Programs & Examples On #Linq expressions

An API for composing code with declarative expression trees, used by LINQ and the DLR.

What do *args and **kwargs mean?

Also, we use them for managing inheritance.

class Super( object ):
   def __init__( self, this, that ):
       self.this = this
       self.that = that

class Sub( Super ):
   def __init__( self, myStuff, *args, **kw ):
       super( Sub, self ).__init__( *args, **kw )
       self.myStuff= myStuff

x= Super( 2.7, 3.1 )
y= Sub( "green", 7, 6 )

This way Sub doesn't really know (or care) what the superclass initialization is. Should you realize that you need to change the superclass, you can fix things without having to sweat the details in each subclass.

Single Form Hide on Startup

This works perfectly for me:

    static void Main()
            frmBase frm = new frmBase();               

When I launch the project, everything was hidden including in the taskbar unless I need to show it..

Bootstrap 3 Collapse show state with Chevron icon

I wanted a pure html approach as I wanted to collapse and expand html that was added on the fly via a template! I came up with this...

var noJavascript = ":)";

Which might be of use to someone :)

WARNING: API 'variant.getJavaCompile()' is obsolete and has been replaced with 'variant.getJavaCompileProvider()'

That's mostly due to libraries which are obsolete. To check for new updates manually, you should navigate to

Analyze > "Run Inspection By Name"

run inspection by name android result

That should be enough. Another option is to run a gradle dependency update using

./gradlew dependencyUpdates

that will produce a report like this:


: Project Dependency Updates (report to plain text file)

The following dependencies are using the latest milestone version:
 - com.github.ben-manes:gradle-versions-plugin:0.15.0

The following dependencies have later milestone versions:
 - [1.4 -> 1.4.1]
 - [2.0.19 -> 2.0.21]
 - [21.0 -> 23.0-rc1]
 - net.ltgt.gradle:gradle-apt-plugin [0.9 -> 0.10]
 - net.ltgt.gradle:gradle-errorprone-plugin [0.0.10 -> 0.0.11]


How to return a custom object from a Spring Data JPA GROUP BY query

I just solved this problem :

  • Class-based Projections doesn't work with query native(@Query(value = "SELECT ...", nativeQuery = true)) so I recommend to define custom DTO using interface .
  • Before using DTO should verify the query syntatically correct or not

Switch tabs using Selenium WebDriver with Java

It is A very simple process: assume you have two tabs so you need to first close the current tab by using client.window(callback) because the switch command "switches to the first available one". Then you can easily switch tab using client.switchTab.

New self vs. new static

will I get the same results?

Not really. I don't know of a workaround for PHP 5.2, though.

What is the difference between new self and new static?

self refers to the same class in which the new keyword is actually written.

static, in PHP 5.3's late static bindings, refers to whatever class in the hierarchy you called the method on.

In the following example, B inherits both methods from A. The self invocation is bound to A because it's defined in A's implementation of the first method, whereas static is bound to the called class (also see get_called_class()).

class A {
    public static function get_self() {
        return new self();

    public static function get_static() {
        return new static();

class B extends A {}

echo get_class(B::get_self());  // A
echo get_class(B::get_static()); // B
echo get_class(A::get_self()); // A
echo get_class(A::get_static()); // A

How to "add existing frameworks" in Xcode 4?

I would like to point out that if you can't find "Link Binaries With Libraries" in your build phases tab click the "Add build phase" button in the lower right corner.

How to initialize a private static const map in C++?

If you find boost::assign::map_list_of useful, but can't use it for some reason, you could write your own:

template<class K, class V>
struct map_list_of_type {
  typedef std::map<K, V> Map;
  Map data;
  map_list_of_type(K k, V v) { data[k] = v; }
  map_list_of_type& operator()(K k, V v) { data[k] = v; return *this; }
  operator Map const&() const { return data; }
template<class K, class V>
map_list_of_type<K, V> my_map_list_of(K k, V v) {
  return map_list_of_type<K, V>(k, v);

int main() {
  std::map<int, char> example = 
    my_map_list_of(1, 'a') (2, 'b') (3, 'c');
  cout << example << '\n';

It's useful to know how such things work, especially when they're so short, but in this case I'd use a function:


struct A {
  static map<int, int> const m;


namespace {
map<int,int> create_map() {
  map<int, int> m;
  m[1] = 2; // etc.
  return m;

map<int, int> const A::m = create_map();

Fitting empirical distribution to theoretical ones with Scipy (Python)?

