Programs & Examples On #Taglib

TagLibs is a shortened form of "Tag Libraries". Tag Libraries are libraries that include "tags". Tags are usually used to address presentation concerns and encapsulate view-specific logic.

Running CMake on Windows

There is a vcvars32.bat in your Visual Studio installation directory. You can add call cmd.exe at the end of that batch program and launch it. From that shell you can use CMake or cmake-gui and cl.exe would be known to CMake.

Eclipse "cannot find the tag library descriptor" for custom tags (not JSTL!)

You can simply go to Build Path -> Add Libraries and for the library type to add select "Server Runtime." Click Next and select a server runtime to add to the classpath and the problem goes away if jstl.jar and standard.jar are in your server's classpath.

Capitalize words in string

The answer provided by vsync works as long as you don't have accented letters in the input string.

I don't know the reason, but apparently the \b in regexp matches also accented letters (tested on IE8 and Chrome), so a string like "località" would be wrongly capitalized converted into "LocalitÀ" (the à letter gets capitalized cause the regexp thinks it's a word boundary)

A more general function that works also with accented letters is this one:

String.prototype.toCapitalize = function()
   return this.toLowerCase().replace(/^.|\s\S/g, function(a) { return a.toUpperCase(); });

You can use it like this:

alert( "hello località".toCapitalize() );

Populating a dictionary using for loops (python)

dicts = {}
keys = range(4)
values = ["Hi", "I", "am", "John"]
for i in keys:
        dicts[i] = values[i]


In [7]: dict(list(enumerate(values)))
Out[7]: {0: 'Hi', 1: 'I', 2: 'am', 3: 'John'}

How to add button in ActionBar(Android)?

you have to create an entry inside res/menu,override onCreateOptionsMenu and inflate it

public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(, menu);
    return true;

an entry for the menu could be:

<menu xmlns:android="" >

A monad is just a monoid in the category of endofunctors, what's the problem?

First, the extensions and libraries that we're going to use:

{-# LANGUAGE RankNTypes, TypeOperators #-}

import Control.Monad (join)

Of these, RankNTypes is the only one that's absolutely essential to the below. I once wrote an explanation of RankNTypes that some people seem to have found useful, so I'll refer to that.

Quoting Tom Crockett's excellent answer, we have:

A monad is...

  • An endofunctor, T : X -> X
  • A natural transformation, µ : T × T -> T, where × means functor composition
  • A natural transformation, ? : I -> T, where I is the identity endofunctor on X

...satisfying these laws:

  • µ(µ(T × T) × T)) = µ(T × µ(T × T))
  • µ(?(T)) = T = µ(T(?))

How do we translate this to Haskell code? Well, let's start with the notion of a natural transformation:

-- | A natural transformations between two 'Functor' instances.  Law:
-- > fmap f . eta g == eta g . fmap f
-- Neat fact: the type system actually guarantees this law.
newtype f :-> g =
    Natural { eta :: forall x. f x -> g x }

A type of the form f :-> g is analogous to a function type, but instead of thinking of it as a function between two types (of kind *), think of it as a morphism between two functors (each of kind * -> *). Examples:

listToMaybe :: [] :-> Maybe
listToMaybe = Natural go
    where go [] = Nothing
          go (x:_) = Just x

maybeToList :: Maybe :-> []
maybeToList = Natural go
    where go Nothing = []
          go (Just x) = [x]

reverse' :: [] :-> []
reverse' = Natural reverse

Basically, in Haskell, natural transformations are functions from some type f x to another type g x such that the x type variable is "inaccessible" to the caller. So for example, sort :: Ord a => [a] -> [a] cannot be made into a natural transformation, because it's "picky" about which types we may instantiate for a. One intuitive way I often use to think of this is the following:

  • A functor is a way of operating on the content of something without touching the structure.
  • A natural transformation is a way of operating on the structure of something without touching or looking at the content.

Now, with that out of the way, let's tackle the clauses of the definition.

The first clause is "an endofunctor, T : X -> X." Well, every Functor in Haskell is an endofunctor in what people call "the Hask category," whose objects are Haskell types (of kind *) and whose morphisms are Haskell functions. This sounds like a complicated statement, but it's actually a very trivial one. All it means is that that a Functor f :: * -> * gives you the means of constructing a type f a :: * for any a :: * and a function fmap f :: f a -> f b out of any f :: a -> b, and that these obey the functor laws.

Second clause: the Identity functor in Haskell (which comes with the Platform, so you can just import it) is defined this way:

newtype Identity a = Identity { runIdentity :: a }

instance Functor Identity where
    fmap f (Identity a) = Identity (f a)

So the natural transformation ? : I -> T from Tom Crockett's definition can be written this way for any Monad instance t:

return' :: Monad t => Identity :-> t
return' = Natural (return . runIdentity)

Third clause: The composition of two functors in Haskell can be defined this way (which also comes with the Platform):

newtype Compose f g a = Compose { getCompose :: f (g a) }

-- | The composition of two 'Functor's is also a 'Functor'.
instance (Functor f, Functor g) => Functor (Compose f g) where
    fmap f (Compose fga) = Compose (fmap (fmap f) fga)

So the natural transformation µ : T × T -> T from Tom Crockett's definition can be written like this:

join' :: Monad t => Compose t t :-> t
join' = Natural (join . getCompose)

The statement that this is a monoid in the category of endofunctors then means that Compose (partially applied to just its first two parameters) is associative, and that Identity is its identity element. I.e., that the following isomorphisms hold:

  • Compose f (Compose g h) ~= Compose (Compose f g) h
  • Compose f Identity ~= f
  • Compose Identity g ~= g

These are very easy to prove because Compose and Identity are both defined as newtype, and the Haskell Reports define the semantics of newtype as an isomorphism between the type being defined and the type of the argument to the newtype's data constructor. So for example, let's prove Compose f Identity ~= f:

Compose f Identity a
    ~= f (Identity a)                 -- newtype Compose f g a = Compose (f (g a))
    ~= f a                            -- newtype Identity a = Identity a

How to Install Font Awesome in Laravel Mix

This is for new users who are using Laravel 5.7(and above) and Fontawesome 5.3

npm install @fortawesome/fontawesome-free --save

and in app.scss

@import '~@fortawesome/fontawesome-free/css/all.min.css';


npm run watch

Use in layout

<link href="{{ asset('css/app.css') }}" rel="stylesheet">

how can I enable scrollbars on the WPF Datagrid?


<DataGrid AutoGenerateColumns="True" Grid.Column="0" Grid.Row="0"

with : <ColumnDefinition Width="350" /> & <RowDefinition Height="300" /> works fine.

Scrollbars don't show with <ColumnDefinition Width="Auto" /> & <RowDefinition Height="300" />.

Also works fine with: <ColumnDefinition Width="*" /> & <RowDefinition Height="300" /> in the case where this is nested within an outer <Grid>.

How to get selected value of a html select with

<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html>
<html xmlns="">    
    <title> HtmlSelect Example </title>
    <script runat="server">
      void Button_Click (Object sender, EventArgs e)
         Label1.Text = "Selected index: " + Select1.SelectedIndex.ToString()
                       + ", value: " + Select1.Value;    
   <form id="form1" runat="server">

      Select an item: 

      <select id="Select1" runat="server">    
         <option value="Text for Item 1" selected="selected"> Item 1 </option>
         <option value="Text for Item 2"> Item 2 </option>
         <option value="Text for Item 3"> Item 3 </option>
         <option value="Text for Item 4"> Item 4 </option>

      <button onserverclick="Button_Click" runat="server" Text="Submit"/>

      <asp:Label id="Label1" runat="server"/>    

Source from Microsoft. Hope this is helpful!

How can I check if a command exists in a shell script?

Check if a program exists from a Bash script covers this very well. In any shell script, you're best off running command -v $command_name for testing if $command_name can be run. In bash you can use hash $command_name, which also hashes the result of any path lookup, or type -P $binary_name if you only want to see binaries (not functions etc.)

Download/Stream file from URL -

If you are looking for a .NET Core version of @Dallas's answer, use the below.

        Stream stream = null;

        //This controls how many bytes to read at a time and send to the client
        int bytesToRead = 10000;

        // Buffer to read bytes in chunk size specified above
        byte[] buffer = new Byte[bytesToRead];

        // The number of bytes read
            //Create a WebRequest to get the file
            HttpWebRequest fileReq = (HttpWebRequest)HttpWebRequest.Create(@"file url");

            //Create a response for this request
            HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse();

            if (fileReq.ContentLength > 0)
                fileResp.ContentLength = fileReq.ContentLength;

            //Get the Stream returned from the response
            stream = fileResp.GetResponseStream();

            // prepare the response to the client. resp is the client Response
            var resp = HttpContext.Response;

            //Indicate the type of data being sent
            resp.ContentType = "application/octet-stream";

            //Name the file 
            resp.Headers.Add("Content-Disposition", "attachment;");
            resp.Headers.Add("Content-Length", fileResp.ContentLength.ToString());

            int length;
                // Verify that the client is connected.
                if (!HttpContext.RequestAborted.IsCancellationRequested)
                    // Read data into the buffer.
                    length = stream.Read(buffer, 0, bytesToRead);

                    // and write it out to the response's output stream
                    resp.Body.Write(buffer, 0, length);

                    //Clear the buffer
                    buffer = new Byte[bytesToRead];
                    // cancel the download if client has disconnected
                    length = -1;
            } while (length > 0); //Repeat until no data is read
            if (stream != null)
                //Close the input stream

Oracle date "Between" Query

As APC rightly pointed out, your start_date column appears to be a TIMESTAMP but it could be a TIMESTAMP WITH LOCAL TIMEZONE or TIMESTAMP WITH TIMEZONE datatype too. These could well influence any queries you were doing on the data if your database server was in a different timezone to yourself. However, let's keep this simple and assume you are in the same timezone as your server. First, to give you the confidence, check that the start_date is a TIMESTAMP data type.

Use the SQLPlus DESCRIBE command (or the equivalent in your IDE) to verify this column is a TIMESTAMP data type.


DESCRIBE mytable

Should report :

Name        Null? Type
----------- ----- ------------
NAME              VARHAR2(20) 

If it is reported as a Type = TIMESTAMP then you can query your date ranges with simplest TO_TIMESTAMP date conversion, one which requires no argument (or picture).

We use TO_TIMESTAMP to ensure that any index on the START_DATE column is considered by the optimizer. APC's answer also noted that a function based index could have been created on this column and that would influence the SQL predicate but we cannot comment on that in this query. If you want to know how to find out what indexes have been applied to table, post another question and we can answer that separately.

So, assuming there is an index on start_date, which is a TIMESTAMP datatype and you want the optimizer to consider it, your SQL would be :

select * from mytable where start_date between to_timestamp('15-JAN-10') AND to_timestamp('17-JAN-10')+.9999999

+.999999999 is very close to but isn't quite 1 so the conversion of 17-JAN-10 will be as close to midnight on that day as possible, therefore you query returns both rows.

The database will see the BETWEEN as from 15-JAN-10 00:00:00:0000000 to 17-JAN-10 23:59:59:99999 and will therefore include all dates from 15th,16th and 17th Jan 2010 whatever the time component of the timestamp.

Hope that helps.


What are the basic rules and idioms for operator overloading?

Conversion Operators (also known as User Defined Conversions)

In C++ you can create conversion operators, operators that allow the compiler to convert between your types and other defined types. There are two types of conversion operators, implicit and explicit ones.

Implicit Conversion Operators (C++98/C++03 and C++11)

An implicit conversion operator allows the compiler to implicitly convert (like the conversion between int and long) the value of a user-defined type to some other type.

The following is a simple class with an implicit conversion operator:

class my_string {
  operator const char*() const {return data_;} // This is the conversion operator
  const char* data_;

Implicit conversion operators, like one-argument constructors, are user-defined conversions. Compilers will grant one user-defined conversion when trying to match a call to an overloaded function.

void f(const char*);

my_string str;
f(str); // same as f( str.operator const char*() )

At first this seems very helpful, but the problem with this is that the implicit conversion even kicks in when it isn’t expected to. In the following code, void f(const char*) will be called because my_string() is not an lvalue, so the first does not match:

void f(my_string&);
void f(const char*);


Beginners easily get this wrong and even experienced C++ programmers are sometimes surprised because the compiler picks an overload they didn’t suspect. These problems can be mitigated by explicit conversion operators.

Explicit Conversion Operators (C++11)

Unlike implicit conversion operators, explicit conversion operators will never kick in when you don't expect them to. The following is a simple class with an explicit conversion operator:

class my_string {
  explicit operator const char*() const {return data_;}
  const char* data_;

Notice the explicit. Now when you try to execute the unexpected code from the implicit conversion operators, you get a compiler error:

prog.cpp: In function ‘int main()’:
prog.cpp:15:18: error: no matching function for call to ‘f(my_string)’
prog.cpp:15:18: note: candidates are:
prog.cpp:11:10: note: void f(my_string&)
prog.cpp:11:10: note:   no known conversion for argument 1 from ‘my_string’ to ‘my_string&’
prog.cpp:12:10: note: void f(const char*)
prog.cpp:12:10: note:   no known conversion for argument 1 from ‘my_string’ to ‘const char*’

To invoke the explicit cast operator, you have to use static_cast, a C-style cast, or a constructor style cast ( i.e. T(value) ).

However, there is one exception to this: The compiler is allowed to implicitly convert to bool. In addition, the compiler is not allowed to do another implicit conversion after it converts to bool (a compiler is allowed to do 2 implicit conversions at a time, but only 1 user-defined conversion at max).

Because the compiler will not cast "past" bool, explicit conversion operators now remove the need for the Safe Bool idiom. For example, smart pointers before C++11 used the Safe Bool idiom to prevent conversions to integral types. In C++11, the smart pointers use an explicit operator instead because the compiler is not allowed to implicitly convert to an integral type after it explicitly converted a type to bool.

Continue to Overloading new and delete.

Subtract two dates in SQL and get days of the result


Select I.Fee
From   Item I
WHERE  DATEDIFF(day, GETDATE(), I.DateCreated)  < 365

http://localhost/ not working on Windows 7. What's the problem?

Got any other Programs running ? msn ect... ? some bind to port 8080 then your webserver wouldnt start and would cause a 404 , try binding it to a different port 80 which its default should be

How to access parent Iframe from JavaScript

I would recommend using the postMessage API.

In your iframe, call:

window.parent.postMessage({message: 'Hello world'}, 'http://localhost/');

In the page you're including the iframe you can listen for events like this:

window.addEventListener('message', function(event) {
      if(event.origin === 'http://localhost/')
        alert('Received message: ' +;
        alert('Origin not allowed!');

    }, false);

By the way, it is also possible to do calls to other windows, and not only iframes.

Read more about the postMessage API on John Resigs blog here

Is it possible to see more than 65536 rows in Excel 2007?

Here is an interesting blog entry about numbers / limitations of Excel 2007. According to the author the new limit is approximately one million rows.

Sounds like you have a pre-Excel 2007 workbook open in Excel 2007 in compatibility mode (look in the title bar and see if it says compatibility mode). If so, the workbook has 65,536 rows, not 1,048,576. You can save the workbook as an Excel workbook which will be in Excel 2007 format, close the workbook and re-open it.

