDB.dbo.AQ 
where A_ID in
    (SELECT DISTINCT TOP (0.1) PERCENT A_ID
    FROM myDB.dbo.AQ 
    WHERE M > 1 and B = 0
    GROUP BY A_ID 
    ORDER BY COUNT(DISTINCT dNum) DESC)

Python/Django: log to console under runserver, log to file under Apache

This works quite well in my local.py, saves me messing up the regular logging:

from .settings import *

LOGGING['handlers']['console'] = {
    'level': 'DEBUG',
    'class': 'logging.StreamHandler',
    'formatter': 'verbose'
}
LOGGING['loggers']['foo.bar'] = {
    'handlers': ['console'],
    'propagate': False,
    'level': 'DEBUG',
}

How to save and load cookies using Python + Selenium WebDriver

Remember, you can only add a cookie for the current domain.

If you want to add a cookie for your Google account, do

browser.get('http://google.com')
for cookie in cookies:
    browser.add_cookie(cookie)

Cloning a private Github repo

git clone https://myusername:[email protected]/myusername/project.git

When you are trying to use private repo from the repo at the time you need to pass username and password for that.

Uncaught SyntaxError: Unexpected end of JSON input at JSON.parse (<anonymous>)

Issue is with the Json.parse of empty array - scatterSeries , as you doing console log of scatterSeries before pushing ch

_x000D_
_x000D_
var data = { "results":[  _x000D_
  [  _x000D_
     {  _x000D_
        "b":"0.110547334",_x000D_
        "cost":"0.000000",_x000D_
        "w":"1.998889"_x000D_
     }_x000D_
  ],_x000D_
  [  _x000D_
     {  _x000D_
        "x":0,_x000D_
        "y":0_x000D_
     },_x000D_
     {  _x000D_
        "x":1,_x000D_
        "y":2_x000D_
     },_x000D_
     {  _x000D_
        "x":2,_x000D_
        "y":4_x000D_
     },_x000D_
     {  _x000D_
        "x":3,_x000D_
        "y":6_x000D_
     },_x000D_
     {  _x000D_
        "x":4,_x000D_
        "y":8_x000D_
     },_x000D_
     {  _x000D_
        "x":5,_x000D_
        "y":10_x000D_
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        "x":6,_x000D_
        "y":12_x000D_
     },_x000D_
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        "x":7,_x000D_
        "y":14_x000D_
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     },_x000D_
     {  _x000D_
        "x":88,_x000D_
        "y":176_x000D_
     },_x000D_
     {  _x000D_
        "x":89,_x000D_
        "y":178_x000D_
     },_x000D_
     {  _x000D_
        "x":90,_x000D_
        "y":180_x000D_
     },_x000D_
     {  _x000D_
        "x":91,_x000D_
        "y":182_x000D_
     },_x000D_
     {  _x000D_
        "x":92,_x000D_
        "y":184_x000D_
     },_x000D_
     {  _x000D_
        "x":93,_x000D_
        "y":186_x000D_
     },_x000D_
     {  _x000D_
        "x":94,_x000D_
        "y":188_x000D_
     },_x000D_
     {  _x000D_
        "x":95,_x000D_
        "y":190_x000D_
     },_x000D_
     {  _x000D_
        "x":96,_x000D_
        "y":192_x000D_
     },_x000D_
     {  _x000D_
        "x":97,_x000D_
        "y":194_x000D_
     },_x000D_
     {  _x000D_
        "x":98,_x000D_
        "y":196_x000D_
     },_x000D_
     {  _x000D_
        "x":99,_x000D_
        "y":198_x000D_
     }_x000D_
  ]]};_x000D_
_x000D_
var scatterSeries = []; _x000D_
_x000D_
var ch = '{"name":"graphe1","items":'+JSON.stringify(data.results[1])+ '}';_x000D_
               console.info(ch);_x000D_
               _x000D_
               scatterSeries.push(JSON.parse(ch));_x000D_
console.info(scatterSeries);
_x000D_
_x000D_
_x000D_

code sample - https://codepen.io/nagasai/pen/GGzZVB

How to save .xlsx data to file as a blob

This works as of: v0.14.0 of https://github.com/SheetJS/js-xlsx

/* generate array buffer */
var wbout = XLSX.write(wb, {type:"array", bookType:'xlsx'});
/* create data URL */
var url = URL.createObjectURL(new Blob([wbout], {type: 'application/octet-stream'}));
/* trigger download with chrome API */
chrome.downloads.download({ url: url, filename: "testsheet.xlsx", saveAs: true });

What is the difference between call and apply?

A well explained by flatline. I just want to add a simple example. which makes it easy to understand for beginners.

func.call(context, args1 , args2 ); // pass arguments as "," saprated value

func.apply(context, [args1 , args2 ]);   //  pass arguments as "Array"

we also use "Call" and "Apply" method for changing reference as defined in code below

_x000D_
_x000D_
    let Emp1 = {_x000D_
        name: 'X',_x000D_
        getEmpDetail: function (age, department) {_x000D_
            console.log('Name :', this.name, '  Age :', age, '  Department :', department)_x000D_
        }_x000D_
    }_x000D_
    Emp1.getEmpDetail(23, 'Delivery')_x000D_
_x000D_
    // 1st approch of chenging "this"_x000D_
    let Emp2 = {_x000D_
        name: 'Y',_x000D_
        getEmpDetail: Emp1.getEmpDetail_x000D_
    }_x000D_
    Emp2.getEmpDetail(55, 'Finance')_x000D_
_x000D_
    // 2nd approch of changing "this" using "Call" and "Apply"_x000D_
    let Emp3 = {_x000D_
        name: 'Z',_x000D_
    }_x000D_
_x000D_
    Emp1.getEmpDetail.call(Emp3, 30, 'Admin')        _x000D_
// here we have change the ref from **Emp1 to Emp3**  object_x000D_
// now this will print "Name =  X" because it is pointing to Emp3 object_x000D_
    Emp1.getEmpDetail.apply(Emp3, [30, 'Admin']) //
_x000D_
_x000D_
_x000D_

Why doesn't catching Exception catch RuntimeException?

Catching Exception will catch a RuntimeException

How do I compare two columns for equality in SQL Server?

What's wrong with CASE for this? In order to see the result, you'll need at least a byte, and that's what you get with a single character.

CASE WHEN COLUMN1 = COLUMN2 THEN '1' ELSE '0' END AS MyDesiredResult

should work fine, and for all intents and purposes accomplishes the same thing as using a bit field.

adding css class to multiple elements

You need to qualify the a part of the selector too:

.button input, .button a {
    //css stuff here
}

Basically, when you use the comma to create a group of selectors, each individual selector is completely independent. There is no relationship between them.

Your original selector therefore matched "all elements of type 'input' that are descendants of an element with the class name 'button', and all elements of type 'a'".

How can I programmatically check whether a keyboard is present in iOS app?

SWIFT 4.2 / SWIFT 5

class Listener {
   public static let shared = Listener()
   var isVisible = false

   // Start this listener if you want to present the toast above the keyboard.
   public func startKeyboardListener() {
      NotificationCenter.default.addObserver(self, selector: #selector(didShow), name: UIResponder.keyboardWillShowNotification, object: nil)
      NotificationCenter.default.addObserver(self, selector: #selector(didHide), name: UIResponder.keyboardWillHideNotification, object: nil)
   }

   @objc func didShow() {
     isVisible = true
   }

    @objc func didHide(){
       isVisible = false
    }
}

Java String to SHA1

Using Guava Hashing class:

Hashing.sha1().hashString( "password", Charsets.UTF_8 ).toString()

How can I clear an HTML file input with JavaScript?

I changed to type text and back to type to file using setAttribute

'<input file-model="thefilePic" style="width:95%;" type="file" name="file" id="filepicture" accept="image/jpeg" />'

'var input=document.querySelector('#filepicture');'

if(input != null)
{
    input.setAttribute("type", "text");
    input.setAttribute("type", "file");
}

Disabling Minimize & Maximize On WinForm?

Right Click the form you want to hide them on, choose Controls -> Properties.

In Properties, set

  • Control Box -> False
  • Minimize Box -> False
  • Maximize Box -> False

You'll do this in the designer.

C# Equivalent of SQL Server DataTypes

In case anybody is looking for methods to convert from/to C# and SQL Server formats, here goes a simple implementation:

private readonly string[] SqlServerTypes = { "bigint", "binary", "bit",  "char", "date",     "datetime", "datetime2", "datetimeoffset", "decimal", "filestream", "float",  "geography",                              "geometry",                              "hierarchyid",                              "image",  "int", "money",   "nchar",  "ntext",  "numeric", "nvarchar", "real",   "rowversion", "smalldatetime", "smallint", "smallmoney", "sql_variant", "text",   "time",     "timestamp", "tinyint", "uniqueidentifier", "varbinary", "varchar", "xml" };
private readonly string[] CSharpTypes    = { "long",   "byte[]", "bool", "char", "DateTime", "DateTime", "DateTime",  "DateTimeOffset", "decimal", "byte[]",     "double", "Microsoft.SqlServer.Types.SqlGeography", "Microsoft.SqlServer.Types.SqlGeometry", "Microsoft.SqlServer.Types.SqlHierarchyId", "byte[]", "int", "decimal", "string", "string", "decimal", "string",   "Single", "byte[]",     "DateTime",      "short",    "decimal",    "object",      "string", "TimeSpan", "byte[]",    "byte",    "Guid",             "byte[]",    "string",  "string" };

public string ConvertSqlServerFormatToCSharp(string typeName)
{
    var index = Array.IndexOf(SqlServerTypes, typeName);

    return index > -1
        ? CSharpTypes[index]
        : "object";
}

public string ConvertCSharpFormatToSqlServer(string typeName)
{
    var index = Array.IndexOf(CSharpTypes, typeName);

    return index > -1
        ? SqlServerTypes[index]
        : null;
}

Edit: fixed typo

How to implement class constants?

Constants can be declare outside of classes and use within your class. Otherwise the get property is a nice workaround

const MY_CONSTANT: string = "wazzup";

export class MyClass {

    public myFunction() {

        alert(MY_CONSTANT);
    }
}

How to change the font color of a disabled TextBox?

I've just found a great way of doing that. In my example I'm using a RichTextBox but it should work with any Control:

public class DisabledRichTextBox : System.Windows.Forms.RichTextBox
{
    // See: http://wiki.winehq.org/List_Of_Windows_Messages

    private const int WM_SETFOCUS   = 0x07;
    private const int WM_ENABLE     = 0x0A;
    private const int WM_SETCURSOR  = 0x20;

    protected override void WndProc(ref System.Windows.Forms.Message m)
    {
        if (!(m.Msg == WM_SETFOCUS || m.Msg == WM_ENABLE || m.Msg == WM_SETCURSOR))
            base.WndProc(ref m);
    }
}

You can safely set Enabled = true and ReadOnly = false, and it will act like a label, preventing focus, user input, cursor change, without being actually disabled.

See if it works for you. Greetings

Hook up Raspberry Pi via Ethernet to laptop without router?

You don't need a cross-over cable. You can use a normal network cable since the Raspberry Pi LAN chip is smart enough to reconfigure itself for direct network connections. Cheers

Removing trailing newline character from fgets() input

If using getline is an option - Not neglecting its security issues and if you wish to brace pointers - you can avoid string functions as the getline returns the number of characters. Something like below

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char *fname, *lname;
    size_t size = 32, nchar; // Max size of strings and number of characters read
    fname = malloc(size * sizeof *fname);
    lname = malloc(size * sizeof *lname);
    if (NULL == fname || NULL == lname)
    {
        printf("Error in memory allocation.");
        exit(1);
    }
    printf("Enter first name ");
    nchar = getline(&fname, &size, stdin);
    if (nchar == -1) // getline return -1 on failure to read a line.
    {
        printf("Line couldn't be read..");
        // This if block could be repeated for next getline too
        exit(1);
    }
    printf("Number of characters read :%zu\n", nchar);
    fname[nchar - 1] = '\0';
    printf("Enter last name ");
    nchar = getline(&lname, &size, stdin);
    printf("Number of characters read :%zu\n", nchar);
    lname[nchar - 1] = '\0';
    printf("Name entered %s %s\n", fname, lname);
    return 0;
}

Note: The [ security issues ] with getline shouldn't be neglected though.

Update multiple tables in SQL Server using INNER JOIN

You can update with a join if you only affect one table like this:

UPDATE table1 
SET table1.name = table2.name 
FROM table1, table2 
WHERE table1.id = table2.id 
AND table2.foobar ='stuff'

But you are trying to affect multiple tables with an update statement that joins on multiple tables. That is not possible.

However, updating two tables in one statement is actually possible but will need to create a View using a UNION that contains both the tables you want to update. You can then update the View which will then update the underlying tables.

