SyntaxFix

Programs & Examples On #Topological sort

A topological sort of a directed graph produces a linear ordering of its vertices such that, for every edge uv, u comes before v in the ordering.

ASP MVC href to a controller/view

how about

<li>
<a href="@Url.Action("Index", "Users")" class="elements"><span>Clients</span></a>
</li>

If hasClass then addClass to parent

The dot is not part of the class name. It's only used in CSS/jQuery selector notation. Try this instead:

if ($('#navigation a').hasClass('active')) {
    $(this).parent().addClass('active');
}

If $(this) refers to that anchor, you have to change it to $('#navigation a') as well because the if condition does not have jQuery callback scope.

How do I turn off Oracle password expiration?

For development you can disable password policy if no other profile was set (i.e. disable password expiration in default one):

ALTER PROFILE "DEFAULT" LIMIT PASSWORD_VERIFY_FUNCTION NULL;

Then, reset password and unlock user account. It should never expire again:

alter user user_name identified by new_password account unlock;

How to check if cursor exists (open status)

Close the cursor, if it is empty then deallocate it:

IF CURSOR_STATUS('global','myCursor') >= -1
 BEGIN
  IF CURSOR_STATUS('global','myCursor') > -1
   BEGIN
    CLOSE myCursor
   END
 DEALLOCATE myCursor
END

How do I convert a string to enum in TypeScript?

If you are using namespaces to extend the functionality of your enum then you can also do something like

    enum Color {
        Red, Green
    }

    export namespace Color {
      export function getInstance(color: string) : Color {
        if(color == 'Red') {
          return Color.Red;
        } else if (color == 'Green') {
          return Color.Green;
        }
      }
    }

and use it like this

  Color.getInstance('Red');

Add support library to Android Studio project

This is way more simpler with Maven dependency feature:

  1. Open File -> Project Structure... menu.
  2. Select Modules in the left pane, choose your project's main module in the middle pane and open Dependencies tab in the right pane.
  3. Click the plus sign in the right panel and select "Maven dependency" from the list. A Maven dependency dialog will pop up.
  4. Enter "support-v4" into the search field and click the icon with magnifying glass.
  5. Select "com.google.android:support-v4:r7@jar" from the drop-down list.
  6. Click "OK".
  7. Clean and rebuild your project.

Hope this will help!

How to add background image for input type="button"?

You need to type it without the word image.

background: url('/image/btn.png') no-repeat;

Tested both ways and this one works.

Example:

<html>
    <head>
        <style type="text/css">
            .button{
                background: url(/image/btn.png) no-repeat;
                cursor:pointer;
                border: none;
            }
        </style>
    </head>
    <body>
        <input type="button" name="button" value="Search" onclick="showUser()" class="button"/>
        <input type="image" name="button" value="Search" onclick="showUser()" class="button"/>
        <input type="submit" name="button" value="Search" onclick="showUser()" class="button"/>
    </body>
</html>

Check if an HTML input element is empty or has no value entered by user

getElementById will return false if the element was not found in the DOM.

var el = document.getElementById("customx");
if (el !== null && el.value === "")
{
  //The element was found and the value is empty.
}

DataTables fixed headers misaligned with columns in wide tables

I have fixed the column issue bu using below concept

$(".panel-title a").click(function(){
    setTimeout( function(){
           $('#tblSValidationFilerGrid').DataTable().search( '' ).draw();
        }, 10 );
})

An implementation of the fast Fourier transform (FFT) in C#

Here's another; a C# port of the Ooura FFT. It's reasonably fast. The package also includes overlap/add convolution and some other DSP stuff, under the MIT license.

https://github.com/hughpyle/inguz-DSPUtil/blob/master/Fourier.cs

How to terminate script execution when debugging in Google Chrome?

In Chrome, there is "Task Manager", accessible via Shift+ESC or through

Menu → More Tools → Task Manager

You can select your page task and end it by pressing "End Process" button.

Chrome Dev Tools - Modify javascript and reload

Great news, the fix is coming in March 2018, see this link: https://developers.google.com/web/updates/2018/01/devtools

"Local Overrides let you make changes in DevTools, and keep those changes across page loads. Previously, any changes that you made in DevTools would be lost when you reloaded the page. Local Overrides work for most file types

How it works:

  • You specify a directory where DevTools should save changes. When you make changes in DevTools, DevTools saves a copy of the modified file to your directory.
  • When you reload the page, DevTools serves the local, modified file, rather than the network resource.

To set up Local Overrides:

  1. Open the Sources panel.
  2. Open the Overrides tab.
  3. Click Setup Overrides.
  4. Select which directory you want to save your changes to.
  5. At the top of your viewport, click Allow to give DevTools read and write access to the directory.
  6. Make your changes."

UPDATE (March 19, 2018): It's live, detailed explanations here: https://developers.google.com/web/updates/2018/01/devtools#overrides

pip issue installing almost any library

As posted above by blackjar, the below lines worked for me

pip --trusted-host pypi.python.org --trusted-host files.pythonhosted.org --trusted-host pypi.org install xxx

You need to give all three --trusted-host options. I was trying with only the first one after looking at the answers but it didn't work for me like that.

A terminal command for a rooted Android to remount /System as read/write

This is what works on my first generation Droid X with Android version 2.3.4. I suspect that this will be universal. Steps:

  1. root system and install su.

  2. Install busybox

  3. Install a terminal program.

  4. to mount system rw first su then

    busybox mount -o rw,remount system

  5. To remount ro

    busybox mount -o ro,remount system

Note that there are no slashes on "system".

SQL Server command line backup statement

Combine Remove Old Backup files with above script then this can perform backup by a scheduler, keep last 10 backup files

echo off
:: set folder to save backup files ex. BACKUPPATH=c:\backup
set BACKUPPATH=<<back up folder here>>

:: set Sql Server location ex. set SERVERNAME=localhost\SQLEXPRESS
set SERVERNAME=<<sql host here>>

:: set Database name to backup
set DATABASENAME=<<db name here>>

:: filename format Name-Date (eg MyDatabase-2009-5-19_1700.bak)
For /f "tokens=2-4 delims=/ " %%a in ('date /t') do (set mydate=%%c-%%a-%%b)
For /f "tokens=1-2 delims=/:" %%a in ("%TIME%") do (set mytime=%%a%%b)

set DATESTAMP=%mydate%_%mytime%
set BACKUPFILENAME=%BACKUPPATH%\%DATABASENAME%-%DATESTAMP%.bak
echo.

sqlcmd -E -S %SERVERNAME% -d master -Q "BACKUP DATABASE [%DATABASENAME%] TO DISK = N'%BACKUPFILENAME%' WITH INIT , NOUNLOAD , NAME = N'%DATABASENAME% backup', NOSKIP , STATS = 10, NOFORMAT"
echo.

:: In this case, we are choosing to keep the most recent 10 files
:: Also, the files we are looking for have a 'bak' extension
for /f "skip=10 delims=" %%F in ('dir %BACKUPPATH%\*.bak /s/b/o-d/a-d') do del "%%F"

ASP.NET IIS Web.config [Internal Server Error]

I got similar error when i run legacy application in Visual studio 2013 iis express and solved the issue by following steps 1.Navigate to "Documents\IISExpress\config" 2.Open "applicationhost.config" using notepad or any preferred editor 3.scroll down and find for section name="anonymousAuthentication" under 4. Update overrideModeDefault="Deny" to "Allow" 5. save the config file 6. Run the legacy application and worked fine for me.

C# Creating an array of arrays

This loops vertically but might work for you.

int rtn = 0;    
foreach(int[] L in lists){
    for(int i = 0; i<L.Length;i++){
          rtn = L[i];
      //Do something with rtn
    }
}

Java - checking if parseInt throws exception

Check if it is integer parseable

public boolean isInteger(String string) {
    try {
        Integer.valueOf(string);
        return true;
    } catch (NumberFormatException e) {
        return false;
    }
}

or use Scanner

Scanner scanner = new Scanner("Test string: 12.3 dog 12345 cat 1.2E-3");

while (scanner.hasNext()) {
    if (scanner.hasNextDouble()) {
        Double doubleValue = scanner.nextDouble();
    } else {
        String stringValue = scanner.next();
    }
}

or use Regular Expression like

private static Pattern doublePattern = Pattern.compile("-?\\d+(\\.\\d*)?");

public boolean isDouble(String string) {
    return doublePattern.matcher(string).matches();
}

Deserializing JSON data to C# using JSON.NET

You can use:

JsonConvert.PopulateObject(json, obj);

here: json is the json string,obj is the target object. See: example

Note: PopulateObject() will not erase obj's list data, after Populate(), obj's list member will contains its original data and data from json string

__FILE__, __LINE__, and __FUNCTION__ usage in C++

In rare cases, it can be useful to change the line that is given by __LINE__ to something else. I've seen GNU configure does that for some tests to report appropriate line numbers after it inserted some voodoo between lines that do not appear in original source files. For example:

#line 100

Will make the following lines start with __LINE__ 100. You can optionally add a new file-name

#line 100 "file.c"

It's only rarely useful. But if it is needed, there are no alternatives I know of. Actually, instead of the line, a macro can be used too which must result in any of the above two forms. Using the boost preprocessor library, you can increment the current line by 50:

#line BOOST_PP_ADD(__LINE__, 50)

I thought it's useful to mention it since you asked about the usage of __LINE__ and __FILE__. One never gets enough surprises out of C++ :)

Edit: @Jonathan Leffler provides some more good use-cases in the comments:

Messing with #line is very useful for pre-processors that want to keep errors reported in the user's C code in line with the user's source file. Yacc, Lex, and (more at home to me) ESQL/C preprocessors do that.

How to test if a string is JSON or not?

I use just 2 lines to perform that:

var isValidJSON = true;
try { JSON.parse(jsonString) } catch { isValidJSON = false }

That's all!

But keep in mind there are 2 traps:
1. JSON.parse(null) returns null
2. Any number or string can be parsed with JSON.parse() method.
   JSON.parse("5") returns 5
   JSON.parse(5) returns 5

Let's some play on code:

// TEST 1
var data = '{ "a": 1 }'

// Avoiding 'null' trap! Null is confirmed as JSON.
var isValidJSON = data ? true : false
try { JSON.parse(data) } catch(e) { isValidJSON = false }

console.log("data isValidJSON: ", isValidJSON);
console.log("data isJSONArray: ", isValidJSON && JSON.parse(data).length ? true : false);

Console outputs:
data isValidJSON:  true
data isJSONArray:  false


// TEST 2
var data2 = '[{ "b": 2 }]'

var isValidJSON = data ? true : false
try { JSON.parse(data2) } catch(e) { isValidJSON = false }

console.log("data2 isValidJSON: ", isValidJSON);
console.log("data2 isJSONArray: ", isValidJSON && JSON.parse(data2).length ? true : false);

Console outputs:
data2 isValidJSON:  true
data2 isJSONArray:  true


// TEST 3
var data3 = '[{ 2 }]'

var isValidJSON = data ? true : false
try { JSON.parse(data3) } catch(e) { isValidJSON = false }

console.log("data3 isValidJSON: ", isValidJSON);
console.log("data3 isJSONArray: ", isValidJSON && JSON.parse(data3).length ? true : false);

Console outputs:
data3 isValidJSON:  false
data3 isJSONArray:  false


// TEST 4
var data4 = '2'

var isValidJSON = data ? true : false
try { JSON.parse(data4) } catch(e) { isValidJSON = false }

console.log("data4 isValidJSON: ", isValidJSON);
console.log("data4 isJSONArray: ", isValidJSON && JSON.parse(data4).length ? true : false);


Console outputs:
data4 isValidJSON:  true
data4 isJSONArray:  false


// TEST 5
var data5 = ''

var isValidJSON = data ? true : false
try { JSON.parse(data5) } catch(e) { isValidJSON = false }

console.log("data5 isValidJSON: ", isValidJSON);
console.log("data5 isJSONArray: ", isValidJSON && JSON.parse(data5).length ? true : false);


Console outputs:
data5 isValidJSON:  false
data5 isJSONArray:  false

// TEST 6
var data6; // undefined

var isValidJSON = data ? true : false
try { JSON.parse(data6) } catch(e) { isValidJSON = false }

console.log("data6 isValidJSON: ", isValidJSON);
console.log("data6 isJSONArray: ", isValidJSON && JSON.parse(data6).length ? true : false);

Console outputs:
data6 isValidJSON:  false
data6 isJSONArray:  false

ReferenceError: describe is not defined NodeJs

You can also do like this:

  var mocha = require('mocha')
  var describe = mocha.describe
  var it = mocha.it
  var assert = require('chai').assert

  describe('#indexOf()', function() {
    it('should return -1 when not present', function() {
      assert.equal([1,2,3].indexOf(4), -1)
    })
  })

Reference: http://mochajs.org/#require

The type java.io.ObjectInputStream cannot be resolved. It is indirectly referenced from required .class files

Okay, this question was a year ago but I recently got this problem as well.

So what I did :

  1. Update tomcat 7 to tomcat 8.
  2. Update to the latest java (java 1.8.0_141).
  3. Update the JRE System Library in Project > Properties > Java Build Path. Make sure it has the latest version which in my case is jre1.8.0_141 (before it was the previous version jre1.8.0_111)

When I did the first two steps it still doesn't remove the error so the last step is important. It didn't automatically change the build path for jre.

Jquery select this + class

Use $(this).find(), or pass this in context, using jQuery context with selector.

Using $(this).find()

$(".class").click(function(){
     $(this).find(".subclass").css("visibility","visible");
});

Using this in context, $( selector, context ), it will internally call find function, so better to use find on first place.

$(".class").click(function(){
     $(".subclass", this).css("visibility","visible");
});

Scanner vs. StringTokenizer vs. String.Split

They're essentially horses for courses.

  • Scanner is designed for cases where you need to parse a string, pulling out data of different types. It's very flexible, but arguably doesn't give you the simplest API for simply getting an array of strings delimited by a particular expression.
  • String.split() and Pattern.split() give you an easy syntax for doing the latter, but that's essentially all that they do. If you want to parse the resulting strings, or change the delimiter halfway through depending on a particular token, they won't help you with that.
  • StringTokenizer is even more restrictive than String.split(), and also a bit fiddlier to use. It is essentially designed for pulling out tokens delimited by fixed substrings. Because of this restriction, it's about twice as fast as String.split(). (See my comparison of String.split() and StringTokenizer.) It also predates the regular expressions API, of which String.split() is a part.

You'll note from my timings that String.split() can still tokenize thousands of strings in a few milliseconds on a typical machine. In addition, it has the advantage over StringTokenizer that it gives you the output as a string array, which is usually what you want. Using an Enumeration, as provided by StringTokenizer, is too "syntactically fussy" most of the time. From this point of view, StringTokenizer is a bit of a waste of space nowadays, and you may as well just use String.split().

Hashmap does not work with int, char

Generic Collection classes cant be used with primitives. Use the Character and Integer wrapper classes instead.

Map<Character , Integer > checkSum = new HashMap<Character, Integer>();

How to simulate target="_blank" in JavaScript

 
<script>
    window.open('http://www.example.com?ReportID=1', '_blank');
</script>

The second parameter is optional and is the name of the target window.

Can a JSON value contain a multiline string

Per the specification, the JSON grammar's char production can take the following values:

  • any-Unicode-character-except-"-or-\-or-control-character
  • \"
  • \\
  • \/
  • \b
  • \f
  • \n
  • \r
  • \t
  • \u four-hex-digits

Newlines are "control characters", so no, you may not have a literal newline within your string. However, you may encode it using whatever combination of \n and \r you require.

The JSONLint tool confirms that your JSON is invalid.

And, if you want to write newlines inside your JSON syntax without actually including newlines in the data, then you're doubly out of luck. While JSON is intended to be human-friendly to a degree, it is still data and you're trying to apply arbitrary formatting to that data. That is absolutely not what JSON is about.

Formatting Numbers by padding with leading zeros in SQL Server

Change the number 6 to whatever your total length needs to be:

SELECT REPLICATE('0',6-LEN(EmployeeId)) + EmployeeId

If the column is an INT, you can use RTRIM to implicitly convert it to a VARCHAR 

SELECT REPLICATE('0',6-LEN(RTRIM(EmployeeId))) + RTRIM(EmployeeId)

And the code to remove these 0s and get back the 'real' number:

SELECT RIGHT(EmployeeId,(LEN(EmployeeId) - PATINDEX('%[^0]%',EmployeeId)) + 1)

How to use string.substr() function?