The following code is the version of the general answer but with corrections and clarity.

import numpy as np
import pandas as pd
import scipy.stats as st
import statsmodels.api as sm
import matplotlib as mpl
import matplotlib.pyplot as plt
import math
import random"ggplot")

def danoes_formula(data):
    DANOE'S FORMULA's_formula
    N = len(data)
    skewness = st.skew(data)
    sigma_g1 = math.sqrt((6*(N-2))/((N+1)*(N+3)))
    num_bins = 1 + math.log(N,2) + math.log(1+abs(skewness)/sigma_g1,2)
    num_bins = round(num_bins)
    return num_bins

def plot_histogram(data, results, n):
    ## n first distribution of the ranking
    N_DISTRIBUTIONS = {k: results[k] for k in list(results)[:n]}

    ## Histogram of data
    plt.figure(figsize=(10, 5))
    plt.hist(data, density=True, ec='white', color=(63/235, 149/235, 170/235))

    ## Plot n distributions
    for distribution, result in N_DISTRIBUTIONS.items():
        # print(i, distribution)
        sse = result[0]
        arg = result[1]
        loc = result[2]
        scale = result[3]
        x_plot = np.linspace(min(data), max(data), 1000)
        y_plot = distribution.pdf(x_plot, loc=loc, scale=scale, *arg)
        plt.plot(x_plot, y_plot, label=str(distribution)[32:-34] + ": " + str(sse)[0:6], color=(random.uniform(0, 1), random.uniform(0, 1), random.uniform(0, 1)))
    plt.legend(title='DISTRIBUTIONS', bbox_to_anchor=(1.05, 1), loc='upper left')

def fit_data(data):
    ## st.frechet_r,st.frechet_l: are disbled in current SciPy version
    ## st.levy_stable: a lot of time of estimation parameters
    ALL_DISTRIBUTIONS = [        
        st.foldcauchy,st.foldnorm, st.genlogistic,st.genpareto,st.gennorm,st.genexpon,
    MY_DISTRIBUTIONS = [st.beta, st.expon, st.norm, st.uniform, st.johnsonsb, st.gennorm, st.gausshyper]

    ## Calculae Histogram
    num_bins = danoes_formula(data)
    frequencies, bin_edges = np.histogram(data, num_bins, density=True)
    central_values = [(bin_edges[i] + bin_edges[i+1])/2 for i in range(len(bin_edges)-1)]

    results = {}
    for distribution in MY_DISTRIBUTIONS:
        ## Get parameters of distribution
        params =
        ## Separate parts of parameters
        arg = params[:-2]
        loc = params[-2]
        scale = params[-1]
        ## Calculate fitted PDF and error with fit in distribution
        pdf_values = [distribution.pdf(c, loc=loc, scale=scale, *arg) for c in central_values]
        ## Calculate SSE (sum of squared estimate of errors)
        sse = np.sum(np.power(frequencies - pdf_values, 2.0))
        ## Build results and sort by sse
        results[distribution] = [sse, arg, loc, scale]
    results = {k: results[k] for k in sorted(results, key=results.get)}
    return results
def main():
    ## Import data
    data = pd.Series(sm.datasets.elnino.load_pandas().data.set_index('YEAR').values.ravel())
    results = fit_data(data)
    plot_histogram(data, results, 5)

if __name__ == "__main__":

enter image description here

What's the difference between disabled="disabled" and readonly="readonly" for HTML form input fields?

A readonly element is just not editable, but gets sent when the according form submits. A disabled element isn't editable and isn't sent on submit. Another difference is that readonly elements can be focused (and getting focused when "tabbing" through a form) while disabled elements can't.