SQL JOINS

But this is a really hacky parlor trick, use the transaction and multiple updates, it's much more intuitive.

Pass PDO prepared statement to variables

Instead of using ->bindParam() you can pass the data only at the time of ->execute():

$data = [   ':item_name' => $_POST['item_name'],   ':item_type' => $_POST['item_type'],   ':item_price' => $_POST['item_price'],   ':item_description' => $_POST['item_description'],   ':image_location' => 'images/'.$_FILES['file']['name'],   ':status' => 0,   ':id' => 0, ];  $stmt->execute($data); 

In this way you would know exactly what values are going to be sent.

Find duplicate records in a table using SQL Server

To get the list of multiple records use following command

select field1,field2,field3, count(*)
  from table_name
  group by field1,field2,field3
  having count(*) > 1

MySql Error: Can't update table in stored function/trigger because it is already used by statement which invoked this stored function/trigger

A "BEFORE-INSERT"-trigger is the only way to realize same-table updates on an insert, and is only possible from MySQL 5.5+. However, the value of an auto-increment field is only available to an "AFTER-INSERT" trigger - it defaults to 0 in the BEFORE-case. Therefore the following example code which would set a previously-calculated surrogate key value based on the auto-increment value id will compile, but not actually work since NEW.id will always be 0:

create table products(id int not null auto_increment, surrogatekey varchar(10), description text);
create trigger trgProductSurrogatekey before insert on product
for each row set NEW.surrogatekey = 
  (select surrogatekey from surrogatekeys where id = NEW.id);

How do I set the driver's python version in spark?

Run:

ls -l /usr/local/bin/python*

The first row in this example shows the python3 symlink. To set it as the default python symlink run the following:

ln -s -f /usr/local/bin/python3 /usr/local/bin/python

then reload your shell.

How to commit changes to a new branch

If I understand right, you've made a commit to changed_branch and you want to copy that commit to other_branch? Easy:

git checkout other_branch
git cherry-pick changed_branch

How to compute the similarity between two text documents?

Identical to @larsman, but with some preprocessing

import nltk, string
from sklearn.feature_extraction.text import TfidfVectorizer

nltk.download('punkt') # if necessary...


stemmer = nltk.stem.porter.PorterStemmer()
remove_punctuation_map = dict((ord(char), None) for char in string.punctuation)

def stem_tokens(tokens):
    return [stemmer.stem(item) for item in tokens]

'''remove punctuation, lowercase, stem'''
def normalize(text):
    return stem_tokens(nltk.word_tokenize(text.lower().translate(remove_punctuation_map)))

vectorizer = TfidfVectorizer(tokenizer=normalize, stop_words='english')

def cosine_sim(text1, text2):
    tfidf = vectorizer.fit_transform([text1, text2])
    return ((tfidf * tfidf.T).A)[0,1]


print cosine_sim('a little bird', 'a little bird')
print cosine_sim('a little bird', 'a little bird chirps')
print cosine_sim('a little bird', 'a big dog barks')

Stop form refreshing page on submit

You can use this code for form submission without a page refresh. I have done this in my project.

$(function () {
    $('#myFormName').on('submit',function (e) {

              $.ajax({
                type: 'post',
                url: 'myPageName.php',
                data: $('#myFormName').serialize(),
                success: function () {
                 alert("Email has been sent!");
                }
              });
          e.preventDefault();
        });
});

Parse (split) a string in C++ using string delimiter (standard C++)

This should work perfectly for string (or single character) delimiters. Don't forget to include #include <sstream>.

std::string input = "Alfa=,+Bravo=,+Charlie=,+Delta";
std::string delimiter = "=,+"; 
std::istringstream ss(input);
std::string token;
std::string::iterator it;

while(std::getline(ss, token, *(it = delimiter.begin()))) {
    std::cout << token << " " << '\n'; // Token is extracted using '='
    while(*(++it)) ss.get();           // Skip the rest of delimiter if exists ",+"
}

The first while loop extracts a token using the first character of the string delimiter. The second while loop skips the rest of the delimiter and stops at the beginning of the next token.

What exactly is a Maven Snapshot and why do we need it?

Maven versions can contain a string literal "SNAPSHOT" to signify that a project is currently under active development.

For example, if your project has a version of “1.0-SNAPSHOT” and you deploy this project’s artifacts to a Maven repository, Maven would expand this version to “1.0-20080207-230803-1” if you were to deploy a release at 11:08 PM on February 7th, 2008 UTC. In other words, when you deploy a snapshot, you are not making a release of a software component; you are releasing a snapshot of a component at a specific time.

So mainly snapshot versions are used for projects under active development. If your project depends on a software component that is under active development, you can depend on a snapshot release, and Maven will periodically attempt to download the latest snapshot from a repository when you run a build. Similarly, if the next release of your system is going to have a version “1.8,” your project would have a “1.8-SNAPSHOT” version until it was formally released.

For example , the following dependency would always download the latest 1.8 development JAR of spring:

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring</artifactId>
        <version>1.8-SNAPSHOT”</version>
    </dependency>

Maven

An example of maven release process

enter image description here

What does the 'export' command do?

In simple terms, environment variables are set when you open a new shell session. At any time if you change any of the variable values, the shell has no way of picking that change. that means the changes you made become effective in new shell sessions. The export command, on the other hand, provides the ability to update the current shell session about the change you made to the exported variable. You don't have to wait until new shell session to use the value of the variable you changed.

Get the current language in device

To save others time and/or confusion I wanted to share that I have tried the two alternatives proposed by Johan Pelgrim above and on my device they are equivalent - whether or not the default location is changed.

So my device's default setting is English(United Kindom) and in this state as expected both Strings in Johan's answer give the same result. If I then change the locale in the phone settings (say to italiano(Italia)) and re-run then both Strings in Johan's answer give the locale as italiano(Italia).

Therefore I believe Johan's original post to be correct and gregm's comment to be incorrect.

Delay/Wait in a test case of Xcode UI testing

Based on @Ted's answer, I've used this extension:

extension XCTestCase {

    // Based on https://stackoverflow.com/a/33855219
    func waitFor<T>(object: T, timeout: TimeInterval = 5, file: String = #file, line: UInt = #line, expectationPredicate: @escaping (T) -> Bool) {
        let predicate = NSPredicate { obj, _ in
            expectationPredicate(obj as! T)
        }
        expectation(for: predicate, evaluatedWith: object, handler: nil)

        waitForExpectations(timeout: timeout) { error in
            if (error != nil) {
                let message = "Failed to fulful expectation block for \(object) after \(timeout) seconds."
                let location = XCTSourceCodeLocation(filePath: file, lineNumber: line)
                let issue = XCTIssue(type: .assertionFailure, compactDescription: message, detailedDescription: nil, sourceCodeContext: .init(location: location), associatedError: nil, attachments: [])
                self.record(issue)
            }
        }
    }

}

You can use it like this

let element = app.staticTexts["Name of your element"]
waitFor(object: element) { $0.exists }

It also allows for waiting for an element to disappear, or any other property to change (by using the appropriate block)

waitFor(object: element) { !$0.exists } // Wait for it to disappear

How to add a primary key to a MySQL table?

Not sure if this matters to anyone else, but I prefer the id for the table to be the first column in the database. The syntax for that is:

ALTER TABLE your_db.your_table ADD COLUMN `id` int(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT FIRST;

Which is just a slight improvement over the first answer. If you wanted it to be in a different position, then

ALTER TABLE unique_address ADD COLUMN `id` int(10) UNSIGNED PRIMARY KEY AUTO_INCREMENT AFTER some_other_column;

HTH, -ft

Check if key exists and iterate the JSON array using Python

If all you want is to check if key exists or not

h = {'a': 1}
'b' in h # returns False

If you want to check if there is a value for key

h.get('b') # returns None

Return a default value if actual value is missing

h.get('b', 'Default value')

Python: most idiomatic way to convert None to empty string?

A neat one-liner to do this building on some of the other answers:

s = (lambda v: v or '')(a) + (lambda v: v or '')(b)

or even just:

s = (a or '') + (b or '')

What does a just-in-time (JIT) compiler do?

I know this is an old thread, but runtime optimization is another important part of JIT compilation that doesn't seemed to be discussed here. Basically, the JIT compiler can monitor the program as it runs to determine ways to improve execution. Then, it can make those changes on the fly - during runtime. Google JIT optimization (javaworld has a pretty good article about it.)

How to uninstall jupyter

If you don't want to use pip-autoremove (since it removes dependencies shared among other packages) and pip3 uninstall jupyter just removed some packages, then do the following:

Copy-Paste:

sudo may be needed as per your need.

python3 -m pip uninstall -y jupyter jupyter_core jupyter-client jupyter-console jupyterlab_pygments notebook qtconsole nbconvert nbformat

Note:

The above command will only uninstall jupyter specific packages. I have not added other packages to uninstall since they might be shared among other packages (eg: Jinja2 is used by Flask, ipython is a separate set of packages themselves, tornado again might be used by others).

In any case, all the dependencies are mentioned below(as of 21 Nov, 2020. jupyter==4.4.0 )

If you are sure you want to remove all the dependencies, then you can use Stan_MD's answer.

attrs
backcall
bleach
decorator
defusedxml
entrypoints
importlib-metadata
ipykernel
ipython
ipython-genutils
ipywidgets
jedi
Jinja2
jsonschema
jupyter
jupyter-client
jupyter-console
jupyter-core
jupyterlab-pygments
MarkupSafe
mistune
more-itertools
nbconvert
nbformat
notebook
pandocfilters
parso
pexpect
pickleshare
prometheus-client
prompt-toolkit
ptyprocess
Pygments
pyrsistent
python-dateutil
pyzmq
qtconsole
Send2Trash
six
terminado
testpath
tornado
traitlets
wcwidth
webencodings
widgetsnbextension
zipp

Executive Edit:

pip3 uninstall jupyter
pip3 uninstall jupyter_core
pip3 uninstall jupyter-client
pip3 uninstall jupyter-console
pip3 uninstall jupyterlab_pygments
pip3 uninstall notebook
pip3 uninstall qtconsole
pip3 uninstall nbconvert
pip3 uninstall nbformat

Explanation of each:

  1. Uninstall jupyter dist-packages:

    pip3 uninstall jupyter

  2. Uninstall jupyter_core dist-packages (It also uninstalls following binaries: jupyter, jupyter-migrate,jupyter-troubleshoot):

    pip3 uninstall jupyter_core

  3. Uninstall jupyter-client:

    pip3 uninstall jupyter-client

  4. Uninstall jupyter-console:

    pip3 uninstall jupyter-console

  5. Uninstall jupyter-notebook (It also uninstalls following binaries: jupyter-bundlerextension, jupyter-nbextension, jupyter-notebook, jupyter-serverextension):

    pip3 uninstall notebook

  6. Uninstall jupyter-qtconsole :

    pip3 uninstall qtconsole

  7. Uninstall jupyter-nbconvert:

    pip3 uninstall nbconvert

  8. Uninstall jupyter-trust:

    pip3 uninstall nbformat

What is the difference between map and flatMap and a good use case for each?

all examples are good....Here is nice visual illustration... source courtesy : DataFlair training of spark

Map : A map is a transformation operation in Apache Spark. It applies to each element of RDD and it returns the result as new RDD. In the Map, operation developer can define his own custom business logic. The same logic will be applied to all the elements of RDD.

Spark RDD map function takes one element as input process it according to custom code (specified by the developer) and returns one element at a time. Map transforms an RDD of length N into another RDD of length N. The input and output RDDs will typically have the same number of records.

enter image description here

Example of map using scala :

val x = spark.sparkContext.parallelize(List("spark", "map", "example",  "sample", "example"), 3)
val y = x.map(x => (x, 1))
y.collect
// res0: Array[(String, Int)] = 
//    Array((spark,1), (map,1), (example,1), (sample,1), (example,1))

// rdd y can be re writen with shorter syntax in scala as 
val y = x.map((_, 1))
y.collect
// res1: Array[(String, Int)] = 
//    Array((spark,1), (map,1), (example,1), (sample,1), (example,1))

// Another example of making tuple with string and it's length
val y = x.map(x => (x, x.length))
y.collect
// res3: Array[(String, Int)] = 
//    Array((spark,5), (map,3), (example,7), (sample,6), (example,7))

FlatMap :

A flatMap is a transformation operation. It applies to each element of RDD and it returns the result as new RDD. It is similar to Map, but FlatMap allows returning 0, 1 or more elements from map function. In the FlatMap operation, a developer can define his own custom business logic. The same logic will be applied to all the elements of the RDD.

What does "flatten the results" mean?