NameError: name 'datetime' is not defined

It can also be used as below:

from datetime import datetime
start_date = datetime(2016,3,1)
end_date = datetime(2016,3,10)

Detect merged cells in VBA Excel with MergeArea

There are several helpful bits of code for this.

Place your cursor in a merged cell and ask these questions in the Immidiate Window:

Is the activecell a merged cell?

? Activecell.Mergecells

How many cells are merged?

? Activecell.MergeArea.Cells.Count

How many columns are merged?

? Activecell.MergeArea.Columns.Count

How many rows are merged?

? Activecell.MergeArea.Rows.Count

What's the merged range address?

? activecell.MergeArea.Address

C# How to change font of a label

You can't change a Font once it's created - so you need to create a new one:

  mainForm.lblName.Font = new Font("Arial", mainForm.lblName.Font.Size);

Difference between two DateTimes C#?

Are you perhaps looking for:

int Difference = (a-b).Hours;

How to insert new row to database with AUTO_INCREMENT column without specifying column names?

Just add the column names, yes you can use Null instead but is is a very bad idea to not use column names in any insert, ever.

What's the proper way to compare a String to an enum value?

Doing an static import of the GestureTypes and then using the valuesOf() method could make it look much cleaner:

enum GestureTypes{ROCK,PAPER,SCISSORS};


import static com.example.GestureTypes.*;
public class GestureFactory {

    public static Gesture getInstance(final String gesture) {
        if (ROCK == valueOf(gesture))
            //do somthing
        if (PAPER == valueOf(gesture))
            //do somthing

Add missing dates to pandas dataframe

One issue is that reindex will fail if there are duplicate values. Say we're working with timestamped data, which we want to index by date:

df = pd.DataFrame({
    'timestamps': pd.to_datetime(
        ['2016-11-15 1:00','2016-11-16 2:00','2016-11-16 3:00','2016-11-18 4:00']),
df.index = pd.DatetimeIndex(df['timestamps']).floor('D')


            timestamps             values
2016-11-15  "2016-11-15 01:00:00"  a
2016-11-16  "2016-11-16 02:00:00"  b
2016-11-16  "2016-11-16 03:00:00"  c
2016-11-18  "2016-11-18 04:00:00"  d

Due to the duplicate 2016-11-16 date, an attempt to reindex:

all_days = pd.date_range(df.index.min(), df.index.max(), freq='D')

fails with:

ValueError: cannot reindex from a duplicate axis

(by this it means the index has duplicates, not that it is itself a dup)

Instead, we can use .loc to look up entries for all dates in range:



            timestamps             values
2016-11-15  "2016-11-15 01:00:00"  a
2016-11-16  "2016-11-16 02:00:00"  b
2016-11-16  "2016-11-16 03:00:00"  c
2016-11-17  NaN                    NaN
2016-11-18  "2016-11-18 04:00:00"  d

fillna can be used on the column series to fill blanks if needed.

Can Mockito stub a method without regard to the argument?

Use like this:


Before you need to import Mockito.Matchers

Using lambda expressions for event handlers

There are no performance implications since the compiler will translate your lambda expression into an equivalent delegate. Lambda expressions are nothing more than a language feature that the compiler translates into the exact same code that you are used to working with.

The compiler will convert the code you have to something like this:

public partial class MyPage : System.Web.UI.Page
    protected void Page_Load(object sender, EventArgs e)
        MyButton.Click += new EventHandler(delegate (Object o, EventArgs a) 

Copy to Clipboard for all Browsers using javascript

I spent a lot of time looking for a solution to this problem too. Here's what i've found thus far:

If you want your users to be able to click on a button and copy some text, you may have to use Flash.

If you want your users to press Ctrl+C anywhere on the page, but always copy xyz to the clipboard, I wrote an all-JS solution in YUI3 (although it could easily be ported to other frameworks, or raw JS if you're feeling particularly self-loathing).

It involves creating a textbox off the screen which gets highlighted as soon as the user hits Ctrl/CMD. When they hit 'C' shortly after, they copy the hidden text. If they hit 'V', they get redirected to a container (of your choice) before the paste event fires.

This method can work well, because while you listen for the Ctrl/CMD keydown anywhere in the body, the 'A', 'C' or 'V' keydown listeners only attach to the hidden text box (and not the whole body). It also doesn't have to break the users expectations - you only get redirected to the hidden box if you had nothing selected to copy anyway!

Here's what i've got working on my site, but check for updates if there are any:

YUI.add('clipboard', function(Y) {

// Change this to the id of the text area you would like to always paste in to:

pasteBox ='#pasteDIV');

// Make a hidden textbox somewhere off the page.'body').append('<input id="copyBox" type="text" name="result" style="position:fixed; top:-20%;" onkeyup="pasteBox.focus()">');
copyBox ='#copyBox');

// Key bindings for Ctrl+A, Ctrl+C, Ctrl+V, etc:

// Catch Ctrl/Window/Apple keydown anywhere on the page.
Y.on('key', function(e) {
        //  Uncomment below alert and remove keyCodes after 'down:' to figure out keyCodes for other buttons.
        //  alert(e.keyCode);
        //  }, 'body',  'down:', Y);
}, 'body',  'down:91,224,17', Y);

// Catch V - BUT ONLY WHEN PRESSED IN THE copyBox!!!
Y.on('key', function(e) {
    // Oh no! The user wants to paste, but their about to paste into the hidden #copyBox!!
    // Luckily, pastes happen on keyPress (which is why if you hold down the V you get lots of pastes), and we caught the V on keyDown (before keyPress).
    // Thus, if we're quick, we can redirect the user to the right box and they can unload their paste into the appropriate container. phew.;
}, '#copyBox',  'down:86', Y);

// Catch A - BUT ONLY WHEN PRESSED IN THE copyBox!!!
Y.on('key', function(e) {
    // User wants to select all - but he/she is in the hidden #copyBox! That wont do.. select the pasteBox instead (which is probably where they wanted to be).;
}, '#copyBox',  'down:65', Y);

// What to do when keybindings are fired:

// User has pressed Ctrl/Meta, and is probably about to press A,C or V. If they've got nothing selected, or have selected what you want them to copy, redirect to the hidden copyBox!
function copyData() {
    var txt = '';
    // props to Sabarinathan Arthanari for sharing with the world how to get the selected text on a page, cheers mate!
        if (window.getSelection) { txt = window.getSelection(); }
        else if (document.getSelection) { txt = document.getSelection(); }
        else if (document.selection) { txt = document.selection.createRange().text; }
        else alert('Something went wrong and I have no idea why - please contact me with your browser type (Firefox, Safari, etc) and what you tried to copy and I will fix this immediately!');

    // If the user has nothing selected after pressing Ctrl/Meta, they might want to copy what you want them to copy. 
        if(txt=='') {
    // They also might have manually selected what you wanted them to copy! How unnecessary! Maybe now is the time to tell them how silly they are..?!
        else if (txt == copyBox.get('value')) {
        alert('This site uses advanced copy/paste technology, possibly from the future.\n \nYou do not need to select things manually - just press Ctrl+C! \n \n(Ctrl+V will always paste to the main box too.)');
        } else {
                // They also might have selected something completely different! If so, let them. It's only fair.

Hope someone else finds this useful :]

How do I spool to a CSV formatted file using SQLPLUS?

You can explicitly format the query to produce a delimited string with something along the lines of:

select '"'||foo||'","'||bar||'"'
  from tab

And set up the output options as appropriate. As an option, the COLSEP variable on SQLPlus will let you produce delimited files without having to explicitly generate a string with the fields concatenated together. However, you will have to put quotes around strings on any columns that might contain embedded comma characters.

How to start color picker on Mac OS?

You can turn the color picker into an application by following the guide here:

From the guide:

Simply fire up AppleScript (Applications -> AppleScript Editor) and enter this text:

choose color

Now, save it as an application (File -> Save As, and set the File Format pop-up to Application), and you're done

Refresh Page and Keep Scroll Position

This might be useful for refreshing also. But if you want to keep track of position on the page before you click on a same position.. The following code will help.

Also added a data-confirm for prompting the user if they really want to do that..

Note: I'm using jQuery and js-cookie.js to store cookie info.

$(document).ready(function() {
    // make all links with data-confirm prompt the user first.
    $('[data-confirm]').on("click", function (e) {
        var msg = $(this).data("confirm");
        if(confirm(msg)==true) {
            var url = this.href;
            if(url.length>0) window.location = url;
            return true;
        return false;

    // on certain links save the scroll postion.
    $('.saveScrollPostion').on("click", function (e) {
        var currentYOffset = window.pageYOffset;  // save current page postion.
        Cookies.set('jumpToScrollPostion', currentYOffset);
        if(!$(this).attr("data-confirm")) {  // if there is no data-confirm on this link then trigger the click. else we have issues.
            var url = this.href;
            window.location = url;
            //$(this).trigger('click');  // continue with click event.

    // check if we should jump to postion.
    if(Cookies.get('jumpToScrollPostion') !== "undefined") {
        var jumpTo = Cookies.get('jumpToScrollPostion');
        window.scrollTo(0, jumpTo);
        Cookies.remove('jumpToScrollPostion');  // and delete cookie so we don't jump again.

A example of using it like this.

<a href='gotopage.html' class='saveScrollPostion' data-confirm='Are you sure?'>Goto what the heck</a>

How to move text up using CSS when nothing is working

try a negative margin.

margin-top: -10px; /* as an example */

What is the difference between C and embedded C?

C is a only programming language its used in system programming. but embedded C is used to implement the projects like real time applications

How are zlib, gzip and zip related? What do they have in common and how are they different?

ZIP is a file format used for storing an arbitrary number of files and folders together with lossless compression. It makes no strict assumptions about the compression methods used, but is most frequently used with DEFLATE.

Gzip is both a compression algorithm based on DEFLATE but less encumbered with potential patents et al, and a file format for storing a single compressed file. It supports compressing an arbitrary number of files and folders when combined with tar. The resulting file has an extension of .tgz or .tar.gz and is commonly called a tarball.

zlib is a library of functions encapsulating DEFLATE in its most common LZ77 incarnation.

Changing Font Size For UITableView Section Headers

Unfortunately, you may have to override this:

In Objective-C:

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section

In Swift:

func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView?

Try something like this:

In Objective-C:

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {

    UILabel *myLabel = [[UILabel alloc] init];
    myLabel.frame = CGRectMake(20, 8, 320, 20);
    myLabel.font = [UIFont boldSystemFontOfSize:18];
    myLabel.text = [self tableView:tableView titleForHeaderInSection:section];

    UIView *headerView = [[UIView alloc] init];
    [headerView addSubview:myLabel];

    return headerView;

In Swift:

func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {

    let myLabel = UILabel()
    myLabel.frame = CGRect(x: 20, y: 8, width: 320, height: 20)
    myLabel.font = UIFont.boldSystemFont(ofSize: 18)
    myLabel.text = self.tableView(tableView, titleForHeaderInSection: section)

    let headerView = UIView()

    return headerView

Convert .class to .java

This is for Mac users:

first of all you have to clarify where the class file is... so for example, in 'Terminal' (A Mac Application) you would type:


then wherever you file is e.g:

cd /Users/CollarBlast/Desktop/JavaFiles/

then you would hit enter. After that you would do the command. e.g:

cd /Users/CollarBlast/Desktop/JavaFiles/ (then i would press enter...)

Then i would type the command:

javap -c JavaTestClassFile.class (then i would press enter again...)

and hopefully it should work!

Why does PEP-8 specify a maximum line length of 79 characters?

Printing a monospaced font at default sizes is (on A4 paper) 80 columns by 66 lines.

Uncaught TypeError: Cannot read property 'ownerDocument' of undefined

Make sure you're passing a selector to jQuery, not some form of data:

$( '.my-selector' )


$( [ 'my-data' ] )

how to set start page in webconfig file in c#

I think this will help

    <directoryBrowse enabled="false" />
        <clear />
        <add value="index.aspx" />
        <add value="Default.htm" />
        <add value="Default.asp" />
        <add value="index.htm" />
        <add value="index.html" />
        <add value="iisstart.htm" />
        <add value="default.aspx" />
        <add value="index.php" />

The way to check a HDFS directory's size?

To get the size of the directory hdfs dfs -du -s -h /$yourDirectoryName can be used. hdfs dfsadmin -report can be used to see a quick cluster level storage report.

Can't connect to local MySQL server through socket '/var/mysql/mysql.sock' (38)

If you are using AWS (Amazon Web Services) Micro version, then it is a memory issue. When I ran


from the terminal it would say

ERROR 2002 (HY000): Can't connect to local MySQL server through socket /var/run/mysqld/mysqld.sock' (111)

So I tried the following and it would just fail.

service mysqld restart

After much searching, I found out that you have to create a swap file for MySQL to have enough memory. Instructions are listed:

Then, I was able to restart mysqld.

jQuery - disable selected options

Add this line to your change event handler

    $("#theSelect option:selected").attr('disabled','disabled')

This will disable the selected option, and enable any previously disabled options.


If you did not want to re-enable the previous ones, just remove this part of the line:



To re-enable when you click remove, add this to your click handler.

$("#theSelect option[value=" + value + "]").removeAttr('disabled');

Dynamically create and submit form

Yes, you just forgot the quotes ...


PHP: If internet explorer 6, 7, 8 , or 9

You could use something like this for different messages or div/css

<!--[if IE 6]>
<style type="text/css">
div.ie6 { display:block; }

<!--[if IE 7]>
<style type="text/css">
div.ie7 { display:block; }

<!--[if IE 8]>
<style type="text/css">
div.ie8 { display:block; }

<!--[if IE 9]>

<!--[if !IE 6]>

<!--[if lt IE 8]>

OR use different div of css

<!--[if lte IE 8]>
<style type="text/css">
div.lteie8 { display:block; }

<!--[if gt IE 6]>
<style type="text/css">
div.gtie6 { display:block; }

<!--[if gte IE 6]>
<style type="text/css">
div.gteie6 { display:block; }

Something like 'contains any' for Java set?

I would recommend creating a HashMap from set A, and then iterating through set B and checking if any element of B is in A. This would run in O(|A|+|B|) time (as there would be no collisions), whereas retainAll(Collection<?> c) must run in O(|A|*|B|) time.

How to redirect the output of the time command to a file in Linux?

If you want just the time in a shell variable then this works:

var=`{ time <command> ; } 2>&1 1>/dev/null`

Appending the same string to a list of strings in Python

my_list = ['foo', 'fob', 'faz', 'funk']
string = 'bar'
my_new_list = [x + string for x in my_list]
print my_new_list

This will print:

['foobar', 'fobbar', 'fazbar', 'funkbar']

XPath - Selecting elements that equal a value

The XPath spec. defines the string value of an element as the concatenation (in document order) of all of its text-node descendents.

This explains the "strange results".

"Better" results can be obtained using the expressions below:

//*[text() = 'qwerty']

The above selects every element in the document that has at least one text-node child with value 'qwerty'.