Read more about this in this great article or the definition by w3c. To quote the important part:

Key Differences

The Disabled attribute

  • Values for disabled form elements are not passed to the processor method. The W3C calls this a successful element.(This works similar to form check boxes that are not checked.)
  • Some browsers may override or provide default styling for disabled form elements. (Gray out or emboss text) Internet Explorer 5.5 is particularly nasty about this.
  • Disabled form elements do not receive focus.
  • Disabled form elements are skipped in tabbing navigation.

The Read Only Attribute

  • Not all form elements have a readonly attribute. Most notable, the <SELECT> , <OPTION> , and <BUTTON> elements do not have readonly attributes (although they both have disabled attributes)
  • Browsers provide no default overridden visual feedback that the form element is read only. (This can be a problem… see below.)
  • Form elements with the readonly attribute set will get passed to the form processor.
  • Read only form elements can receive the focus
  • Read only form elements are included in tabbed navigation.

Binary Data Posting with curl

You don't need --header "Content-Length: $LENGTH".

curl --request POST --data-binary "@template_entry.xml" $URL

Note that GET request does not support content body widely.

Also remember that POST request have 2 different coding schema. This is first form:

  $ nc -l -p 6666 &
  $ curl  --request POST --data-binary "@README" http://localhost:6666

User-Agent: curl/7.21.0 (x86_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o zlib/ libidn/1.15 libssh2/1.2.6
Host: localhost:6666
Accept: */*
Content-Length: 9309
Content-Type: application/x-www-form-urlencoded
Expect: 100-continue

.. -*- mode: rst; coding: cp1251; fill-column: 80 -*-
.. contents::

You probably request this:

-F/--form name=content
           (HTTP) This lets curl emulate a filled-in form in
              which a user has pressed the submit button. This
              causes curl to POST data using the Content- Type
              multipart/form-data according to RFC2388. This
              enables uploading of binary files etc. To force the
              'content' part to be a file, prefix the file name
              with an @ sign. To just get the content part from a
              file, prefix the file name with the symbol <. The
              difference between @ and < is then that @ makes a
              file get attached in the post as a file upload,
              while the < makes a text field and just get the
              contents for that text field from a file.

How do I invoke a Java method when given the method name as a string?

For those who want a straight-forward code example in Java 7:

Dog class:

package com.mypackage.bean;

public class Dog {
    private String name;
    private int age;

    public Dog() {
        // empty constructor

    public Dog(String name, int age) { = name;
        this.age = age;

    public String getName() {
        return name;

    public void setName(String name) { = name;

    public int getAge() {
        return age;

    public void setAge(int age) {
        this.age = age;

    public void printDog(String name, int age) {
        System.out.println(name + " is " + age + " year(s) old.");

ReflectionDemo class:

package com.mypackage.demo;

import java.lang.reflect.*;

public class ReflectionDemo {

    public static void main(String[] args) throws Exception {
        String dogClassName = "com.mypackage.bean.Dog";
        Class<?> dogClass = Class.forName(dogClassName); // convert string classname to class
        Object dog = dogClass.newInstance(); // invoke empty constructor

        String methodName = "";

        // with single parameter, return void
        methodName = "setName";
        Method setNameMethod = dog.getClass().getMethod(methodName, String.class);
        setNameMethod.invoke(dog, "Mishka"); // pass arg

        // without parameters, return string
        methodName = "getName";
        Method getNameMethod = dog.getClass().getMethod(methodName);
        String name = (String) getNameMethod.invoke(dog); // explicit cast

        // with multiple parameters
        methodName = "printDog";
        Class<?>[] paramTypes = {String.class, int.class};
        Method printDogMethod = dog.getClass().getMethod(methodName, paramTypes);
        printDogMethod.invoke(dog, name, 3); // pass args

Output: Mishka is 3 year(s) old.