A FlatMap function takes one element as input process it according to custom code (specified by the developer) and returns 0 or more element at a time. flatMap() transforms an RDD of length N into another RDD of length M.

enter image description here

Example of flatMap using scala :

val x = spark.sparkContext.parallelize(List("spark flatmap example",  "sample example"), 2)

// map operation will return Array of Arrays in following case : check type of res0
val y = x.map(x => x.split(" ")) // split(" ") returns an array of words
y.collect
// res0: Array[Array[String]] = 
//  Array(Array(spark, flatmap, example), Array(sample, example))

// flatMap operation will return Array of words in following case : Check type of res1
val y = x.flatMap(x => x.split(" "))
y.collect
//res1: Array[String] = 
//  Array(spark, flatmap, example, sample, example)

// RDD y can be re written with shorter syntax in scala as 
val y = x.flatMap(_.split(" "))
y.collect
//res2: Array[String] = 
//  Array(spark, flatmap, example, sample, example)

MySQL: Error dropping database (errno 13; errno 17; errno 39)

This was how I solved it:

mysql> DROP DATABASE mydatabase;
ERROR 1010 (HY000): Error dropping database (can't rmdir '.\mydatabase', errno: 13)
mysql> 

I went to delete this directory: C:\...\UniServerZ\core\mysql\data\mydatabase.

mysql> DROP DATABASE mydatabase;
ERROR 1008 (HY000): Can't drop database 'mydatabase'; database doesn't exist

Pandas: Return Hour from Datetime Column Directly

Since the quickest, shortest answer is in a comment (from Jeff) and has a typo, here it is corrected and in full:

sales['time_hour'] = pd.DatetimeIndex(sales['timestamp']).hour

JPA or JDBC, how are they different?

JDBC is a much lower-level (and older) specification than JPA. In it's bare essentials, JDBC is an API for interacting with a database using pure SQL - sending queries and retrieving results. It has no notion of objects or hierarchies. When using JDBC, it's up to you to translate a result set (essentially a row/column matrix of values from one or more database tables, returned by your SQL query) into Java objects.

Now, to understand and use JDBC it's essential that you have some understanding and working knowledge of SQL. With that also comes a required insight into what a relational database is, how you work with it and concepts such as tables, columns, keys and relationships. Unless you have at least a basic understanding of databases, SQL and data modelling you will not be able to make much use of JDBC since it's really only a thin abstraction on top of these things.

Open a new tab on button click in AngularJS

You should use the $location service

Angular docs:

Are parameters in strings.xml possible?

If you need to format your strings using String.format(String, Object...), then you can do so by putting your format arguments in the string resource. For example, with the following resource:

<string name="welcome_messages">Hello, %1$s! You have %2$d new messages.</string>

In this example, the format string has two arguments: %1$s is a string and %2$d is a decimal number. You can format the string with arguments from your application like this:

Resources res = getResources();
String text = String.format(res.getString(R.string.welcome_messages), username, mailCount);

If you wish more look at: http://developer.android.com/intl/pt-br/guide/topics/resources/string-resource.html#FormattingAndStyling

Update Fragment from ViewPager

If you use Kotlin, you can do the following:

1. On first, you should be create Interface and implemented him in your Fragment

interface RefreshData {
    fun refresh()
}

class YourFragment : Fragment(), RefreshData {
    ...
    override fun refresh() {
        //do what you want
    }
}

2. Next step is add OnPageChangeListener to your ViewPager

viewPager.addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
    override fun onPageScrollStateChanged(state: Int) { }

    override fun onPageSelected(position: Int) {
        viewPagerAdapter.notifyDataSetChanged()
        viewPager.currentItem = position
    }

    override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) { }
})

3. override getItemPosition in your Adapter

override fun getItemPosition(obj: Any): Int {
    if (obj is RefreshData) {
        obj.refresh()
    }
    return super.getItemPosition(obj)
}

How to remove the URL from the printing page?

Nowadays, you can use history API to modify the URL before print, then change back:

var curURL = window.location.href;
history.replaceState(history.state, '', '/');
window.print();
history.replaceState(history.state, '', curURL);

But you need to make a custom PRINT button for user to click.

Correct syntax to compare values in JSTL <c:if test="${values.type}=='object'">

The comparison needs to be evaluated fully inside EL ${ ... }, not outside.

<c:if test="${values.type eq 'object'}">

As to the docs, those ${} things are not JSTL, but EL (Expression Language) which is a whole subject at its own. JSTL (as every other JSP taglib) is just utilizing it. You can find some more EL examples here.

<c:if test="#{bean.booleanValue}" />
<c:if test="#{bean.intValue gt 10}" />
<c:if test="#{bean.objectValue eq null}" />
<c:if test="#{bean.stringValue ne 'someValue'}" />
<c:if test="#{not empty bean.collectionValue}" />
<c:if test="#{not bean.booleanValue and bean.intValue ne 0}" />
<c:if test="#{bean.enumValue eq 'ONE' or bean.enumValue eq 'TWO'}" />

See also:


By the way, unrelated to the concrete problem, if I guess your intent right, you could also just call Object#getClass() and then Class#getSimpleName() instead of adding a custom getter.

<c:forEach items="${list}" var="value">
    <c:if test="${value['class'].simpleName eq 'Object'}">
        <!-- code here -->
    </c:if>
</c:forEeach>

See also:

Difference between xcopy and robocopy

I have written lot of scripts to automate daily backups etc. Previously I used XCopy and then moved to Robocopy. Anyways Robocopy and XCopy both are frequently used in terms of file transfers in Windows. Robocopy stands for Robust File Copy. All type of huge file copying both these commands are used but Robocopy has added options which makes copying easier as well as for debugging purposes.

Having said that lets talk about features between these two.

  • Robocopy becomes handy for mirroring or synchronizing directories. It also checks the files in the destination directory against the files to be copied and doesn't waste time copying unchanged files.

  • Just like myself, if you are into automation to take daily backups etc, "Run Hours - /RH" becomes very useful without any interactions. This is supported by Robocopy. It allows you to set when copies should be done rather than the time of the command as with XCopy. You will see robocopy.exe process in task list since it will run background to monitor clock to execute when time is right to copy.

  • Robocopy supports file and directory monitoring with the "/MON" or "/MOT" commands.

  • Robocopy gives extra support for copying over the "archive" attribute on files, it supports copying over all attributes including timestamps, security, owner, and auditing information.

Hope this helps you.

Oracle DateTime in Where Clause?

You could also do:

SELECT EMP_NAME, DEPT
FROM EMPLOYEE
WHERE TRUNC(TIME_CREATED) = DATE '2011-01-26'

How to get a Docker container's IP address from the host

Just another classic solution:

docker ps -aq | xargs docker inspect -f '{{.Name}} - {{.NetworkSettings.IPAddress }}'

Converting Columns into rows with their respective data in sql server

As an alternative:

Using CROSS APPLY and VALUES performs this operation quite simply and efficiently with just a single pass of the table (unlike union queries that do one pass for every column)

SELECT
    ca.ColName, ca.ColValue
FROM YOurTable
CROSS APPLY (
      Values
         ('ScripName' , ScripName),
         ('ScripCode' , ScripCode),
         ('Price'     , cast(Price as varchar(50)) )
  ) as CA (ColName, ColValue)

Personally I find this syntax easier than using unpivot.

NB: You must take care that all source columns are converted into compatible types for the single value column

Multi-character constant warnings

Simplest C/C++ any compiler/standard compliant solution, was mentioned by @leftaroundabout in comments above:

int x = *(int*)"abcd";

Or a bit more specific:

int x = *(int32_t*)"abcd";

One more solution, also compliant with C/C++ compiler/standard since C99 (except clang++, which has a known bug):

int x = ((union {char s[5]; int number;}){"abcd"}).number;

/* just a demo check: */
printf("x=%d stored %s byte first\n", x, x==0x61626364 ? "MSB":"LSB");

Here anonymous union is used to give a nice symbol-name to the desired numeric result, "abcd" string is used to initialize the lvalue of compound literal (C99).

How to check if two words are anagrams

I know this is an old question. However, I'm hoping this can be of help to someone. The time complexity of this solution is O(n^2).

public boolean areAnagrams(final String word1, final String word2) {
        if (word1.length() != word2.length())
            return false;

        if (word1.equals(word2))
            return true;

        if (word1.length() == 0 && word2.length() == 0)
            return true;

        String secondWord = word2;
        for (int i = 0; i < word1.length(); i++) {
            if (secondWord.indexOf(word1.charAt(i)) == -1)
                return false;

            secondWord = secondWord.replaceFirst(word1.charAt(i) + "", "");
        }

        if (secondWord.length() > 0)
            return false;

        return true;
}

Check if a string is html or not

All of the answers here are over-inclusive, they just look for < followed by >. There is no perfect way to detect if a string is HTML, but you can do better.

Below we look for end tags, and will be much tighter and more accurate:

import re
re_is_html = re.compile(r"(?:</[^<]+>)|(?:<[^<]+/>)")

And here it is in action:

# Correctly identified as not HTML:
print re_is_html.search("Hello, World")
print re_is_html.search("This is less than <, this is greater than >.")
print re_is_html.search(" a < 3 && b > 3")
print re_is_html.search("<<Important Text>>")
print re_is_html.search("<a>")

# Correctly identified as HTML
print re_is_html.search("<a>Foo</a>")
print re_is_html.search("<input type='submit' value='Ok' />")
print re_is_html.search("<br/>")

# We don't handle, but could with more tweaking:
print re_is_html.search("<br>")
print re_is_html.search("Foo &amp; bar")
print re_is_html.search("<input type='submit' value='Ok'>")

How does a Java HashMap handle different objects with the same hash code?

You can find excellent information at http://javarevisited.blogspot.com/2011/02/how-hashmap-works-in-java.html

To Summarize:

HashMap works on the principle of hashing

put(key, value): HashMap stores both key and value object as Map.Entry. Hashmap applies hashcode(key) to get the bucket. if there is collision ,HashMap uses LinkedList to store object.

get(key): HashMap uses Key Object's hashcode to find out bucket location and then call keys.equals() method to identify correct node in LinkedList and return associated value object for that key in Java HashMap.

x86 Assembly on a Mac

After installing any version of Xcode targeting Intel-based Macs, you should be able to write assembly code. Xcode is a suite of tools, only one of which is the IDE, so you don't have to use it if you don't want to. (That said, if there are specific things you find clunky, please file a bug at Apple's bug reporter - every bug goes to engineering.) Furthermore, installing Xcode will install both the Netwide Assembler (NASM) and the GNU Assembler (GAS); that will let you use whatever assembly syntax you're most comfortable with.

You'll also want to take a look at the Compiler & Debugging Guides, because those document the calling conventions used for the various architectures that Mac OS X runs on, as well as how the binary format and the loader work. The IA-32 (x86-32) calling conventions in particular may be slightly different from what you're used to.

Another thing to keep in mind is that the system call interface on Mac OS X is different from what you might be used to on DOS/Windows, Linux, or the other BSD flavors. System calls aren't considered a stable API on Mac OS X; instead, you always go through libSystem. That will ensure you're writing code that's portable from one release of the OS to the next.

Finally, keep in mind that Mac OS X runs across a pretty wide array of hardware - everything from the 32-bit Core Single through the high-end quad-core Xeon. By coding in assembly you might not be optimizing as much as you think; what's optimal on one machine may be pessimal on another. Apple regularly measures its compilers and tunes their output with the "-Os" optimization flag to be decent across its line, and there are extensive vector/matrix-processing libraries that you can use to get high performance with hand-tuned CPU-specific implementations.

Going to assembly for fun is great. Going to assembly for speed is not for the faint of heart these days.

Delete last commit in bitbucket

As others have said, usually you want to use hg backout or git revert. However, sometimes you really want to get rid of a commit.

First, you'll want to go to your repository's settings. Click on the Strip commits link.

Strip commits link in bitbucket settings

Enter the changeset ID for the changeset you want to destroy, and click Preview strip. That will let you see what kind of damage you're about to do before you do it. Then just click Confirm and your commit is no longer history. Make sure you tell all your collaborators what you've done, so they don't accidentally push the offending commit back.

Regular expression for not allowing spaces in the input field

This one will only match the input field or string if there are no spaces. If there are any spaces, it will not match at all.

/^([A-z0-9!@#$%^&*().,<>{}[\]<>?_=+\-|;:\'\"\/])*[^\s]\1*$/

Matches from the beginning of the line to the end. Accepts alphanumeric characters, numbers, and most special characters.

If you want just alphanumeric characters then change what is in the [] like so:

/^([A-z])*[^\s]\1*$/

Disable Auto Zoom in Input "Text" tag - Safari on iPhone

Setting a font-size (for input fields) equal to the body's font-size, seems to be what prevents the browser from zooming out or in. I'd suggest to use font-size: 1rem as a more elegant solution.

How to count the number of files in a directory using Python

For all kind of files, subdirectories included:

import os

list = os.listdir(dir) # dir is your directory path
number_files = len(list)
print number_files

Only files (avoiding subdirectories):

import os

onlyfiles = next(os.walk(dir))[2] #dir is your directory path as string
print len(onlyfiles)

How to detect Safari, Chrome, IE, Firefox and Opera browser?