//*[text() = 'qwerty' and not(text()[2])]

The above selects every element in the document that has only one text-node child and its value is: 'qwerty'.

How do you dynamically allocate a matrix?

const int nRows = 20;
const int nCols = 10;
int (*name)[nCols] = new int[nRows][nCols];
std::memset(name, 0, sizeof(int) * nRows * nCols); //row major contiguous memory
name[0][0] = 1; //first element
name[nRows-1][nCols-1] = 1; //last element
delete[] name;

get one item from an array of name,value JSON

To answer your exact question you can get the exact behaviour you want by extending the Array prototype with:

Array.prototype.get = function(name) {
    for (var i=0, len=this.length; i<len; i++) {
        if (typeof this[i] != "object") continue;
        if (this[i].name === name) return this[i].value;

this will add the get() method to all arrays and let you do what you want, i.e:

arr.get('k1'); //= abc

Why is Visual Studio 2013 very slow?

What fixed it for me was disabling Git by setting Current source control plug-in to None in Visual Studio, menu OptionsSource Control:

Enter image description here

What is the purpose of willSet and didSet in Swift?

My understanding is that set and get are for computed properties (no backing from stored properties)

if you are coming from an Objective-C bare in mind that the naming conventions have changed. In Swift an iVar or instance variable is named stored property

Example 1 (read only property) - with warning:

var test : Int {
    get {
        return test

This will result in a warning because this results in a recursive function call (the getter calls itself).The warning in this case is "Attempting to modify 'test' within its own getter".

Example 2. Conditional read/write - with warning

var test : Int {
    get {
        return test
    set (aNewValue) {
        //I've contrived some condition on which this property can be set
        //(prevents same value being set)
        if (aNewValue != test) {
            test = aNewValue

Similar problem - you cannot do this as it's recursively calling the setter. Also, note this code will not complain about no initialisers as there is no stored property to initialise.

Example 3. read/write computed property - with backing store

Here is a pattern that allows conditional setting of an actual stored property

//True model data
var _test : Int = 0

var test : Int {
    get {
        return _test
    set (aNewValue) {
        //I've contrived some condition on which this property can be set
        if (aNewValue != test) {
            _test = aNewValue

Note The actual data is called _test (although it could be any data or combination of data) Note also the need to provide an initial value (alternatively you need to use an init method) because _test is actually an instance variable

Example 4. Using will and did set

//True model data
var _test : Int = 0 {

    //First this
    willSet {
        println("Old value is \(_test), new value is \(newValue)")

    //value is set

    //Finaly this
    didSet {
        println("Old value is \(oldValue), new value is \(_test)")

var test : Int {
    get {
        return _test
    set (aNewValue) {
        //I've contrived some condition on which this property can be set
        if (aNewValue != test) {
            _test = aNewValue

Here we see willSet and didSet intercepting a change in an actual stored property. This is useful for sending notifications, synchronisation etc... (see example below)

Example 5. Concrete Example - ViewController Container

//Underlying instance variable (would ideally be private)
var _childVC : UIViewController? {
    willSet {
        //REMOVE OLD VC
        println("Property will set")
        if (_childVC != nil) {
            self.setOverrideTraitCollection(nil, forChildViewController: _childVC)
        if (newValue) {


    //I can't see a way to 'stop' the value being set to the same controller - hence the computed property

    didSet {
        //ADD NEW VC
        println("Property did set")
        if (_childVC) {
//                var views  = NSDictionaryOfVariableBindings(self.view)    .. NOT YET SUPPORTED (NSDictionary bridging not yet available)

            //Add subviews + constraints
            _childVC!.view.setTranslatesAutoresizingMaskIntoConstraints(false)       //For now - until I add my own constraints
            let views = ["view" : _childVC!.view] as NSMutableDictionary
            let layoutOpts = NSLayoutFormatOptions(0)
            let lc1 : AnyObject[] = NSLayoutConstraint.constraintsWithVisualFormat("|[view]|",  options: layoutOpts, metrics: NSDictionary(), views: views)
            let lc2 : AnyObject[] = NSLayoutConstraint.constraintsWithVisualFormat("V:|[view]|", options: layoutOpts, metrics: NSDictionary(), views: views)

            //Forward messages to child

//Computed property - this is the property that must be used to prevent setting the same value twice
//unless there is another way of doing this?
var childVC : UIViewController? {
    get {
        return _childVC
    set(suggestedVC) {
        if (suggestedVC != _childVC) {
            _childVC = suggestedVC

Note the use of BOTH computed and stored properties. I've used a computed property to prevent setting the same value twice (to avoid bad things happening!); I've used willSet and didSet to forward notifications to viewControllers (see UIViewController documentation and info on viewController containers)

I hope this helps, and please someone shout if I've made a mistake anywhere here!

ORA-01008: not all variables bound. They are bound

Came here looking for help as got same error running a statement listed below while going through a Udemy course:

INSERT INTO departments (department_id, department_name)
                  values( &dpet_id, '&dname');  

I'd been able to run statements with substitution variables before. Comment by Charles Burns about possibility of server reaching some threshold while recreating the variables prompted me to log out and restart the SQL Developer. The statement ran fine after logging back in.

Thought I'd share for anyone else venturing here with a limited scope issue as mine.

Getting value from a cell from a gridview on RowDataBound event

use RowDataBound function to bind data with a perticular cell, and to get control use (ASP Control Name like DropDownList) GridView.FindControl("Name of Control")

How to filter keys of an object with lodash?

Just change filter to omitBy

const data = { aaa: 111, abb: 222, bbb: 333 };_x000D_
const result = _.omitBy(data, (value, key) => !key.startsWith("a"));_x000D_
<script src=""></script>

docker mounting volumes on host

Let me add my own answer, because I believe the others are missing the point of Docker.

Using VOLUME in the Dockerfile is the Right Way™, because you let Docker know that a certain directory contains permanent data. Docker will create a volume for that data and never delete it, even if you remove all the containers that use it.

It also bypasses the union file system, so that the volume is in fact an actual directory that gets mounted (read-write or readonly) in the right place in all the containers that share it.

Now, in order to access that data from the host, you only need to inspect your container:

# docker inspect myapp
    "Volumes": {
        "/var/www": "/var/lib/docker/vfs/dir/b3ef4bc28fb39034dd7a3aab00e086e6...",
        "/var/cache/nginx": "/var/lib/docker/vfs/dir/62499e6b31cb3f7f59bf00d8a16b48d2...",
        "/var/log/nginx": "/var/lib/docker/vfs/dir/71896ce364ef919592f4e99c6e22ce87..."
    "VolumesRW": {
        "/var/www": false,
        "/var/cache/nginx": true,
        "/var/log/nginx": true

What I usually do is make symlinks in some standard place such as /srv, so that I can easily access the volumes and manage the data they contain (only for the volumes you care about):

ln -s /var/lib/docker/vfs/dir/b3ef4bc28fb39034dd7a3aab00e086e6... /srv/myapp-www
ln -s /var/lib/docker/vfs/dir/71896ce364ef919592f4e99c6e22ce87... /srv/myapp-log

Insert picture into Excel cell

Now we can add a picture to Excel directly and easely. Just follow these instructions:

  1. Go to the Insert tab.
  2. Click on the Pictures option (it’s in the illustrations group). image1
  3. In the ‘Insert Picture’ dialog box, locate the pictures that you want to insert into a cell in Excel. image2
  4. Click on the Insert button. image3
  5. Re-size the picture/image so that it can fit perfectly within the cell. image4
  6. Place the picture in the cell. A cool way to do this is to first press the ALT key and then move the picture with the mouse. It will snap and arrange itself with the border of the cell as soon it comes close to it.

If you have multiple images, you can select and insert all the images at once (as shown in step 4).

You can also resize images by selecting it and dragging the edges. In the case of logos or product images, you may want to keep the aspect ratio of the image intact. To keep the aspect ratio intact, use the corners of an image to resize it.

When you place an image within a cell using the steps above, it will not stick with the cell in case you resize, filter, or hide the cells. If you want the image to stick to the cell, you need to lock the image to the cell it’s placed n.

To do this, you need to follow the additional steps as shown below.

  1. Right-click on the picture and select Format Picture. image5
  2. In the Format Picture pane, select Size & Properties and with the options in Properties, select ‘Move and size with cells’. image6

Now you can move cells, filter it, or hide it, and the picture will also move/filter/hide.


This answer was taken from this link: Insert Picture into a Cell in Excel.

How to measure time elapsed on Javascript?

The Date documentation states that :

The JavaScript date is based on a time value that is milliseconds since midnight January 1, 1970, UTC

Click on start button then on end button. It will show you the number of seconds between the 2 clicks.

The milliseconds diff is in variable timeDiff. Play with it to find seconds/minutes/hours/ or what you need

var startTime, endTime;_x000D_
function start() {_x000D_
  startTime = new Date();_x000D_
function end() {_x000D_
  endTime = new Date();_x000D_
  var timeDiff = endTime - startTime; //in ms_x000D_
  // strip the ms_x000D_
  timeDiff /= 1000;_x000D_
  // get seconds _x000D_
  var seconds = Math.round(timeDiff);_x000D_
  console.log(seconds + " seconds");_x000D_
<button onclick="start()">Start</button>_x000D_
<button onclick="end()">End</button>

OR another way of doing it for modern browser

Using which returns a value representing the time elapsed since the time origin. This value is a double with microseconds in the fractional.

The time origin is a standard time which is considered to be the beginning of the current document's lifetime.

var startTime, endTime;_x000D_
function start() {_x000D_
  startTime =;_x000D_
function end() {_x000D_
  endTime =;_x000D_
  var timeDiff = endTime - startTime; //in ms _x000D_
  // strip the ms _x000D_
  timeDiff /= 1000; _x000D_
  // get seconds _x000D_
  var seconds = Math.round(timeDiff);_x000D_
  console.log(seconds + " seconds");_x000D_
<button onclick="start()">Start</button>_x000D_
<button onclick="end()">End</button>

Are parameters in strings.xml possible?

Note that for this particular application there's a standard library function, android.text.format.DateUtils.getRelativeTimeSpanString().

Can I get Unix's pthread.h to compile in Windows?

As @Ninefingers mentioned, pthreads are unix-only. Posix only, really.

That said, Microsoft does have a library that duplicates pthreads:

Microsoft Windows Services for UNIX Version 3.5

Library Download

Sending data from HTML form to a Python script in Flask

The form tag needs some attributes set:

  1. action: The URL that the form data is sent to on submit. Generate it with url_for. It can be omitted if the same URL handles showing the form and processing the data.
  2. method="post": Submits the data as form data with the POST method. If not given, or explicitly set to get, the data is submitted in the query string (request.args) with the GET method instead.
  3. enctype="multipart/form-data": When the form contains file inputs, it must have this encoding set, otherwise the files will not be uploaded and Flask won't see them.

The input tag needs a name parameter.

Add a view to handle the submitted data, which is in request.form under the same key as the input's name. Any file inputs will be in request.files.

@app.route('/handle_data', methods=['POST'])
def handle_data():
    projectpath = request.form['projectFilepath']
    # your code
    # return a response

Set the form's action to that view's URL using url_for:

<form action="{{ url_for('handle_data') }}" method="post">
    <input type="text" name="projectFilepath">
    <input type="submit">

How does String.Index work in Swift

Create a UITextView inside of a tableViewController. I used function: textViewDidChange and then checked for return-key-input. then if it detected return-key-input, delete the input of return key and dismiss keyboard.

func textViewDidChange(_ textView: UITextView) {
    if textView.text.contains("\n"){
        textView.text.remove(at: textView.text.index(before: textView.text.endIndex))

How to read Data from Excel sheet in selenium webdriver

import jxl.Sheet;
import jxl.Workbook;

String FilePath = "/home/lahiru/Desktop/Sample.xls";
FileInputStream fs = new FileInputStream(FilePath);
Workbook wb = Workbook.getWorkbook(fs);

String <variable> = sh.getCell("A2").getContents();

Convert date to datetime in Python

The accepted answer is correct, but I would prefer to avoid using datetime.min.time() because it's not obvious to me exactly what it does. If it's obvious to you, then more power to you. I also feel the same way about the timetuple method and the reliance on the ordering.

In my opinion, the most readable, explicit way of doing this without relying on the reader to be very familiar with the datetime module API is:

from datetime import date, datetime
today =
today_with_time = datetime(

That's my take on "explicit is better than implicit."

Where is nodejs log file?

There is no log file. Each node.js "app" is a separate entity. By default it will log errors to STDERR and output to STDOUT. You can change that when you run it from your shell to log to a file instead.

node my_app.js > my_app_log.log 2> my_app_err.log

Alternatively (recommended), you can add logging inside your application either manually or with one of the many log libraries:

ERROR: Cannot open source file " "

Just in case there is someone out there who's a bit new like me, double check that you are spelling your header folders correctly.

For example:

<#include "Component/BoxComponent.h"

This will result in the error. Instead, it needs to be:

<#include "Components/BoxComponent.h"

How do I lock the orientation to portrait mode in a iPhone Web Application?

Inspired from @Grumdrig's answer, and because some of the used instructions would not work, I suggest the following script if needed by someone else:

    $(document).ready(function () {

      function reorient(e) {
        var orientation = window.screen.orientation.type;
        $("body > div").css("-webkit-transform", (orientation == 'landscape-primary' || orientation == 'landscape-secondary') ? "rotate(-90deg)" : "");
      window.setTimeout(reorient, 0);

iPhone SDK on Windows (alternative solutions)

You could do what saurik of Cydia does, and write your code on a PC then build it on the iPhone itself (it is a Mac, technically!) after you jailbreak it. However, you don't get Interface Builder, so you're basically creating UIs in code by hand. It'd also be pretty tough to actually submit your app without a Mac.

Migration: Cannot add foreign key constraint

One thing that I think is missing from the answers on here, and please correct me if I am wrong, but the foreign keys need to be indexed on the pivot table. At least in mysql that seems to be the case.

public function up()
    Schema::create('image_post', function (Blueprint $table) {
        $table->engine = 'InnoDB';

    Schema::table('image_post', function($table) {


Jquery UI Datepicker not displaying

it's the css file in the new one doesn't work. Try to include the old 1.7.* css file on your header too, and try again.

Also, did you try to do a .datepicker( "show" ) right after it constructed?

How do I add a newline using printf?

To write a newline use \n not /n the latter is just a slash and a n

How to select the first element of a set with JSTL?

Since i have have just one element in my Set the order is not important So I can access to the first element like this :

${ attachments.iterator().next().id }

If else embedding inside html

 <?php if (date("H") < "12" && date("H")>"6") { ?>
   src="<?php bloginfo('template_url'); ?>/images/img/morning.gif" 
 <?php } elseif (date("H") > "12" && date("H")<"17") { ?>
 src="<?php bloginfo('template_url'); ?>/images/img/noon.gif" 
  <?php } elseif (date("H") > "17" && date("H")<"21") { ?>
   src="<?php bloginfo('template_url'); ?>/images/img/evening.gif" 
  <?php } elseif (date("H") > "21" && date("H")<"24") { ?>
  src="<?php bloginfo('template_url'); ?>/images/img/night.gif" 
  <?php }else { ?>
  src="<?php bloginfo('template_url'); ?>/images/img/mid_night.gif" 
  <?php } ?>

AssertNull should be used or AssertNotNull

Use assertNotNull(obj). assert means must be.