You can invoke the constructor with parameters this way:

Constructor<?> dogConstructor = dogClass.getConstructor(String.class, int.class);
Object dog = dogConstructor.newInstance("Hachiko", 10);

Alternatively, you can remove

String dogClassName = "com.mypackage.bean.Dog";
Class<?> dogClass = Class.forName(dogClassName);
Object dog = dogClass.newInstance();

and do

Dog dog = new Dog();

Method method = Dog.class.getMethod(methodName, ...);
method.invoke(dog, ...);

Suggested reading: Creating New Class Instances

How to generate random colors in matplotlib?

Improving the answer to work with Python3. That piece of code would sometimes generate numbers greater than 1 and matplotlib would throw an error.

for X,Y in data:
   scatter(X, Y, c=numpy.random.random(3))

Normalize data in pandas

This is how you do it column-wise:

[df[col].update((df[col] - df[col].min()) / (df[col].max() - df[col].min())) for col in df.columns]

How would you count occurrences of a string (actually a char) within a string?

int count = new Regex(Regex.Escape(needle)).Matches(haystack).Count;

"Could not find a valid gem in any repository" (rubygame and others)

This worked for me to bypass the proxy definitions:

1) become root

2) gem install -u gem_name gem_name

Hope you can work it out

How do I set the time zone of MySQL?

I thought this might be useful:

There are three places where the timezone might be set in MySQL:

In the file "my.cnf" in the [mysqld] section


@@global.time_zone variable

To see what value they are set to:

SELECT @@global.time_zone;

To set a value for it use either one:

SET GLOBAL time_zone = '+8:00';
SET GLOBAL time_zone = 'Europe/Helsinki';
SET @@global.time_zone = '+00:00';

(Using named timezones like 'Europe/Helsinki' means that you have to have a timezone table properly populated.)

Keep in mind that +02:00 is an offset. Europe/Berlin is a timezone (that has two offsets) and CEST is a clock time that corresponds to a specific offset.

@@session.time_zone variable

SELECT @@session.time_zone;

To set it use either one:

SET time_zone = 'Europe/Helsinki';
SET time_zone = "+00:00";
SET @@session.time_zone = "+00:00";

Both might return SYSTEM which means that they use the timezone set in my.cnf.

For timezone names to work, you must setup your timezone information tables need to be populated: I also mention how to populate those tables in this answer.

To get the current timezone offset as TIME


It will return 02:00:00 if your timezone is +2:00.

To get the current UNIX timestamp:


To get the timestamp column as a UNIX timestamp

SELECT UNIX_TIMESTAMP(`timestamp`) FROM `table_name`

To get a UTC datetime column as a UNIX timestamp

SELECT UNIX_TIMESTAMP(CONVERT_TZ(`utc_datetime`, '+00:00', @@session.time_zone)) FROM `table_name`

Note: Changing the timezone will not change the stored datetime or timestamp, but it will show a different datetime for existing timestamp columns as they are internally stored as UTC timestamps and externally displayed in the current MySQL timezone.

I made a cheatsheet here: Should MySQL have its timezone set to UTC?

HtmlEncode from Class Library

In case you are working with silverlight, use this:


How to run PowerShell in CMD

You need to separate the arguments from the file path:

powershell.exe -noexit "& 'D:\Work\SQLExecutor.ps1 ' -gettedServerName 'MY-PC'"

Another option that may ease the syntax using the File parameter and positional parameters:

powershell.exe -noexit -file "D:\Work\SQLExecutor.ps1" "MY-PC"

Best way to structure a tkinter application?

Probably the best way to learn how to structure your program is by reading other people's code, especially if it's a large program to which many people have contributed. After looking at the code of many projects, you should get an idea of what the consensus style should be.

Python, as a language, is special in that there are some strong guidelines as to how you should format your code. The first is the so-called "Zen of Python":

  • Beautiful is better than ugly.
  • Explicit is better than implicit.
  • Simple is better than complex.
  • Complex is better than complicated.
  • Flat is better than nested.
  • Sparse is better than dense.
  • Readability counts.
  • Special cases aren't special enough to break the rules.
  • Although practicality beats purity.
  • Errors should never pass silently.
  • Unless explicitly silenced.
  • In the face of ambiguity, refuse the temptation to guess.
  • There should be one-- and preferably only one --obvious way to do it.
  • Although that way may not be obvious at first unless you're Dutch.
  • Now is better than never.
  • Although never is often better than right now.
  • If the implementation is hard to explain, it's a bad idea.
  • If the implementation is easy to explain, it may be a good idea.
  • Namespaces are one honking great idea -- let's do more of those!