Simple, single line of JavaScript code will give you the name of browser:

function GetBrowser()
{
    return  navigator ? navigator.userAgent.toLowerCase() : "other";
}

Changing Placeholder Text Color with Swift

For Swift 3 and 3.1 this works perfectly fine:

passField.attributedPlaceholder = NSAttributedString(string: "password", attributes: [NSForegroundColorAttributeName: UIColor.white])

TNS Protocol adapter error while starting Oracle SQL*Plus

Another possibility (esp. with multiple Oracle homes)

set ORACLE_SID=$SID

sqlplus /nolog

conn / as sysdba;

C++ for each, pulling from vector elements

The for each syntax is supported as an extension to native c++ in Visual Studio.

The example provided in msdn

#include <vector>
#include <iostream>

using namespace std;

int main() 
{
  int total = 0;

  vector<int> v(6);
  v[0] = 10; v[1] = 20; v[2] = 30;
  v[3] = 40; v[4] = 50; v[5] = 60;

  for each(int i in v) {
    total += i;
  }

  cout << total << endl;
}

(works in VS2013) is not portable/cross platform but gives you an idea of how to use for each.

The standard alternatives (provided in the rest of the answers) apply everywhere. And it would be best to use those.

Printing column separated by comma using Awk command line

Try this awk

awk -F, '{$0=$3}1' file
column3
  • , Divide fields by ,
  • $0=$3 Set the line to only field 3
  • 1 Print all out. (explained here)

This could also be used:

awk -F, '{print $3}' file

Should Jquery code go in header or footer?

For me jQuery is a little bit special. Maybe an exception to the norm. There are so many other scripts that rely on it, so its quite important that it loads early so the other scripts that come later will work as intended. As someone else pointed out even this page loads jQuery in the head section.

Adding script tag to React/JSX

The answer Alex Mcmillan provided helped me the most but didn't quite work for a more complex script tag.

I slightly tweaked his answer to come up with a solution for a long tag with various functions that was additionally already setting "src".

(For my use case the script needed to live in head which is reflected here as well):

  componentWillMount () {
      const script = document.createElement("script");

      const scriptText = document.createTextNode("complex script with functions i.e. everything that would go inside the script tags");

      script.appendChild(scriptText);
      document.head.appendChild(script);
  }

PHP Deprecated: Methods with the same name

As mentioned in the error, the official manual and the comments:

Replace

public function TSStatus($host, $queryPort)

with

public function __construct($host, $queryPort)

How do I read a response from Python Requests?

If you push for example image to some API and want the result address(response) back you could do:

import requests
url = 'https://uguu.se/api.php?d=upload-tool'
data = {"name": filename}
files = {'file': open(full_file_path, 'rb')}
response = requests.post(url, data=data, files=files)
current_url = response.text
print(response.text)

CSS image overlay with color and transparency

JSFiddle Demo

HTML:

<div class="image-holder">
    <img src="http://codemancers.com/img/who-we-are-bg.png" />
</div>

CSS:

.image-holder {
    display:inline-block;
    position: relative;
}
.image-holder:after {
    content:'';
    top: 0;
    left: 0;
    z-index: 10;
    width: 100%;
    height: 100%;
    display: block;
    position: absolute;
    background: blue;
    opacity: 0.1;
}
.image-holder:hover:after {
    opacity: 0;
}

How is Perl's @INC constructed? (aka What are all the ways of affecting where Perl modules are searched for?)

As it was said already @INC is an array and you're free to add anything you want.

My CGI REST script looks like:

#!/usr/bin/perl
use strict;
use warnings;
BEGIN {
    push @INC, 'fully_qualified_path_to_module_wiht_our_REST.pm';
}
use Modules::Rest;
gone(@_);

Subroutine gone is exported by Rest.pm.

What's the best way to use R scripts on the command line (terminal)?

Try littler. littler provides hash-bang (i.e. script starting with #!/some/path) capability for GNU R, as well as simple command-line and piping use.

Model summary in pytorch

Keras like model summary using torchsummary:

from torchsummary import summary
summary(model, input_size=(3, 224, 224))

C# DataTable.Select() - How do I format the filter criteria to include null?

try this:

var result = from r in myDataTable.AsEnumerable()  
            where r.Field<string>("Name") != "n/a" &&  
                  r.Field<string>("Name") != "" select r;  
DataTable dtResult = result.CopyToDataTable();  

Can't Autowire @Repository annotated interface in Spring Boot

I had a similar issue with Spring Data MongoDB: I had to add the package path to @EnableMongoRepositories

How to use an output parameter in Java?

Java passes by value; there's no out parameter like in C#.

You can either use return, or mutate an object passed as a reference (by value).

Related questions


Code sample

public class FunctionSample {
    static String fReturn() {
        return "Hello!";
    }
    static void fArgNoWorkie(String s) {
        s = "What am I doing???"; // Doesn't "work"! Java passes by value!
    }
    static void fMutate(StringBuilder sb) {
        sb.append("Here you go!");
    }
    public static void main(String[] args) {
        String s = null;

        s = fReturn();
        System.out.println(s); // prints "Hello!"

        fArgNoWorkie(s);
        System.out.println(s); // prints "Hello!"

        StringBuilder sb = new StringBuilder();
        fMutate(sb);
        s = sb.toString();
        System.out.println(s); // prints "Here you go!"
    }

}

See also


As for the code that OP needs help with, here's a typical solution of using a special value (usually null for reference types) to indicate success/failure:

Instead of:

String oPerson= null;
if (CheckAddress("5556", oPerson)) {
   print(oPerson); // DOESN'T "WORK"! Java passes by value; String is immutable!
}

private boolean CheckAddress(String iAddress, String oPerson) {
   // on search succeeded:
   oPerson = something; // DOESN'T "WORK"!
   return true;
   :
   // on search failed:
   return false;
}

Use a String return type instead, with null to indicate failure.

String person = checkAddress("5556");
if (person != null) {
   print(person);
}

private String checkAddress(String address) {
   // on search succeeded:
   return something;
   :
   // on search failed:
   return null;
}

This is how java.io.BufferedReader.readLine() works, for example: it returns instanceof String (perhaps an empty string!), until it returns null to indicate end of "search".

This is not limited to a reference type return value, of course. The key is that there has to be some special value(s) that is never a valid value, and you use that value for special purposes.

Another classic example is String.indexOf: it returns -1 to indicate search failure.

Note: because Java doesn't have a concept of "input" and "output" parameters, using the i- and o- prefix (e.g. iAddress, oPerson) is unnecessary and unidiomatic.


A more general solution

If you need to return several values, usually they're related in some way (e.g. x and y coordinates of a single Point). The best solution would be to encapsulate these values together. People have used an Object[] or a List<Object>, or a generic Pair<T1,T2>, but really, your own type would be best.

For this problem, I recommend an immutable SearchResult type like this to encapsulate the boolean and String search results:

public class SearchResult {
   public final String name;
   public final boolean isFound;

   public SearchResult(String name, boolean isFound) {
      this.name = name;
      this.isFound = isFound;
   }
}

Then in your search function, you do the following:

private SearchResult checkAddress(String address) {
  // on address search succeed
  return new SearchResult(foundName, true);
  :
  // on address search failed
  return new SearchResult(null, false);
}

And then you use it like this:

SearchResult sr = checkAddress("5556");
if (sr.isFound) {
  String name = sr.name;
  //...
}

If you want, you can (and probably should) make the final immutable fields non-public, and use public getters instead.

How to actually search all files in Visual Studio

Press Ctrl+,

Then you will see a docked window under name of "Go to all"

This a picture of the "Go to all" in my IDE

Picture

What is the meaning of "operator bool() const"

It's user-defined implicit conversion function to convert your class into either true or false.

//usage
bool value = yourclassinstance; //yourclassinstance is converted into bool!

What are differences between AssemblyVersion, AssemblyFileVersion and AssemblyInformationalVersion?

AssemblyVersion pretty much stays internal to .NET, while AssemblyFileVersion is what Windows sees. If you go to the properties of an assembly sitting in a directory and switch to the version tab, the AssemblyFileVersion is what you'll see up top. If you sort files by version, this is what's used by Explorer.

The AssemblyInformationalVersion maps to the "Product Version" and is meant to be purely "human-used".

AssemblyVersion is certainly the most important, but I wouldn't skip AssemblyFileVersion, either. If you don't provide AssemblyInformationalVersion, the compiler adds it for you by stripping off the "revision" piece of your version number and leaving the major.minor.build.

How to create directory automatically on SD card

Just completing the Vijay's post...


Manifest

uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"

Function

public static boolean createDirIfNotExists(String path) {
    boolean ret = true;

    File file = new File(Environment.getExternalStorageDirectory(), path);
    if (!file.exists()) {
        if (!file.mkdirs()) {
            Log.e("TravellerLog :: ", "Problem creating Image folder");
            ret = false;
        }
    }
    return ret;
}

Usage

createDirIfNotExists("mydir/"); //Create a directory sdcard/mydir
createDirIfNotExists("mydir/myfile") //Create a directory and a file in sdcard/mydir/myfile.txt

You could check for errors

if(createDirIfNotExists("mydir/")){
     //Directory Created Success
}
else{
    //Error
}

How can I shutdown Spring task executor/scheduler pools before all other beans in the web app are destroyed?

If it is going to be a web based application, you can also use the ServletContextListener interface.

public class SLF4JBridgeListener implements ServletContextListener {

   @Autowired 
   ThreadPoolTaskExecutor executor;

   @Autowired 
   ThreadPoolTaskScheduler scheduler;

    @Override
    public void contextInitialized(ServletContextEvent sce) {

    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
         scheduler.shutdown();
         executor.shutdown();     

    }

}

What I can do to resolve "1 commit behind master"?

  1. Clone your fork:

  2. Add remote from original repository in your forked repository:

    • cd into/cloned/fork-repo
    • git remote add upstream git://github.com/ORIGINAL-DEV-USERNAME/REPO-YOU-FORKED-FROM.git
    • git fetch upstream
  3. Updating your fork from original repo to keep up with their changes:

    • git pull upstream master
    • git push

How to run a .jar in mac?

Make Executable your jar and after that double click on it on Mac OS then it works successfully.

sudo chmod +x filename.jar

Try this, I hope this works.

ConcurrentHashMap vs Synchronized HashMap

The short answer:

Both maps are thread-safe implementations of the Map interface. ConcurrentHashMap is implemented for higher throughput in cases where high concurrency is expected.

Brian Goetz's article on the idea behind ConcurrentHashMap is a very good read. Highly recommended.

Windows equivalent of $export

There is not an equivalent statement for export in Windows Command Prompt. In Windows the environment is copied so when you exit from the session (from a called command prompt or from an executable that set a variable) the variable in Windows get lost. You can set it in user registry or in machine registry via setx but you won't see it if you not start a new command prompt.

change image opacity using javascript

First set the opacity explicitly in your HTML thus:

<div id="box" style="height:150px; width:150px; background-color:orange; margin:25px; opacity:1"></div>

otherwise it is 0 or null

this is then in my .js file

document.getElementById("fadeButton90").addEventListener("click", function(){
document.getElementById("box").style.opacity  =   document.getElementById("box").style.opacity*0.90; });

List all employee's names and their managers by manager name using an inner join

Your query is close you need to join using the mgr and the empid

on e1.mgr = e2.empid

So the full query is:

select e1.ename Emp,
  e2.eName Mgr
from employees e1
inner join employees e2
  on e1.mgr = e2.empid

See SQL Fiddle with Demo

If you want to return all rows including those without a manager then you would change it to a LEFT JOIN (for example the president):

select e1.ename Emp,
  e2.eName Mgr
from employees e1
left join employees e2
  on e1.mgr = e2.empid

See SQL Fiddle with Demo

The president in your sample data will return a null value for the manager because they do not have a manager.

how to check for null with a ng-if values in a view with angularjs?

See the correct way with your example:

<div ng-if="!test.view">1</div>
<div ng-if="!!test.view">2</div>

Regards, Nicholls

how can I check if a file exists?

an existing folder will FAIL with FileExists

Function FileExists(strFileName)
' Check if a file exists - returns True or False

use instead or in addition:

Function FolderExists(strFolderPath)
' Check if a path exists

Case insensitive 'in'

I needed this for a dictionary instead of list, Jochen solution was the most elegant for that case so I modded it a bit:

class CaseInsensitiveDict(dict):
    ''' requests special dicts are case insensitive when using the in operator,
     this implements a similar behaviour'''
    def __contains__(self, name): # implements `in`
        return name.casefold() in (n.casefold() for n in self.keys())

now you can convert a dictionary like so USERNAMESDICT = CaseInsensitiveDict(USERNAMESDICT) and use if 'MICHAEL89' in USERNAMESDICT:

Link entire table row?