You can get the above output using following code in c

#include<stdio.h>
#include<conio.h>
#include<string.h>
int main()
{
  char *str;
  clrscr();
  printf("\n Enter the string");
  gets(str);
  for(int i=0;i<strlen(str)-1;i++)
  {
    for(int j=i;j<=i+1;j++)
      printf("%c",str[j]);
    printf("\t");
  }
  getch();
  return 0;
}

How to wait 5 seconds with jQuery?

Have been using this one for a message overlay that can be closed immediately on click or it does an autoclose after 10 seconds.

button = $('.status-button a', whatever);
if(button.hasClass('close')) {
  button.delay(10000).queue(function() {
    $(this).click().dequeue();
  });
}

Create random list of integers in Python

It is not entirely clear what you want, but I would use numpy.random.randint:

import numpy.random as nprnd
import timeit

t1 = timeit.Timer('[random.randint(0, 1000) for r in xrange(10000)]', 'import random') # v1

### Change v2 so that it picks numbers in (0, 10000) and thus runs...
t2 = timeit.Timer('random.sample(range(10000), 10000)', 'import random') # v2
t3 = timeit.Timer('nprnd.randint(1000, size=10000)', 'import numpy.random as nprnd') # v3

print t1.timeit(1000)/1000
print t2.timeit(1000)/1000
print t3.timeit(1000)/1000

which gives on my machine:

0.0233682730198
0.00781716918945
0.000147947072983

Note that randint is very different from random.sample (in order for it to work in your case I had to change the 1,000 to 10,000 as one of the commentators pointed out -- if you really want them from 0 to 1,000 you could divide by 10).

And if you really don't care what distribution you are getting then it is possible that you either don't understand your problem very well, or random numbers -- with apologies if that sounds rude...

XMLHttpRequest cannot load an URL with jQuery

In new jQuery 1.5 you can use:

$.ajax({
    type: "GET",
    url: "http://localhost:99000/Services.svc/ReturnPersons",
    dataType: "jsonp",
    success: readData(data),
    error: function (xhr, ajaxOptions, thrownError) {
      alert(xhr.status);
      alert(thrownError);
    }
})

How do I print out the contents of an object in Rails for easy debugging?

inspect is great but sometimes not good enough. E.g. BigDecimal prints like this: #<BigDecimal:7ff49f5478b0,'0.1E2',9(18)>.

To have full control over what's printed you could redefine to_s or inspect methods. Or create your own one to not confuse future devs too much.

  class Something < ApplicationRecord

    def to_s
      attributes.map{ |k, v| { k => v.to_s } }.inject(:merge)
    end

  end

This will apply a method (i.e. to_s) to all attributes. This example will get rid of the ugly BigDecimals.

You can also redefine a handful of attributes only:

  def to_s
    attributes.merge({ my_attribute: my_attribute.to_s })
  end

You can also create a mix of the two or somehow add associations.

Change directory command in Docker?

To change into another directory use WORKDIR. All the RUN, CMD and ENTRYPOINT commands after WORKDIR will be executed from that directory.

RUN git clone XYZ 
WORKDIR "/XYZ"
RUN make

Create dynamic variable name

This is not possible, it will give you a compile time error,

You can use array for this type of requirement .

For your Reference :

http://msdn.microsoft.com/en-us/library/aa288453%28v=vs.71%29.aspx

How can I replace a newline (\n) using sed?

@OP, if you want to replace newlines in a file, you can just use dos2unix (or unix2dox)

dos2unix yourfile yourfile

How do I iterate through each element in an n-dimensional matrix in MATLAB?

these solutions are more faster (about 11%) than using numel;)

for idx = reshape(array,1,[]),
     element = element + idx;
end

or 

for idx = array(:)',
    element = element + idx;
end

UPD. tnx @rayryeng for detected error in last answer

Disclaimer

The timing information that this post has referenced is incorrect and inaccurate due to a fundamental typo that was made (see comments stream below as well as the edit history - specifically look at the first version of this answer). Caveat Emptor.

Removing nan values from an array

Doing the above :

x = x[~numpy.isnan(x)]

or

x = x[numpy.logical_not(numpy.isnan(x))]

I found that resetting to the same variable (x) did not remove the actual nan values and had to use a different variable. Setting it to a different variable removed the nans. e.g. 

y = x[~numpy.isnan(x)]

Use chrome as browser in C#?

I use Awesomium, I think it is better than GeckoFX/WebKit http://awesomium.com

What is duck typing?

Tree Traversal with duck typing technique

def traverse(t):
    try:
        t.label()
    except AttributeError:
        print(t, end=" ")
    else:
        # Now we know that t.node is defined
        print('(', t.label(), end=" ")
        for child in t:
            traverse(child)
        print(')', end=" ")

C - function inside struct

How about this?

#include <stdio.h>

typedef struct hello {
    int (*someFunction)();
} hello;

int foo() {
    return 0;
}

hello Hello() {
    struct hello aHello;
    aHello.someFunction = &foo;
    return aHello;
}

int main()
{
    struct hello aHello = Hello();
    printf("Print hello: %d\n", aHello.someFunction());

    return 0;
}

Serving favicon.ico in ASP.NET MVC

Found that in .Net Core, placing the favicon.ico in /lib rather than wwwroot fixes the issue

Differences between contentType and dataType in jQuery ajax function

From the documentation:

contentType (default: 'application/x-www-form-urlencoded; charset=UTF-8')

Type: String

When sending data to the server, use this content type. Default is "application/x-www-form-urlencoded; charset=UTF-8", which is fine for most cases. If you explicitly pass in a content-type to $.ajax(), then it'll always be sent to the server (even if no data is sent). If no charset is specified, data will be transmitted to the server using the server's default charset; you must decode this appropriately on the server side.

and:

dataType (default: Intelligent Guess (xml, json, script, or html))

Type: String

The type of data that you're expecting back from the server. If none is specified, jQuery will try to infer it based on the MIME type of the response (an XML MIME type will yield XML, in 1.4 JSON will yield a JavaScript object, in 1.4 script will execute the script, and anything else will be returned as a string).

They're essentially the opposite of what you thought they were.

How to set combobox default value?

Suppose you bound your combobox to a List<Person>

List<Person> pp = new List<Person>();
pp.Add(new Person() {id = 1, name="Steve"});
pp.Add(new Person() {id = 2, name="Mark"});
pp.Add(new Person() {id = 3, name="Charles"});

cbo1.DisplayMember = "name";
cbo1.ValueMember = "id";
cbo1.DataSource = pp;

At this point you cannot set the Text property as you like, but instead you need to add an item to your list before setting the datasource 

pp.Insert(0, new Person() {id=-1, name="--SELECT--"});
cbo1.DisplayMember = "name";
cbo1.ValueMember = "id";
cbo1.DataSource = pp;
cbo1.SelectedIndex = 0;

Of course this means that you need to add a checking code when you try to use the info from the combobox

if(cbo1.SelectedValue != null && Convert.ToInt32(cbo1.SelectedValue) == -1)
    MessageBox.Show("Please select a person name");
else
    ......

The code is the same if you use a DataTable instead of a list. You need to add a fake row at the first position of the Rows collection of the datatable and set the initial index of the combobox to make things clear. The only thing you need to look at are the name of the datatable columns and which columns should contain a non null value before adding the row to the collection

In a table with three columns like ID, FirstName, LastName with ID,FirstName and LastName required you need to

DataRow row = datatable.NewRow();
row["ID"] = -1;
row["FirstName"] = "--Select--";    
row["LastName"] = "FakeAddress";
dataTable.Rows.InsertAt(row, 0);

Insertion sort vs Bubble Sort Algorithms

Insertion sort can be resumed as "Look for the element which should be at first position(the minimum), make some space by shifting next elements, and put it at first position. Good. Now look at the element which should be at 2nd...." and so on...

Bubble sort operate differently which can be resumed as "As long as I find two adjacent elements which are in the wrong order, I swap them".

What is App.config in C#.NET? How to use it?

At its simplest, the app.config is an XML file with many predefined configuration sections available and support for custom configuration sections. A "configuration section" is a snippet of XML with a schema meant to store some type of information.

Settings can be configured using built-in configuration sections such as connectionStrings or appSettings. You can add your own custom configuration sections; this is an advanced topic, but very powerful for building strongly-typed configuration files.

Web applications typically have a web.config, while Windows GUI/service applications have an app.config file.

Application-level config files inherit settings from global configuration files, e.g. the machine.config.

Reading from the App.Config

Connection strings have a predefined schema that you can use. Note that this small snippet is actually a valid app.config (or web.config) file:

<?xml version="1.0"?>
<configuration>
    <connectionStrings>   
        <add name="MyKey" 
             connectionString="Data Source=localhost;Initial Catalog=ABC;"
             providerName="System.Data.SqlClient"/>
    </connectionStrings>
</configuration>

Once you have defined your app.config, you can read it in code using the ConfigurationManager class. Don't be intimidated by the verbose MSDN examples; it's actually quite simple.

string connectionString = ConfigurationManager.ConnectionStrings["MyKey"].ConnectionString;

Writing to the App.Config

Frequently changing the *.config files is usually not a good idea, but it sounds like you only want to perform one-time setup.

See: Change connection string & reload app.config at run time which describes how to update the connectionStrings section of the *.config file at runtime.

Note that ideally you would perform such configuration changes from a simple installer.

Location of the App.Config at Runtime

Q: Suppose I manually change some <value> in app.config, save it and then close it. Now when I go to my bin folder and launch the .exe file from here, why doesn't it reflect the applied changes?

A: When you compile an application, its app.config is copied to the bin directory1 with a name that matches your exe. For example, if your exe was named "test.exe", there should be a "text.exe.config" in your bin directory. You can change the configuration without a recompile, but you will need to edit the config file that was created at compile time, not the original app.config.

1: Note that web.config files are not moved, but instead stay in the same location at compile and deployment time. One exception to this is when a web.config is transformed.

.NET Core

New configuration options were introduced with .NET Core. The way that *.config files works does not appear to have changed, but developers are free to choose new, more flexible configuration paradigms.

What are the basic rules and idioms for operator overloading?

Why can't operator<< function for streaming objects to std::cout or to a file be a member function?

Let's say you have:

struct Foo
{
   int a;
   double b;

   std::ostream& operator<<(std::ostream& out) const
   {
      return out << a << " " << b;
   }
};

Given that, you cannot use:

Foo f = {10, 20.0};
std::cout << f;

Since operator<< is overloaded as a member function of Foo, the LHS of the operator must be a Foo object. Which means, you will be required to use:

Foo f = {10, 20.0};
f << std::cout

which is very non-intuitive.

If you define it as a non-member function,

struct Foo
{
   int a;
   double b;
};

std::ostream& operator<<(std::ostream& out, Foo const& f)
{
   return out << f.a << " " << f.b;
}

You will be able to use:

Foo f = {10, 20.0};
std::cout << f;

which is very intuitive.

Bootstrap 3.0 Sliding Menu from left

I believe that although javascript is an option here, you have a smoother animation through forcing hardware accelerate with CSS3. You can achieve this by setting the following CSS3 properties on the moving div:

div.hardware-accelarate {
     -webkit-transform: translate3d(0,0,0);
        -moz-transform: translate3d(0,0,0);
         -ms-transform: translate3d(0,0,0);
          -o-transform: translate3d(0,0,0);
             transform: translate3d(0,0,0);
}

I've made a plunkr setup for ya'll to test and tweak...

Android. Fragment getActivity() sometimes returns null

Ok, I know that this question is actually solved but I decided to share my solution for this. I've created abstract parent class for my Fragment:

public abstract class ABaseFragment extends Fragment{

    protected IActivityEnabledListener aeListener;

    protected interface IActivityEnabledListener{
        void onActivityEnabled(FragmentActivity activity);
    }

    protected void getAvailableActivity(IActivityEnabledListener listener){
        if (getActivity() == null){
            aeListener = listener;

        } else {
            listener.onActivityEnabled(getActivity());
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        if (aeListener != null){
            aeListener.onActivityEnabled((FragmentActivity) activity);
            aeListener = null;
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);

        if (aeListener != null){
            aeListener.onActivityEnabled((FragmentActivity) context);
            aeListener = null;
        }
    }
}

As you can see, I've added a listener so, whenever I'll need to get Fragments Activity instead of standard getActivity(), I'll need to call

 getAvailableActivity(new IActivityEnabledListener() {
        @Override
        public void onActivityEnabled(FragmentActivity activity) {
            // Do manipulations with your activity
        }
    });

How do you pull first 100 characters of a string in PHP

 
$x = '1234567';

echo substr ($x, 0, 3);  // outputs 123

echo substr ($x, 1, 1);  // outputs 2

echo substr ($x, -2);    // outputs 67

echo substr ($x, 1);     // outputs 234567

echo substr ($x, -2, 1); // outputs 6

Install IPA with iTunes 11

For OS X Yosemite and above, and Xcode 6+

Open Xcode > Window > Devices

Choose your device. You can see the installed application list and add a new one by hitting +

screenshot of Xcode Devices

What is a good naming convention for vars, methods, etc in C++?

For what it is worth, Bjarne Stroustrup, the original author of C++ has his own favorite style, described here: http://www.stroustrup.com/bs_faq2.html

What is the Record type in typescript?

A Record lets you create a new type from a Union. The values in the Union are used as attributes of the new type.

For example, say I have a Union like this:

type CatNames = "miffy" | "boris" | "mordred";

Now I want to create an object that contains information about all the cats, I can create a new type using the values in the CatName Union as keys.

type CatList = Record<CatNames, {age: number}>

If I want to satisfy this CatList, I must create an object like this:

const cats:CatList = {
  miffy: { age:99 },
  boris: { age:16 },
  mordred: { age:600 }
}

You get very strong type safety:

  • If I forget a cat, I get an error.
  • If I add a cat that's not allowed, I get an error.
  • If I later change CatNames, I get an error. This is especially useful because CatNames is likely imported from another file, and likely used in many places.

Real-world React example.

I used this recently to create a Status component. The component would receive a status prop, and then render an icon. I've simplified the code quite a lot here for illustrative purposes

I had a union like this:

type Statuses = "failed" | "complete";

I used this to create an object like this:

const icons: Record<
  Statuses,
  { iconType: IconTypes; iconColor: IconColors }
> = {
  failed: {
    iconType: "warning",
    iconColor: "red"
  },
  complete: {
    iconType: "check",
    iconColor: "green"
  };

I could then render by destructuring an element from the object into props, like so:

const Status = ({status}) => <Icon {...icons[status]} />

If the Statuses union is later extended or changed, I know my Status component will fail to compile and I'll get an error that I can fix immediately. This allows me to add additional error states to the app.

Note that the actual app had dozens of error states that were referenced in multiple places, so this type safety was extremely useful.

convert a JavaScript string variable to decimal/money

I made a little helper function to do this and catch all malformed data

function convertToPounds(str) { 
    var n = Number.parseFloat(str);
    if(!str || isNaN(n) || n < 0) return 0;
    return n.toFixed(2);
}

Demo is here

Switch/toggle div (jQuery)

You could write a simple jQuery plugin to do this. The plugin would look like:

(function($) {
    $.fn.expandcollapse = function() {
        return this.each(function() {
            obj = $(this);
            switch (obj.css("display")) {
                case "block":
                    displayValue = "none";
                    break;

                case "none":
                default:
                    displayValue = "block";
            }

            obj.css("display", displayValue);
        });
    };
} (jQuery));

Then wire the plugin up to the click event for the anchor tag:

$(document).ready(function() {
    $("#mylink").click(function() {
        $("div").expandcollapse();
    });
});

Providing that you set the initial 'display' attributes for each div to be 'block' and 'none' respectively, they should switch to being shown/hidden when the link is clicked.

What is the best way to insert source code examples into a Microsoft Word document?

Use this - http://hilite.me/

hilite.me converts your code snippets into pretty-printed HTML format, easily embeddable into blog posts, emails and websites.

How: Just copy the source code to the left pane, select the language and the color scheme, and click "Highlight!". The HTML from the right pane can now be pasted to your blog or email, no external CSS or Javascript files are required.

For Microsoft Word document: Copy the the content from the Preview section and paste to your Microsoft Word document.

3 sections : Source Code , HTML and Preview

How to resize image automatically on browser width resize but keep same height?

I've used Perfect Full Page Background Image to accomplish this on a previous site.

You can use background-size: cover; if you only need to support modern browsers.

SQL Server: converting UniqueIdentifier to string in a case statement

Instead of Str(RequestID), try convert(varchar(38), RequestID)

What's the meaning of "=>" (an arrow formed from equals & greater than) in JavaScript?