Python Dictionary Comprehension

The main purpose of a list comprehension is to create a new list based on another one without changing or destroying the original list.

Instead of writing

l = []
for n in range(1, 11):


l = [n for n in range(1, 11)]

you should write only

l = range(1, 11)

In the two top code blocks you're creating a new list, iterating through it and just returning each element. It's just an expensive way of creating a list copy.

To get a new dictionary with all keys set to the same value based on another dict, do this:

old_dict = {'a': 1, 'c': 3, 'b': 2}
new_dict = { key:'your value here' for key in old_dict.keys()}

You're receiving a SyntaxError because when you write

d = {}
d[i for i in range(1, 11)] = True

you're basically saying: "Set my key 'i for i in range(1, 11)' to True" and "i for i in range(1, 11)" is not a valid key, it's just a syntax error. If dicts supported lists as keys, you would do something like

d[[i for i in range(1, 11)]] = True

and not

d[i for i in range(1, 11)] = True

but lists are not hashable, so you can't use them as dict keys.

Copying data from one SQLite database to another

If you use DB Browser for SQLite, you can copy the table from one db to another in following steps:

  1. Open two instances of the app and load the source db and target db side by side.
  2. If the target db does not have the table, "Copy Create Statement" from the source db and then paste the sql statement in "Execute SQL" tab and run the sql to create the table.
  3. In the source db, export the table as a CSV file.
  4. In the target db, import the CSV file to the table with the same table name. The app will ask you do you want to import the data to the existing table, click yes. Done.

docker-compose up for only certain containers


Starting with docker-compose 1.28.0 the new service profiles are just made for that! With profiles you can mark services to be only started in specific profiles:

    # ...
    # ...
    profiles: ["cli-only"]
    # ...
docker-compose up # start main services, no npm
docker-compose run --rm npm # run npm service
docker-compose --profile cli-only # start main and all "cli-only" services

original answer

Since docker-compose v1.5 it is possible to pass multiple docker-compose.yml files with the -f flag. This allows you to split your dev tools into a separate docker-compose.yml which you then only include on-demand:

# start and attach to all your essential services
docker-compose up

# execute a defined command in
docker-compose -f run npm update

# if your command depends_on a service you need to include both configs
docker-compose -f docker-compose.yml -f run npm update

For an in-depth discussion on this see docker/compose#1896.

How to count the number of set bits in a 32-bit integer?

Another Hamming weight algorithm if you're on a BMI2 capable CPU


Have fun!

When to use single quotes, double quotes, and backticks in MySQL

Backticks are generally used to indicate an identifier and as well be safe from accidentally using the Reserved Keywords.

For example:

Use `database`;

Here the backticks will help the server to understand that the database is in fact the name of the database, not the database identifier.

Same can be done for the table names and field names. This is a very good habit if you wrap your database identifier with backticks.

Check this answer to understand more about backticks.

Now about Double quotes & Single Quotes (Michael has already mentioned that).

But, to define a value you have to use either single or double quotes. Lets see another example.

INSERT INTO `tablename` (`id, `title`) VALUES ( NULL, title1);

Here I have deliberately forgotten to wrap the title1 with quotes. Now the server will take the title1 as a column name (i.e. an identifier). So, to indicate that it's a value you have to use either double or single quotes.

INSERT INTO `tablename` (`id, `title`) VALUES ( NULL, 'title1');

Now, in combination with PHP, double quotes and single quotes make your query writing time much easier. Let's see a modified version of the query in your question.

$query = "INSERT INTO `table` (`id`, `col1`, `col2`) VALUES (NULL, '$val1', '$val2')";

Now, using double quotes in the PHP, you will make the variables $val1, and $val2 to use their values thus creating a perfectly valid query. Like

$val1 = "my value 1";
$val2 = "my value 2";
$query = "INSERT INTO `table` (`id`, `col1`, `col2`) VALUES (NULL, '$val1', '$val2')";

will make

INSERT INTO `table` (`id`, `col1`, `col2`) VALUES (NULL, 'my value 1', 'my value 2')

How to create a fixed-size array of objects

If what you want is a fixed size array, and initialize it with nil values, you can use an UnsafeMutableBufferPointer, allocate memory for 64 nodes with it, and then read/write from/to the memory by subscripting the pointer type instance. This also has the benefit of avoiding checking if the memory must be reallocated, which Array does. I would however be surprised if the compiler doesn't optimize that away for arrays that don't have any more calls to methods that may require resizing, other than at the creation site.

let count = 64
let sprites = UnsafeMutableBufferPointer<SKSpriteNode>.allocate(capacity: count)

for i in 0..<count {
    sprites[i] = ...

for sprite in sprites {


This is however not very user friendly. So, let's make a wrapper!

class ConstantSizeArray<T>: ExpressibleByArrayLiteral {
    typealias ArrayLiteralElement = T
    private let memory: UnsafeMutableBufferPointer<T>
    public var count: Int {
        get {
            return memory.count
    private init(_ count: Int) {
        memory = UnsafeMutableBufferPointer.allocate(capacity: count)
    public convenience init(count: Int, repeating value: T) {
        memory.initialize(repeating: value)
    public required convenience init(arrayLiteral: ArrayLiteralElement...) {
        memory.initialize(from: arrayLiteral)
    deinit {
    public subscript(index: Int) -> T {
        set(value) {
            memory[index] = value;
        get {
            return memory[index]

extension ConstantSizeArray: MutableCollection {
    public var startIndex: Int {
        return 0
    public var endIndex: Int {
        return count - 1
    func index(after i: Int) -> Int {
        return i + 1;

Now, this is a class, and not a structure, so there's some reference counting overhead incurred here. You can change it to a struct instead, but because Swift doesn't provide you with an ability to use copy initializers and deinit on structures, you'll need a deallocation method (func release() { memory.deallocate() }), and all copied instances of the structure will reference the same memory.

Now, this class may just be good enough. Its use is simple:

let sprites = ConstantSizeArray<SKSpriteNode?>(count: 64, repeating: nil)

for i in 0..<sprites.count {
    sprite[i] = ...

for sprite in sprites {

For more protocols to implement conformance to, see the Array documentation (scroll to Relationships).

How to convert Set to Array?

Perhaps to late to the party, but you could just do the following:

const set = new Set(['a', 'b']);
const values = set.values();
const array = Array.from(values);

This should work without problems in browsers that have support for ES6 or if you have a shim that correctly polyfills the above functionality.

Edit: Today you can just use what @c69 suggests:

const set = new Set(['a', 'b']);
const array = [...set]; // or Array.from(set)

How to use clock() in C++

#include <iostream>
#include <cstdio>
#include <ctime>

int main() {
    std::clock_t start;
    double duration;

    start = std::clock();

    /* Your algorithm here */

    duration = ( std::clock() - start ) / (double) CLOCKS_PER_SEC;

    std::cout<<"printf: "<< duration <<'\n';

How to set the margin or padding as percentage of height of parent container?

Other way to center one line text is:

  position: relative;

   position: absolute;
   top: 50%;
   line-height: 0;

or just

  overflow: hidden; /* if this ins't here the parent will adopt the 50% margin of the child */

   margin-top: 50%;
   line-height: 0;

Run a PostgreSQL .sql file using command line arguments

You can open a command prompt and run as administrator. Then type

../bin>psql -f c:/...-h localhost -p 5432 -d databasename -U "postgres"

Password for user postgres: will show up.

Type your password and enter. I couldn't see the password what I was typing, but this time when I press enter it worked. Actually I was loading data into the database.

Yes/No message box using QMessageBox

Python equivalent code for a QMessageBox which consist of a question in it and Yes and No button. When Yes Button is clicked it will pop up another message box saying yes is clicked and same for No button also. You can push your own code after if block.

button_reply = QMessageBox.question(self,"Test", "Are you sure want to quit??", QMessageBox.Yes,QMessageBox.No,)

if button_reply == QMessageBox.Yes:
    QMessageBox.information(self, "Test", "Yes Button Was Clicked")
else :
    QMessageBox.information(self, "Test", "No Button Was Clicked")

How to disable Google Chrome auto update?

Simple hacky way is to rename Updates folder in C:\Program Files (x86)\Google. Done it to freeze my chrome at 44 untill proper NPAPI replacement is supported by majority of plugins.

How to find common elements from multiple vectors?

There might be a cleverer way to go about this, but


will do the job.

EDIT: More cleverly, and more conveniently if you have a lot of arguments:

Reduce(intersect, list(a,b,c))

How to get first and last element in an array in java?

If you have a double array named numbers, you can use:

firstNum = numbers[0];
lastNum = numbers[numbers.length-1];

or with ArrayList

firstNum = numbers.get(0);
lastNum = numbers.get(numbers.size() - 1); 

Installed SSL certificate in certificate store, but it's not in IIS certificate list

I ran into this problem today. Due to the timeframe and some other issues, getting the key from the provider was not possible.

I found the following solution here (under pixelloa's comment) and thought it would be good to have the answer on Stack Overflow as well.

If the certificate does not have a private key, you can fix this by doing the following:

To fix this, use the MMC snapin to import the cert into PERSONAL store of the computer account, click it and grab the serial # line. Go to dos, run certutil -repairstore my "paste the serial # in here" (you need the quotes unless you remove the spaces from the serial number) then refresh MMC with personal certs, right click it - export - select everything except DELETE PRIVATE KEY, hit ok. Then go to IIS and IMPORT cert instead of finish request.

For what it's worth, all I actually had to do was run the certutil -repairstore command, and my certificate worked. I did run the export and set a password for the export itself, but I did not have to reimport the certificate. The certificate now shows up in IIS's list of certificates and can be used for HTTPS bindings.

I hope this helped someone.

Command-line Unix ASCII-based charting / plotting tool

Check the package plotext which allows to plot data directly on terminal using python3. It is very intuitive as its use is very similar to the matplotlib package.

Here is a basic example:

enter image description here

You can install it with the following command:

sudo -H pip install plotext

As for matplotlib, the main functions are scatter (for single points), plot (for points joined by lines) and show (to actually print the plot on terminal). It is easy to specify the plot dimensions, the point and line styles and whatever to show the axes, number ticks and final equations, which are used to convert the plotted coordinates to the original real values.

Here is the code to produce the plot shown above:

import plotext.plot as plx
import numpy as np

x=np.arange(0, l)

plx.scatter(x, y, rows = 17, cols = 70) = 0)

The option clear=True inside show is used to clear the terminal before plotting: this is useful, for example, when plotting a continuous flow of data. An example of plotting a continuous data flow is shown here: enter image description here

The package description provides more information how to customize the plot. The package has been tested on Ubuntu 16 where it works perfectly. Possible future developments (upon request) could involve extension to python2 and to other graphical interfaces (e.g. jupiter). Please let me know if you have any issues using it. Thanks.

I hope this answers your problem.

How to define a two-dimensional array?

That's what dictionary is made for!

matrix = {}

You can define keys and values in two ways:

matrix[0,0] = value


matrix = { (0,0)  : value }


   [ value,  value,  value,  value,  value],
   [ value,  value,  value,  value,  value],

Difference between private, public, and protected inheritance

To answer that question, I'd like to describe member's accessors first in my own words. If you already know this, skip to the heading "next:".

There are three accessors that I'm aware of: public, protected and private.


class Base {
        int publicMember;
        int protectedMember;
        int privateMember;
  • Everything that is aware of Base is also aware that Base contains publicMember.
  • Only the children (and their children) are aware that Base contains protectedMember.
  • No one but Base is aware of privateMember.

By "is aware of", I mean "acknowledge the existence of, and thus be able to access".


The same happens with public, private and protected inheritance. Let's consider a class Base and a class Child that inherits from Base.

  • If the inheritance is public, everything that is aware of Base and Child is also aware that Child inherits from Base.
  • If the inheritance is protected, only Child, and its children, are aware that they inherit from Base.
  • If the inheritance is private, no one other than Child is aware of the inheritance.

Java: How to stop thread?

The recommended way will be to build this into the thread. So no you can't (or rather shouldn't) kill the thread from outside.

Have the thread check infrequently if it is required to stop. (Instead of blocking on a socket until there is data. Use a timeout and every once in a while check if the user indicated wanting to stop)

JPA CriteriaBuilder - How to use "IN" comparison operator

If I understand well, you want to Join ScheduleRequest with User and apply the in clause to the userName property of the entity User.

I'd need to work a bit on this schema. But you can try with this trick, that is much more readable than the code you posted, and avoids the Join part (because it handles the Join logic outside the Criteria Query).

List<String> myList = new ArrayList<String> ();
for (User u : usersList) {
Expression<String> exp = scheduleRequest.get("createdBy");
Predicate predicate =;

In order to write more type-safe code you could also use Metamodel by replacing this line:

Expression<String> exp = scheduleRequest.get("createdBy");

with this:

Expression<String> exp = scheduleRequest.get(ScheduleRequest_.createdBy);

If it works, then you may try to add the Join logic into the Criteria Query. But right now I can't test it, so I prefer to see if somebody else wants to try.

Not a perfect answer though may be code snippets might help.

public <T> List<T> findListWhereInCondition(Class<T> clazz,
            String conditionColumnName, Serializable... conditionColumnValues) {
        QueryBuilder<T> queryBuilder = new QueryBuilder<T>(clazz);
        addWhereInClause(queryBuilder, conditionColumnName,
        return queryBuilder.getResultList();


private <T> void addWhereInClause(QueryBuilder<T> queryBuilder,
            String conditionColumnName, Serializable... conditionColumnValues) {

        Path<Object> path = queryBuilder.root.get(conditionColumnName);
        In<Object> in =;
        for (Serializable conditionColumnValue : conditionColumnValues) {


Java program to find the largest & smallest number in n numbers without using arrays

@user3168844: try the below code:

import java.util.Scanner;

public class LargestSmallestNum {

    public void findLargestSmallestNo() {

        int smallest = Integer.MAX_VALUE;
        int large = 0;
        int num;

        System.out.println("enter the number");

        Scanner input = new Scanner(;

        int n = input.nextInt();

        for (int i = 0; i < n; i++) {

            num = input.nextInt();

            if (num > large)
                large = num;

            if (num < smallest)
                smallest = num;

            System.out.println("the largest is:" + large);
            System.out.println("Smallest no is : "  + smallest);

    public static void main(String...strings){
        LargestSmallestNum largestSmallestNum = new LargestSmallestNum();

H.264 file size for 1 hr of HD video

If you know the bitrate, it's simply bitrate (bits per second) multiplied by number of seconds. Given that HDV is 25 Mbit/s and one hour has 3,600 seconds, non-transcoded it would be:

25 Mbit/s * 3,600 s/hr  =  3.125 MB/s * 3,600 s/hr  =  11,250 MB/hr  ˜  11 GB/hr

Google's calculator can confirm

The same applies with H.264 footage, although the above might not be as accurate (being variable bitrate and such).

I want to archive approximately 100 hours of such content and want to figure out whether I'm looking at a big hard drive, a multi-drive unit like a Drobo, or an enterprise-level storage system.