Unfortunately, no. Not with HTML and CSS. You need an a element to make a link, and you can't wrap an entire table row in one.

The closest you can get is linking every table cell. Personally I'd just link one cell and use JavaScript to make the rest clickable. It's good to have at least one cell that really looks like a link, underlined and all, for clarity anyways.

Here's a simple jQuery snippet to make all table rows with links clickable (it looks for the first link and "clicks" it)

$("table").on("click", "tr", function(e) {
    if ($(e.target).is("a,input")) // anything else you don't want to trigger the click
        return;

    location.href = $(this).find("a").attr("href");
});

react-router go back a page how do you configure history?

React Router v6

useNavigate Hook is the recommended way to go back now:

import { useNavigate } from 'react-router-dom';

function App() {
  const navigate = useNavigate();

  return (
    <>
      <button onClick={() => navigate(-1)}>go back</button>
      <button onClick={() => navigate(1)}>go forward</button>
    </>
  );
}

Codesandbox sample

Go back/forward multiple history stack entries:
<button onClick={() => navigate(-2)}>go two back</button>
<button onClick={() => navigate(2)}>go two forward</button>
Go to specific route:
navigate("users") // go to users route, like history.push
navigate("users", { replace: true }) // go to users route, like history.replace
navigate("users", { state }) // go to users route, pass some state in

useNavigate replaces useHistory to support upcoming React Suspense/Concurrent mode better.

back button callback in navigationController in iOS

If you can't use "viewWillDisappear" or similar method, try to subclass UINavigationController. This is the header class:

#import <Foundation/Foundation.h>
@class MyViewController;

@interface CCNavigationController : UINavigationController

@property (nonatomic, strong) MyViewController *viewController;

@end

Implementation class:

#import "CCNavigationController.h"
#import "MyViewController.h"

@implementation CCNavigationController {

}
- (UIViewController *)popViewControllerAnimated:(BOOL)animated {
    @"This is the moment for you to do whatever you want"
    [self.viewController doCustomMethod];
    return [super popViewControllerAnimated:animated];
}

@end

In the other hand, you need to link this viewController to your custom NavigationController, so, in your viewDidLoad method for your regular viewController do this:

@implementation MyViewController {
    - (void)viewDidLoad
    {
        [super viewDidLoad];
        ((CCNavigationController*)self.navigationController).viewController = self;
    }
}

WiX tricks and tips

Creating Custom Action for WIX written in managed code (C#) without Votive

http://www.codeproject.com/KB/install/wixcustomaction.aspx

PHP "php://input" vs $_POST

If post data is malformed, $_POST will not contain anything. Yet, php://input will have the malformed string.

For example there is some ajax applications, that do not form correct post key-value sequence for uploading a file, and just dump all the file as post data, without variable names or anything. $_POST will be empty, $_FILES empty also, and php://input will contain exact file, written as a string.

Clear text from textarea with selenium

I ran into a field where .clear() did not work. Using a combination of the first two answers worked for this field.

from selenium.webdriver.common.keys import Keys

#...your code (I was using python 3)

driver.find_element_by_id('foo').send_keys(Keys.CONTROL + "a");
driver.find_element_by_id('foo').send_keys(Keys.DELETE);

How can I hide/show a div when a button is clicked?

You can do this entirely with html and css and i have.


HTML First you give the div you wish to hide an ID to target like #view_element and a class to target like #hide_element. You can if you wish make both of these classes but i don't know if you can make them both IDs. Then have your Show button target your show id and your Hide button target your hide class. That is it for the html the hiding and showing is done in the CSS.

CSS The css to show and hide this should look something like this

#hide_element:target {
    display:none;
}

.show_element:target{
    display:block;
}

This should allow you to hide and show elements at will. This should work nicely on spans and divs.

Understanding typedefs for function pointers in C

A function pointer is like any other pointer, but it points to the address of a function instead of the address of data (on heap or stack). Like any pointer, it needs to be typed correctly. Functions are defined by their return value and the types of parameters they accept. So in order to fully describe a function, you must include its return value and the type of each parameter is accepts. When you typedef such a definition, you give it a 'friendly name' which makes it easier to create and reference pointers using that definition.

So for example assume you have a function:

float doMultiplication (float num1, float num2 ) {
    return num1 * num2; }

then the following typedef:

typedef float(*pt2Func)(float, float);

can be used to point to this doMulitplication function. It is simply defining a pointer to a function which returns a float and takes two parameters, each of type float. This definition has the friendly name pt2Func. Note that pt2Func can point to ANY function which returns a float and takes in 2 floats.

So you can create a pointer which points to the doMultiplication function as follows:

pt2Func *myFnPtr = &doMultiplication;

and you can invoke the function using this pointer as follows:

float result = (*myFnPtr)(2.0, 5.1);

This makes good reading: http://www.newty.de/fpt/index.html

kill -3 to get java thread dump

In Jboss you can perform the following

nohup $JBOSS_HOME/bin/run.sh -c  yourinstancename $JBOSS_OPTS >> console-$(date +%Y%m%d).out  2>&1 < /dev/null &
kill -3 <java_pid>

This will redirect your output/threadump to the file console specified in the above command.

javascript create empty array of a given size

We use Array.from({length: 500}) since 2017.

Python Hexadecimal

Use the format() function with a '02x' format.

>>> format(255, '02x')
'ff'
>>> format(2, '02x')
'02'

The 02 part tells format() to use at least 2 digits and to use zeros to pad it to length, x means lower-case hexadecimal.

The Format Specification Mini Language also gives you X for uppercase hex output, and you can prefix the field width with # to include a 0x or 0X prefix (depending on wether you used x or X as the formatter). Just take into account that you need to adjust the field width to allow for those extra 2 characters:

>>> format(255, '02X')
'FF'
>>> format(255, '#04x')
'0xff'
>>> format(255, '#04X')
'0XFF'

Android Button click go to another xml page

Write below code in your MainActivity.java file instead of your code.

public class MainActivity extends Activity implements OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button mBtn1 = (Button) findViewById(R.id.mBtn1);
        mBtn1.setOnClickListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    public void onClick(View v) {
        Log.i("clicks","You Clicked B1");
        Intent i=new Intent(MainActivity.this, MainActivity2.class);
        startActivity(i);
    }
}

And Declare MainActivity2 into your Androidmanifest.xml file using below code.

<activity
    android:name=".MainActivity2"
    android:label="@string/title_activity_main">
</activity>

How to drop a PostgreSQL database if there are active connections to it?

In my case i had to execute a command to drop all connections including my active administrator connection

SELECT pg_terminate_backend(pg_stat_activity.pid)
FROM pg_stat_activity
WHERE datname = current_database()

which terminated all connections and show me a fatal ''error'' message :

FATAL: terminating connection due to administrator command SQL state: 57P01

After that it was possible to drop the database

Generate ER Diagram from existing MySQL database, created for CakePHP

CakePHP was intended to be used as Ruby on Rails framework clone, done in PHP, so any reverse-engineering of underlying database is pointless. EER diagrams should be reverse-engineered from Model layer.

Such tools do exist for Ruby Here you can see Redmine database EER diagrams reverse-engineered from Models. Not from database. http://redminecookbook.com/Redmine-erd-diagrams.html

With following tools: http://rails-erd.rubyforge.org/ http://railroady.prestonlee.com/

ssh connection refused on Raspberry Pi

I think pi has ssh server enabled by default. Mine have always worked out of the box. Depends which operating system version maybe.

Most of the time when it fails for me it is because the ip address has been changed. Perhaps you are pinging something else now? Also sometimes they just refuse to connect and need a restart.

Cannot start GlassFish 4.1 from within Netbeans 8.0.1 Service area

I have the same problem. Mine is caused by a vmware installation. It is vmware worstation v8 on windows 7 and was a default installation.

Running netstat -aon | find ":80" | find "LISTENING" from cmd showed PID of the service causing the problem, this related to vmware. Going to services, I manually stopped all of the running vmware services (did not change their start up type, just a manual stop - I want them to work again after the next reboot) I could immediately test my webservice, glassfish 4 started as it should.

Hope it helps

How to get main window handle from process id?

As an extension to Hiale's solution, you could provide a different or modified version that supports processes that have multiple main windows.

First, amend the structure to allow storing of multiple handles:

struct handle_data {
    unsigned long process_id;
    std::vector<HWND> handles;
};

Second, amend the callback function:

BOOL CALLBACK enum_windows_callback(HWND handle, LPARAM lParam)
{
    handle_data& data = *(handle_data*)lParam;
    unsigned long process_id = 0;
    GetWindowThreadProcessId(handle, &process_id);
    if (data.process_id != process_id || !is_main_window(handle)) {
        return TRUE;
    }
    // change these 2 lines to allow storing of handle and loop again
    data.handles.push_back(handle);
    return TRUE;   
 }

Finally, amend the returns on the main function:

std::vector<HWD> find_main_window(unsigned long process_id)
{
    handle_data data;
    data.process_id = process_id;
    EnumWindows(enum_windows_callback, (LPARAM)&data);
    return data.handles;
}

Why should hash functions use a prime number modulus?

I've read the popular wordpress website linked in some of the above popular answers at the top. From what I've understood, I'd like to share a simple observation I made.

You can find all the details in the article here, but assume the following holds true:

  • Using a prime number gives us the "best chance" of an unique value

A general hashmap implementation wants 2 things to be unique.

  • Unique hash code for the key
  • Unique index to store the actual value

How do we get the unique index? By making the initial size of the internal container a prime as well. So basically, prime is involved because it possesses this unique trait of producing unique numbers which we end up using to ID objects and finding indexes inside the internal container.

Example:

key = "key"

value = "value" uniqueId = "k" * 31 ^ 2 + "e" * 31 ^ 1` + "y"

maps to unique id

Now we want a unique location for our value - so we

uniqueId % internalContainerSize == uniqueLocationForValue , assuming internalContainerSize is also a prime.

I know this is simplified, but I'm hoping to get the general idea through.

Python error: TypeError: 'module' object is not callable for HeadFirst Python code

You module and class AthleteList have the same name. Change:

import AthleteList

to:

from AthleteList import AthleteList

This now means that you are importing the module object and will not be able to access any module methods you have in AthleteList

set div height using jquery (stretch div height)

well you can do this:

$(function(){

    var $header = $('#header');
    var $footer = $('#footer');
    var $content = $('#content');
    var $window = $(window).on('resize', function(){
       var height = $(this).height() - $header.height() + $footer.height();
       $content.height(height);
    }).trigger('resize'); //on page load

});

see fiddle here: http://jsfiddle.net/maniator/JVKbR/
demo: http://jsfiddle.net/maniator/JVKbR/show/

Display open transactions in MySQL

How can I display these open transactions and commit or cancel them?

There is no open transaction, MySQL will rollback the transaction upon disconnect.
You cannot commit the transaction (IFAIK).

You display threads using

SHOW FULL PROCESSLIST  

See: http://dev.mysql.com/doc/refman/5.1/en/thread-information.html

It will not help you, because you cannot commit a transaction from a broken connection.

What happens when a connection breaks
From the MySQL docs: http://dev.mysql.com/doc/refman/5.0/en/mysql-tips.html

4.5.1.6.3. Disabling mysql Auto-Reconnect

If the mysql client loses its connection to the server while sending a statement, it immediately and automatically tries to reconnect once to the server and send the statement again. However, even if mysql succeeds in reconnecting, your first connection has ended and all your previous session objects and settings are lost: temporary tables, the autocommit mode, and user-defined and session variables. Also, any current transaction rolls back.

This behavior may be dangerous for you, as in the following example where the server was shut down and restarted between the first and second statements without you knowing it:

Also see: http://dev.mysql.com/doc/refman/5.0/en/auto-reconnect.html

How to diagnose and fix this
To check for auto-reconnection:

If an automatic reconnection does occur (for example, as a result of calling mysql_ping()), there is no explicit indication of it. To check for reconnection, call mysql_thread_id() to get the original connection identifier before calling mysql_ping(), then call mysql_thread_id() again to see whether the identifier has changed.

Make sure you keep your last query (transaction) in the client so that you can resubmit it if need be.
And disable auto-reconnect mode, because that is dangerous, implement your own reconnect instead, so that you know when a drop occurs and you can resubmit that query.

How would I get everything before a : in a string Python

I have benchmarked these various technics under Python 3.7.0 (IPython).

TLDR

  • fastest (when the split symbol c is known): pre-compiled regex.
  • fastest (otherwise): s.partition(c)[0].
  • safe (i.e., when c may not be in s): partition, split.
  • unsafe: index, regex.