I've read, this is a symbol of Arrow Functions in ES6

this 

var a2 = a.map(function(s){ return s.length });

using Arrow Function can be written as

var a3 = a.map( s => s.length );

MDN Docs

How to use php serialize() and unserialize()

Most storage mediums can store string types. They can not directly store a PHP data structure such as an array or object, and they shouldn't, as that would couple the data storage medium with PHP.

Instead, serialize() allows you to store one of these structs as a string. It can be de-serialised from its string representation with unserialize().

If you are familiar with json_encode() and json_decode() (and JSON in general), the concept is similar.

Using logging in multiple modules

There are several answers. i ended up with a similar yet different solution that makes sense to me, maybe it will make sense to you as well. My main objective was to be able to pass logs to handlers by their level (debug level logs to the console, warnings and above to files):

from flask import Flask
import logging
from logging.handlers import RotatingFileHandler

app = Flask(__name__)

# make default logger output everything to the console
logging.basicConfig(level=logging.DEBUG)

rotating_file_handler = RotatingFileHandler(filename="logs.log")
rotating_file_handler.setLevel(logging.INFO)

app.logger.addHandler(rotating_file_handler)

created a nice util file named logger.py:

import logging

def get_logger(name):
    return logging.getLogger("flask.app." + name)

the flask.app is a hardcoded value in flask. the application logger is always starting with flask.app as its the module's name.

now, in each module, i'm able to use it in the following mode:

from logger import get_logger
logger = get_logger(__name__)

logger.info("new log")

This will create a new log for "app.flask.MODULE_NAME" with minimum effort.

forward declaration of a struct in C?

Try this

#include <stdio.h>

struct context;

struct funcptrs{
  void (*func0)(struct context *ctx);
  void (*func1)(void);
};

struct context{
    struct funcptrs fps;
}; 

void func1 (void) { printf( "1\n" ); }
void func0 (struct context *ctx) { printf( "0\n" ); }

void getContext(struct context *con){
    con->fps.func0 = func0;  
    con->fps.func1 = func1;  
}

int main(int argc, char *argv[]){
 struct context c;
   c.fps.func0 = func0;
   c.fps.func1 = func1;
   getContext(&c);
   c.fps.func0(&c);
   getchar();
   return 0;
}

How do I get a list of files in a directory in C++?

C++11/Linux version:

#include <dirent.h>

if (auto dir = opendir("some_dir/")) {
    while (auto f = readdir(dir)) {
        if (!f->d_name || f->d_name[0] == '.')
            continue; // Skip everything that starts with a dot

        printf("File: %s\n", f->d_name);
    }
    closedir(dir);
}

The developers of this app have not set up this app properly for Facebook Login?

do setup by following bellow link and domain name you need to mention as like wht you have mentioned in facebook app domain name.

Go to https://developers.facebook.com/

Click on the Apps menu on the top bar.

How to check whether a Button is clicked by using JavaScript

This will do it

<input id="button" type="submit" name="button" onclick="myFunction();" value="enter"/>

<script>
function myFunction(){
    alert("You button was pressed");
};   
</script>

Display curl output in readable JSON format in Unix shell script

Motivation: You want to print prettify JSON response after curl command request.

Solution: json_pp - commandline tool that converts between some input and output formats (one of them is JSON). This program was copied from json_xs and modified. The default input format is json and the default output format is json with pretty option.

Synposis: json_pp [-v] [-f from_format] [-t to_format] [-json_opt options_to_json1[,options_to_json2[,...]]]

Formula: <someCommand> | json_pp

Example:

Request

curl -X https://jsonplaceholder.typicode.com/todos/1 | json_pp

Response

{
   "completed" : false,
   "id" : 1,
   "title" : "delectus aut autem",
   "userId" : 1
}

How can I remove an element from a list, with lodash?

Just use vanilla JS. You can use splice to remove the element:

obj.subTopics.splice(1, 1);

Demo

Differences between INDEX, PRIMARY, UNIQUE, FULLTEXT in MySQL?

All of these are kinds of indices.

primary: must be unique, is an index, is (likely) the physical index, can be only one per table.

unique: as it says. You can't have more than one row with a tuple of this value. Note that since a unique key can be over more than one column, this doesn't necessarily mean that each individual column in the index is unique, but that each combination of values across these columns is unique.

index: if it's not primary or unique, it doesn't constrain values inserted into the table, but it does allow them to be looked up more efficiently.

fulltext: a more specialized form of indexing that allows full text search. Think of it as (essentially) creating an "index" for each "word" in the specified column.

Rounding integer division (instead of truncating)

 
double a=59.0/4;
int b=59/4;
if(a-b>=0.5){
    b++;
}
printf("%d",b);
  1. let exact float value of 59.0/4 be x(here it is 14.750000)
  2. let smallest integer less than x be y(here it is 14)
  3. if x-y<0.5 then y is the solution
  4. else y+1 is the solution

Bootstrap number validation

You should use jquery validation because if you use type="number" then you can also enter "E" character in input type, which is not correct.

Solution:

HTML

<input class="form-control floatNumber" name="energy1_total_power_generated" type="text" required="" >

JQuery

//integer value validation
$('input.floatNumber').on('input', function() {
    this.value = this.value.replace(/[^0-9.]/g,'').replace(/(\..*)\./g, '$1');
});

How to access parameters in a Parameterized Build?

As per Pipeline plugin tutorial:

If you have configured your pipeline to accept parameters when it is built — Build with Parameters — they are accessible as Groovy variables of the same name.

So try to access the variable directly, e.g.:

node()
{
     print "DEBUG: parameter foo = " + foo
     print "DEBUG: parameter bar = ${bar}"
}

When to use %r instead of %s in Python?

This is a version of Ben James's answer, above:

>>> import datetime
>>> x = datetime.date.today()
>>> print x
2013-01-11
>>> 
>>> 
>>> print "Today's date is %s ..." % x
Today's date is 2013-01-11 ...
>>> 
>>> print "Today's date is %r ..." % x
Today's date is datetime.date(2013, 1, 11) ...
>>>

When I ran this, it helped me see the usefulness of %r.

How to define custom configuration variables in rails

In Rails 3, Application specific custom configuration data can be placed in the application configuration object. The configuration can be assigned in the initialization files or the environment files -- say for a given application MyApp:

MyApp::Application.config.custom_config_variable = :my_config_setting

or

Rails.configuration.custom_config_variable = :my_config_setting

To read the setting, simply call the configuration variable without setting it:

Rails.configuration.custom_config_variable
=> :my_config_setting

UPDATE Rails 4

In Rails 4 there a new way for this => http://guides.rubyonrails.org/configuring.html#custom-configuration

enter image description here

How to deploy correctly when using Composer's develop / production switch?

Now require-dev is enabled by default, for local development you can do composer install and composer update without the --dev option.

When you want to deploy to production, you'll need to make sure composer.lock doesn't have any packages that came from require-dev.

You can do this with

composer update --no-dev

Once you've tested locally with --no-dev you can deploy everything to production and install based on the composer.lock. You need the --no-dev option again here, otherwise composer will say "The lock file does not contain require-dev information".

composer install --no-dev

Note: Be careful with anything that has the potential to introduce differences between dev and production! I generally try to avoid require-dev wherever possible, as including dev tools isn't a big overhead.

How to properly overload the << operator for an ostream?

Just telling you about one other possibility: I like using friend definitions for that:

namespace Math
{
    class Matrix
    {
    public:

        [...]

        friend std::ostream& operator<< (std::ostream& stream, const Matrix& matrix) {
            [...]
        }
    };
}

The function will be automatically targeted into the surrounding namespace Math (even though its definition appears within the scope of that class) but will not be visible unless you call operator<< with a Matrix object which will make argument dependent lookup find that operator definition. That can sometimes help with ambiguous calls, since it's invisible for argument types other than Matrix. When writing its definition, you can also refer directly to names defined in Matrix and to Matrix itself, without qualifying the name with some possibly long prefix and providing template parameters like Math::Matrix<TypeA, N>.

How do I properly force a Git push?

use this following command:

git push -f origin master

How to invoke function from external .c file in C?

you shouldn't include c-files in other c-files. Instead create a header file where the function is declared that you want to call. Like so: file ClasseAusiliaria.h:

int addizione(int a, int b); // this tells the compiler that there is a function defined and the linker will sort the right adress to call out.

In your Main.c file you can then include the newly created header file: 

#include <stdlib.h>
#include <stdio.h>
#include <ClasseAusiliaria.h>

int main(void)
{
    int risultato;
    risultato = addizione(5,6);
    printf("%d\n",risultato);
}

How to read a file in reverse order?

you would need to first open your file in read format, save it to a variable, then open the second file in write format where you would write or append the variable using a the [::-1] slice, completely reversing the file. You can also use readlines() to make it into a list of lines, which you can manipulate

def copy_and_reverse(filename, newfile):
    with open(filename) as file:
        text = file.read()
    with open(newfile, "w") as file2:
        file2.write(text[::-1])

Issue with parsing the content from json file with Jackson & message- JsonMappingException -Cannot deserialize as out of START_ARRAY token

I sorted this problem as verifying the json from JSONLint.com and then, correcting it. And this is code for the same.

String jsonStr = "[{\r\n" + "\"name\":\"New York\",\r\n" + "\"number\": \"732921\",\r\n"+ "\"center\": {\r\n" + "\"latitude\": 38.895111,\r\n"  + " \"longitude\": -77.036667\r\n" + "}\r\n" + "},\r\n" + " {\r\n"+ "\"name\": \"San Francisco\",\r\n" +\"number\":\"298732\",\r\n"+ "\"center\": {\r\n" + "    \"latitude\": 37.783333,\r\n"+ "\"longitude\": -122.416667\r\n" + "}\r\n" + "}\r\n" + "]";

ObjectMapper mapper = new ObjectMapper();
MyPojo[] jsonObj = mapper.readValue(jsonStr, MyPojo[].class);

for (MyPojo itr : jsonObj) {
    System.out.println("Val of name is: " + itr.getName());
    System.out.println("Val of number is: " + itr.getNumber());
    System.out.println("Val of latitude is: " + 
        itr.getCenter().getLatitude());
    System.out.println("Val of longitude is: " + 
        itr.getCenter().getLongitude() + "\n");
}

Note: MyPojo[].class is the class having getter and setter of json properties.

Result:

Val of name is: New York
Val of number is: 732921
Val of latitude is: 38.895111
Val of longitude is: -77.036667
Val of name is: San Francisco
Val of number is: 298732
Val of latitude is: 37.783333
Val of longitude is: -122.416667

Incrementing in C++ - When to use x++ or ++x?

Understanding the language syntax is important when considering clarity of code. Consider copying a character string, for example with post-increment:

char a[256] = "Hello world!";
char b[256];
int i = 0;
do {
  b[i] = a[i];
} while (a[i++]);

We want the loop to execute through encountering the zero character (which tests false) at the end of the string. That requires testing the value pre-increment and also incrementing the index. But not necessarily in that order - a way to code this with the pre-increment would be:

int i = -1;
do {
  ++i;
  b[i] = a[i];
} while (a[i]);

It is a matter of taste which is clearer and if the machine has a handfull of registers both should have identical execution time, even if a[i] is a function that is expensive or has side-effects. A significant difference might be the exit value of the index.

What is a classpath and how do I set it?

For linux users, and to sum up and add to what others have said here, you should know the following:

  1. $CLASSPATH is what Java uses to look through multiple directories to find all the different classes it needs for your script (unless you explicitly tell it otherwise with the -cp override). Using -cp requires that you keep track of all the directories manually and copy-paste that line every time you run the program (not preferable IMO).

  2. The colon (":") character separates the different directories. There is only one $CLASSPATH and it has all the directories in it. So, when you run "export CLASSPATH=...." you want to include the current value "$CLASSPATH" in order to append to it. For example:

    export CLASSPATH=.
export CLASSPATH=$CLASSPATH:/usr/share/java/mysql-connector-java-5.1.12.jar

    In the first line above, you start CLASSPATH out with just a simple 'dot' which is the path to your current working directory. With that, whenever you run java it will look in the current working directory (the one you're in) for classes. In the second line above, $CLASSPATH grabs the value that you previously entered (.) and appends the path to a mysql dirver. Now, java will look for the driver AND for your classes.

  3. echo $CLASSPATH

    is super handy, and what it returns should read like a colon-separated list of all the directories, and .jar files, you want java looking in for the classes it needs.

  4. Tomcat does not use CLASSPATH. Read what to do about that here: https://tomcat.apache.org/tomcat-8.0-doc/class-loader-howto.html

bootstrap 4 file input doesn't show the file name

 
$(document).on('change', '.custom-file-input', function (event) {
    $(this).next('.custom-file-label').html(event.target.files[0].name);
})

Best of all worlds. Works on dynamically created inputs, and uses actual file name.

Android: Create a toggle button with image and no text

  1. Can I replace the toggle text with an image

    No, we can not, although we can hide the text by overiding the default style of the toggle button, but still that won't give us a toggle button you want as we can't replace the text with an image.

  2. How can I make a normal toggle button

    Create a file ic_toggle in your res/drawable folder 

    <selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_checked="false"
          android:drawable="@drawable/ic_slide_switch_off" />

    <item android:state_checked="true"
          android:drawable="@drawable/ic_slide_switch_on" />

</selector>

    Here @drawable/ic_slide_switch_on & @drawable/ic_slide_switch_off are images you create.

    Then create another file in the same folder, name it ic_toggle_bg

    <?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:id="@+android:id/background"  
          android:drawable="@android:color/transparent" />

    <item android:id="@+android:id/toggle"
          android:drawable="@drawable/ic_toggle" />

</layer-list>

    Now add to your custom theme, (if you do not have one create a styles.xml file in your res/values/folder)

    <style name="Widget.Button.Toggle" parent="android:Widget">
   <item name="android:background">@drawable/ic_toggle_bg</item>
   <item name="android:disabledAlpha">?android:attr/disabledAlpha</item>
</style>

<style name="toggleButton"  parent="@android:Theme.Black">
   <item name="android:buttonStyleToggle">@style/Widget.Button.Toggle</item>
   <item name="android:textOn"></item>
   <item name="android:textOff"></item>
</style>

    This creates a custom toggle button for you.

  3. How to use it

    Use the custom style and background in your view.

      <ToggleButton
        android:id="@+id/toggleButton"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="right"
        style="@style/toggleButton"
        android:background="@drawable/ic_toggle_bg"/>

How can I find out if an .EXE has Command-Line Options?

Invoke it from the shell, with an argument like /? or --help. Those are the usual help switches.

How to change button text or link text in JavaScript?

You can simply use:

document.getElementById(button_id).innerText = 'Your text here';

If you want to use HTML formatting, use the innerHTML property instead.

Django CSRF Cookie Not Set

This can also occur if CSRF_COOKIE_SECURE = True is set and you are accessing the site non-securely or if CSRF_COOKIE_HTTPONLY = True is set as stated here and here

Skipping error in for-loop

One (dirty) way to do it is to use tryCatch with an empty function for error handling. For example, the following code raises an error and breaks the loop :

for (i in 1:10) {
    print(i)
    if (i==7) stop("Urgh, the iphone is in the blender !")
}

[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
Erreur : Urgh, the iphone is in the blender !

But you can wrap your instructions into a tryCatch with an error handling function that does nothing, for example :

for (i in 1:10) {
  tryCatch({
    print(i)
    if (i==7) stop("Urgh, the iphone is in the blender !")
  }, error=function(e){})
}

[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
[1] 8
[1] 9
[1] 10

But I think you should at least print the error message to know if something bad happened while letting your code continue to run :

for (i in 1:10) {
  tryCatch({
    print(i)
    if (i==7) stop("Urgh, the iphone is in the blender !")
  }, error=function(e){cat("ERROR :",conditionMessage(e), "\n")})
}

[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
ERROR : Urgh, the iphone is in the blender ! 
[1] 8
[1] 9
[1] 10

EDIT : So to apply tryCatch in your case would be something like :

for (v in 2:180){
    tryCatch({
        mypath=file.path("C:", "file1", (paste("graph",names(mydata[columnname]), ".pdf", sep="-")))
        pdf(file=mypath)
        mytitle = paste("anything")
        myplotfunction(mydata[,columnnumber]) ## this function is defined previously in the program
        dev.off()
    }, error=function(e){cat("ERROR :",conditionMessage(e), "\n")})
}

How can I directly view blobs in MySQL Workbench

Doesn't seem to be possible I'm afraid, its listed as a bug in workbench: http://bugs.mysql.com/bug.php?id=50692 It would be very useful though!