First, do not buy an "enterprise-level" storage system (you almost certainly don't need things like hot-swap drives and the same level of support - given the costs)..

I would suggest buying two big drives: One would be your main drive, another in a USB enclosure, and would be connected daily and mirror the primary system (as a backup).

Drives are incredibly cheap, using the above calculation of ~11 GB/hour, that's only 1.1 TB of data (for 100 hours, uncompressed). and you can buy 2 TB drives now.

Drobo, or a machine with a few drives and software RAID is an option, but a single large drive plus backups would be simpler.

Storage is almost a non-issue now, but encode time can still be an issue. Encoding H.264 is very resource-intensive. On a quad-core ~2.5 GHz Xeon, I think I got around 60 fps encoding standard-def (DVD) to H.264 (compared to around 300 fps with MPEG 4). I suppose that's only about 50 hours, but it's something worth considering. Also, assuming the HDV is on tapes, it's a 1:1 capture time, so that's 150 hours of straight processing, never mind things like changing tapes, entering metadata, and general delays (sleep) and errors ("opps, wrong tape").

What is the difference between a 'closure' and a 'lambda'?

Concept is same as described above, but if you are from PHP background, this further explain using PHP code.

$input = array(1, 2, 3, 4, 5);
$output = array_filter($input, function ($v) { return $v > 2; });

function ($v) { return $v > 2; } is the lambda function definition. We can even store it in a variable, so it can be reusable:

$max = function ($v) { return $v > 2; };

$input = array(1, 2, 3, 4, 5);
$output = array_filter($input, $max);

Now, what if you want to change the maximum number allowed in the filtered array? You would have to write another lambda function or create a closure (PHP 5.3):

$max_comp = function ($max) {
  return function ($v) use ($max) { return $v > $max; };

$input = array(1, 2, 3, 4, 5);
$output = array_filter($input, $max_comp(2));

A closure is a function that is evaluated in its own environment, which has one or more bound variables that can be accessed when the function is called. They come from the functional programming world, where there are a number of concepts in play. Closures are like lambda functions, but smarter in the sense that they have the ability to interact with variables from the outside environment of where the closure is defined.

Here is a simpler example of PHP closure:

$string = "Hello World!";
$closure = function() use ($string) { echo $string; };


Nicely explained in this article.

Change the default editor for files opened in the terminal? (e.g. set it to TextEdit/Coda/Textmate)

For OS X and Sublime Text

Make subl available.

Put this in ~/.bash_profile

[[ -s ~/.bashrc ]] && source ~/.bashrc

Put this in ~/.bashrc

export EDITOR=subl

How to Generate unique file names in C#

DateTime.Now.Ticks is not safe, Guid.NewGuid() is too ugly, if you need something clean and almost safe (it's not 100% safe for example if you call it 1,000,000 times in 1ms), try:


By safe I mean safe to be unique when you call it so many times in very short period few ms of time.

remove kernel on jupyter notebook

You can delete it in the terminal via:

jupyter kernelspec uninstall yourKernel

where yourKernel is the name of the kernel you want to delete.

How to compile C++ under Ubuntu Linux?

Use g++. And make sure you have the relevant libraries installed.

Presto SQL - Converting a date string to date format

Converted DateID having date in Int format to date format: Presto Query

Select CAST(date_format(date_parse(cast(dateid as varchar(10)), '%Y%m%d'), '%Y/%m-%d') AS DATE)
limit 10;

Replacing all non-alphanumeric characters with empty strings


return value.replaceAll("[^A-Za-z0-9]", "");


return value.replaceAll("[\\W]|_", "");

What exactly does the T and Z mean in timestamp?

The T doesn't really stand for anything. It is just the separator that the ISO 8601 combined date-time format requires. You can read it as an abbreviation for Time.

The Z stands for the Zero timezone, as it is offset by 0 from the Coordinated Universal Time (UTC).

Both characters are just static letters in the format, which is why they are not documented by the datetime.strftime() method. You could have used Q or M or Monty Python and the method would have returned them unchanged as well; the method only looks for patterns starting with % to replace those with information from the datetime object.

How to increase font size in NeatBeans IDE?

Alt + scroll wheel will increase / decrease the font size of the main code window

Fastest way(s) to move the cursor on a terminal command line?

Hold down the Option key and click where you'd like the cursor to move, and Terminal rushes the cursor that precise spot.

Counting number of characters in a file through shell script


wc -m $1 | awk '{print $1}'

wc -m counts the number of characters; the awk command prints the number of characters only, omitting the filename.

wc -c would give you the number of bytes (which can be different to the number of characters, as depending on the encoding you may have a character encoded on several bytes).

Setting SMTP details for php mail () function

Check out your php.ini, you can set these values there.

Here's the description in the php manual:

If you want to use several different SMTP servers in your application, I recommend using a "bigger" mailing framework, p.e. Swiftmailer

Rails: Using greater than/less than with a where statement

If you want a more intuitive writing, it exist a gem called squeel that will let you write your instruction like this:

User.where{id > 200}

Notice the 'brace' characters { } and id being just a text.

All you have to do is to add squeel to your Gemfile:

gem "squeel"

This might ease your life a lot when writing complex SQL statement in Ruby.

Xcode : Adding a project as a build dependency

Xcode 10

  1. drag-n-drop a project into another project - is called cross-project references[About]
  2. add the added project as a build dependency - is called Explicit dependency[About]
//Xcode 10
Build Phases -> Target Dependencies -> + Add items 

//Xcode 11
Build Phases -> Dependencies -> + Add items 

In Choose items to add: dialog you will see only targets from your project and the sub-project

enter image description here

Excel: replace part of cell's string value

You have a character = STQ8QGpaM4CU6149665!7084880820, and you have a another column = 7084880820.

If you want to get only this in excel using the formula: STQ8QGpaM4CU6149665!, use this:


H11 is an old character and for starting number use search option then for no of character needs to replace use len option then replace to new character. I am replacing this to blank.

How to call external url in jquery?

Follow the below simple steps you will able to get the result

Step 1- Create one internal function getDetailFromExternal in your back end. step 2- In that function call the external url by using cUrl like below function

 function getDetailFromExternal($p1,$p2) {

        $url = "http://request url with parameters";
        $ch = curl_init();
        curl_setopt_array($ch, array(
            CURLOPT_URL => $url,
            CURLOPT_RETURNTRANSFER => true            

        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
        $output = curl_exec($ch);
        echo $output;

Step 3- Call that internal function from your front end by using javascript/jquery Ajax.

m2e lifecycle-mapping not found

You can use this dummy plugin:

mvn archetype:generate -DgroupId=org.eclipse.m2e -DartifactId=lifecycle-mapping -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-mojo

After generating the project install/deploy it.

How do I select the "last child" with a specific class name in CSS?

You can't target the last instance of the class name in your list without JS.

However, you may not be entirely out-of-css-luck, depending on what you are wanting to achieve. For example, by using the next sibling selector, I have added a visual divider after the last of your .list elements here:,css,output

Get value from a string after a special character

Assuming you have your hidden input in a jQuery object $myHidden, you then use JavaScript (not jQuery) to get the part after ?:

var myVal = $myHidden.val ();
var tmp = myVal.substr ( myVal.indexOf ( '?' ) + 1 ); // tmp now contains whatever is after ?

MySQL table is marked as crashed and last (automatic?) repair failed

If this happend to your XAMPP installation, just copy global_priv.MAD and global_priv.MAI files from ./xampp/mysql/backup/mysql/ to ./xampp/mysql/data/mysql/.

Java Class that implements Map and keeps insertion order?

You can maintain a Map (for fast lookup) and List (for order) but a LinkedHashMap may be the simplest. You can also try a SortedMap e.g. TreeMap, which an have any order you specify.

Multiple dex files define Landroid/support/v4/accessibilityservice/AccessibilityServiceInfoCompat

I had the same problem, and my solution is changing the support version '27.+'(27.1.0) to '27.0.1'

How to target only IE (any version) within a stylesheet?

Here's a collection of media queries that will allow you to do that for any version of Internet Explorer (from IE6 to IE11+), Firefox, Chrome & Safari (EDIT: also added Opera).

IE 6

* html .ie6 { property: value; }


.ie6 { _property: value; }

IE 7

*+html .ie7 { property: value; }


*:first-child+html .ie7 { property: value; }

IE 6 and 7

@media screen\9 { 
    .ie67 {
        property: value; 


.ie67 { *property: value; }


.ie67 { #property: value; }

IE 6, 7 and 8

@media \0screen\,screen\9 {
    .ie678 {
        property: value;

IE 8

html>/**/body .ie8 { property: value; }


@media \0screen {
    .ie8 {
        property: value;

IE 8 Standards Mode

.ie8 { property /*\**/: value\9 }

IE 8,9 and 10

@media screen\0 {
    .ie8910 {
        property: value;

IE 9 only

@media screen and (min-width:0\0) and (min-resolution: .001dpcm) { 
    // IE9 CSS
        property: value;

IE 9 and above

@media screen and (min-width:0\0) and (min-resolution: +72dpi) {
    // IE9+ CSS
    .ie9up { 
        property: value; 

IE 9 and 10

@media screen and (min-width:0\0) {
    .ie910 {
        property: value\9;
    } /* backslash-9 removes ie11+ & old Safari 4 */

IE 10 only

_:-ms-lang(x), .ie10 { property: value\9; }

IE 10 and above

_:-ms-lang(x), .ie10up { property: value; }


@media all and (-ms-high-contrast: none), (-ms-high-contrast: active) {
    .ie10up {

IE 11 (and above..)

_:-ms-fullscreen, :root .ie11up { property: value; }

Firefox (any version)

@-moz-document url-prefix() {
    .ff {
        color: red;

Firefox (Quantum Only / Stylo)

@-moz-document url-prefix() {
    @supports (animation: calc(0s)) {
        /* Stylo */
        .ffStylo {
            property: value;

Firefox Legacy (pre-Stylo)

@-moz-document url-prefix() {
    @supports not (animation: calc(0s)) {
        /* Gecko */
        .ffGecko {
            property: value;

Webkit (Chrome & Safari, any version)

@media screen and (-webkit-min-device-pixel-ratio:0) { 
    property: value;

Google Chrome (29+)

@media screen and (-webkit-min-device-pixel-ratio:0) and (min-resolution:.001dpcm) {
    .chrome {
        property: value;

Safari (7.1+)

_::-webkit-full-page-media, _:future, :root .safari_only {
    property: value;

Safari (from 6.1 to 10.0)

@media screen and (min-color-index:0) and(-webkit-min-device-pixel-ratio:0) { 
    @media {
        .safari6 { 

Safari (10.1+)

@media not all and (min-resolution:.001dpcm) { 
    @media {
        .safari10 { 

Opera (12+)

@media (min-resolution: .001dpcm) {
    _:-o-prefocus, .selector {
        .opera12 {

Opera (11 and lower)

@media all and (-webkit-min-device-pixel-ratio:10000), not all and (-webkit-min-device-pixel-ratio:0) {
    .opera11 {

For further info or additional media queries, visit the web site and/or check out this blog post that I wrote on this topic.

How do I find which application is using up my port?

On the command prompt, do:

netstat -nb

How to declare an array of strings in C++?

One possiblity is to use a NULL pointer as a flag value:

const char *list[] = {"dog", "cat", NULL};
for (char **iList = list; *iList != NULL; ++iList)
    cout << *iList;

Insert value into a string at a certain position?

If you just want to insert a value at a certain position in a string, you can use the String.Insert method:

public string Insert(int startIndex, string value)


"abc".Insert(2, "XYZ") == "abXYZc"

How do I trap ctrl-c (SIGINT) in a C# console app

I can carry out some cleanups before exiting. What is the best way of doing this Thats is the real goal: trap exit, to make your own stuff. And neigther answers above not makeing it right. Because, Ctrl+C is just one of many ways to exiting app.

What in dotnet c# is needed for it - so called cancellation token passed to Host.RunAsync(ct) and then, in exit signals traps, for Windows it would be

    private static readonly CancellationTokenSource cts = new CancellationTokenSource();
    public static int Main(string[] args)
        // For gracefull shutdown, trap unload event
        AppDomain.CurrentDomain.ProcessExit += (sender, e) =>

        Console.CancelKeyPress += (sender, e) =>

        Console.WriteLine("Shutting down");
        return 0;


Pie chart with jQuery

Chart.js is quite useful, supporting numerous other types of charts as well.

It can be used both with jQuery and without.

In a Git repository, how to properly rename a directory?

lots of correct answers, but as I landed here to copy & paste a folder rename with history, I found that this

git mv <old name> <new name>

will move the old folder (itself) to nest within the new folder


git mv <old name>/ <new name>

(note the '/') will move the nested content from the old folder to the new folder

both commands didn't copy along the history of nested files. I eventually renamed each nested folder individually ?

git mv <old name>/<nest-folder> <new name>/<nest-folder>

Laravel 5.4 redirection to custom url after login

  1. Go to Providers->RouteServiceProvider.php

  2. There change the route, given below:

    class RouteServiceProvider extends ServiceProvider
     protected $namespace = 'App\Http\Controllers';
      * The path to the "home" route for your application.
      * @var string
     public const HOME = '/dashboard';

Swift double to string

In addition to @Zaph answer, you can create extension:

extension Double {
    func toString() -> String {
        return String(format: "%.1f",self)


var a:Double = 1.5
println("output: \(a.toString())")  // output: 1.5

How to define constants in Visual C# like #define in C?

In C#, per MSDN library, we have the "const" keyword that does the work of the "#define" keyword in other languages.

"...when the compiler encounters a constant identifier in C# source code (for example, months), it substitutes the literal value directly into the intermediate language (IL) code that it produces." ( )

Initialize constants at time of declaration since there is no changing them.

public const int cMonths = 12;

Table Height 100% inside Div element

This is how you can do it-


<div style="overflow:hidden; height:100%">
     <div style="float:left">a<br>b</div>
     <table cellpadding="0" cellspacing="0" style="height:100%;">     
          <tr><td>This is the content of a table that takes 100% height</td></tr>  



See the DEMO

Update: Well, if you are not looking for applying 100% height to your parent containers, then here is a jQuery solution that should help you-

Demo-using jQuery


    var b= $(window).height(); //gets the window's height, change the selector if you are looking for height relative to some other element

__init__() got an unexpected keyword argument 'user'

I got the same error.

On my view I was overriding get_form_kwargs() like this:

class UserAccountView(FormView):
    form_class = UserAccountForm
    success_url = '/'
    template_name = 'user_account/user-account.html'

def get_form_kwargs(self):
    kwargs = super(UserAccountView, self).get_form_kwargs()
    kwargs.update({'user': self.request.user})
    return kwargs

But on my form I failed to override the init() method. Once I did it. Problem solved

class UserAccountForm(forms.Form):
    first_name = forms.CharField(label='Your first name', max_length=30)
    last_name = forms.CharField(label='Your last name', max_length=30)
    email = forms.EmailField(max_length=75)

    def __init__(self, *args, **kwargs):
        user = kwargs.pop('user')
        super(UserAccountForm, self).__init__(*args, **kwargs)

Declaring a boolean in JavaScript using just var

Variables in Javascript don't have a type. Non-zero, non-null, non-empty and true are "true". Zero, null, undefined, empty string and false are "false".