Code

import string, random, re

SYMBOLS = string.ascii_uppercase + string.digits
SIZE = 100

def create_test_set(string_length):
    for _ in range(SIZE):
        random_string = ''.join(random.choices(SYMBOLS, k=string_length))
        yield (random.choice(random_string), random_string)

for string_length in (2**4, 2**8, 2**16, 2**32):
    print("\nString length:", string_length)
    print("  regex (compiled):", end=" ")
    test_set_for_regex = ((re.compile("(.*?)" + c).match, s) for (c, s) in test_set)
    %timeit [re_match(s).group() for (re_match, s) in test_set_for_regex]
    test_set = list(create_test_set(16))
    print("  partition:       ", end=" ")
    %timeit [s.partition(c)[0] for (c, s) in test_set]
    print("  index:           ", end=" ")
    %timeit [s[:s.index(c)] for (c, s) in test_set]
    print("  split (limited): ", end=" ")
    %timeit [s.split(c, 1)[0] for (c, s) in test_set]
    print("  split:           ", end=" ")
    %timeit [s.split(c)[0] for (c, s) in test_set]
    print("  regex:           ", end=" ")
    %timeit [re.match("(.*?)" + c, s).group() for (c, s) in test_set]

Results

String length: 16
  regex (compiled): 156 ns ± 4.41 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        19.3 µs ± 430 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
  index:            26.1 µs ± 341 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  26.8 µs ± 1.26 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            26.3 µs ± 835 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            128 µs ± 4.02 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

String length: 256
  regex (compiled): 167 ns ± 2.7 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        20.9 µs ± 694 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  index:            28.6 µs ± 2.73 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  27.4 µs ± 979 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            31.5 µs ± 4.86 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            148 µs ± 7.05 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

String length: 65536
  regex (compiled): 173 ns ± 3.95 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        20.9 µs ± 613 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
  index:            27.7 µs ± 515 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  27.2 µs ± 796 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            26.5 µs ± 377 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            128 µs ± 1.5 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

String length: 4294967296
  regex (compiled): 165 ns ± 1.2 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
  partition:        19.9 µs ± 144 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
  index:            27.7 µs ± 571 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split (limited):  26.1 µs ± 472 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  split:            28.1 µs ± 1.69 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
  regex:            137 µs ± 6.53 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

Sum up a column from a specific row down

This seems like the easiest (but not most robust) way to me. Simply compute the sum from row 6 to the maximum allowed row number, as specified by Excel. According to this site, the maximum is currently 1048576, so the following should work for you:

=sum(c6:c1048576)

For more robust solutions, see the other answers.

process.waitFor() never returns

There are many reasons that waitFor() doesn't return.

But it usually boils down to the fact that the executed command doesn't quit.

This, again, can have many reasons.

One common reason is that the process produces some output and you don't read from the appropriate streams. This means that the process is blocked as soon as the buffer is full and waits for your process to continue reading. Your process in turn waits for the other process to finish (which it won't because it waits for your process, ...). This is a classical deadlock situation.

You need to continually read from the processes input stream to ensure that it doesn't block.

There's a nice article that explains all the pitfalls of Runtime.exec() and shows ways around them called "When Runtime.exec() won't" (yes, the article is from 2000, but the content still applies!)

How to convert a Base64 string into a Bitmap image to show it in a ImageView?

I've found this easy solution

To convert from bitmap to Base64 use this method.

private String convertBitmapToBase64(Bitmap bitmap) {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOutputStream);
    byte[] byteArray = byteArrayOutputStream .toByteArray();
    return Base64.encodeToString(byteArray, Base64.DEFAULT);
}

To convert from Base64 to bitmap OR revert.

private Bitmap convertBase64ToBitmap(String b64) {
    byte[] imageAsBytes = Base64.decode(b64.getBytes(), Base64.DEFAULT);
    return BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length);
}

How to install VS2015 Community Edition offline

The following worked for me on a Windows 8.1 machine to download and prepare the setup folder, and then on a Windows 10 laptop to install:

  1. Go to https://my.visualstudio.com/downloads?q=visual%20studio%20community%202015
  2. Select “Visual Studio Community 2015 with Update 3” x64, English, DVD, and Download.
  3. Open the folder containing the download, which is called: en_visual_studio_community_2015_with_update_3_x86_x64_dvd_8923300.iso and its size is 7,617,847,296 bytes.
  4. Right-click on the file name: Mount
  5. On the mount folder, shift-right-click on an empty space: Open command window here
  6. On the command window: vs_community.exe /layout "blah blah blah blah \Visual Studio 2015\Setup" (or whatever path you want; the Setup folder gets created).
  7. Follow the dialog box instructions.

When I did this, it remained for exactly two hours and ten secs in the Acquiring: Optional items. Don’t despair.

When it completed, the size of the Setup folder was 12.9 GB. Compare with the size of the .iso above.

After completion, I succeeded on installing without a network connection, and that even though on completion I had got the following: enter image description here

How to round up with excel VBA round()?

Try the RoundUp function:

Dim i As Double

i = Application.WorksheetFunction.RoundUp(Cells(1, 1).Value * Cells(1, 2).Value, 2)

How can I get System variable value in Java?

Are you on a linux system? If so be sure you are exporting your variable.

myVar=testvalue; export myVar

I get null unless I use export to define the value globally.

Why not inherit from List<T>?

class FootballTeam : List<FootballPlayer> 
{ 
    public string TeamName; 
    public int RunningTotal;
}

Previous code means: a bunch of guys from the street playing football, and they happen to have a name. Something like:

People playing football

Anyway, this code (from m-y's answer)

public class FootballTeam
{
    // A team's name
    public string TeamName; 

    // Football team rosters are generally 53 total players.
    private readonly List<T> _roster = new List<T>(53);

    public IList<T> Roster
    {
        get { return _roster; }
    }

    public int PlayerCount
    {
        get { return _roster.Count(); }
    }

    // Any additional members you want to expose/wrap.
}

Means: this is a football team which has management, players, admins, etc. Something like:

Image showing members (and other attributes) of the Manchester United team

This is how is your logic presented in pictures…

How do I style appcompat-v7 Toolbar like Theme.AppCompat.Light.DarkActionBar?

Ok after having sunk way to much time into this problem this is the way I managed to get the appearance I was hoping for. I'm making it a separate answer so I can get everything in one place.

It's a combination of factors.

Firstly, don't try to get the toolbars to play nice through just themes. It seems to be impossible.

So apply themes explicitly to your Toolbars like in oRRs answer

layout/toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_alignParentTop="true"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    app:theme="@style/Dark.Overlay"
    app:popupTheme="@style/Dark.Overlay.LightPopup" />

However this is the magic sauce. In order to actually get the background colors I was hoping for you have to override the background attribute in your Toolbar themes

values/styles.xml:

<!-- 
    I expected android:colorBackground to be what I was looking for but
    it seems you have to override android:background
-->
<style name="Dark.Overlay" parent="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
    <item name="android:background">?attr/colorPrimary</item>
</style>

<style name="Dark.Overlay.LightPopup" parent="ThemeOverlay.AppCompat.Light">
    <item name="android:background">@color/material_grey_200</item>
</style>

then just include your toolbar layout in your other layouts

<include android:id="@+id/mytoolbar" layout="@layout/toolbar" />

and you're good to go.

Hope this helps someone else so you don't have to spend as much time on this as I have.

(if anyone can figure out how to make this work using just themes, ie not having to apply the themes explicitly in the layout files I'll gladly support their answer instead)

EDIT:

So apparently posting a more complete answer was a downvote magnet so I'll just accept the imcomplete answer above but leave this answer here in case someone actually needs it. Feel free to keep downvoting if it makes you happy though.

How do I access my webcam in Python?

OpenCV has support for getting data from a webcam, and it comes with Python wrappers by default, you also need to install numpy for the OpenCV Python extension (called cv2) to work. As of 2019, you can install both of these libraries with pip: pip install numpy pip install opencv-python

More information on using OpenCV with Python.

An example copied from Displaying webcam feed using opencv and python:

import cv2

cv2.namedWindow("preview")
vc = cv2.VideoCapture(0)

if vc.isOpened(): # try to get the first frame
    rval, frame = vc.read()
else:
    rval = False

while rval:
    cv2.imshow("preview", frame)
    rval, frame = vc.read()
    key = cv2.waitKey(20)
    if key == 27: # exit on ESC
        break
cv2.destroyWindow("preview")

Creating a chart in Excel that ignores #N/A or blank cells

If you make the vertical scale on your chart (using format axis) run from 0.0001 (say) then a value that Excel thinks is zero will not be plotted. Your axis in the chart will still look like it runs from zero upwards.

Convert HTML string to image

Try the following:

using System;
using System.Drawing;
using System.Threading;
using System.Windows.Forms;

class Program
{
    static void Main(string[] args)
    {
        var source =  @"
        <!DOCTYPE html>
        <html>
            <body>
                <p>An image from W3Schools:</p>
                <img 
                    src=""http://www.w3schools.com/images/w3schools_green.jpg"" 
                    alt=""W3Schools.com"" 
                    width=""104"" 
                    height=""142"">
            </body>
        </html>";
        StartBrowser(source);
        Console.ReadLine();
    }

    private static void StartBrowser(string source)
    {
        var th = new Thread(() =>
        {
            var webBrowser = new WebBrowser();
            webBrowser.ScrollBarsEnabled = false;
            webBrowser.DocumentCompleted +=
                webBrowser_DocumentCompleted;
            webBrowser.DocumentText = source;
            Application.Run();
        });
        th.SetApartmentState(ApartmentState.STA);
        th.Start();
    }

    static void 
        webBrowser_DocumentCompleted(
        object sender, 
        WebBrowserDocumentCompletedEventArgs e)
    {
        var webBrowser = (WebBrowser)sender;
        using (Bitmap bitmap = 
            new Bitmap(
                webBrowser.Width, 
                webBrowser.Height))
        {
            webBrowser
                .DrawToBitmap(
                bitmap, 
                new System.Drawing
                    .Rectangle(0, 0, bitmap.Width, bitmap.Height));
            bitmap.Save(@"filename.jpg", 
                System.Drawing.Imaging.ImageFormat.Jpeg);
        }
    }
}

Note: Credits should go to Hans Passant for his excellent answer on the question WebBrowser Control in a new thread which inspired this solution.

typecast string to integer - Postgres

I'm not able to comment (too little reputation? I'm pretty new) on Lukas' post.

On my PG setup to_number(NULL) does not work, so my solution would be:

SELECT CASE WHEN column = NULL THEN NULL ELSE column :: Integer END
FROM table

Why use Ruby's attr_accessor, attr_reader and attr_writer?

All of the answers above are correct; attr_reader and attr_writer are more convenient to write than manually typing the methods they are shorthands for. Apart from that they offer much better performance than writing the method definition yourself. For more info see slide 152 onwards from this talk (PDF) by Aaron Patterson.

How to disable submit button once it has been clicked?

You need to disable the button in the onsubmit event of the <form>:

<form action='/' method='POST' onsubmit='disableButton()'>
    <input name='txt' type='text' required />
    <button id='btn' type='submit'>Post</button>
</form>

<script>
    function disableButton() {
        var btn = document.getElementById('btn');
        btn.disabled = true;
        btn.innerText = 'Posting...'
    }
</script>

Note: this way if you have a form element which has the required attribute will work.

Angular 2 two way binding using ngModel is not working

Angular 2 Beta

This answer is for those who use Javascript for angularJS v.2.0 Beta.

To use ngModel in your view you should tell the angular's compiler that you are using a directive called ngModel.

How?

To use ngModel there are two libraries in angular2 Beta, and they are ng.common.FORM_DIRECTIVES and ng.common.NgModel.

Actually ng.common.FORM_DIRECTIVES is nothing but group of directives which are useful when you are creating a form. It includes NgModel directive also.

app.myApp = ng.core.Component({
    selector: 'my-app',
    templateUrl: 'App/Pages/myApp.html',
    directives: [ng.common.NgModel] // specify all your directives here
}).Class({
    constructor: function () {
        this.myVar = {};
        this.myVar.text = "Testing";
    },

});

Delete all SYSTEM V shared memory and semaphores on UNIX-like systems

Here, save and try this script (kill_ipcs.sh) on your shell:

#!/bin/bash

ME=`whoami`

IPCS_S=`ipcs -s | egrep "0x[0-9a-f]+ [0-9]+" | grep $ME | cut -f2 -d" "`
IPCS_M=`ipcs -m | egrep "0x[0-9a-f]+ [0-9]+" | grep $ME | cut -f2 -d" "`
IPCS_Q=`ipcs -q | egrep "0x[0-9a-f]+ [0-9]+" | grep $ME | cut -f2 -d" "`


for id in $IPCS_M; do
  ipcrm -m $id;
done

for id in $IPCS_S; do
  ipcrm -s $id;
done

for id in $IPCS_Q; do
  ipcrm -q $id;
done

We use it whenever we run IPCS programs in the university student server. Some people don't always cleanup so...it's needed :P

open link in iframe

Try this:

<iframe name="iframe1" src="target.html"></iframe>

<a href="link.html" target="iframe1">link</a>

The "target" attribute should open in the iframe.