How to make the division of 2 ints produce a float instead of another int?

JLS Standard

JLS 7 15.17.2. Division Operator / says:

Integer division rounds toward 0. That is, the quotient produced for operands n and d that are integers after binary numeric promotion (§5.6.2) is an integer value q whose magnitude is as large as possible while satisfying |d · q| = |n|. Moreover, q is positive when |n| = |d| and n and d have the same sign, but q is negative when |n| = |d| and n and d have opposite signs.

This is why 1/2 does not give a float.

Converting just either one to float as in (float)1/2 suffices because 15.17. Multiplicative Operators says:

Binary numeric promotion is performed on the operands

and 5.6.2. Binary Numeric Promotion says:

  • If either operand is of type double, the other is converted to double.
  • Otherwise, if either operand is of type float, the other is converted to float

How to config routeProvider and locationProvider in angularJS?

Try this

If you are deploying your app into the root context (e.g. https://myapp.com/), set the base URL to /:

<head>
  <base href="/">
  ...
</head>

Angular Documentation

How to pass an array to a function in VBA?

Your function worked for me after changing its declaration to this ...

Function processArr(Arr As Variant) As String

You could also consider a ParamArray like this ...

Function processArr(ParamArray Arr() As Variant) As String
    'Dim N As Variant
    Dim N As Long
    Dim finalStr As String
    For N = LBound(Arr) To UBound(Arr)
        finalStr = finalStr & Arr(N)
    Next N
    processArr = finalStr
End Function

And then call the function like this ...

processArr("foo", "bar")

Java, return if trimmed String in List contains String

You can use your own code. You don't need to use the looping structure, if you don't want to use the looping structure as you said above. Only you have to focus to remove space or trim the String of the list.

If you are using java8 you can simply trim the String using the single line of the code:

myList = myList.stream().map(String :: trim).collect(Collectors.toList());

The importance of the above line is, in the future, you can use a List or set as well. Now you can use your own code:

if(myList.contains("A")){
    //true
}else{
    // false
}

Programmatically saving image to Django ImageField

Your can use Django REST framework and python Requests library to Programmatically saving image to Django ImageField

Here is a Example:

import requests


def upload_image():
    # PATH TO DJANGO REST API
    url = "http://127.0.0.1:8080/api/gallery/"

    # MODEL FIELDS DATA
    data = {'first_name': "Rajiv", 'last_name': "Sharma"}

    #  UPLOAD FILES THROUGH REST API
    photo = open('/path/to/photo'), 'rb')
    resume = open('/path/to/resume'), 'rb')
    files = {'photo': photo, 'resume': resume}

    request = requests.post(url, data=data, files=files)
    print(request.status_code, request.reason)

Running an executable in Mac Terminal

To run an executable in mac

1). Move to the path of the file:

cd/PATH_OF_THE_FILE

2). Run the following command to set the file's executable bit using the chmod command:

chmod +x ./NAME_OF_THE_FILE

3). Run the following command to execute the file:

./NAME_OF_THE_FILE

Once you have run these commands, going ahead you just have to run command 3, while in the files path.

Generating PDF files with JavaScript

Another interesting project is texlive.js.

It allows you to compile (La)TeX to PDF in the browser.

How do you make Git work with IntelliJ?

For Linux users, check the value of GIT_HOME in your .env file in the home directory.

  1. Open terminal
  2. Type cd home/<username>/
  3. Open the .env file and check the value of GIT_HOME and select the git path appropriately

PS: If you are not able to find the .env file, click on View on the formatting tool bar, select Show hidden files. You should be able to find the .env file now.

How to keep environment variables when using sudo

For individual variables you want to make available on a one off basis you can make it part of the command.

sudo http_proxy=$http_proxy wget "http://stackoverflow.com"

How to add a boolean datatype column to an existing table in sql?

The answer given by P????? creates a nullable bool, not a bool, which may be fine for you. For example in C# it would create: bool? AdminApprovednot bool AdminApproved.

If you need to create a bool (defaulting to false):

    ALTER TABLE person
    ADD AdminApproved BIT
    DEFAULT 0 NOT NULL;

When should we use intern method of String on String literals

http://en.wikipedia.org/wiki/String_interning

string interning is a method of storing only one copy of each distinct string value, which must be immutable. Interning strings makes some string processing tasks more time- or space-efficient at the cost of requiring more time when the string is created or interned. The distinct values are stored in a string intern pool.

How do I write to the console from a Laravel Controller?

Aha!

This can be done with the following PHP function:

error_log('Some message here.');

Found the answer here: Print something in PHP built-in web server

phpMyAdmin says no privilege to create database, despite logged in as root user

Use these:

  • username : root
  • password : (nothing)

Then you will get the page you want (more options than the admin page) with privileges.

MySQL Insert query doesn't work with WHERE clause

its totall wrong. INSERT QUERY does not have a WHERE clause, Only UPDATE QUERY has it. If you want to add data Where id = 1 then your Query will be 

UPDATE Users SET weight=160, desiredWeight= 145 WHERE id = 1;

how to set the default value to the drop down list control?

After your DataBind():

lstDepartment.SelectedIndex = 0;  //first item

or

lstDepartment.SelectedValue = "Yourvalue"

or 
//add error checking, just an example, FindByValue may return null
lstDepartment.Items.FindByValue("Yourvalue").Selected = true;

or
//add error checking, just an example, FindByText may return null
lstDepartment.Items.FindByText("Yourvalue").Selected = true;

How to split a file into equal parts, without breaking individual lines?

The script isn't even necessary, split(1) supports the wanted feature out of the box:
split -l 75 auth.log auth.log. The above command splits the file in chunks of 75 lines a piece, and outputs file on the form: auth.log.aa, auth.log.ab, ...

wc -l on the original file and output gives:

  321 auth.log
   75 auth.log.aa
   75 auth.log.ab
   75 auth.log.ac
   75 auth.log.ad
   21 auth.log.ae
  642 total

Histogram using gnuplot?

As usual, Gnuplot is a fantastic tool for plotting sweet looking graphs and it can be made to perform all sorts of calculations. However, it is intended to plot data rather than to serve as a calculator and it is often easier to use an external programme (e.g. Octave) to do the more "complicated" calculations, save this data in a file, then use Gnuplot to produce the graph. For the above problem, check out the "hist" function is Octave using [freq,bins]=hist(data), then plot this in Gnuplot using 

set style histogram rowstacked gap 0
set style fill solid 0.5 border lt -1
plot "./data.dat" smooth freq with boxes

How do you put an image file in a json object?

I can think of doing it in two ways:

1.

Storing the file in file system in any directory (say dir1) and renaming it which ensures that the name is unique for every file (may be a timestamp) (say xyz123.jpg), and then storing this name in some DataBase. Then while generating the JSON you pull this filename and generate a complete URL (which will be http://example.com/dir1/xyz123.png )and insert it in the JSON.

2.

Base 64 Encoding, It's basically a way of encoding arbitrary binary data in ASCII text. It takes 4 characters per 3 bytes of data, plus potentially a bit of padding at the end. Essentially each 6 bits of the input is encoded in a 64-character alphabet. The "standard" alphabet uses A-Z, a-z, 0-9 and + and /, with = as a padding character. There are URL-safe variants. So this approach will allow you to put your image directly in the MongoDB, while storing it Encode the image and decode while fetching it, it has some of its own drawbacks:

  • base64 encoding makes file sizes roughly 33% larger than their original binary representations, which means more data down the wire (this might be exceptionally painful on mobile networks)
  • data URIs aren’t supported on IE6 or IE7.
  • base64 encoded data may possibly take longer to process than binary data.

Source

Converting Image to DATA URI

A.) Canvas

Load the image into an Image-Object, paint it to a canvas and convert the canvas back to a dataURL.

function convertToDataURLviaCanvas(url, callback, outputFormat){
    var img = new Image();
    img.crossOrigin = 'Anonymous';
    img.onload = function(){
        var canvas = document.createElement('CANVAS');
        var ctx = canvas.getContext('2d');
        var dataURL;
        canvas.height = this.height;
        canvas.width = this.width;
        ctx.drawImage(this, 0, 0);
        dataURL = canvas.toDataURL(outputFormat);
        callback(dataURL);
        canvas = null; 
    };
    img.src = url;
}

Usage

convertToDataURLviaCanvas('http://bit.ly/18g0VNp', function(base64Img){
    // Base64DataURL
});

Supported input formats image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx

B.) FileReader

Load the image as blob via XMLHttpRequest and use the FileReader API to convert it to a data URL.

function convertFileToBase64viaFileReader(url, callback){
    var xhr = new XMLHttpRequest();
    xhr.responseType = 'blob';
    xhr.onload = function() {
      var reader  = new FileReader();
      reader.onloadend = function () {
          callback(reader.result);
      }
      reader.readAsDataURL(xhr.response);
    };
    xhr.open('GET', url);
    xhr.send();
}

This approach

  • lacks in browser support
  • has better compression
  • works for other file types as well.

Usage

convertFileToBase64viaFileReader('http://bit.ly/18g0VNp', function(base64Img){
    // Base64DataURL
});

Source

Case Function Equivalent in Excel

Without reference to the original problem (which I suspect is long since solved), I very recently discovered a neat trick that makes the Choose function work exactly like a select case statement without any need to modify data. There's only one catch: only one of your choose conditions can be true at any one time.

The syntax is as follows:

CHOOSE( 
    (1 * (CONDITION_1)) + (2 * (CONDITION_2)) + ... + (N * (CONDITION_N)),
    RESULT_1, RESULT_2, ... , RESULT_N
)

On the assumption that only one of the conditions 1 to N will be true, everything else is 0, meaning the numeric value will correspond to the appropriate result.

If you are not 100% certain that all conditions are mutually exclusive, you might prefer something like:

CHOOSE(
    (1 * TEST1) + (2 * TEST2) + (4 * TEST3) + (8 * TEST4) ... (2^N * TESTN)
    OUT1, OUT2, , OUT3, , , , OUT4 , , <LOTS OF COMMAS> , OUT5
)

That said, if Excel has an upper limit on the number of arguments a function can take, you'd hit it pretty quickly.

Honestly, can't believe it's taken me years to work it out, but I haven't seen it before, so figured I'd leave it here to help others.

EDIT: Per comment below from @aTrusty: Silly numbers of commas can be eliminated (and as a result, the choose statement would work for up to 254 cases) by using a formula of the following form:

CHOOSE(
    1 + LOG(1 + (2*TEST1) + (4*TEST2) + (8*TEST3) + (16*TEST4),2), 
    OTHERWISE, RESULT1, RESULT2, RESULT3, RESULT4
)

Note the second argument to the LOG clause, which puts it in base 2 and makes the whole thing work.

Edit: Per David's answer, there's now an actual switch statement if you're lucky enough to be working on office 2016. Aside from difficulty in reading, this also means you get the efficiency of switch, not just the behaviour!

Find document with array that contains a specific value

I know this topic is old, but for future people who could wonder the same question, another incredibly inefficient solution could be to do:

PersonModel.find({$where : 'this.favouriteFoods.indexOf("sushi") != -1'});

This avoids all optimisations by MongoDB so do not use in production code.

How to darken an image on mouseover?

Create black png with lets say 50% transparency. Overlay this on mouseover.

Using UPDATE in stored procedure with optional parameters

 
UPDATE tbl_ClientNotes 
SET ordering=@ordering, title=@title, content=@content 
WHERE id=@id 
AND @ordering IS NOT NULL
AND @title IS NOT NULL
AND @content IS NOT NULL

Or if you meant you only want to update individual columns you would use the post above mine. I read it as do not update if any values are null

In C#, how to check whether a string contains an integer?

You can check if string contains numbers only:

Regex.IsMatch(myStringVariable, @"^-?\d+$")

But number can be bigger than Int32.MaxValue or less than Int32.MinValue - you should keep that in mind.

Another option - create extension method and move ugly code there:

public static bool IsInteger(this string s)
{
   if (String.IsNullOrEmpty(s))
       return false;

   int i;
   return Int32.TryParse(s, out i);
}

That will make your code more clean:

if (myStringVariable.IsInteger())
    // ...

What are the rules for JavaScript's automatic semicolon insertion (ASI)?

I could not understand those 3 rules in the specs too well -- hope to have something that is more plain English -- but here is what I gathered from JavaScript: The Definitive Guide, 6th Edition, David Flanagan, O'Reilly, 2011:

Quote:

JavaScript does not treat every line break as a semicolon: it usually treats line breaks as semicolons only if it can’t parse the code without the semicolons.

Another quote: for the code

var a
a
=
3 console.log(a)

JavaScript does not treat the second line break as a semicolon because it can continue parsing the longer statement a = 3;

and:

two exceptions to the general rule that JavaScript interprets line breaks as semicolons when it cannot parse the second line as a continuation of the statement on the first line. The first exception involves the return, break, and continue statements

... If a line break appears after any of these words ... JavaScript will always interpret that line break as a semicolon.

... The second exception involves the ++ and -- operators ... If you want to use either of these operators as postfix operators, they must appear on the same line as the expression they apply to. Otherwise, the line break will be treated as a semicolon, and the ++ or -- will be parsed as a prefix operator applied to the code that follows. Consider this code, for example:

x 
++ 
y

It is parsed as x; ++y;, not as x++; y

So I think to simplify it, that means:

In general, JavaScript will treat it as continuation of code as long as it makes sense -- except 2 cases: (1) after some keywords like return, break, continue, and (2) if it sees ++ or -- on a new line, then it will add the ; at the end of the previous line.

The part about "treat it as continuation of code as long as it makes sense" makes it feel like regular expression's greedy matching.

With the above said, that means for return with a line break, the JavaScript interpreter will insert a ;

(quoted again: If a line break appears after any of these words [such as return] ... JavaScript will always interpret that line break as a semicolon)

and due to this reason, the classic example of

return
{ 
  foo: 1
}

will not work as expected, because the JavaScript interpreter will treat it as:

return;   // returning nothing
{
  foo: 1
}

There has to be no line-break immediately after the return:

return { 
  foo: 1
}

for it to work properly. And you may insert a ; yourself if you were to follow the rule of using a ; after any statement:

return { 
  foo: 1
};

How do I perform a Perl substitution on a string while keeping the original?

The statement:

(my $newstring = $oldstring) =~ s/foo/bar/g;

Which is equivalent to:

my $newstring = $oldstring;
$newstring =~ s/foo/bar/g;

Alternatively, as of Perl 5.13.2 you can use /r to do a non destructive substitution:

use 5.013;
#...
my $newstring = $oldstring =~ s/foo/bar/gr;

check if "it's a number" function in Oracle

well, you could create the is_number function to call so your code works.

create or replace function is_number(param varchar2) return boolean
 as
   ret number;
 begin
    ret := to_number(param);
    return true;
 exception
    when others then return false;
 end;

EDIT: Please defer to Justin's answer. Forgot that little detail for a pure SQL call....

How to make HTML input tag only accept numerical values?

_x000D_
_x000D_ 
function AllowOnlyNumbers(e) {_x000D_
_x000D_
e = (e) ? e : window.event;_x000D_
var clipboardData = e.clipboardData ? e.clipboardData : window.clipboardData;_x000D_
var key = e.keyCode ? e.keyCode : e.which ? e.which : e.charCode;_x000D_
var str = (e.type && e.type == "paste") ? clipboardData.getData('Text') : String.fromCharCode(key);_x000D_
_x000D_
return (/^\d+$/.test(str));_x000D_
}
_x000D_ 
<h1>Integer Textbox</h1>_x000D_
    <input type="text" autocomplete="off" id="txtIdNum" onkeypress="return AllowOnlyNumbers(event);" />
_x000D_
_x000D_
_x000D_

JSFiddle: https://jsfiddle.net/ug8pvysc/

Roblox Admin Command Script

 
for i=1,#target do
    game.Players.target[i].Character:BreakJoints()
end

Is incorrect, if "target" contains "FakeNameHereSoNoStalkers" then the run code would be:

game.Players.target.1.Character:BreakJoints()

Which is completely incorrect. 

c = game.Players:GetChildren()

Never use "Players:GetChildren()", it is not guaranteed to return only players.

Instead use:

c = Game.Players:GetPlayers()

if msg:lower()=="me" then
    table.insert(people, source)
    return people

Here you add the player's name in the list "people", where you in the other places adds the player object.