There's a Boolean type though, as are literals true and false.

compare two files in UNIX

Well, you can just sort the files first, and diff the sorted files.

sort file1 > file1.sorted
sort file2 > file2.sorted
diff file1.sorted file2.sorted

You can also filter the output to report lines in file2 which are absent from file1:

diff -u file1.sorted file2.sorted | grep "^+" 

As indicated in comments, you in fact do not need to sort the files. Instead, you can use a process substitution and say:

diff <(sort file1) <(sort file2)

How can I convert a stack trace to a string?

I wrote a few methods for this a while ago, so I figured why not throw my two cents at this.

/** @param stackTraceElements The elements to convert
 * @return The resulting string */
public static final String stackTraceElementsToStr(StackTraceElement[] stackTraceElements) {
    return stackTraceElementsToStr(stackTraceElements, "\n");

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @return The resulting string */
public static final String stackTraceElementsToStr(StackTraceElement[] stackTraceElements, String lineSeparator) {
    return stackTraceElementsToStr(stackTraceElements, lineSeparator, "");

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting string */
public static final String stackTraceElementsToStr(StackTraceElement[] stackTraceElements, String lineSeparator, String padding) {
    String str = "";
    if(stackTraceElements != null) {
        for(StackTraceElement stackTrace : stackTraceElements) {
            str += padding + (!stackTrace.toString().startsWith("Caused By") ? "\tat " : "") + stackTrace.toString() + lineSeparator;
    return str;

/** @param stackTraceElements The elements to convert
 * @return The resulting string */
public static final String stackTraceCausedByElementsOnlyToStr(StackTraceElement[] stackTraceElements) {
    return stackTraceCausedByElementsOnlyToStr(stackTraceElements, "\n");

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @return The resulting string */
public static final String stackTraceCausedByElementsOnlyToStr(StackTraceElement[] stackTraceElements, String lineSeparator) {
    return stackTraceCausedByElementsOnlyToStr(stackTraceElements, lineSeparator, "");

/** @param stackTraceElements The elements to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting string */
public static final String stackTraceCausedByElementsOnlyToStr(StackTraceElement[] stackTraceElements, String lineSeparator, String padding) {
    String str = "";
    if(stackTraceElements != null) {
        for(StackTraceElement stackTrace : stackTraceElements) {
            str += (!stackTrace.toString().startsWith("Caused By") ? "" : padding + stackTrace.toString() + lineSeparator);
    return str;

/** @param e The {@link Throwable} to convert
 * @return The resulting String */
public static final String throwableToStrNoStackTraces(Throwable e) {
    return throwableToStrNoStackTraces(e, "\n");

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @return The resulting String */
public static final String throwableToStrNoStackTraces(Throwable e, String lineSeparator) {
    return throwableToStrNoStackTraces(e, lineSeparator, "");

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting String */
public static final String throwableToStrNoStackTraces(Throwable e, String lineSeparator, String padding) {
    if(e == null) {
        return "null";
    String str = e.getClass().getName() + ": ";
    if((e.getMessage() != null) && !e.getMessage().isEmpty()) {
        str += e.getMessage() + lineSeparator;
    } else {
        str += lineSeparator;
    str += padding + stackTraceCausedByElementsOnlyToStr(e.getStackTrace(), lineSeparator, padding);
    for(Throwable suppressed : e.getSuppressed()) {
        str += padding + throwableToStrNoStackTraces(suppressed, lineSeparator, padding + "\t");
    Throwable cause = e.getCause();
    while(cause != null) {
        str += padding + "Caused by:" + lineSeparator + throwableToStrNoStackTraces(e.getCause(), lineSeparator, padding);
        cause = cause.getCause();
    return str;

/** @param e The {@link Throwable} to convert
 * @return The resulting String */
public static final String throwableToStr(Throwable e) {
    return throwableToStr(e, "\n");

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @return The resulting String */
public static final String throwableToStr(Throwable e, String lineSeparator) {
    return throwableToStr(e, lineSeparator, "");

/** @param e The {@link Throwable} to convert
 * @param lineSeparator The line separator to use
 * @param padding The string to be used at the start of each line
 * @return The resulting String */
public static final String throwableToStr(Throwable e, String lineSeparator, String padding) {
    if(e == null) {
        return "null";
    String str = padding + e.getClass().getName() + ": ";
    if((e.getMessage() != null) && !e.getMessage().isEmpty()) {
        str += e.getMessage() + lineSeparator;
    } else {
        str += lineSeparator;
    str += padding + stackTraceElementsToStr(e.getStackTrace(), lineSeparator, padding);
    for(Throwable suppressed : e.getSuppressed()) {
        str += padding + "Suppressed: " + throwableToStr(suppressed, lineSeparator, padding + "\t");
    Throwable cause = e.getCause();
    while(cause != null) {
        str += padding + "Caused by:" + lineSeparator + throwableToStr(e.getCause(), lineSeparator, padding);
        cause = cause.getCause();
    return str;


try(InputStream in = new FileInputStream(file)) {
} catch(IOException e) {
    String exceptionToString = throwableToStr(e);

Prints: C:\test.txt (The system cannot find the file specified)
    at Method)
    at Source)
    at<init>(Unknown Source)

Formatting doubles for output in C#

Digits after decimal point
// just two decimal places
String.Format("{0:0.00}", 123.4567);      // "123.46"
String.Format("{0:0.00}", 123.4);         // "123.40"
String.Format("{0:0.00}", 123.0);         // "123.00"

// max. two decimal places
String.Format("{0:0.##}", 123.4567);      // "123.46"
String.Format("{0:0.##}", 123.4);         // "123.4"
String.Format("{0:0.##}", 123.0);         // "123"
// at least two digits before decimal point
String.Format("{0:00.0}", 123.4567);      // "123.5"
String.Format("{0:00.0}", 23.4567);       // "23.5"
String.Format("{0:00.0}", 3.4567);        // "03.5"
String.Format("{0:00.0}", -3.4567);       // "-03.5"

Thousands separator
String.Format("{0:0,0.0}", 12345.67);     // "12,345.7"
String.Format("{0:0,0}", 12345.67);       // "12,346"

Following code shows how can be formatted a zero (of double type).

String.Format("{0:0.0}", 0.0);            // "0.0"
String.Format("{0:0.#}", 0.0);            // "0"
String.Format("{0:#.0}", 0.0);            // ".0"
String.Format("{0:#.#}", 0.0);            // ""

Align numbers with spaces
String.Format("{0,10:0.0}", 123.4567);    // "     123.5"
String.Format("{0,-10:0.0}", 123.4567);   // "123.5     "
String.Format("{0,10:0.0}", -123.4567);   // "    -123.5"
String.Format("{0,-10:0.0}", -123.4567);  // "-123.5    "

Custom formatting for negative numbers and zero
String.Format("{0:0.00;minus 0.00;zero}", 123.4567);   // "123.46"
String.Format("{0:0.00;minus 0.00;zero}", -123.4567);  // "minus 123.46"
String.Format("{0:0.00;minus 0.00;zero}", 0.0);        // "zero"

Some funny examples
String.Format("{0:my number is 0.0}", 12.3);   // "my number is 12.3"
String.Format("{0:0aaa.bbb0}", 12.3);

nodejs vs node on ubuntu 12.04

Apparently the solution differs between Ubuntu versions. Following worked for me on Ubuntu 13.10:

sudo apt-get install nodejs-legacy


Edit: Rule of thumb:

If you have installed nodejs but are missing the /usr/bin/node binary, then also install nodejs-legacy. This just creates the missing softlink.

According to my tests, Ubuntu 17.10 and above already have the compatibility-softlink /usr/bin/node in place after nodejs is installed, so nodejs-legacy is missing from these releases as it is no more needed.

Spring MVC Multipart Request with JSON

This must work!

client (angular):

$scope.saveForm = function () {
      var formData = new FormData();
      var file = $scope.myFile;
      var json = $scope.myJson;
      formData.append("file", file);
      formData.append("ad",JSON.stringify(json));//important: convert to JSON!
      var req = {
        url: '/upload',
        method: 'POST',
        headers: {'Content-Type': undefined},
        data: formData,
        transformRequest: function (data, headersGetterFunction) {
          return data;

Backend-Spring Boot:

@RequestMapping(value = "/upload", method = RequestMethod.POST)
    public @ResponseBody
    Advertisement storeAd(@RequestPart("ad") String adString, @RequestPart("file") MultipartFile file) throws IOException {

        Advertisement jsonAd = new ObjectMapper().readValue(adString, Advertisement.class);
//do whatever you want with your file and jsonAd

Dataset - Vehicle make/model/year (free)

How about Freebase? I think they have an API available, too.

Input type DateTime - Value format?

That one shows up correctly as HTML5-Tag for those looking for this:

<input type="datetime" name="somedatafield" value="2011-12-21T11:33:23Z" />

Lightbox to show videos from Youtube and Vimeo?

Check out Fancybox. If you need the video to autoplay this example site was helpful!

Create Pandas DataFrame from a string

Simplest way is to save it to temp file and then read it:

import pandas as pd

CSV_FILE_NAME = 'temp_file.csv'  # Consider creating temp file, look URL below
with open(CSV_FILE_NAME, 'w') as outfile:
df = pd.read_csv(CSV_FILE_NAME, sep=';')

Right way of creating temp file: How can I create a tmp file in Python?

SQL: How to to SUM two values from different tables

For your current structure, you could also try the following:

select cash.Country, cash.Value, cheque.Value, cash.Value + cheque.Value as [Total]
from Cash
join Cheque
on cash.Country = cheque.Country

I think I prefer a union between the two tables, and a group by on the country name as mentioned above.

But I would also recommend normalising your tables. Ideally you'd have a country table, with Id and Name, and a payments table with: CountryId (FK to countries), Total, Type (cash/cheque)

What does yield mean in PHP?

What is yield?

The yield keyword returns data from a generator function:

The heart of a generator function is the yield keyword. In its simplest form, a yield statement looks much like a return statement, except that instead of stopping execution of the function and returning, yield instead provides a value to the code looping over the generator and pauses execution of the generator function.

What is a generator function?

A generator function is effectively a more compact and efficient way to write an Iterator. It allows you to define a function (your xrange) that will calculate and return values while you are looping over it:

function xrange($min, $max) {
    for ($i = $min; $i <= $max; $i++) {
        yield $i;


foreach (xrange(1, 10) as $key => $value) {
    echo "$key => $value", PHP_EOL;

This would create the following output:

0 => 1
1 => 2
9 => 10

You can also control the $key in the foreach by using

yield $someKey => $someValue;

In the generator function, $someKey is whatever you want appear for $key and $someValue being the value in $val. In the question's example that's $i.

What's the difference to normal functions?

Now you might wonder why we are not simply using PHP's native range function to achieve that output. And right you are. The output would be the same. The difference is how we got there.

When we use range PHP, will execute it, create the entire array of numbers in memory and return that entire array to the foreach loop which will then go over it and output the values. In other words, the foreach will operate on the array itself. The range function and the foreach only "talk" once. Think of it like getting a package in the mail. The delivery guy will hand you the package and leave. And then you unwrap the entire package, taking out whatever is in there.

When we use the generator function, PHP will step into the function and execute it until it either meets the end or a yield keyword. When it meets a yield, it will then return whatever is the value at that time to the outer loop. Then it goes back into the generator function and continues from where it yielded. Since your xrange holds a for loop, it will execute and yield until $max was reached. Think of it like the foreach and the generator playing ping pong.

Why do I need that?

Obviously, generators can be used to work around memory limits. Depending on your environment, doing a range(1, 1000000) will fatal your script whereas the same with a generator will just work fine. Or as Wikipedia puts it:

Because generators compute their yielded values only on demand, they are useful for representing sequences that would be expensive or impossible to compute at once. These include e.g. infinite sequences and live data streams.

Generators are also supposed to be pretty fast. But keep in mind that when we are talking about fast, we are usually talking in very small numbers. So before you now run off and change all your code to use generators, do a benchmark to see where it makes sense.

Another Use Case for Generators is asynchronous coroutines. The yield keyword does not only return values but it also accepts them. For details on this, see the two excellent blog posts linked below.

Since when can I use yield?

Generators have been introduced in PHP 5.5. Trying to use yield before that version will result in various parse errors, depending on the code that follows the keyword. So if you get a parse error from that code, update your PHP.

Sources and further reading:

Fetch API with Cookie

Just adding to the correct answers here for .net webapi2 users.

If you are using cors because your client site is served from a different address as your webapi then you need to also include SupportsCredentials=true on the server side configuration.

        // Access-Control-Allow-Origin
        var cors = new EnableCorsAttribute(Settings.CORSSites,"*", "*");
        cors.SupportsCredentials = true;

Permutation of array

Example with primitive array:

public static void permute(int[] intArray, int start) {
    for(int i = start; i < intArray.length; i++){
        int temp = intArray[start];
        intArray[start] = intArray[i];
        intArray[i] = temp;
        permute(intArray, start + 1);
        intArray[i] = intArray[start];
        intArray[start] = temp;
    if (start == intArray.length - 1) {

public static void main(String[] args){
    int intArr[] = {1, 2, 3};
    permute(intArr, 0);

How to stick <footer> element at the bottom of the page (HTML5 and CSS3)?

For footer change from position: relative; to position:fixed;

 footer {
            background-color: #333;
            width: 100%;
            bottom: 0;
            position: fixed;


Play local (hard-drive) video file with HTML5 video tag?

It is possible to play a local video file.

<input type="file" accept="video/*"/>
<video controls autoplay></video>

When a file is selected via the input element:

  1. 'change' event is fired
  2. Get the first File object from the input.files FileList
  3. Make an object URL that points to the File object
  4. Set the object URL to the video.src property
  5. Lean back and watch :),js,html,css/

(function localFileVideoPlayer() {_x000D_
  'use strict'_x000D_
  var URL = window.URL || window.webkitURL_x000D_
  var displayMessage = function(message, isError) {_x000D_
    var element = document.querySelector('#message')_x000D_
    element.innerHTML = message_x000D_
    element.className = isError ? 'error' : 'info'_x000D_
  var playSelectedFile = function(event) {_x000D_
    var file = this.files[0]_x000D_
    var type = file.type_x000D_
    var videoNode = document.querySelector('video')_x000D_
    var canPlay = videoNode.canPlayType(type)_x000D_
    if (canPlay === '') canPlay = 'no'_x000D_
    var message = 'Can play type "' + type + '": ' + canPlay_x000D_
    var isError = canPlay === 'no'_x000D_
    displayMessage(message, isError)_x000D_
    if (isError) {_x000D_
    var fileURL = URL.createObjectURL(file)_x000D_
    videoNode.src = fileURL_x000D_
  var inputNode = document.querySelector('input')_x000D_
  inputNode.addEventListener('change', playSelectedFile, false)_x000D_
input {_x000D_
  display: block;_x000D_
input {_x000D_
  width: 100%;_x000D_
.info {_x000D_
  background-color: aqua;_x000D_
.error {_x000D_
  background-color: red;_x000D_
  color: white;_x000D_
<h1>HTML5 local video file player example</h1>_x000D_
<div id="message"></div>_x000D_
<input type="file" accept="video/*" />_x000D_
<video controls autoplay></video>

How does DISTINCT work when using JPA and Hibernate

I would use JPA's constructor expression feature. See also following answer:

JPQL Constructor Expression - org.hibernate.hql.ast.QuerySyntaxException:Table is not mapped

Following the example in the question, it would be something like this.