How to build x86 and/or x64 on Windows from command line with CMAKE?

Besides CMAKE_GENERATOR_PLATFORM variable, there is also the -A switch

cmake -G "Visual Studio 16 2019" -A Win32
cmake -G "Visual Studio 16 2019" -A x64

https://cmake.org/cmake/help/v3.16/generator/Visual%20Studio%2016%202019.html#platform-selection

  -A <platform-name>           = Specify platform name if supported by
                                 generator.

Is there a way to get a list of all current temporary tables in SQL Server?

If you need to 'see' the list of temporary tables, you could simply log the names used. (and as others have noted, it is possible to directly query this information)

If you need to 'see' the content of temporary tables, you will need to create real tables with a (unique) temporary name.

You can trace the SQL being executed using SQL Profiler:

[These articles target SQL Server versions later than 2000, but much of the advice is the same.]

If you have a lengthy process that is important to your business, it's a good idea to log various steps (step name/number, start and end time) in the process. That way you have a baseline to compare against when things don't perform well, and you can pinpoint which step(s) are causing the problem more quickly.

How to pop an alert message box using PHP?

You could use Javascript:

// This is in the PHP file and sends a Javascript alert to the client
$message = "wrong answer";
echo "<script type='text/javascript'>alert('$message');</script>";

Close a MessageBox after several seconds

DMitryG's code "get the return value of the underlying MessageBox" has a bug so the timerResult is never actually correctly returned (MessageBox.Show call returns AFTER OnTimerElapsed completes). My fix is below:

public class TimedMessageBox {
    System.Threading.Timer _timeoutTimer;
    string _caption;
    DialogResult _result;
    DialogResult _timerResult;
    bool timedOut = false;

    TimedMessageBox(string text, string caption, int timeout, MessageBoxButtons buttons = MessageBoxButtons.OK, DialogResult timerResult = DialogResult.None)
    {
        _caption = caption;
        _timeoutTimer = new System.Threading.Timer(OnTimerElapsed,
            null, timeout, System.Threading.Timeout.Infinite);
        _timerResult = timerResult;
        using(_timeoutTimer)
            _result = MessageBox.Show(text, caption, buttons);
        if (timedOut) _result = _timerResult;
    }

    public static DialogResult Show(string text, string caption, int timeout, MessageBoxButtons buttons = MessageBoxButtons.OK, DialogResult timerResult = DialogResult.None) {
        return new TimedMessageBox(text, caption, timeout, buttons, timerResult)._result;
    }

    void OnTimerElapsed(object state) {
        IntPtr mbWnd = FindWindow("#32770", _caption); // lpClassName is #32770 for MessageBox
        if(mbWnd != IntPtr.Zero)
            SendMessage(mbWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
        _timeoutTimer.Dispose();
        timedOut = true;
    }

    const int WM_CLOSE = 0x0010;
    [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true, CharSet = System.Runtime.InteropServices.CharSet.Auto)]
    static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
    [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
    static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
}

Test method is inconclusive: Test wasn't run. Error?

If you are using xUnit, I solved the issue installing xunit.running.visualstudio package. (currently using xUnit 2.3.1 and VS17 Enterprise 15.3.5)

What are intent-filters in Android?

When there are multiple activities entries in AndroidManifest.xml, how does android know which activity to start first?

There is no "first". In your case, with your manifest as shown, you will have two icons in your launcher. Whichever one the user taps on is the one that gets launched.

I could not understand intent-filters. Can anyone please explain.

There is quite a bit of documentation on the subject. Please consider reading that, then asking more specific questions.

Also, when you get "application has stopped unexpectedly, try again", use adb logcat, DDMS, or the DDMS perspective in Eclipse to examine the Java stack trace associated with the error.

How to calculate time difference in java?

Java 8 has a cleaner solution - Instant and Duration

Example:

import java.time.Duration;
import java.time.Instant;
...
Instant start = Instant.now();
//your code
Instant end = Instant.now();
Duration timeElapsed = Duration.between(start, end);
System.out.println("Time taken: "+ timeElapsed.toMillis() +" milliseconds");

Can you get a Windows (AD) username in PHP?

try this code :

$user= shell_exec("echo %username%"); 
    echo "user : $user";

you get your windows(AD) username in php

Format output string, right alignment

Simple tabulation of the output:

a = 0.3333333
b = 200/3
print("variable a    variable b")
print("%10.2f    %10.2f" % (a, b))

output:

variable a    variable b
      0.33         66.67

%10.2f: 10 is the minimum length and 2 is the number of decimal places.

Is it really impossible to make a div fit its size to its content?

it works well on Edge and Chrome:

  width: fit-content;
  height: fit-content;

Python name 'os' is not defined

The problem is that you forgot to import os. Add this line of code:

import os

And everything should be fine. Hope this helps!

When to use: Java 8+ interface default method, vs. abstract method

Although its an old question let me give my input on it as well.

  1. abstract class: Inside abstract class we can declare instance variables, which are required to the child class

    Interface: Inside interface every variables is always public static and final we cannot declare instance variables

  2. abstract class: Abstract class can talk about state of object

    Interface: Interface can never talk about state of object

  3. abstract class: Inside Abstract class we can declare constructors

    Interface: Inside interface we cannot declare constructors as purpose of
    constructors is to initialize instance variables. So what is the need of constructor there if we cannot have instance variables in interfaces.

  4. abstract class: Inside abstract class we can declare instance and static blocks

    Interface: Interfaces cannot have instance and static blocks.

  5. abstract class: Abstract class cannot refer lambda expression

    Interfaces: Interfaces with single abstract method can refer lambda expression

  6. abstract class: Inside abstract class we can override OBJECT CLASS methods

    Interfaces: We cannot override OBJECT CLASS methods inside interfaces.

I will end on the note that:

Default method concepts/static method concepts in interface came just to save implementation classes but not to provide meaningful useful implementation. Default methods/static methods are kind of dummy implementation, "if you want you can use them or you can override them (in case of default methods) in implementation class" Thus saving us from implementing new methods in implementation classes whenever new methods in interfaces are added. Therefore interfaces can never be equal to abstract classes.

How to get JQuery.trigger('click'); to initiate a mouse click

jQuery's .trigger('click'); will only cause an event to trigger on this event, it will not trigger the default browser action as well.

You can simulate the same functionality with the following JavaScript:

jQuery('#foo').on('click', function(){
    var bar = jQuery('#bar');
    var href = bar.attr('href');
    if(bar.attr("target") === "_blank")
    {
        window.open(href);
    }else{
        window.location = href;
    }
});

Java Code for calculating Leap Year

As wikipedia states algorithm for the leap year should be

(((year%4 == 0) && (year%100 !=0)) || (year%400==0))  

Here is a sample program how to check for leap year.

Can I set variables to undefined or pass undefined as an argument?

Just for fun, here's a fairly safe way to assign "unassigned" to a variable. For this to have a collision would require someone to have added to the prototype for Object with exactly the same name as the randomly generated string. I'm sure the random string generator could be improved, but I just took one from this question: Generate random string/characters in JavaScript

This works by creating a new object and trying to access a property on it with a randomly generated name, which we are assuming wont exist and will hence have the value of undefined.

function GenerateRandomString() {
    var text = "";
    var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

    for (var i = 0; i < 50; i++)
        text += possible.charAt(Math.floor(Math.random() * possible.length));

    return text;
}

var myVar = {}[GenerateRandomString()];

How to make Java honor the DNS Caching Timeout?

This has obviously been fixed in newer releases (SE 6 and 7). I experience a 30 second caching time max when running the following code snippet while watching port 53 activity using tcpdump.

/**
 * http://stackoverflow.com/questions/1256556/any-way-to-make-java-honor-the-dns-caching-timeout-ttl
 *
 * Result: Java 6 distributed with Ubuntu 12.04 and Java 7 u15 downloaded from Oracle have
 * an expiry time for dns lookups of approx. 30 seconds.
 */

import java.util.*;
import java.text.*;
import java.security.*;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

public class Test {
    final static String hostname = "www.google.com";
    public static void main(String[] args) {
        // only required for Java SE 5 and lower:
        //Security.setProperty("networkaddress.cache.ttl", "30");

        System.out.println(Security.getProperty("networkaddress.cache.ttl"));
        System.out.println(System.getProperty("networkaddress.cache.ttl"));
        System.out.println(Security.getProperty("networkaddress.cache.negative.ttl"));
        System.out.println(System.getProperty("networkaddress.cache.negative.ttl"));

        while(true) {
            int i = 0;
            try {
                makeRequest();
                InetAddress inetAddress = InetAddress.getLocalHost();
                System.out.println(new Date());
                inetAddress = InetAddress.getByName(hostname);
                displayStuff(hostname, inetAddress);
            } catch (UnknownHostException e) {
                e.printStackTrace();
            }
            try {
                Thread.sleep(5L*1000L);
            } catch(Exception ex) {}
            i++;
        }
    }

    public static void displayStuff(String whichHost, InetAddress inetAddress) {
        System.out.println("Which Host:" + whichHost);
        System.out.println("Canonical Host Name:" + inetAddress.getCanonicalHostName());
        System.out.println("Host Name:" + inetAddress.getHostName());
        System.out.println("Host Address:" + inetAddress.getHostAddress());
    }

    public static void makeRequest() {
        try {
            URL url = new URL("http://"+hostname+"/");
            URLConnection conn = url.openConnection();
            conn.connect();
            InputStream is = conn.getInputStream();
            InputStreamReader ird = new InputStreamReader(is);
            BufferedReader rd = new BufferedReader(ird);
            String res;
            while((res = rd.readLine()) != null) {
                System.out.println(res);
                break;
            }
            rd.close();
        } catch(Exception ex) {
            ex.printStackTrace();
        }
    }
}

Mongoose delete array element in document and save

The checked answer does work but officially in MongooseJS latest, you should use pull.

doc.subdocs.push({ _id: 4815162342 }) // added
doc.subdocs.pull({ _id: 4815162342 }) // removed

https://mongoosejs.com/docs/api.html#mongoosearray_MongooseArray-pull

I was just looking that up too.

See Daniel's answer for the correct answer. Much better.

Multi-dimensional arrays in Bash

Lots of answers found here for creating multidimensional arrays in bash.

And without exception, all are obtuse and difficult to use.

If MD arrays are a required criteria, it is time to make a decision:

Use a language that supports MD arrays

My preference is Perl. Most would probably choose Python. Either works.

Store the data elsewhere

JSON and jq have already been suggested. XML has also been suggested, though for your use JSON and jq would likely be simpler.

It would seem though that Bash may not be the best choice for what you need to do.

Sometimes the correct question is not "How do I do X in tool Y?", but rather "Which tool would be best to do X?"

Hive Alter table change Column Name

Change Column Name/Type/Position/Comment:

ALTER TABLE table_name CHANGE [COLUMN] col_old_name col_new_name column_type [COMMENT col_comment] [FIRST|AFTER column_name]

Example:

CREATE TABLE test_change (a int, b int, c int);

// will change column a's name to a1
ALTER TABLE test_change CHANGE a a1 INT;

Rails: Default sort order for a rails model?

default_scope

This works for Rails 4+:

class Book < ActiveRecord::Base
  default_scope { order(created_at: :desc) }
end

For Rails 2.3, 3, you need this instead:

default_scope order('created_at DESC')

For Rails 2.x:

default_scope :order => 'created_at DESC'

Where created_at is the field you want the default sorting to be done on.

Note: ASC is the code to use for Ascending and DESC is for descending (desc, NOT dsc !).

scope

Once you're used to that you can also use scope:

class Book < ActiveRecord::Base
  scope :confirmed, :conditions => { :confirmed => true }
  scope :published, :conditions => { :published => true }
end

For Rails 2 you need named_scope.

:published scope gives you Book.published instead of Book.find(:published => true).

Since Rails 3 you can 'chain' those methods together by concatenating them with periods between them, so with the above scopes you can now use Book.published.confirmed.

With this method, the query is not actually executed until actual results are needed (lazy evaluation), so 7 scopes could be chained together but only resulting in 1 actual database query, to avoid performance problems from executing 7 separate queries.

You can use a passed in parameter such as a date or a user_id (something that will change at run-time and so will need that 'lazy evaluation', with a lambda, like this:

scope :recent_books, lambda 
  { |since_when| where("created_at >= ?", since_when) }
  # Note the `where` is making use of AREL syntax added in Rails 3.

Finally you can disable default scope with:

Book.with_exclusive_scope { find(:all) } 

or even better:

Book.unscoped.all

which will disable any filter (conditions) or sort (order by).