Fixed code:

local Admins = {"FakeNameHereSoNoStalkers"}

function Kill(Players)
    for i,Player in ipairs(Players) do
        if Player.Character then
            Player.Character:BreakJoints()
        end
    end
end

function IsAdmin(Player)
    for i,AdminName in ipairs(Admins) do
        if Player.Name:lower() == AdminName:lower() then return true end
    end
    return false
end

function GetPlayers(Player,Msg)
    local Targets = {}
    local Players = Game.Players:GetPlayers()

    if Msg:lower() == "me" then
        Targets = { Player }
    elseif Msg:lower() == "all" then
        Targets = Players
    elseif Msg:lower() == "others" then
        for i,Plr in ipairs(Players) do
            if Plr ~= Player then
                table.insert(Targets,Plr)
            end
        end
    else
        for i,Plr in ipairs(Players) do
            if Plr.Name:lower():sub(1,Msg:len()) == Msg then
                table.insert(Targets,Plr)
            end
        end
    end
    return Targets
end

Game.Players.PlayerAdded:connect(function(Player)
    if IsAdmin(Player) then
        Player.Chatted:connect(function(Msg)
            if Msg:lower():sub(1,6) == ":kill " then
                Kill(GetPlayers(Player,Msg:sub(7)))
            end
        end)
    end
end)

Creating a UICollectionView programmatically

  1. Building off @Warewolf's answer, the next step is to create your own custom cell.

    Go to File -> New -> File -> User Interface -> Empty -> Call this nib "customNib".

  2. In your customNib drag a UICollectionView Cell in. Give it reuse cell identifier @"Cell".

  3. File -> New -> File -> Cocoa Touch Class -> Class named "CustomCollectionViewCell" subclass if UICollectionViewCell.

  4. Go back to the custom nib, click cell and make this custom class "CustomCollectionViewCell".

  5. Go to your viewDidLoad viewcontroller and instead of

    [_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cellIdentifier"];

    have

    UINib *nib = [UINib nibWithNibName:@"customNib" bundle:nil]; [_collectionView registerNib:nib forCellWithReuseIdentifier:@"Cell"];

  6. Also, change (to your new cell identifier)

    UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];

Maven2: Missing artifact but jars are in place

The following steps worked for me.

1) Cut all the contents from pom.xml file and keep it another file and save the pom.xml
2) Just delete .m2 folder(entire maven repository) and restart the eclipse(or jbdevstudio)
3) paste the previous pom.xml file content(from the cut file) and all the error are gone.

Close Current Tab

Found a one-liner that works in Chrome 66 from: http://www.yournewdesigner.com/css-experiments/javascript-window-close-firefox.html

TLDR: tricks the browser into believing JavaScirpt opened the current tab/window

window.open('', '_parent', '').close();

So for completeness 

<input type="button" name="close" value="close" onclick="window.close();">

Though let it also be noted that readers may want to place this into a function that fingerprints which browsers require such trickery, because Firefox 59 doesn't work with the above.

Position a CSS background image x pixels from the right?

If the container has a fixed height: Tweek the percentages (background-position) until it fits correctly.

If the container has a dynamic height: If you want a padding between your background and your container (such as when custom styling inputs, selects), add your padding to your image and set the background position to right or bottom.

I stumbled on this question while I was trying to get the background for a select box to fit say 5 px from the right of my select. In my case, my background is an arrow down that would replace the basic drop down icon. In my case, the padding will always remain the same (5-10 pixels from the right) for the background, so it's an easy modification to bring to the actual background image (making its dimensions 5-10 pixels wider on the right side.

Hope this helps!

git reset --hard HEAD leaves untracked files behind

You can use git stash. You have to specify --include-untracked, otherwise you'll end up with the original problem.

git stash --include-untracked

Then just drop the last entry in the stash

git stash drop

You can make a handy-dandy alias for that, and call it git discard for example:

git config --global alias.discard "! git stash -q --include-untracked && git stash drop -q"

How to test an Internet connection with bash?

I've written scripts before that simply use telnet to connect to port 80, then transmit the text:

HTTP/1.0 GET /index.html

followed by two CR/LF sequences.

Provided you get back some form of HTTP response, you can generally assume the site is functioning.

convert HTML ( having Javascript ) to PDF using JavaScript

You can do it using a jquery,

Use this code to link the button...

$(document).ready(function() {
    $("#button_id").click(function() {
        window.print();
        return false;
    });
});

This link may be also helpful: jQuery Print HTML Pdf Page Options Link

PHP, display image with Header()

if you know the file name, but don't know the file extention you can use this function:

public function showImage($name)
    {

         $types = [
             'gif'=> 'image/gif',
             'png'=> 'image/png',
             'jpeg'=> 'image/jpeg',
             'jpg'=> 'image/jpeg',
         ];
         $root_path  = '/var/www/my_app'; //use your framework to get this properly ..
         foreach($types as $type=>$meta){
             if(file_exists($root_path .'/uploads/'.$name  .'.'. $type)){
                 header('Content-type: ' . $meta);
                 readfile($root_path .'/uploads/'.$name .'.'. $type);
                 return;
             }
         }
    }

Note: the correct content-type for JPG files is image/jpeg.

Best XML parser for Java

Here is a nice comparision on DOM, SAX, StAX & TrAX (Source: http://download.oracle.com/docs/cd/E17802_01/webservices/webservices/docs/1.6/tutorial/doc/SJSXP2.html )

Feature                  StAX                  SAX                      DOM                  TrAX

API Type                Pull,streaming     Push,streaming    In memory tree    XSLT Rule

Ease of Use          High                    Medium                 High                    Medium

XPath Capability   No                       No                        Yes                      Yes

CPU & Memory     Good                  Good                    Varies                  Varies

Forward Only        Yes                    Yes                        No                       No

Read XML              Yes                    Yes                        Yes                     Yes

Write XML              Yes                    No                          Yes                     Yes

CRUD                      No                      No                         Yes                     No

Syntax for if/else condition in SCSS mixin

You can assign default parameter values inline when you first create the mixin:

@mixin clearfix($width: 'auto') {

  @if $width == 'auto' {

    // if width is not passed, or empty do this

  } @else {

    display: inline-block;
    width: $width;

  }
}

Bulk Insert Correctly Quoted CSV File in SQL Server

I had the same problem, with data that only occasionally double-quotes some text. My solution is to let the BULK LOAD import the double-quotes, then run a REPLACE on the imported data.

For example:

bulk insert CodePoint_tbl from "F:\Data\Map\CodePointOpen\Data\CSV\ab.csv" with (FIRSTROW = 1, FIELDTERMINATOR = ',', ROWTERMINATOR='\n');

update CodePoint_tbl set Postcode = replace(Postcode,'"','') where charindex('"',Postcode) > 0

To make it less painful to write the REPLACE script, just copy and paste what you need from the results of something like this:

select C.ColID, C.[name] as Columnname into #Columns
from syscolumns C
join sysobjects T on C.id = T.id
where T.[name] = 'User_tbl'
order by 1;

declare @QUOTE char(1);
set @QUOTE = Char(39);
select 'Update User_tbl set '+ColumnName+'=replace('+ColumnName+','
 + @QUOTE + '"' + @QUOTE + ',' + @QUOTE + @QUOTE + ');
GO'
from #Columns
where ColID > 2
order by ColID;

Adding blur effect to background in swift

You should always use .dark for style and add the following code to make it look cool

    blurEffectView.backgroundColor = .black
    blurEffectView.alpha = 0.4

Good Java graph algorithm library?

http://incubator.apache.org/hama/ is a distributed scientific package on Hadoop for massive matrix and graph data.

Java - How to create new Entry (key, value)

Starting from Java 9, there is a new utility method allowing to create an immutable entry which is Map#entry(Object, Object).

Here is a simple example:

Entry<String, String> entry = Map.entry("foo", "bar");

As it is immutable, calling setValue will throw an UnsupportedOperationException. The other limitations are the fact that it is not serializable and null as key or value is forbidden, if it is not acceptable for you, you will need to use AbstractMap.SimpleImmutableEntry or AbstractMap.SimpleEntry instead.

NB: If your need is to create directly a Map with 0 to up to 10 (key, value) pairs, you can instead use the methods of type Map.of(K key1, V value1, ...).

int to unsigned int conversion

This conversion is well defined and will yield the value UINT_MAX - 61. On a platform where unsigned int is a 32-bit type (most common platforms, these days), this is precisely the value that others are reporting. Other values are possible, however.

The actual language in the standard is

If the destination type is unsigned, the resulting value is the least unsigned integer congruent to the source integer (modulo 2^n where n is the number of bits used to represent the unsigned type).

PHP code to remove everything but numbers

Try this:

preg_replace('/[^0-9]/', '', '604-619-5135');

preg_replace uses PCREs which generally start and end with a /.

Using Mysql WHERE IN clause in codeigniter

 
$data = $this->db->get_where('columnname',array('code' => 'B'));
$this->db->where_in('columnname',$data);
$this->db->where('code !=','B');
$query =  $this->db->get();
return $query->result_array();

Can You Get A Users Local LAN IP Address Via JavaScript?

Chrome 76+

Last year I used Linblow's answer (2018-Oct-19) to successfully discover my local IP via javascript. However, recent Chrome updates (76?) have wonked this method so that it now returns an obfuscated IP, such as: 1f4712db-ea17-4bcf-a596-105139dfd8bf.local

If you have full control over your browser, you can undo this behavior by turning it off in Chrome Flags, by typing this into your address bar:

chrome://flags

and DISABLING the flag Anonymize local IPs exposed by WebRTC

In my case, I require the IP for a TamperMonkey script to determine my present location and do different things based on my location. I also have full control over my own browser settings (no Corporate Policies, etc). So for me, changing the chrome://flags setting does the trick.

Sources:

https://groups.google.com/forum/#!topic/discuss-webrtc/6stQXi72BEU

https://codelabs.developers.google.com/codelabs/webrtc-web/index.html

What's the difference between a word and byte?

It seems all the answers assume high level languages and mainly C/C++.

But the question is tagged "assembly" and in all assemblers I know (for 8bit, 16bit, 32bit and 64bit CPUs), the definitions are much more clear:

byte  = 8 bits 
word  = 2 bytes
dword = 4 bytes = 2Words (dword means "double word")
qword = 8 bytes = 2Dwords = 4Words ("quadruple word")

SQL DELETE with JOIN another table for WHERE condition

Try this sample SQL scripts for easy understanding,

CREATE TABLE TABLE1 (REFNO VARCHAR(10))
CREATE TABLE TABLE2 (REFNO VARCHAR(10))

--TRUNCATE TABLE TABLE1
--TRUNCATE TABLE TABLE2

INSERT INTO TABLE1 SELECT 'TEST_NAME'
INSERT INTO TABLE1 SELECT 'KUMAR'
INSERT INTO TABLE1 SELECT 'SIVA'
INSERT INTO TABLE1 SELECT 'SUSHANT'

INSERT INTO TABLE2 SELECT 'KUMAR'
INSERT INTO TABLE2 SELECT 'SIVA'
INSERT INTO TABLE2 SELECT 'SUSHANT'

SELECT * FROM TABLE1
SELECT * FROM TABLE2

DELETE T1 FROM TABLE1 T1 JOIN TABLE2 T2 ON T1.REFNO = T2.REFNO

Your case is:

   DELETE pgc
     FROM guide_category pgc 
LEFT JOIN guide g
       ON g.id_guide = gc.id_guide 
    WHERE g.id_guide IS NULL

How to add "active" class to Html.ActionLink in ASP.NET MVC

I know this question is old, but I will just like to add my voice here. I believe it is a good idea to leave the knowledge of whether or not a link is active to the controller of the view.

I would just set a unique value for each view in the controller action. For instance, if I wanted to make the home page link active, I would do something like this:

public ActionResult Index()
{            
    ViewBag.Title = "Home";
    ViewBag.Home = "class = active";
    return View();
}

Then in my view, I will write something like this:

<li @ViewBag.Home>@Html.ActionLink("Home", "Index", "Home", null, new { title = "Go home" })</li>

When you navigate to a different page, say Programs, ViewBag.Home does not exist (instead ViewBag.Programs does); therefore, nothing is rendered, not even class="". I think this is cleaner both for maintainability and cleanliness. I tend to always want to leave logic out of the view as much as I can.

java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/dbname

In your code you are missing Class.forName("com.mysql.jdbc.Driver");

This is what you are missing to have everything working.

Read Post Data submitted to ASP.Net Form

 
NameValueCollection nvclc = Request.Form;
string   uName= nvclc ["txtUserName"];
string   pswod= nvclc ["txtPassword"];
//try login
CheckLogin(uName, pswod);

How can I change the width and height of slides on Slick Carousel?

I made this plugin. There is some css interference taking place.

It's your border on the slider itself. Either use 

box-sizing: border-box

to absorb the border width, or put the border on the content inside the slide.

Getting current unixtimestamp using Moment.js

for UNIX time-stamp in milliseconds

moment().format('x') // lowerCase x

for UNIX time-stamp in seconds moment().format('X') // capital X

sys.path different in Jupyter and Python - how to import own modules in Jupyter?

Jupyter has its own PATH variable, JUPYTER_PATH.

Adding this line to the .bashrc file worked for me:

export JUPYTER_PATH=<directory_for_your_module>:$JUPYTER_PATH

SQLAlchemy: What's the difference between flush() and commit()?

commit () records these changes in the database. flush () is always called as part of the commit () (1) call. When you use a Session object to query a database, the query returns results from both the database and the reddened parts of the unrecorded transaction it is performing.

how to get the child node in div using javascript

 
var tds = document.getElementById("ctl00_ContentPlaceHolder1_Jobs_dlItems_ctl01_a").getElementsByTagName("td");
time = tds[0].firstChild.value;
address = tds[3].firstChild.value;

jQuery Datepicker close datepicker after selected date

This is my edited version : you just need to add an extra argument "autoClose".

example :

 $('input[name="fieldName"]').datepicker({ autoClose: true});

also you can specify a close callback if you want. :)

replace datepicker.js with this:

!function( $ ) {

// Picker object

var Datepicker = function(element, options , closeCallBack){
    this.element = $(element);
    this.format = DPGlobal.parseFormat(options.format||this.element.data('date-format')||'dd/mm/yyyy');
    this.autoClose = options.autoClose||this.element.data('date-autoClose')|| true;
    this.closeCallback = closeCallBack || function(){};
    this.picker = $(DPGlobal.template)
                        .appendTo('body')
                        .on({
                            click: $.proxy(this.click, this)//,
                            //mousedown: $.proxy(this.mousedown, this)
                        });
    this.isInput = this.element.is('input');
    this.component = this.element.is('.date') ? this.element.find('.add-on') : false;

    if (this.isInput) {
        this.element.on({
            focus: $.proxy(this.show, this),
            //blur: $.proxy(this.hide, this),
            keyup: $.proxy(this.update, this)
        });
    } else {
        if (this.component){
            this.component.on('click', $.proxy(this.show, this));
        } else {
            this.element.on('click', $.proxy(this.show, this));
        }
    }

    this.minViewMode = options.minViewMode||this.element.data('date-minviewmode')||0;
    if (typeof this.minViewMode === 'string') {
        switch (this.minViewMode) {
            case 'months':
                this.minViewMode = 1;
                break;
            case 'years':
                this.minViewMode = 2;
                break;
            default:
                this.minViewMode = 0;
                break;
        }
    }
    this.viewMode = options.viewMode||this.element.data('date-viewmode')||0;
    if (typeof this.viewMode === 'string') {
        switch (this.viewMode) {
            case 'months':
                this.viewMode = 1;
                break;
            case 'years':
                this.viewMode = 2;
                break;
            default:
                this.viewMode = 0;
                break;
        }
    }
    this.startViewMode = this.viewMode;
    this.weekStart = options.weekStart||this.element.data('date-weekstart')||0;
    this.weekEnd = this.weekStart === 0 ? 6 : this.weekStart - 1;
    this.onRender = options.onRender;
    this.fillDow();
    this.fillMonths();
    this.update();
    this.showMode();
};