SELECT DISTINCT new com.mypackage.MyNameType( from Customer c

jquery change style of a div on click

$(document).ready(function() {
  $('#div_one').bind('click', function() {

If I understood your question.

Or you can modify css directly:

var $speech = $('div.speech');
var currentSize = $speech.css('fontSize');
$speech.css('fontSize', '10px');

C++ program converts fahrenheit to celsius

In your code sample you are trying to divide an integer with another integer. This is the cause of all your trouble. Here is an article that might find interesting on that subject.

With the notion of integer division you can see right away that this is not what you want in your formula. Instead, you need to use some floating point literals.

I am a rather confused by the title of this thread and your code sample. Do you want to convert Celsius degrees to Fahrenheit or do the opposite?

I will base my code sample on your own code sample until you give more details on what you want.

Here is an example of what you can do :

#include <iostream>
//no need to use the whole std namespace... use what you need :)                        
using std::cout;
using std::cin;
using std::endl;                      

int main() 
    float celsius,    //represents the temperature in Celsius degrees
          fahrenheit; //represents the converted temperature in Fahrenheit degrees

    //Ask for the temperature in Celsius degrees
    cout << "Enter Celsius temperature: "; 
    cin >> celsius;

    //Formula to convert degrees in Celsius to Fahrenheit degrees
    //Important note: floating point literals need to have the '.0'!
    fahrenheit = celsius * 9.0/5.0 + 32.0;

    //Print the converted temperature to the console
    cout << "Fahrenheit = " << fahrenheit << endl;                            

What are named pipes?

This is an exeprt from Technet (so not sure why the marked answer says named pipes are faster??):

Named Pipes vs. TCP/IP Sockets

In a fast local area network (LAN) environment, Transmission Control Protocol/Internet Protocol (TCP/IP) Sockets and Named Pipes clients are comparable with regard to performance. However, the performance difference between the TCP/IP Sockets and Named Pipes clients becomes apparent with slower networks, such as across wide area networks (WANs) or dial-up networks. This is because of the different ways the interprocess communication (IPC) mechanisms communicate between peers.

For named pipes, network communications are typically more interactive. A peer does not send data until another peer asks for it using a read command. A network read typically involves a series of peek named pipes messages before it starts to read the data. These can be very costly in a slow network and cause excessive network traffic, which in turn affects other network clients.

It is also important to clarify if you are talking about local pipes or network pipes. If the server application is running locally on the computer that is running an instance of SQL Server, the local Named Pipes protocol is an option. Local named pipes runs in kernel mode and is very fast.

For TCP/IP Sockets, data transmissions are more streamlined and have less overhead. Data transmissions can also take advantage of TCP/IP Sockets performance enhancement mechanisms such as windowing, delayed acknowledgements, and so on. This can be very helpful in a slow network. Depending on the type of applications, such performance differences can be significant.

TCP/IP Sockets also support a backlog queue. This can provide a limited smoothing effect compared to named pipes that could lead to pipe-busy errors when you are trying to connect to SQL Server.

Generally, TCP/IP is preferred in a slow LAN, WAN, or dial-up network, whereas named pipes can be a better choice when network speed is not the issue, as it offers more functionality, ease of use, and configuration options.

How to create a sub array from another array in Java?

You can use

JDK > 1.5

Arrays.copyOfRange(Object[] src, int from, int to)


JDK <= 1.5

System.arraycopy(Object[] src, int srcStartIndex, Object[] dest, int dstStartIndex, int lengthOfCopiedIndices); 


Can I execute a function after setState is finished updating?

Making setState return a Promise

In addition to passing a callback to setState() method, you can wrap it around an async function and use the then() method -- which in some cases might produce a cleaner code:

(async () => new Promise(resolve => this.setState({dummy: true}), resolve)()
    .then(() => { console.log('state:', this.state) });

And here you can take this one more step ahead and make a reusable setState function that in my opinion is better than the above version:

const promiseState = async state =>
    new Promise(resolve => this.setState(state, resolve));

    .then(() => promiseState({...})
    .then(() => {
        ...  // other code
        return promiseState({...});
    .then(() => {...});

This works fine in React 16.4, but I haven't tested it in earlier versions of React yet.

Also worth mentioning that keeping your callback code in componentDidUpdate method is a better practice in most -- probably all, cases.

How to convert Nonetype to int or string?

I've successfully used int(x or 0) for this type of error, so long as None should equate to 0 in the logic. Note that this will also resolve to 0 in other cases where testing x returns False. e.g. empty list, set, dictionary or zero length string. Sorry, Kindall already gave this answer.

How do I minimize the command prompt from my bat file

One option is to find one of the various utilities that can change the window state of the currently running console window and make a call to it from within the batch script.

You can run it as the first thing in your batch script. Here are two such tools:



org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoRestController'

To me it happened in DogController that autowired DogService that autowired DogRepository. Dog class used to have field name but I changed it to coolName, but didn't change methods in DogRepository: Dog findDogByName(String name). I change that method to Dog findDogByCoolName(String name) and now it works.

Returning JSON response from Servlet to Javascript/JSP page

I think that what you want to do is turn the JSON string back into an object when it arrives back in your XMLHttpRequest - correct?

If so, you need to eval the string to turn it into a JavaScript object - note that this can be unsafe as you're trusting that the JSON string isn't malicious and therefore executing it. Preferably you could use jQuery's parseJSON

How to create a new variable in a data.frame based on a condition?

If you have a very limited number of levels, you could try converting y into factor and change its levels.

> xy <- data.frame(x = c(1, 2, 4), y = c(1, 4, 5))
> xy$w <- as.factor(xy$y)
> levels(xy$w) <- c("good", "fair", "bad")
> xy
  x y    w
1 1 1 good
2 2 4 fair
3 4 5  bad

convert big endian to little endian in C [without using provided func]

This code snippet can convert 32bit little Endian number to Big Endian number.

#include <stdio.h>
    unsigned int i = 0xfafbfcfd;
    unsigned int j;    
    j= ((i&0xff000000)>>24)| ((i&0xff0000)>>8) | ((i&0xff00)<<8) | ((i&0xff)<<24);    
    printf("unsigned int j = %x\n ", j);    

Get record counts for all tables in MySQL database

The following query produces a(nother) query that will get the value of count(*) for every table, from every schema, listed in information_schema.tables. The entire result of the query shown here - all rows taken together - comprise a valid SQL statement ending in a semicolon - no dangling 'union'. The dangling union is avoided by use of a union in the query below.

select concat('select "', table_schema, '.', table_name, '" as `schema.table`,
                 from ', table_schema, '.', table_name, ' union ') as 'Query Row'
  from information_schema.tables
 select '(select null, null limit 0);';

What does $1 [QSA,L] mean in my .htaccess file?

If the following conditions are true, then rewrite the URL:
If the requested filename is not a directory,

RewriteCond %{REQUEST_FILENAME} !-d

and if the requested filename is not a regular file that exists,

RewriteCond %{REQUEST_FILENAME} !-f

and if the requested filename is not a symbolic link,

RewriteCond %{REQUEST_FILENAME} !-l

then rewrite the URL in the following way:
Take the whole request filename and provide it as the value of a "url" query parameter to index.php. Append any query string from the original URL as further query parameters (QSA), and stop processing this .htaccess file (L).

RewriteRule ^(.+)$ index.php?url=$1 [QSA,L]

Apache docs #flag_qsa

Another Example:

RewriteRule "/pages/(.+)" "/page.php?page=$1" [QSA]

With the [QSA] flag, a request for


will be mapped to


Average of multiple columns

Select Req_ID, sum(R1+R2+R3+R4+R5)/5 as Average
from Request
Group by Req_ID;

Regex to match any character including new lines

If you don't want add the /s regex modifier (perhaps you still want . to retain its original meaning elsewhere in the regex), you may also use a character class. One possibility:


a character which is not a space or is a space. In other words, any character.

You can also change modifiers locally in a small part of the regex, like so:


How do I run a program with a different working directory from current, from Linux shell?

Just change the last "&&" into ";" and it will cd back no matter if the command fails or succeeds:

cd SOME_PATH && run_some_command ; cd -

Add a new element to an array without specifying the index in Bash

As Dumb Guy points out, it's important to note whether the array starts at zero and is sequential. Since you can make assignments to and unset non-contiguous indices ${#array[@]} is not always the next item at the end of the array.

$ array=(a b c d e f g h)
$ array[42]="i"
$ unset array[2]
$ unset array[3]
$ declare -p array     # dump the array so we can see what it contains
declare -a array='([0]="a" [1]="b" [4]="e" [5]="f" [6]="g" [7]="h" [42]="i")'
$ echo ${#array[@]}
$ echo ${array[${#array[@]}]}

Here's how to get the last index:

$ end=(${!array[@]})   # put all the indices in an array
$ end=${end[@]: -1}    # get the last one
$ echo $end

That illustrates how to get the last element of an array. You'll often see this:

$ echo ${array[${#array[@]} - 1]}

As you can see, because we're dealing with a sparse array, this isn't the last element. This works on both sparse and contiguous arrays, though:

$ echo ${array[@]: -1}

jQuery animate backgroundColor

I had the same problem and fixed it by including jQuery UI. Here is the complete script :

<!-- include Google's AJAX API loader -->
<script src=""></script>
<!-- load JQuery and UI from Google (need to use UI to animate colors) -->
<script type="text/javascript">
google.load("jqueryui", "1.5.2");

<script type="text/javascript">
$(document).ready(function() {
$('#menu ul li.item').hover(
    function() {
        $(this).stop().animate({backgroundColor:'#4E1402'}, 300);
        }, function () {
        $(this).stop().animate({backgroundColor:'#943D20'}, 100);

How to make Regular expression into non-greedy?

I believe it would be like this


the g at the end means global, so it doesn't stop at the first match.

Definition of "downstream" and "upstream"

In terms of source control, you're "downstream" when you copy (clone, checkout, etc) from a repository. Information flowed "downstream" to you.

When you make changes, you usually want to send them back "upstream" so they make it into that repository so that everyone pulling from the same source is working with all the same changes. This is mostly a social issue of how everyone can coordinate their work rather than a technical requirement of source control. You want to get your changes into the main project so you're not tracking divergent lines of development.

Sometimes you'll read about package or release managers (the people, not the tool) talking about submitting changes to "upstream". That usually means they had to adjust the original sources so they could create a package for their system. They don't want to keep making those changes, so if they send them "upstream" to the original source, they shouldn't have to deal with the same issue in the next release.

Convert seconds to HH-MM-SS with JavaScript?

I've used this code before to create a simple timespan object:

function TimeSpan(time) {
this.hours = 0;
this.minutes = 0;
this.seconds = 0;

while(time >= 3600)
    time -= 3600;

while(time >= 60)
    time -= 60;

this.seconds = time;

var timespan = new Timespan(3662);

What is the difference between an interface and abstract class?

A simple yet effective explanation of abstract class and interface on

An Interface is like a protocol. It doesn't designate the behavior of the object; it designates how your code tells that object to act. An interface would be like the English Language: defining an interface defines how your code communicates with any object implementing that interface.

An interface is always an agreement or a promise. When a class says "I implement interface Y", it is saying "I promise to have the same public methods that any object with interface Y has".

On the other hand, an Abstract Class is like a partially built class. It is much like a document with blanks to fill in. It might be using English, but that isn't as important as the fact that some of the document is already written.

An abstract class is the foundation for another object. When a class says "I extend abstract class Y", it is saying "I use some methods or properties already defined in this other class named Y".

So, consider the following PHP:

class X implements Y { } // this is saying that "X" agrees to speak language "Y" with your code.

class X extends Y { } // this is saying that "X" is going to complete the partial class "Y".

You would have your class implement a particular interface if you were distributing a class to be used by other people. The interface is an agreement to have a specific set of public methods for your class.

You would have your class extend an abstract class if you (or someone else) wrote a class that already had some methods written that you want to use in your new class.

These concepts, while easy to confuse, are specifically different and distinct. For all intents and purposes, if you're the only user of any of your classes, you don't need to implement interfaces.

Is there a way to view two blocks of code from the same file simultaneously in Sublime Text?

In the nav go View => Layout => Columns:2 (alt+shift+2) and open your file again in the other pane (i.e. click the other pane and use ctrl+p

It appears you can also reopen the file using the command File -> New View into File which will open the current file in a new tab

How can I check if a background image is loaded?

I did a pure javascript hack to make this possible.

<div class="my_background_image" style="background-image: url(broken-image.jpg)">
<img class="image_error" src="broken-image.jpg" onerror="'none';">


onerror="this.parentElement.backgroundImage = "url('image_placeHolder.png')";


.image_error {
    display: none;

Send message to specific client with and node.js

The simplest, most elegant way

verified working with v3.1.1

It's as easy as:

client.emit("your message");

And that's it. Ok, but how does it work?

Minimal working example

Here's an example of a simple client-server interaction where each client regularly receives a message containing a sequence number. There is a unique sequence for each client and that's where the "I need to send a message to a particular client" comes into play.



    {Server} = require(""),
    server = new Server(8000);

    sequenceNumberByClient = new Map();

// event fired every time a new client connects:
server.on("connection", (socket) => {`Client connected [id=${}]`);
    // initialize this client's sequence number
    sequenceNumberByClient.set(socket, 1);

    // when socket disconnects, remove it from the list:
    socket.on("disconnect", () => {
        sequenceNumberByClient.delete(socket);`Client gone [id=${}]`);

// sends each client its current sequence number
setInterval(() => {
    for (const [client, sequenceNumber] of sequenceNumberByClient.entries()) {
        client.emit("seq-num", sequenceNumber);
        sequenceNumberByClient.set(client, sequenceNumber + 1);
}, 1000);

The server starts listening on port 8000 for incoming connections. As soon as a new connection is established, that client is added to a map that keeps track of its sequence number. The server also listens for the disconnect event to remove the client from the map when it leaves.

Each and every second, a timer is fired. When it does, the server walks through the map and sends a message to every client with their current sequence number, incrementing it right after. That's all that is to it. Easy peasy.


The client part is even simpler. It just connects to the server and listens for the seq-num message, printing it to the console every time it arrives.


    io = require(""),
    ioClient = io.connect("http://localhost:8000");

ioClient.on("seq-num", (msg) =>;

Running the example

Install the required libraries:

npm install [email protected] [email protected]

Run the server:

node server

Open other terminal windows and spawn as many clients as you want by running:

node client

I have also prepared a gist with the full code here.

How do I create batch file to rename large number of files in a folder?