Note that the first version works in Rails2+ whereas the second (unscoped) is only for Rails3+


So ... if you're thinking, hmm, so these are just like methods then..., yup, that's exactly what these scopes are!
They are like having def self.method_name ...code... end but as always with ruby they are nice little syntactical shortcuts (or 'sugar') to make things easier for you!

In fact they are Class level methods as they operate on the 1 set of 'all' records.

Their format is changing however, with rails 4 there are deprecation warning when using #scope without passing a callable object. For example scope :red, where(color: 'red') should be changed to scope :red, -> { where(color: 'red') }.

As a side note, when used incorrectly, default_scope can be misused/abused.
This is mainly about when it gets used for actions like where's limiting (filtering) the default selection (a bad idea for a default) rather than just being used for ordering results.
For where selections, just use the regular named scopes. and add that scope on in the query, e.g. Book.all.published where published is a named scope.

In conclusion, scopes are really great and help you to push things up into the model for a 'fat model thin controller' DRYer approach.

IE11 meta element Breaks SVG

It sounds as though you're not in a modern document mode. Internet Explorer 11 shows the SVG just fine when you're in Standards Mode. Make sure that if you have an x-ua-compatible meta tag, you have it set to Edge, rather than an earlier mode.

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

You can determine your document mode by opening up your F12 Developer Tools and checking either the document mode dropdown (seen at top-right, currently "Edge") or the emulation tab:

enter image description here

If you do not have an x-ua-compatible meta tag (or header), be sure to use a doctype that will put the document into Standards mode, such as <!DOCTYPE html>.

enter image description here

How to read a text file into a string variable and strip newlines?

you can compress this into one into two lines of code!!!

content = open('filepath','r').read().replace('\n',' ')
print(content)

if your file reads:

hello how are you?
who are you?
blank blank

python output

hello how are you? who are you? blank blank

Convert time.Time to string

strconv.Itoa(int(time.Now().Unix()))

Get size of folder or file

  • Works for Android and Java
  • Works for both folders and files
  • Checks for null pointer everywhere where needed
  • Ignores symbolic link aka shortcuts
  • Production ready!

Source code:

   public long fileSize(File root) {
        if(root == null){
            return 0;
        }
        if(root.isFile()){
            return root.length();
        }
        try {
            if(isSymlink(root)){
                return 0;
            }
        } catch (IOException e) {
            e.printStackTrace();
            return 0;
        }

        long length = 0;
        File[] files = root.listFiles();
        if(files == null){
            return 0;
        }
        for (File file : files) {
            length += fileSize(file);
        }

        return length;
    }

    private static boolean isSymlink(File file) throws IOException {
        File canon;
        if (file.getParent() == null) {
            canon = file;
        } else {
            File canonDir = file.getParentFile().getCanonicalFile();
            canon = new File(canonDir, file.getName());
        }
        return !canon.getCanonicalFile().equals(canon.getAbsoluteFile());
    }

New Line Issue when copying data from SQL Server 2012 to Excel

Line Split Issues when Copying Data from SQL Server to Excel. see below example and try using replace some characters.

SELECT replace(replace(CountyCode, char(10), ''), char(13), '') 
FROM [MSSQLTipsDemo].[dbo].[CountryInfo]

How to get the android Path string to a file on Assets folder?

You can use this method.

    public static File getRobotCacheFile(Context context) throws IOException {
        File cacheFile = new File(context.getCacheDir(), "robot.png");
        try {
            InputStream inputStream = context.getAssets().open("robot.png");
            try {
                FileOutputStream outputStream = new FileOutputStream(cacheFile);
                try {
                    byte[] buf = new byte[1024];
                    int len;
                    while ((len = inputStream.read(buf)) > 0) {
                        outputStream.write(buf, 0, len);
                    }
                } finally {
                    outputStream.close();
                }
            } finally {
                inputStream.close();
            }
        } catch (IOException e) {
            throw new IOException("Could not open robot png", e);
        }
        return cacheFile;
    }

You should never use InputStream.available() in such cases. It returns only bytes that are buffered. Method with .available() will never work with bigger files and will not work on some devices at all.

In Kotlin (;D):

@Throws(IOException::class)
fun getRobotCacheFile(context: Context): File = File(context.cacheDir, "robot.png")
    .also {
        it.outputStream().use { cache -> context.assets.open("robot.png").use { it.copyTo(cache) } }
    }

oracle.jdbc.driver.OracleDriver ClassNotFoundException

You can add a JAR which having above specified class exist e.g.ojdbc jar which supported by installed java version, also make sure that you have added it into classpath.

uncaught syntaxerror unexpected token U JSON

Just incase u didnt understand

e.g is that lets say i have a JSON STRING ..NOT YET A JSON OBJECT OR ARRAY.

so if in javascript u parse the string as

var body={
  "id": 1,
  "deleted_at": null,
  "open_order": {
    "id": 16,
    "status": "open"}

var jsonBody = JSON.parse(body.open_order); //HERE THE ERROR NOW APPEARS BECAUSE THE STRING IS NOT A JSON OBJECT YET!!!! 
//TODO SO
var jsonBody=JSON.parse(body)//PASS THE BODY FIRST THEN LATER USE THE jsonBody to get the open_order

var OpenOrder=jsonBody.open_order;

Great answers above

Truncating Text in PHP?

$mystring = "this is the text I would like to truncate";

// Pass your variable to the function
$mystring = truncate($mystring);

// Truncated tring printed out;
echo $mystring;

//truncate text function
public function truncate($text) {

    //specify number fo characters to shorten by
    $chars = 25;

    $text = $text." ";
    $text = substr($text,0,$chars);
    $text = substr($text,0,strrpos($text,' '));
    $text = $text."...";
    return $text;
}

SQL Server query to find all permissions/access for all users in a database

This is my first crack at a query, based on Andomar's suggestions. This query is intended to provide a list of permissions that a user has either applied directly to the user account, or through roles that the user has.

/*
Security Audit Report
1) List all access provisioned to a sql user or windows user/group directly 
2) List all access provisioned to a sql user or windows user/group through a database or application role
3) List all access provisioned to the public role

Columns Returned:
UserName        : SQL or Windows/Active Directory user account.  This could also be an Active Directory group.
UserType        : Value will be either 'SQL User' or 'Windows User'.  This reflects the type of user defined for the 
                  SQL Server user account.
DatabaseUserName: Name of the associated user as defined in the database user account.  The database user may not be the
                  same as the server user.
Role            : The role name.  This will be null if the associated permissions to the object are defined at directly
                  on the user account, otherwise this will be the name of the role that the user is a member of.
PermissionType  : Type of permissions the user/role has on an object. Examples could include CONNECT, EXECUTE, SELECT
                  DELETE, INSERT, ALTER, CONTROL, TAKE OWNERSHIP, VIEW DEFINITION, etc.
                  This value may not be populated for all roles.  Some built in roles have implicit permission
                  definitions.
PermissionState : Reflects the state of the permission type, examples could include GRANT, DENY, etc.
                  This value may not be populated for all roles.  Some built in roles have implicit permission
                  definitions.
ObjectType      : Type of object the user/role is assigned permissions on.  Examples could include USER_TABLE, 
                  SQL_SCALAR_FUNCTION, SQL_INLINE_TABLE_VALUED_FUNCTION, SQL_STORED_PROCEDURE, VIEW, etc.   
                  This value may not be populated for all roles.  Some built in roles have implicit permission
                  definitions.          
ObjectName      : Name of the object that the user/role is assigned permissions on.  
                  This value may not be populated for all roles.  Some built in roles have implicit permission
                  definitions.
ColumnName      : Name of the column of the object that the user/role is assigned permissions on. This value
                  is only populated if the object is a table, view or a table value function.                 
*/

--List all access provisioned to a sql user or windows user/group directly 
SELECT  
    [UserName] = CASE princ.[type] 
                    WHEN 'S' THEN princ.[name]
                    WHEN 'U' THEN ulogin.[name] COLLATE Latin1_General_CI_AI
                 END,
    [UserType] = CASE princ.[type]
                    WHEN 'S' THEN 'SQL User'
                    WHEN 'U' THEN 'Windows User'
                 END,  
    [DatabaseUserName] = princ.[name],       
    [Role] = null,      
    [PermissionType] = perm.[permission_name],       
    [PermissionState] = perm.[state_desc],       
    [ObjectType] = obj.type_desc,--perm.[class_desc],       
    [ObjectName] = OBJECT_NAME(perm.major_id),
    [ColumnName] = col.[name]
FROM    
    --database user
    sys.database_principals princ  
LEFT JOIN
    --Login accounts
    sys.login_token ulogin on princ.[sid] = ulogin.[sid]
LEFT JOIN        
    --Permissions
    sys.database_permissions perm ON perm.[grantee_principal_id] = princ.[principal_id]
LEFT JOIN
    --Table columns
    sys.columns col ON col.[object_id] = perm.major_id 
                    AND col.[column_id] = perm.[minor_id]
LEFT JOIN
    sys.objects obj ON perm.[major_id] = obj.[object_id]
WHERE 
    princ.[type] in ('S','U')
UNION
--List all access provisioned to a sql user or windows user/group through a database or application role
SELECT  
    [UserName] = CASE memberprinc.[type] 
                    WHEN 'S' THEN memberprinc.[name]
                    WHEN 'U' THEN ulogin.[name] COLLATE Latin1_General_CI_AI
                 END,
    [UserType] = CASE memberprinc.[type]
                    WHEN 'S' THEN 'SQL User'
                    WHEN 'U' THEN 'Windows User'
                 END, 
    [DatabaseUserName] = memberprinc.[name],   
    [Role] = roleprinc.[name],      
    [PermissionType] = perm.[permission_name],       
    [PermissionState] = perm.[state_desc],       
    [ObjectType] = obj.type_desc,--perm.[class_desc],   
    [ObjectName] = OBJECT_NAME(perm.major_id),
    [ColumnName] = col.[name]
FROM    
    --Role/member associations
    sys.database_role_members members
JOIN
    --Roles
    sys.database_principals roleprinc ON roleprinc.[principal_id] = members.[role_principal_id]
JOIN
    --Role members (database users)
    sys.database_principals memberprinc ON memberprinc.[principal_id] = members.[member_principal_id]
LEFT JOIN
    --Login accounts
    sys.login_token ulogin on memberprinc.[sid] = ulogin.[sid]
LEFT JOIN        
    --Permissions
    sys.database_permissions perm ON perm.[grantee_principal_id] = roleprinc.[principal_id]
LEFT JOIN
    --Table columns
    sys.columns col on col.[object_id] = perm.major_id 
                    AND col.[column_id] = perm.[minor_id]
LEFT JOIN
    sys.objects obj ON perm.[major_id] = obj.[object_id]
UNION
--List all access provisioned to the public role, which everyone gets by default
SELECT  
    [UserName] = '{All Users}',
    [UserType] = '{All Users}', 
    [DatabaseUserName] = '{All Users}',       
    [Role] = roleprinc.[name],      
    [PermissionType] = perm.[permission_name],       
    [PermissionState] = perm.[state_desc],       
    [ObjectType] = obj.type_desc,--perm.[class_desc],  
    [ObjectName] = OBJECT_NAME(perm.major_id),
    [ColumnName] = col.[name]
FROM    
    --Roles
    sys.database_principals roleprinc
LEFT JOIN        
    --Role permissions
    sys.database_permissions perm ON perm.[grantee_principal_id] = roleprinc.[principal_id]
LEFT JOIN
    --Table columns
    sys.columns col on col.[object_id] = perm.major_id 
                    AND col.[column_id] = perm.[minor_id]                   
JOIN 
    --All objects   
    sys.objects obj ON obj.[object_id] = perm.[major_id]
WHERE
    --Only roles
    roleprinc.[type] = 'R' AND
    --Only public role
    roleprinc.[name] = 'public' AND
    --Only objects of ours, not the MS objects
    obj.is_ms_shipped = 0
ORDER BY
    princ.[Name],
    OBJECT_NAME(perm.major_id),
    col.[name],
    perm.[permission_name],
    perm.[state_desc],
    obj.type_desc--perm.[class_desc] 

Android: How to Programmatically set the size of a Layout

my sample code

wv = (WebView) findViewById(R.id.mywebview);
wv.getLayoutParams().height = LayoutParams.MATCH_PARENT; // LayoutParams: android.view.ViewGroup.LayoutParams
// wv.getLayoutParams().height = LayoutParams.WRAP_CONTENT;
wv.requestLayout();//It is necesary to refresh the screen

How to create a DOM node as an object?

Try this:

var div = $('<div></div>').addClass('bar').text('bla');
var li = $('<li></li>').attr('id', '1234');
li.append(div);

$('body').append(li);

Obviously, it doesn't make sense to append a li to the body directly. Basically, the trick is to construct the DOM elementr tree with $('your html here'). I suggest to use CSS modifiers (.text(), .addClass() etc) as opposed to making jquery parse raw HTML, it will make it much easier to change things later.