Datepicker.prototype = {
    constructor: Datepicker,

    show: function(e) {
        this.picker.show();
        this.height = this.component ? this.component.outerHeight() : this.element.outerHeight();
        this.place();
        $(window).on('resize', $.proxy(this.place, this));
        if (e ) {
            e.stopPropagation();
            e.preventDefault();
        }
        if (!this.isInput) {
        }
        var that = this;
        $(document).on('mousedown', function(ev){
            if ($(ev.target).closest('.datepicker').length == 0) {
                that.hide();
            }
        });
        this.element.trigger({
            type: 'show',
            date: this.date
        });
    },

    hide: function(){
        this.picker.hide();
        $(window).off('resize', this.place);
        this.viewMode = this.startViewMode;
        this.showMode();
        if (!this.isInput) {
            $(document).off('mousedown', this.hide);
        }
        //this.set();
        this.element.trigger({
            type: 'hide',
            date: this.date
        });
    },

    set: function() {
        var formated = DPGlobal.formatDate(this.date, this.format);
        if (!this.isInput) {
            if (this.component){
                this.element.find('input').prop('value', formated);
            }
            this.element.data('date', formated);
        } else {
            this.element.prop('value', formated);
        }
    },

    setValue: function(newDate) {
        if (typeof newDate === 'string') {
            this.date = DPGlobal.parseDate(newDate, this.format);
        } else {
            this.date = new Date(newDate);
        }
        this.set();
        this.viewDate = new Date(this.date.getFullYear(), this.date.getMonth(), 1, 0, 0, 0, 0);
        this.fill();
    },

    place: function(){
        var offset = this.component ? this.component.offset() : this.element.offset();
        this.picker.css({
            top: offset.top + this.height,
            left: offset.left
        });
    },

    update: function(newDate){
        this.date = DPGlobal.parseDate(
            typeof newDate === 'string' ? newDate : (this.isInput ? this.element.prop('value') : this.element.data('date')),
            this.format
        );
        this.viewDate = new Date(this.date.getFullYear(), this.date.getMonth(), 1, 0, 0, 0, 0);
        this.fill();
    },

    fillDow: function(){
        var dowCnt = this.weekStart;
        var html = '<tr>';
        while (dowCnt < this.weekStart + 7) {
            html += '<th class="dow">'+DPGlobal.dates.daysMin[(dowCnt++)%7]+'</th>';
        }
        html += '</tr>';
        this.picker.find('.datepicker-days thead').append(html);
    },

    fillMonths: function(){
        var html = '';
        var i = 0
        while (i < 12) {
            html += '<span class="month">'+DPGlobal.dates.monthsShort[i++]+'</span>';
        }
        this.picker.find('.datepicker-months td').append(html);
    },

    fill: function() {
        var d = new Date(this.viewDate),
            year = d.getFullYear(),
            month = d.getMonth(),
            currentDate = this.date.valueOf();
        this.picker.find('.datepicker-days th:eq(1)')
                    .text(DPGlobal.dates.months[month]+' '+year);
        var prevMonth = new Date(year, month-1, 28,0,0,0,0),
            day = DPGlobal.getDaysInMonth(prevMonth.getFullYear(), prevMonth.getMonth());
        prevMonth.setDate(day);
        prevMonth.setDate(day - (prevMonth.getDay() - this.weekStart + 7)%7);
        var nextMonth = new Date(prevMonth);
        nextMonth.setDate(nextMonth.getDate() + 42);
        nextMonth = nextMonth.valueOf();
        var html = [];
        var clsName,
            prevY,
            prevM;
        while(prevMonth.valueOf() < nextMonth) {zs
            if (prevMonth.getDay() === this.weekStart) {
                html.push('<tr>');
            }
            clsName = this.onRender(prevMonth);
            prevY = prevMonth.getFullYear();
            prevM = prevMonth.getMonth();
            if ((prevM < month &&  prevY === year) ||  prevY < year) {
                clsName += ' old';
            } else if ((prevM > month && prevY === year) || prevY > year) {
                clsName += ' new';
            }
            if (prevMonth.valueOf() === currentDate) {
                clsName += ' active';
            }
            html.push('<td class="day '+clsName+'">'+prevMonth.getDate() + '</td>');
            if (prevMonth.getDay() === this.weekEnd) {
                html.push('</tr>');
            }
            prevMonth.setDate(prevMonth.getDate()+1);
        }
        this.picker.find('.datepicker-days tbody').empty().append(html.join(''));
        var currentYear = this.date.getFullYear();

        var months = this.picker.find('.datepicker-months')
                    .find('th:eq(1)')
                        .text(year)
                        .end()
                    .find('span').removeClass('active');
        if (currentYear === year) {
            months.eq(this.date.getMonth()).addClass('active');
        }

        html = '';
        year = parseInt(year/10, 10) * 10;
        var yearCont = this.picker.find('.datepicker-years')
                            .find('th:eq(1)')
                                .text(year + '-' + (year + 9))
                                .end()
                            .find('td');
        year -= 1;
        for (var i = -1; i < 11; i++) {
            html += '<span class="year'+(i === -1 || i === 10 ? ' old' : '')+(currentYear === year ? ' active' : '')+'">'+year+'</span>';
            year += 1;
        }
        yearCont.html(html);
    },

    click: function(e) {
        e.stopPropagation();
        e.preventDefault();
        var target = $(e.target).closest('span, td, th');
        if (target.length === 1) {
            switch(target[0].nodeName.toLowerCase()) {
                case 'th':
                    switch(target[0].className) {
                        case 'switch':
                            this.showMode(1);
                            break;
                        case 'prev':
                        case 'next':
                            this.viewDate['set'+DPGlobal.modes[this.viewMode].navFnc].call(
                                this.viewDate,
                                this.viewDate['get'+DPGlobal.modes[this.viewMode].navFnc].call(this.viewDate) + 
                                DPGlobal.modes[this.viewMode].navStep * (target[0].className === 'prev' ? -1 : 1)
                            );
                            this.fill();
                            this.set();
                            break;
                    }
                    break;
                case 'span':
                    if (target.is('.month')) {
                        var month = target.parent().find('span').index(target);
                        this.viewDate.setMonth(month);
                    } else {
                        var year = parseInt(target.text(), 10)||0;
                        this.viewDate.setFullYear(year);
                    }
                    if (this.viewMode !== 0) {
                        this.date = new Date(this.viewDate);
                        this.element.trigger({
                            type: 'changeDate',
                            date: this.date,
                            viewMode: DPGlobal.modes[this.viewMode].clsName
                        });
                    }
                    this.showMode(-1);
                    this.fill();
                    this.set();
                    break;
                case 'td':
                    if (target.is('.day') && !target.is('.disabled')){
                        var day = parseInt(target.text(), 10)||1;
                        var month = this.viewDate.getMonth();
                        if (target.is('.old')) {
                            month -= 1;
                        } else if (target.is('.new')) {
                            month += 1;
                        }
                        var year = this.viewDate.getFullYear();
                        this.date = new Date(year, month, day,0,0,0,0);
                        this.viewDate = new Date(year, month, Math.min(28, day),0,0,0,0);
                        this.fill();
                        this.set();
                        this.element.trigger({
                            type: 'changeDate',
                            date: this.date,
                            viewMode: DPGlobal.modes[this.viewMode].clsName
                        });
                        if(this.autoClose === true){
                            this.hide();
                            this.closeCallback();
                        }

                    }
                    break;
            }
        }
    },

    mousedown: function(e){
        e.stopPropagation();
        e.preventDefault();
    },

    showMode: function(dir) {
        if (dir) {
            this.viewMode = Math.max(this.minViewMode, Math.min(2, this.viewMode + dir));
        }
        this.picker.find('>div').hide().filter('.datepicker-'+DPGlobal.modes[this.viewMode].clsName).show();
    }
};

$.fn.datepicker = function ( option, val ) {
    return this.each(function () {
        var $this = $(this);
        var datePicker = $this.data('datepicker');
        var options = typeof option === 'object' && option;
        if (!datePicker) {
            if (typeof val === 'function')
                $this.data('datepicker', (datePicker = new Datepicker(this, $.extend({}, $.fn.datepicker.defaults,options),val)));
            else{
                $this.data('datepicker', (datePicker = new Datepicker(this, $.extend({}, $.fn.datepicker.defaults,options))));
            }
        }
        if (typeof option === 'string') datePicker[option](val);

    });
};

$.fn.datepicker.defaults = {
    onRender: function(date) {
        return '';
    }
};
$.fn.datepicker.Constructor = Datepicker;

var DPGlobal = {
    modes: [
        {
            clsName: 'days',
            navFnc: 'Month',
            navStep: 1
        },
        {
            clsName: 'months',
            navFnc: 'FullYear',
            navStep: 1
        },
        {
            clsName: 'years',
            navFnc: 'FullYear',
            navStep: 10
    }],
    dates:{
        days: ["Dimanche", "Lundi", "Mardi", "Mercredi", "Jeudi", "Vendredi", "Samedi", "Dimanche"],
                    daysShort: ["Dim", "Lun", "Mar", "Mer", "Jeu", "Ven", "Sam", "Dim"],
                    daysMin: ["D", "L", "Ma", "Me", "J", "V", "S", "D"],
                    months: ["Janvier", "Février", "Mars", "Avril", "Mai", "Juin", "Juillet", "Août", "Septembre", "Octobre", "Novembre", "Décembre"],
                    monthsShort: ["Jan", "Fév", "Mar", "Avr", "Mai", "Jui", "Jul", "Aou", "Sep", "Oct", "Nov", "Déc"],
                    today: "Aujourd'hui",
                    clear: "Effacer",
                    weekStart: 1,
                    format: "dd/mm/yyyy"
    },
    isLeapYear: function (year) {
        return (((year % 4 === 0) && (year % 100 !== 0)) || (year % 400 === 0))
    },
    getDaysInMonth: function (year, month) {
        return [31, (DPGlobal.isLeapYear(year) ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month]
    },
    parseFormat: function(format){
        var separator = format.match(/[.\/\-\s].*?/),
            parts = format.split(/\W+/);
        if (!separator || !parts || parts.length === 0){
            throw new Error("Invalid date format.");
        }
        return {separator: separator, parts: parts};
    },
    parseDate: function(date, format) {
        var parts = date.split(format.separator),
            date = new Date(),
            val;
        date.setHours(0);
        date.setMinutes(0);
        date.setSeconds(0);
        date.setMilliseconds(0);
        if (parts.length === format.parts.length) {
            var year = date.getFullYear(), day = date.getDate(), month = date.getMonth();
            for (var i=0, cnt = format.parts.length; i < cnt; i++) {
                val = parseInt(parts[i], 10)||1;
                switch(format.parts[i]) {
                    case 'dd':
                    case 'd':
                        day = val;
                        date.setDate(val);
                        break;
                    case 'mm':
                    case 'm':
                        month = val - 1;
                        date.setMonth(val - 1);
                        break;
                    case 'yy':
                        year = 2000 + val;
                        date.setFullYear(2000 + val);
                        break;
                    case 'yyyy':
                        year = val;
                        date.setFullYear(val);
                        break;
                }
            }
            date = new Date(year, month, day, 0 ,0 ,0);
        }
        return date;
    },
    formatDate: function(date, format){
        var val = {
            d: date.getDate(),
            m: date.getMonth() + 1,
            yy: date.getFullYear().toString().substring(2),
            yyyy: date.getFullYear()
        };
        val.dd = (val.d < 10 ? '0' : '') + val.d;
        val.mm = (val.m < 10 ? '0' : '') + val.m;
        var date = [];
        for (var i=0, cnt = format.parts.length; i < cnt; i++) {
            date.push(val[format.parts[i]]);
        }
        return date.join(format.separator);
    },
    headTemplate: '<thead>'+
                        '<tr>'+
                            '<th class="prev">&lsaquo;</th>'+
                            '<th colspan="5" class="switch"></th>'+
                            '<th class="next">&rsaquo;</th>'+
                        '</tr>'+
                    '</thead>',
    contTemplate: '<tbody><tr><td colspan="7"></td></tr></tbody>'
};
DPGlobal.template = '<div class="datepicker dropdown-menu">'+
                        '<div class="datepicker-days">'+
                            '<table class=" table-condensed">'+
                                DPGlobal.headTemplate+
                                '<tbody></tbody>'+
                            '</table>'+
                        '</div>'+
                        '<div class="datepicker-months">'+
                            '<table class="table-condensed">'+
                                DPGlobal.headTemplate+
                                DPGlobal.contTemplate+
                            '</table>'+
                        '</div>'+
                        '<div class="datepicker-years">'+
                            '<table class="table-condensed">'+
                                DPGlobal.headTemplate+
                                DPGlobal.contTemplate+
                            '</table>'+
                        '</div>'+
                    '</div>';

}( window.jQuery );

Execute command without keeping it in history

If you are using zsh you can run:

setopt histignorespace

After this is set, each command starting with a space will be excluded from history.

You can use aliases in .zshrc to turn this on/off:

# Toggle ignore-space. Useful when entering passwords.
alias history-ignore-space-on='\
setopt hist_ignore_space;\
echo "Commands starting with space are now EXCLUDED from history."'

alias history-ignore-space-off='\
unsetopt hist_ignore_space;\
echo "Commands starting with space are now ADDED to history."'

Add Bean Programmatically to Spring Web App Context

In Spring 3.0 you can make your bean implement BeanDefinitionRegistryPostProcessor and add new beans via BeanDefinitionRegistry.

In previous versions of Spring you can do the same thing in BeanFactoryPostProcessor (though you need to cast BeanFactory to BeanDefinitionRegistry, which may fail).

Refer to a cell in another worksheet by referencing the current worksheet's name?

Unless you want to go the VBA route to work out the Tab name, the Excel formula is fairly ugly based upon Mid functions, etc. But both these methods can be found here if you want to go that way.

Rather, the way I would do it is:

1) Make one cell on your sheet named, for example, Reference_Sheet and put in that cell the value "Jan Item" for example.

2) Now, use the Indirect function like:

=INDIRECT(Reference_Sheet&"!J3")

3) Now, for each month's sheet, you just have to change that one Reference_Sheet cell.

Hope this gives you what you're looking for!

Best way to generate a random float in C#

Best approach, no crazed values, distributed with respect to the representable intervals on the floating-point number line (removed "uniform" as with respect to a continuous number line it is decidedly non-uniform):

static float NextFloat(Random random)
{
    double mantissa = (random.NextDouble() * 2.0) - 1.0;
    // choose -149 instead of -126 to also generate subnormal floats (*)
    double exponent = Math.Pow(2.0, random.Next(-126, 128));
    return (float)(mantissa * exponent);
}

(*) ... check here for subnormal floats

Warning: generates positive infinity as well! Choose exponent of 127 to be on the safe side.

Another approach which will give you some crazed values (uniform distribution of bit patterns), potentially useful for fuzzing:

static float NextFloat(Random random)
{
    var buffer = new byte[4];
    random.NextBytes(buffer);
    return BitConverter.ToSingle(buffer,0);
}

An improvement over the previous version is this one, which does not create "crazed" values (neither infinities nor NaN) and is still fast (also distributed with respect to the representable intervals on the floating-point number line):

public static float Generate(Random prng)
{
    var sign = prng.Next(2);
    var exponent = prng.Next((1 << 8) - 1); // do not generate 0xFF (infinities and NaN)
    var mantissa = prng.Next(1 << 23);

    var bits = (sign << 31) + (exponent << 23) + mantissa;
    return IntBitsToFloat(bits);
}

private static float IntBitsToFloat(int bits)
{
    unsafe
    {
        return *(float*) &bits;
    }
}

Least useful approach:

static float NextFloat(Random random)
{
    // Not a uniform distribution w.r.t. the binary floating-point number line
    // which makes sense given that NextDouble is uniform from 0.0 to 1.0.
    // Uniform w.r.t. a continuous number line.
    //
    // The range produced by this method is 6.8e38.
    //
    // Therefore if NextDouble produces values in the range of 0.0 to 0.1
    // 10% of the time, we will only produce numbers less than 1e38 about
    // 10% of the time, which does not make sense.
    var result = (random.NextDouble()
                  * (Single.MaxValue - (double)Single.MinValue))
                  + Single.MinValue;
    return (float)result;
}

Floating point number line from: Intel Architecture Software Developer's Manual Volume 1: Basic Architecture. The Y-axis is logarithmic (base-2) because consecutive binary floating point numbers do not differ linearly.

Comparison of distributions, logarithmic Y-axis

Uncaught TypeError: data.push is not a function

I think you set it as

var data = [];

but after some time you made it like:

data = 'some thing which is not an array';

then data.push('') will not work as it is not an array anymore.

How do I encode/decode HTML entities in Ruby?

 
<% str="<h1> Test </h1>" %>

result: &lt; h1 &gt; Test &lt; /h1 &gt;

<%= CGI.unescapeHTML(str).html_safe %>

asp:TextBox ReadOnly=true or Enabled=false?

Readonly will allow the user to copy text from it. Disabled will not.