@ECHO off & SETLOCAL EnableDelayedExpansion

SET "_dir=" REM Must finish with '\'
SET "_ext=jpg"
SET "_toEdit=Vacation2010"
SET "_with=December"
FOR %%f IN ("%_dir%*.%_ext%") DO (
    CALL :modifyString "%_toEdit%" "%_with%" "%%~Nf" fileName 
    RENAME "%%f" "!fileName!%%~Xf"
GOTO end

:modifyString what with in toReturn
    SET "__in=%~3"
    SET "__in=!__in:%~1=%~2!"
    IF NOT "%~4" == "" (
        SET %~4=%__in%
    ) ELSE (
        ECHO %__in%
    EXIT /B


This script allows you to change the name of all the files that contain Vacation2010 with the same name, but with December instead of Vacation2010.

If you copy and paste the code, you have to save the .bat in the same folder of the photos. If you want to save the script in another directory [E.G. you have a favorite folder for the utilities] you have to change the value of _dir with the path of the photos.

If you have to do the same work for other photos [or others files changig _ext] you have to change the value of _toEdit with the string you want to change [or erase] and the value of _with with the string you want to put instead of _toEdit [SET "_with=" if you simply want to erase the string specified in _toEdit].

import .css file into .less file

since 1.5.0 u can use the 'inline' keyword.

Example: @import (inline) "not-less-compatible.css";

You will use this when a CSS file may not be Less compatible; this is because although Less supports most known standards CSS, it does not support comments in some places and does not support all known CSS hacks without modifying the CSS. So you can use this to include the file in the output so that all CSS will be in one file.


How can I convert a Timestamp into either Date or DateTime object?

You can also get DateTime object from timestamp, including your current daylight saving time:

public DateTime getDateTimeFromTimestamp(Long value) {
    TimeZone timeZone = TimeZone.getDefault();
    long offset = timeZone.getOffset(value);
    if (offset < 0) {
        value -= offset;
    } else {
        value += offset;
    return new DateTime(value);

C# guid and SQL uniqueidentifier

Store it in the database in a field with a data type of uniqueidentifier.

Is there a way to break a list into columns?

2021 - keep it simple, use CSS Grid

Lots of these answers are outdated, it's 2020 and we shouldn't be enabling people who are still using IE9. It's way more simple to just use CSS grid.

The code is very simple, and you can easily adjust how many columns there are using the grid-template-columns. See this and then play around with this fiddle to fit your needs.

.grid-list {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
<ul class="grid-list">

Javascript code for showing yesterday's date and todays date

Yesterday Date can be calculated as:-

let now = new Date();
    var defaultDate = now - 1000 * 60 * 60 * 24 * 1;
    defaultDate = new Date(defaultDate);

AttributeError: Can only use .dt accessor with datetimelike values

First you need to define the format of date column.

df['Date'] = pd.to_datetime(df.Date, format='%Y-%m-%d %H:%M:%S')

For your case base format can be set to;

df['Date'] = pd.to_datetime(df.Date, format='%Y-%m-%d')

After that you can set/change your desired output as follows;

df['Date'] = df['Date'].dt.strftime('%Y-%m-%d')

Genymotion Android emulator - adb access?

I know it's way too late to answer this question, but I'll just post the solution that worked for me, in case someone runs into trouble again in the future.

I tried using genymotion's own adb tools and the original Android SDK ones, and even purging and reinstalling adb from my system, but nothing worked. I kept getting the error:

adb server is out of date. killing... cannot bind 'tcp:5037' ADB server didn't ACK *failed to start daemon* error:
So I tried adb connect [ip] as suggested here, but I didn't work either, the same error came up.

What finally worked for me was downloading ADT, and running adb directly from the downloaded folder, instead of the system-wide command. So adb devices will give me the error above, but /yourdownloadpath/adb devices works just fine for me.

Hope it helped.

Laravel PDOException SQLSTATE[HY000] [1049] Unknown database 'forge'

Encountered this issue quite a few times, note that I'm running laravel via Vagrant. So here are the fixes that work for me:

  • Try again several times (refresh page)
  • Reload vagrant (vagrant reload)

You may try reloading your server instead of vagrant (ie MAMP)

How do I write a Python dictionary to a csv file?

You are using DictWriter.writerows() which expects a list of dicts, not a dict. You want DictWriter.writerow() to write a single row.

You will also want to use DictWriter.writeheader() if you want a header for you csv file.

You also might want to check out the with statement for opening files. It's not only more pythonic and readable but handles closing for you, even when exceptions occur.

Example with these changes made:

import csv

my_dict = {"test": 1, "testing": 2}

with open('mycsvfile.csv', 'w') as f:  # You will need 'wb' mode in Python 2.x
    w = csv.DictWriter(f, my_dict.keys())

Which produces:


How many socket connections can a web server handle?

I think that the number of concurrent socket connections one web server can handle largely depends on the amount of resources each connection consumes and the amount of total resource available on the server barring any other web server resource limiting configuration.

To illustrate, if every socket connection consumed 1MB of server resource and the server has 16GB of RAM available (theoretically) this would mean it would only be able to handle (16GB / 1MB) concurrent connections. I think it's as simple as that... REALLY!

So regardless of how the web server handles connections, every connection will ultimately consume some resource.



WITH tab (
  bla bla

INSERT INTO dbo.prf_BatchItemAdditionalAPartyNos (  BatchID,                                                        AccountNo,


Note that this is for SQL Server, which supports multiple CTEs:

WITH x AS (), y AS () INSERT INTO z (a, b, c) SELECT a, b, c FROM y

Teradata allows only one CTE and the syntax is as your example.

Extend contigency table with proportions (percentages)

If it's conciseness you're after, you might like:


and then scale by 100 and round if you like. Or more like your exact output:

tbl <- table(tips$smoker)

If you wanted to do this for multiple columns, there are lots of different directions you could go depending on what your tastes tell you is clean looking output, but here's one option:

tblFun <- function(x){
    tbl <- table(x)
    res <- cbind(tbl,round(prop.table(tbl)*100,2))
    colnames(res) <- c('Count','Percentage')
       Count Percentage
Female    87      35.66
Male     157      64.34
No       151      61.89
Yes       93      38.11
Fri       19       7.79
Sat       87      35.66
Sun       76      31.15
Thur      62      25.41
Dinner   176      72.13
Lunch     68      27.87

If you don't like stack the different tables on top of each other, you can ditch the and leave them in a list.

Win32Exception (0x80004005): The wait operation timed out

EfCore version of @JonSchneider's answer


Where myDbContext is your DbContext instance, and 999 is the timeout value in seconds.

(Syntax current as of Entity Framework Core 3.1)

$(document).click() not working correctly on iPhone. jquery

Short answer:

         cursor: pointer;

Longer answer:

It's important to realize that if you're just using <a> tags everything will work as expected. You can click or drag by mistake on a regular <a> link on an iPhone and everything behaves as the user would expect.

I imagine that you have arbitrary HTML that is not clickable - such as a panel containing text and images that cannot be wrapped with <a>. I found out about this problem when I had such a panel that I wanted to be entirely clickable.

<div class='clickable-div' data-href="">

 ... clickable content here (images/text) ...


To detect a click anywhere within this div I am using jQuery with a data-href html attribute which is shown above (this attribute is invented by myself and is not a standard jQuery or HTML data attribute.)

$(document).on('click', '.clickable-div', function() {

    document.location = $(this).data('href');


This will work on your desktop browser but not iPad no matter how much you click.

You may be tempted to change your event handler from click to click touchstart - and this indeed does trigger the event handler. However if the user wants to drag the page up (to scroll) they'll trigger it too - which is a terrible user experience. [you may have noticed this behavior by sneaky banner ads]

The answer is incredibly simple: Just set the css cursor: pointer.

         cursor: pointer;

This had the added benefit for desktop users to indicate the area is clickable with a hand icon.

Thanks to

Missing Push Notification Entitlement

This was what fixed it for me. (I had already tried toggling the capabilities on/off, recreating the provisioning profile, etc).

In the Build Settings tab, in Code Signing Entitlements, my .entitlements file wasn't link for all sections. Once I added it to the Any SDK section, the error was resolved.

enter image description here

CodeIgniter: How to get Controller, Action, URL information

Use This Code anywhere in class or libraries

    $current_url =& get_instance(); //  get a reference to CodeIgniter
    $current_url->router->fetch_class(); // for Class name or controller
    $current_url->router->fetch_method(); // for method name

Validate phone number using angular js

Check this answer

Basically you can create a regex to fulfil your needs and then assign that pattern to your input field.

Or for a more direct approach:

<input type="number" require ng-pattern="<your regex here>">

More info @ angular docs here and here (built-in validators)

How can I reference a commit in an issue comment on GitHub?

Answer above is missing an example which might not be obvious (it wasn't to me).

Url could be broken down into parts
                  \_____/\________/       \_______________________________________/
                   |        |                              |
            Account name    |                      Hash of revision
                        Project name              

Hash can be found here (you can click it and will get the url from browser).

enter image description here

Hope this saves you some time.

How does cookie based authentication work?

I realize this is years late, but I thought I could expand on Conor's answer and add a little bit more to the discussion.

Can someone give me a step by step description of how cookie based authentication works? I've never done anything involving either authentication or cookies. What does the browser need to do? What does the server need to do? In what order? How do we keep things secure?

Step 1: Client > Signing up

Before anything else, the user has to sign up. The client posts a HTTP request to the server containing his/her username and password.

Step 2: Server > Handling sign up

The server receives this request and hashes the password before storing the username and password in your database. This way, if someone gains access to your database they won't see your users' actual passwords.

Step 3: Client > User login

Now your user logs in. He/she provides their username/password and again, this is posted as a HTTP request to the server.

Step 4: Server > Validating login

The server looks up the username in the database, hashes the supplied login password, and compares it to the previously hashed password in the database. If it doesn't check out, we may deny them access by sending a 401 status code and ending the request.

Step 5: Server > Generating access token

If everything checks out, we're going to create an access token, which uniquely identifies the user's session. Still in the server, we do two things with the access token:

  1. Store it in the database associated with that user
  2. Attach it to a response cookie to be returned to the client. Be sure to set an expiration date/time to limit the user's session

Henceforth, the cookies will be attached to every request (and response) made between the client and server.

Step 6: Client > Making page requests

Back on the client side, we are now logged in. Every time the client makes a request for a page that requires authorization (i.e. they need to be logged in), the server obtains the access token from the cookie and checks it against the one in the database associated with that user. If it checks out, access is granted.

This should get you started. Be sure to clear the cookies upon logout!

New Array from Index Range Swift

#1. Using Array subscript with range

With Swift 5, when you write…

let newNumbers = numbers[0...position]

newNumbers is not of type Array<Int> but is of type ArraySlice<Int>. That's because Array's subscript(_:?) returns an ArraySlice<Element> that, according to Apple, presents a view onto the storage of some larger array.

Besides, Swift also provides Array an initializer called init(_:?) that allows us to create a new array from a sequence (including ArraySlice).

Therefore, you can use subscript(_:?) with init(_:?) in order to get a new array from the first n elements of an array:

let array = Array(10...14) // [10, 11, 12, 13, 14]
let arraySlice = array[0..<3] // using Range
//let arraySlice = array[0...2] // using ClosedRange also works
//let arraySlice = array[..<3] // using PartialRangeUpTo also works
//let arraySlice = array[...2] // using PartialRangeThrough also works
let newArray = Array(arraySlice)
print(newArray) // prints [10, 11, 12]

#2. Using Array's prefix(_:) method

Swift provides a prefix(_:) method for types that conform to Collection protocol (including Array). prefix(_:) has the following declaration:

func prefix(_ maxLength: Int) -> ArraySlice<Element>

Returns a subsequence, up to maxLength in length, containing the initial elements.

Apple also states:

If the maximum length exceeds the number of elements in the collection, the result contains all the elements in the collection.

Therefore, as an alternative to the previous example, you can use the following code in order to create a new array from the first elements of another array:

let array = Array(10...14) // [10, 11, 12, 13, 14]
let arraySlice = array.prefix(3)
let newArray = Array(arraySlice)
print(newArray) // prints [10, 11, 12]

Get root view from current activity

if you are in a activity, assume there is only one root view,you can get it like this.

ViewGroup viewGroup = (ViewGroup) ((ViewGroup) this

you can then cast it to your real class

or you could using


notice this will include the actionbar view, your view is below the actionbar view

Convert python datetime to timestamp in milliseconds

For Python2.7 - modifying MYGz's answer to not strip milliseconds:

from datetime import datetime

d = datetime.strptime("20.12.2016 09:38:42,76", "%d.%m.%Y %H:%M:%S,%f").strftime('%s.%f')
d_in_ms = int(float(d)*1000)



2016-12-20 09:38:42.760000

Saving an image in OpenCV

Sometimes the first call to cvQueryFrame() returns an empty image. Try:

IplImage *pSaveImg = cvQueryFrame(pCapturedImage);
pSaveImg = cvQueryFrame(pCapturedImage);

If that does not work, try to select capture device automatically:

CvCapture *pCapturedImage = cvCreateCameraCapture(-1);

Or you may try to select other capture devices where n=1,2,3...

CvCapture *pCapturedImage = cvCreateCameraCapture(n);

PS: Also I believe there is a misunderstanding about captured image looking at your variable name. The variable pCapturedImage is not an Image it is a Capture. You can always 'read' an image from capture.

How to set opacity in parent div and not affect in child div?

You can do it with pseudo-elements: (demo on enter image description here

your markup:

<div class="parent">
    <div class="child"> Hello I am child </div>


    position: relative;

.parent:before {
    z-index: -1;
    content: '';
    position: absolute;

    opacity: 0.2;
    width: 400px;
    height: 200px;
    background: url('') no-repeat 0 0; 


How to validate IP address in Python?

Don't parse it. Just ask.

import socket

    # legal
except socket.error:
    # Not legal

Show constraints on tables command

There is also a tool that oracle made called mysqlshow

If you run it with the --k keys $table_name option it will display the keys.

   mysqlshow [options] [db_name [tbl_name [col_name]]]
·   --keys, -k
   Show table indexes.


?-?  mysqlshow -h -u root -p --keys database tokens
Database: database  Table: tokens
| Field           | Type             | Collation          | Null | Key | Default | Extra          | Privileges                      | Comment |
| id              | int(10) unsigned |                    | NO   | PRI |         | auto_increment | select,insert,update,references |         |
| token           | text             | utf8mb4_unicode_ci | NO   |     |         |                | select,insert,update,references |         |
| user_id         | int(10) unsigned |                    | NO   | MUL |         |                | select,insert,update,references |         |
| expires_in      | datetime         |                    | YES  |     |         |                | select,insert,update,references |         |
| created_at      | timestamp        |                    | YES  |     |         |                | select,insert,update,references |         |
| updated_at      | timestamp        |                    | YES  |     |         |                | select,insert,update,references |         |
| Table  | Non_unique | Key_name                 | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
| tokens | 0          | PRIMARY                  | 1            | id          | A         | 2           |          |        |      | BTREE      |         |               |
| tokens | 1          | tokens_user_id_foreign   | 1            | user_id     | A         | 2           |          |        |      | BTREE      |         |               |