How to force the input date format to dd/mm/yyyy?

To have a constant date format irrespective of the computer settings, you must use 3 different input elements to capture day, month, and year respectively. However, you need to validate the user input to ensure that you have a valid date as shown bellow

<input id="txtDay" type="text" placeholder="DD" />

<input id="txtMonth" type="text" placeholder="MM" />

<input id="txtYear" type="text" placeholder="YYYY" />
<button id="but" onclick="validateDate()">Validate</button>


  function validateDate() {
    var date = new Date(document.getElementById("txtYear").value, document.getElementById("txtMonth").value, document.getElementById("txtDay").value);

    if (date == "Invalid Date") {
        alert("jnvalid date");

    }
}

How do I install command line MySQL client on mac?

For installing mysql-shell with homebrew, run

brew cask install mysql-shell

you can then launch the mysql shell with

mysqlsh

if you want to enter SQL mode directly, run

mysqlsh --sql

How to remove the bottom border of a box with CSS

You seem to misunderstand the box model - in CSS you provide points for the top and left and then width and height - these are all that are needed for a box to be placed with exact measurements.

The width property is what your C-D is, but it is also what A-B is. If you omit it, the div will not have a defined width and the width will be defined by its contents.

Update (following the comments on the question:

Add a border-bottom-style: none; to your CSS to remove this style from the bottom only.

How can I modify the size of column in a MySQL table?

Have you tried this?

ALTER TABLE <table_name> MODIFY <col_name> VARCHAR(65353);

This will change the col_name's type to VARCHAR(65353)

display Java.util.Date in a specific format

You already has this (that's what you entered) parse will parse a date into a giving format and print the full date object (toString).

how to fetch data from database in Hibernate

I know that it is very late to answer the question, but it may help someone like me who spent lots off time to fetch data using hql

So the thing is you just have to write a query

Query query = session.createQuery("from Employee");

it will give you all the data list but to fetch data from this you have to write this line.

List<Employee> fetchedData = query.list();

As simple as it looks.

'pip install' fails for every package ("Could not find a version that satisfies the requirement")

Upgrade pip as follows:

curl https://bootstrap.pypa.io/get-pip.py | python

Note: You may need to use sudo python above if not in a virtual environment.

What's happening:

Python.org sites are stopping support for TLS versions 1.0 and 1.1. This means that Mac OS X version 10.12 (Sierra) or older will not be able to use pip unless they upgrade pip as above.

(Note that upgrading pip via pip install --upgrade pip will also not upgrade it correctly. It is a chicken-and-egg issue)

This thread explains it (thanks to this Twitter post):

Mac users who use pip and PyPI:

If you are running macOS/OS X version 10.12 or older, then you ought to upgrade to the latest pip (9.0.3) to connect to the Python Package Index securely:

curl https://bootstrap.pypa.io/get-pip.py | python

and we recommend you do that by April 8th.

Pip 9.0.3 supports TLSv1.2 when running under system Python on macOS < 10.13. Official release notes: https://pip.pypa.io/en/stable/news/

Also, the Python status page:

Completed - The rolling brownouts are finished, and TLSv1.0 and TLSv1.1 have been disabled. Apr 11, 15:37 UTC

Update - The rolling brownouts have been upgraded to a blackout, TLSv1.0 and TLSv1.1 will be rejected with a HTTP 403 at all times. Apr 8, 15:49 UTC

Lastly, to avoid other install errors, make sure you also upgrade setuptools after doing the above:

pip install --upgrade setuptools

is there a require for json in node.js

Two of the most common

First way :

let jsonData = require('./JsonFile.json')

let jsonData = require('./JsonFile') // if we omitting .json also works

OR 

import jsonData from ('./JsonFile.json')

Second way :

1) synchronously

const fs = require('fs')
let jsonData = JSON.parse(fs.readFileSync('JsonFile.json', 'utf-8'))

2) asynchronously 

const fs = require('fs')
let jsonData = {}
fs.readFile('JsonFile.json', 'utf-8', (err, data) => {
  if (err) throw err

  jsonData = JSON.parse(data)
})

Note: 1) if we JsonFile.json is changed, we not get the new data, even if we re run require('./JsonFile.json')

2) The fs.readFile or fs.readFileSync will always re read the file, and get changes

Difference between Width:100% and width:100vw?

Havengard's answer doesn't seem to be strictly true. I've found that vw fills the viewport width, but doesn't account for the scrollbars. So, if your content is taller than the viewport (so that your site has a vertical scrollbar), then using vw results in a small horizontal scrollbar. I had to switch out width: 100vw for width: 100% to get rid of the horizontal scrollbar.

ASP.Net which user account running Web Service on IIS 7?

Server 2008

Start Task Manager Find w3wp.exe process (description IIS Worker Process) Check User Name column to find who you're IIS process is running as.

In the IIS GUI you can configure your application pool to run as a specific user: Application Pool default Advanced Settings Identity

Here's the info from Microsoft on setting up Application Pool Identites:

http://learn.iis.net/page.aspx/624/application-pool-identities/

Javascript to convert UTC to local time

 
var offset = new Date().getTimezoneOffset();

offset will be the interval in minutes from Local time to UTC. To get Local time from a UTC date, you would then subtract the minutes from your date.

utc_date.setMinutes(utc_date.getMinutes() - offset);

Setting Remote Webdriver to run tests in a remote computer using Java

This is how I got rid of the error:

WebDriverException: Error forwarding the new session cannot find : {platform=WINDOWS, ensureCleanSession=true, browserName=internet explorer, version=11}

In your nodeconfig.json, the version must be a String, not an integer.

So instead of using "version": 11 use "version": "11" (note the double quotes).

A full example of a working nodecondig.json file for a RemoteWebDriver:

{
  "capabilities":
  [
    {
      "platform": "WIN8_1",
      "browserName": "internet explorer",
      "maxInstances": 1,
      "seleniumProtocol": "WebDriver"
      "version": "11"
    }
    ,{
      "platform": "WIN7",
      "browserName": "chrome",
      "maxInstances": 4,
      "seleniumProtocol": "WebDriver"
      "version": "40"
    }
    ,{
      "platform": "LINUX",
      "browserName": "firefox",
      "maxInstances": 4,
      "seleniumProtocol": "WebDriver"
      "version": "33"
    }
  ],
  "configuration":
  {
    "proxy": "org.openqa.grid.selenium.proxy.DefaultRemoteProxy",
    "maxSession": 3,
    "port": 5555,
    "host": ip,
    "register": true,
    "registerCycle": 5000,
    "hubPort": 4444,
    "hubHost": {your-ip-address}
  }
}

Attribute Error: 'list' object has no attribute 'split'

what i did was a quick fix by converting readlines to string but i do not recommencement it but it works and i dont know if there are limitations or not 

`def getQuakeData():
    filename = input("Please enter the quake file: ")
    readfile = open(filename, "r")
    readlines = str(readfile.readlines())

    Type = readlines.split(",")
    x = Type[1]
    y = Type[2]
    for points in Type:
        print(x,y)
getQuakeData()`

Regex doesn't work in String.matches()

You can make your pattern case insensitive by doing:

Pattern p = Pattern.compile("[a-z]+", Pattern.CASE_INSENSITIVE);

How do I access my webcam in Python?

John Montgomery's, answer is great, but at least on Windows, it is missing the line

vc.release()

before

cv2.destroyWindow("preview")

Without it, the camera resource is locked, and can not be captured again before the python console is killed.

Php header location redirect not working

I had also the similar issue in godaddy hosting. But after putting ob_start(); at the beginning of the php page from where page was redirecting, it was working fine.

Please find the example of the fix:

fileName:index.php

<?php
ob_start();
...
header('Location: page1.php');
...
ob_end_flush();
?>

Pass connection string to code-first DbContext

When using an EF model, I have a connection string in each project that consumes the EF model. For example, I have an EF EDMX model in a separate class library. I have one connection string in my web (mvc) project so that it can access the EF db.

I also have another unit test project for testing the repositories. In order for the repositories to access the EF db, the test project's app.config file has the same connection string.

DB connections should be configured, not coded, IMO.

Filtering Pandas DataFrames on dates

I'm not allowed to write any comments yet, so I'll write an answer, if somebody will read all of them and reach this one.

If the index of the dataset is a datetime and you want to filter that just by (for example) months, you can do following:

df.loc[df.index.month == 3]

That will filter the dataset for you by March.

Getting the actual usedrange

Timings on Excel 2013 fairly slow machine with a big bad used range million rows:

26ms Cells.Find xlPrevious method (as above)

0.4ms Sheet.UsedRange (just call it)

0.14ms Counta binary search + 0.4ms Used Range to start search (12 CountA calls)

So the Find xlPrevious is quite slow if that is of concern.

The CountA binary search approach is to first do a Used Range. Then chop the range in half and see if there are any non-empty cells in the bottom half, and then halve again as needed. It is tricky to get right.

How to get all values from python enum class?

class enum.Enum is a class that solves all your enumeration needs, so you just need to inherit from it, and add your own fields. Then from then on, all you need to do is to just call it's attributes: name & value:

from enum import Enum

class Letter(Enum):
   A = 1
   B = 2
   C = 3

print({i.name: i.value for i in Letter})
# prints {'A': 1, 'B': 2, 'C': 3}

Creating a URL in the controller .NET MVC

I had the same issue, and it appears Gidon's answer has one tiny flaw: it generates a relative URL, which cannot be sent by mail.

My solution looks like this:

string link = HttpContext.Request.Url.Scheme + "://" + HttpContext.Request.Url.Authority + Url.Action("ResetPassword", "Account", new { key = randomString });

This way, a full URL is generated, and it works even if the application is several levels deep on the hosting server, and uses a port other than 80.

EDIT: I found this useful as well.

Azure SQL Database "DTU percentage" metric

To check the accurate usage for your services be it is free (as per always free or 12 months free) or Pay-As-You-Go, it is important to monitor the usage so that you know upfront on the cost incurred or when to upgrade your service tier.

To check your free service usage and its limits, Go to search in Portal, search with "Subscription" and click on it. you will see the details of each service that you have used.

In case of free azure from Microsoft, you get to see the cost incurred for each one.

Visit Check usage of free services included with your Azure free account enter image description here

Hope this helps someone!

Apache HttpClient Android (Gradle)

if you are using target sdk as 23 add below code in your build.gradle

android{
 useLibrary  'org.apache.http.legacy'
}

additional note here: dont try using the gradle versions of those files. they are broken (28.08.15). I tried over 5 hours to get it to work. it just doesnt. not working:

compile 'org.apache.httpcomponents:httpcore:4.4.1'
compile 'org.apache.httpcomponents:httpclient:4.5'

another thing dont use:

'org.apache.httpcomponents:httpclient-android:4.3.5.1'

its referring 21 api level.

SVN remains in conflict?

Ok here's how to fix it:

svn remove --force filename
svn resolve --accept=working  filename
svn commit

more details are at: http://svnbook.red-bean.com/en/1.8/svn.tour.treeconflicts.html

Custom HTTP headers : naming conventions

The format for HTTP headers is defined in the HTTP specification. I'm going to talk about HTTP 1.1, for which the specification is RFC 2616. In section 4.2, 'Message Headers', the general structure of a header is defined:

   message-header = field-name ":" [ field-value ]
   field-name     = token
   field-value    = *( field-content | LWS )
   field-content  = <the OCTETs making up the field-value
                    and consisting of either *TEXT or combinations
                    of token, separators, and quoted-string>

This definition rests on two main pillars, token and TEXT. Both are defined in section 2.2, 'Basic Rules'. Token is:

   token          = 1*<any CHAR except CTLs or separators>

In turn resting on CHAR, CTL and separators:

   CHAR           = <any US-ASCII character (octets 0 - 127)>

   CTL            = <any US-ASCII control character
                    (octets 0 - 31) and DEL (127)>

   separators     = "(" | ")" | "<" | ">" | "@"
                  | "," | ";" | ":" | "\" | <">
                  | "/" | "[" | "]" | "?" | "="
                  | "{" | "}" | SP | HT

TEXT is:

   TEXT           = <any OCTET except CTLs,
                    but including LWS>

Where LWS is linear white space, whose definition i won't reproduce, and OCTET is:

   OCTET          = <any 8-bit sequence of data>

There is a note accompanying the definition:

The TEXT rule is only used for descriptive field contents and values
that are not intended to be interpreted by the message parser. Words
of *TEXT MAY contain characters from character sets other than ISO-
8859-1 [22] only when encoded according to the rules of RFC 2047
[14].

So, two conclusions. Firstly, it's clear that the header name must be composed from a subset of ASCII characters - alphanumerics, some punctuation, not a lot else. Secondly, there is nothing in the definition of a header value that restricts it to ASCII or excludes 8-bit characters: it's explicitly composed of octets, with only control characters barred (note that CR and LF are considered controls). Furthermore, the comment on the TEXT production implies that the octets are to be interpreted as being in ISO-8859-1, and that there is an encoding mechanism (which is horrible, incidentally) for representing characters outside that encoding.

So, to respond to @BalusC in particular, it's quite clear that according to the specification, header values are in ISO-8859-1. I've sent high-8859-1 characters (specifically, some accented vowels as used in French) in a header out of Tomcat, and had them interpreted correctly by Firefox, so to some extent, this works in practice as well as in theory (although this was a Location header, which contains a URL, and these characters are not legal in URLs, so this was actually illegal, but under a different rule!).

That said, i wouldn't rely on ISO-8859-1 working across all servers, proxies, and clients, so i would stick to ASCII as a matter of defensive programming.

How to install PyQt4 on Windows using pip?

If you have error while installing PyQt4.

Error: PyQt4-4.11.4-cp27-cp27m-win_amd64.whl is not a supported wheel on this platform.

My system type is 64 bit, But to solve this error I have installed PyQt4 of 32 bit windows system, i.e PyQt4-4.11.4-cp27-cp27m-win32.whl - click here to see more versions.

enter image description here

Kindly select appropriate version of PyQt4 according to your installed python version.

python 2 instead of python 3 as the (temporary) default python?

 
mkdir ~/bin
PATH=~/bin:$PATH
ln -s /usr/bin/python2 ~/bin/python

To stop using python2, exit or rm ~/bin/python.

How to send objects through bundle

One More way to send objects through bundle is by using bundle.putByteArray
Sample code

public class DataBean implements Serializable {
private Date currentTime;

public setDate() {
    currentTime = Calendar.getInstance().getTime();
 }

public Date getCurrentTime() {
    return currentTime;
 }
}

put Object of DataBean in to Bundle:

class FirstClass{
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Your code...

//When you want to start new Activity...
Intent dataIntent =new Intent(FirstClass.this, SecondClass.class);
            Bundle dataBundle=new Bundle();
            DataBean dataObj=new DataBean();
            dataObj.setDate();
            try {
                dataBundle.putByteArray("Obj_byte_array", object2Bytes(dataObj));

            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();

            }

            dataIntent.putExtras(dataBundle);

            startActivity(dataIntent);
}

Converting objects to byte arrays

/**
 * Converting objects to byte arrays
 */
static public byte[] object2Bytes( Object o ) throws IOException {
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      ObjectOutputStream oos = new ObjectOutputStream( baos );
      oos.writeObject( o );
      return baos.toByteArray();
    }

Get Object back from Bundle: 

class SecondClass{
DataBean dataBean;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Your code...

//Get Info from Bundle...
    Bundle infoBundle=getIntent().getExtras();
    try {
        dataBean = (DataBean)bytes2Object(infoBundle.getByteArray("Obj_byte_array"));
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Method to get objects from byte arrays:

/**
 * Converting byte arrays to objects
 */
static public Object bytes2Object( byte raw[] )
        throws IOException, ClassNotFoundException {
      ByteArrayInputStream bais = new ByteArrayInputStream( raw );
      ObjectInputStream ois = new ObjectInputStream( bais );
      Object o = ois.readObject();
      return o;
    }

Hope this will help to other buddies.

What exactly is RESTful programming?

Old question, newish way of answering. There's a lot of misconception out there about this concept. I always try to remember:

  1. Structured URLs and Http Methods/Verbs are not the definition of restful programming.
  2. JSON is not restful programming
  3. RESTful programming is not for APIs

I define restful programming as

An application is restful if it provides resources (being the combination of data + state transitions controls) in a media type the client understands

To be a restful programmer you must be trying to build applications that allow actors to do things. Not just exposing the database.

State transition controls only make sense if the client and server agree upon a media type representation of the resource. Otherwise there's no way to know what's a control and what isn't and how to execute a control. IE if browsers didn't know <form> tags in html then there'd be nothing for you to submit to transition state in your browser.

I'm not looking to self promote, but i expand on these ideas to great depth in my talk http://techblog.bodybuilding.com/2016/01/video-what-is-restful-200.html .

An excerpt from my talk is about the often referred to richardson maturity model, i don't believe in the levels, you either are RESTful (level 3) or you are not, but what i like to call out about it is what each level does for you on your way to RESTful

annotated richardson maturity model

Angular 5 - Copy to clipboard

You can achieve this using Angular modules:

navigator.clipboard.writeText('your text').then().catch(e => console.error(e));

C# Pass Lambda Expression as Method Parameter

Use a Func<T1, T2, TResult> delegate as the parameter type and pass it in to your Query:

public List<IJob> getJobs(Func<FullTimeJob, Student, FullTimeJob> lambda)
{
  using (SqlConnection connection = new SqlConnection(getConnectionString())) {
    connection.Open();
    return connection.Query<FullTimeJob, Student, FullTimeJob>(sql, 
        lambda,
        splitOn: "user_id",
        param: parameters).ToList<IJob>();   
  }  
}

You would call it:

getJobs((job, student) => {         
        job.Student = student;
        job.StudentId = student.Id;
        return job;
        });

Or assign the lambda to a variable and pass it in.

Environ Function code samples for VBA

As alluded to by Eric, you can use environ with ComputerName argument like so:

MsgBox Environ("USERNAME")

Some additional information that might be helpful for you to know:

  1. The arguments are not case sensitive.
  2. There is a slightly faster performing string version of the Environ function. To invoke it, use a dollar sign. (Ex: Environ$("username")) This will net you a small performance gain.
  3. You can retrieve all System Environment Variables using this function. (Not just username.) A common use is to get the "ComputerName" value to see which computer the user is logging onto from.
  4. I don't recommend it for most situations, but it can be occasionally useful to know that you can also access the variables with an index. If you use this syntax the the name of argument and the value are returned. In this way you can enumerate all available variables. Valid values are 1 - 255.
    Sub EnumSEVars()
        Dim strVar As String
        Dim i As Long
        For i = 1 To 255
            strVar = Environ$(i)
            If LenB(strVar) = 0& Then Exit For
            Debug.Print strVar
        Next
    End Sub

How do I check out a remote Git branch?

I always do: git fetch origin && git checkout --track origin/branch_name

Are PHP Variables passed by value or by reference?

Objects are passed by reference in PHP 5 and by value in PHP 4. Variables are passed by value by default!

Read here: http://www.webeks.net/programming/php/ampersand-operator-used-for-assigning-reference.html

How to add style from code behind?

If no file available for download, I needed to disable the asp:linkButton, change it to grey and eliminate the underline on the hover. This worked: 

.disabled {
    color: grey;
    text-decoration: none !important;
}


LinkButton button = item.FindControl("lnkFileDownload") as LinkButton;
button.Enabled = false;
button.CssClass = "disabled";

The easiest way to transform collection to array?

Here's the final solution for the case in update section (with the help of Google Collections):

Collections2.transform (fooCollection, new Function<Foo, Bar>() {
    public Bar apply (Foo foo) {
        return new Bar (foo);
    }
}).toArray (new Bar[fooCollection.size()]);

But, the key approach here was mentioned in the doublep's answer (I forgot for toArray method).

Get file size, image width and height before upload

As far as I know there is not an easy way to do this since Javascript/JQuery does not have access to the local filesystem. There are some new features in html 5 that allows you to check certain meta data such as file size but I'm not sure if you can actually get the image dimensions.

Here is an article I found regarding the html 5 features, and a work around for IE that involves using an ActiveX control. http://jquerybyexample.blogspot.com/2012/03/how-to-check-file-size-before-uploading.html

TypeError: 'list' object is not callable in python

Close the current interpreter using exit() command and reopen typing python to start your work. And do not name a list as list literally. Then you will be fine.

Connecting to TCP Socket from browser using javascript

See jsocket. Haven't used it myself. Been more than 3 years since last update (as of 26/6/2014).

* Uses flash :(

From the documentation:

<script type='text/javascript'>
    // Host we are connecting to
    var host = 'localhost'; 
    // Port we are connecting on
    var port = 3000;

    var socket = new jSocket();

    // When the socket is added the to document 
    socket.onReady = function(){
            socket.connect(host, port);             
    }

    // Connection attempt finished
    socket.onConnect = function(success, msg){
            if(success){
                    // Send something to the socket
                    socket.write('Hello world');            
            }else{
                    alert('Connection to the server could not be estabilished: ' + msg);            
            }       
    }
    socket.onData = function(data){
            alert('Received from socket: '+data);   
    }

    // Setup our socket in the div with the id="socket"
    socket.setup('mySocket');       
</script>

C++ -- expected primary-expression before ' '

You should not be repeating the string part when sending parameters.

int wordLength = wordLengthFunction(word); //you do not put string word here.

What is a stack pointer used for in microprocessors?

A stack is a LIFO (last in, first out - the last entry you push on to the stack is the first one you get back when you pop) data structure that is typically used to hold stack frames (bits of the stack that belong to the current function).

This includes, but is not limited to:

  • the return address.
  • a place for a return value.
  • passed parameters.
  • local variables.

You push items onto the stack and pop them off. In a microprocessor, the stack can be used for both user data (such as local variables and passed parameters) and CPU data (such as return addresses when calling subroutines).

The actual implementation of a stack depends on the microprocessor architecture. It can grow up or down in memory and can move either before or after the push/pop operations.

Operation which typically affect the stack are:

  • subroutine calls and returns.
  • interrupt calls and returns.
  • code explicitly pushing and popping entries.
  • direct manipulation of the SP register.

Consider the following program in my (fictional) assembly language:

Addr  Opcodes   Instructions    ; Comments
----  --------  --------------  ----------
                                ; 1: pc<-0000, sp<-8000
0000  01 00 07  load r0,7       ; 2: pc<-0003, r0<-7
0003  02 00     push r0         ; 3: pc<-0005, sp<-7ffe, (sp:7ffe)<-0007
0005  03 00 00  call 000b       ; 4: pc<-000b, sp<-7ffc, (sp:7ffc)<-0008
0008  04 00     pop r0          ; 7: pc<-000a, r0<-(sp:7ffe[0007]), sp<-8000
000a  05        halt            ; 8: pc<-000a
000b  06 01 02  load r1,[sp+2]  ; 5: pc<-000e, r1<-(sp+2:7ffe[0007])
000e  07        ret             ; 6: pc<-(sp:7ffc[0008]), sp<-7ffe

Now let's follow the execution, describing the steps shown in the comments above:

  1. This is the starting condition where the program counter is zero and the stack pointer is 8000 (all these numbers are hexadecimal).
  2. This simply loads register r0 with the immediate value 7 and moves to the next step (I'll assume that you understand the default behavior will be to move to the next step unless otherwise specified).
  3. This pushes r0 onto the stack by reducing the stack pointer by two then storing the value of the register to that location.
  4. This calls a subroutine. What would have been the program counter is pushed on to the stack in a similar fashion to r0 in the previous step and then the program counter is set to its new value. This is no different to a user-level push other than the fact it's done more as a system-level thing.
  5. This loads r1 from a memory location calculated from the stack pointer - it shows a way to pass parameters to functions.
  6. The return statement extracts the value from where the stack pointer points and loads it into the program counter, adjusting the stack pointer up at the same time. This is like a system-level pop (see next step).
  7. Popping r0 off the stack involves extracting the value from where the stack pointer points then adjusting that stack pointer up.
  8. Halt instruction simply leaves program counter where it is, an infinite loop of sorts.

Hopefully from that description, it will become clear. Bottom line is: a stack is useful for storing state in a LIFO way and this is generally ideal for the way most microprocessors do subroutine calls.

Unless you're a SPARC of course, in which case you use a circular buffer for your stack :-)

Update: Just to clarify the steps taken when pushing and popping values in the above example (whether explicitly or by call/return), see the following examples:

LOAD R0,7
PUSH R0
                     Adjust sp       Store val
sp-> +--------+      +--------+      +--------+
     |  xxxx  |  sp->|  xxxx  |  sp->|  0007  |
     |        |      |        |      |        |
     |        |      |        |      |        |
     |        |      |        |      |        |
     +--------+      +--------+      +--------+

POP R0
                     Get value       Adjust sp
     +--------+      +--------+  sp->+--------+
sp-> |  0007  |  sp->|  0007  |      |  0007  |
     |        |      |        |      |        |
     |        |      |        |      |        |
     |        |      |        |      |        |
     +--------+      +--------+      +--------+

Center-align a HTML table

 
table
{ 
margin-left: auto;
margin-right: auto;
}

This will definitely work. Cheers

Importing data from a JSON file into R

First install the RJSONIO and RCurl package:

_x000D_
_x000D_ 
install.packages("RJSONIO")_x000D_
install.packages("(RCurl")
_x000D_
_x000D_
_x000D_

Try below code using RJSONIO in console

_x000D_
_x000D_ 
library(RJSONIO)_x000D_
library(RCurl)_x000D_
json_file = getURL("https://raw.githubusercontent.com/isrini/SI_IS607/master/books.json")_x000D_
json_file2 = RJSONIO::fromJSON(json_file)_x000D_
head(json_file2)
_x000D_
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_x000D_

What is a "cache-friendly" code?

Preliminaries

On modern computers, only the lowest level memory structures (the registers) can move data around in single clock cycles. However, registers are very expensive and most computer cores have less than a few dozen registers. At the other end of the memory spectrum (DRAM), the memory is very cheap (i.e. literally millions of times cheaper) but takes hundreds of cycles after a request to receive the data. To bridge this gap between super fast and expensive and super slow and cheap are the cache memories, named L1, L2, L3 in decreasing speed and cost. The idea is that most of the executing code will be hitting a small set of variables often, and the rest (a much larger set of variables) infrequently. If the processor can't find the data in L1 cache, then it looks in L2 cache. If not there, then L3 cache, and if not there, main memory. Each of these "misses" is expensive in time.

(The analogy is cache memory is to system memory, as system memory is too hard disk storage. Hard disk storage is super cheap but very slow).

Caching is one of the main methods to reduce the impact of latency. To paraphrase Herb Sutter (cfr. links below): increasing bandwidth is easy, but we can't buy our way out of latency.

Data is always retrieved through the memory hierarchy (smallest == fastest to slowest). A cache hit/miss usually refers to a hit/miss in the highest level of cache in the CPU -- by highest level I mean the largest == slowest. The cache hit rate is crucial for performance since every cache miss results in fetching data from RAM (or worse ...) which takes a lot of time (hundreds of cycles for RAM, tens of millions of cycles for HDD). In comparison, reading data from the (highest level) cache typically takes only a handful of cycles.

In modern computer architectures, the performance bottleneck is leaving the CPU die (e.g. accessing RAM or higher). This will only get worse over time. The increase in processor frequency is currently no longer relevant to increase performance. The problem is memory access. Hardware design efforts in CPUs therefore currently focus heavily on optimizing caches, prefetching, pipelines and concurrency. For instance, modern CPUs spend around 85% of die on caches and up to 99% for storing/moving data!

There is quite a lot to be said on the subject. Here are a few great references about caches, memory hierarchies and proper programming:

Main concepts for cache-friendly code

A very important aspect of cache-friendly code is all about the principle of locality, the goal of which is to place related data close in memory to allow efficient caching. In terms of the CPU cache, it's important to be aware of cache lines to understand how this works: How do cache lines work?

The following particular aspects are of high importance to optimize caching:

  1. Temporal locality: when a given memory location was accessed, it is likely that the same location is accessed again in the near future. Ideally, this information will still be cached at that point.
  2. Spatial locality: this refers to placing related data close to each other. Caching happens on many levels, not just in the CPU. For example, when you read from RAM, typically a larger chunk of memory is fetched than what was specifically asked for because very often the program will require that data soon. HDD caches follow the same line of thought. Specifically for CPU caches, the notion of cache lines is important.

Use appropriate containers

A simple example of cache-friendly versus cache-unfriendly is 's std::vector versus std::list. Elements of a std::vector are stored in contiguous memory, and as such accessing them is much more cache-friendly than accessing elements in a std::list, which stores its content all over the place. This is due to spatial locality.

A very nice illustration of this is given by Bjarne Stroustrup in this youtube clip (thanks to @Mohammad Ali Baydoun for the link!).

Don't neglect the cache in data structure and algorithm design

Whenever possible, try to adapt your data structures and order of computations in a way that allows maximum use of the cache. A common technique in this regard is cache blocking (Archive.org version), which is of extreme importance in high-performance computing (cfr. for example ATLAS).

Know and exploit the implicit structure of data

Another simple example, which many people in the field sometimes forget is column-major (ex. ,) vs. row-major ordering (ex. ,) for storing two dimensional arrays. For example, consider the following matrix:

1 2
3 4

In row-major ordering, this is stored in memory as 1 2 3 4; in column-major ordering, this would be stored as 1 3 2 4. It is easy to see that implementations which do not exploit this ordering will quickly run into (easily avoidable!) cache issues. Unfortunately, I see stuff like this very often in my domain (machine learning). @MatteoItalia showed this example in more detail in his answer.

When fetching a certain element of a matrix from memory, elements near it will be fetched as well and stored in a cache line. If the ordering is exploited, this will result in fewer memory accesses (because the next few values which are needed for subsequent computations are already in a cache line).

For simplicity, assume the cache comprises a single cache line which can contain 2 matrix elements and that when a given element is fetched from memory, the next one is too. Say we want to take the sum over all elements in the example 2x2 matrix above (lets call it M):

Exploiting the ordering (e.g. changing column index first in ):

M[0][0] (memory) + M[0][1] (cached) + M[1][0] (memory) + M[1][1] (cached)
= 1 + 2 + 3 + 4
--> 2 cache hits, 2 memory accesses

Not exploiting the ordering (e.g. changing row index first in ):

M[0][0] (memory) + M[1][0] (memory) + M[0][1] (memory) + M[1][1] (memory)
= 1 + 3 + 2 + 4
--> 0 cache hits, 4 memory accesses

In this simple example, exploiting the ordering approximately doubles execution speed (since memory access requires much more cycles than computing the sums). In practice, the performance difference can be much larger.

Avoid unpredictable branches

Modern architectures feature pipelines and compilers are becoming very good at reordering code to minimize delays due to memory access. When your critical code contains (unpredictable) branches, it is hard or impossible to prefetch data. This will indirectly lead to more cache misses.

This is explained very well here (thanks to @0x90 for the link): Why is processing a sorted array faster than processing an unsorted array?

Avoid virtual functions

In the context of , virtual methods represent a controversial issue with regard to cache misses (a general consensus exists that they should be avoided when possible in terms of performance). Virtual functions can induce cache misses during look up, but this only happens if the specific function is not called often (otherwise it would likely be cached), so this is regarded as a non-issue by some. For reference about this issue, check out: What is the performance cost of having a virtual method in a C++ class?

Common problems

A common problem in modern architectures with multiprocessor caches is called false sharing. This occurs when each individual processor is attempting to use data in another memory region and attempts to store it in the same cache line. This causes the cache line -- which contains data another processor can use -- to be overwritten again and again. Effectively, different threads make each other wait by inducing cache misses in this situation. See also (thanks to @Matt for the link): How and when to align to cache line size?

An extreme symptom of poor caching in RAM memory (which is probably not what you mean in this context) is so-called thrashing. This occurs when the process continuously generates page faults (e.g. accesses memory which is not in the current page) which require disk access.

Automatically deleting related rows in Laravel (Eloquent ORM)

There are 3 approaches to solving this:

1. Using Eloquent Events On Model Boot (ref: https://laravel.com/docs/5.7/eloquent#events)

class User extends Eloquent
{
    public static function boot() {
        parent::boot();

        static::deleting(function($user) {
             $user->photos()->delete();
        });
    }
}

2. Using Eloquent Event Observers (ref: https://laravel.com/docs/5.7/eloquent#observers)

In your AppServiceProvider, register the observer like so:

public function boot()
{
    User::observe(UserObserver::class);
}

Next, add an Observer class like so:

class UserObserver
{
    public function deleting(User $user)
    {
         $user->photos()->delete();
    }
}

3. Using Foreign Key Constraints (ref: https://laravel.com/docs/5.7/migrations#foreign-key-constraints)

$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

How to Detect if I'm Compiling Code with a particular Visual Studio version?

In visual studio, go to help | about and look at the version of Visual Studio that you're using to compile your app.