On a more practical level, there is PEP8, the style guide for Python.

With those in mind, I would say that your code style doesn't really fit, particularly the nested functions. Find a way to flatten those out, either by using classes or moving them into separate modules. This will make the structure of your program much easier to understand.

What's the difference between a Python module and a Python package?

From the Python glossary:

It’s important to keep in mind that all packages are modules, but not all modules are packages. Or put another way, packages are just a special kind of module. Specifically, any module that contains a __path__ attribute is considered a package.

Python files with a dash in the name, like, cannot be imported with a simple import statement. Code-wise, import my-file is the same as import my - file which will raise an exception. Such files are better characterized as scripts whereas importable files are modules.

Is a Java hashmap search really O(1)?

Academics aside, from a practical perspective, HashMaps should be accepted as having an inconsequential performance impact (unless your profiler tells you otherwise.)

Auto number column in SharePoint list

If you want to control the formatting of the unique identifier you can create your own <FieldType> in SharePoint. MSDN also has a visual How-To. This basically means that you're creating a custom column.

WSS defines the Counter field type (which is what the ID column above is using). I've never had the need to re-use this or extend it, but it should be possible.

A solution might exist without creating a custom <FieldType>. For example: if you wanted unique IDs like CUST1, CUST2, ... it might be possible to create a Calculated column and use the value of the ID column in you formula (="CUST" & [ID]). I haven't tried this, but this should work :)

What is the ultimate postal code and zip regex?

There is none.

Postal/zip codes around the world don't follow a common pattern. In some countries they are made up by numbers, in others they can be combinations of numbers an letters, some can contain spaces, others dots, the number of characters can vary from two to at least six...

What you could do (theoretically) is create a seperate regex for every country in the world, not recommendable IMO. But you would still be missing on the validation part: Zip code 12345 may exist, but 12346 not, maybe 12344 doesn't exist either. How do you check for that with a regex?

You can't.

How to create own dynamic type or dynamic object in C#?

dynamic myDynamic = new { PropertyOne = true, PropertyTwo = false};

List all virtualenv

Run workon with no argument to list available environments.

How to create a Jar file in Netbeans

I also tried to make an executable jar file that I could run with the following command:

java -jar <jarfile>

After some searching I found the following link:

Packaging and Deploying Desktop Java Applications

I set the project's main class:

  1. Right-click the project's node and choose Properties
  2. Select the Run panel and enter the main class in the Main Class field
  3. Click OK to close the Project Properties dialog box
  4. Clean and build project

Then in the fodler dist the newly created jar should be executable with the command I mentioned above. error in opening zip file

On Windows7 I had this problem over a Samba network connection for a Java8 Jar File >80 MBytes big. Copying the file to a local drive fixed the issue.

JavaScript check if variable exists (is defined/initialized)

In many cases, using:

if (elem) { // or !elem

will do the job for you!... this will check these below cases:

  1. undefined: if the value is not defined and it's undefined
  2. null: if it's null, for example, if a DOM element not exists...
  3. empty string: ''
  4. 0: number zero
  5. NaN: not a number
  6. false

So it will cover off kind of all cases, but there are always weird cases which we'd like to cover as well, for example, a string with spaces, like this ' ' one, this will be defined in javascript as it has spaces inside string... for example in this case you add one more check using trim(), like:

if(elem) {

if(typeof elem === 'string' && elem.trim()) {

Also, these checks are for values only, as objects and arrays work differently in Javascript, empty array [] and empty object {} are always true.

I create the image below to show a quick brief of the answer:

undefined, null, etc

re.sub erroring with "Expected string or bytes-like object"

The simplest solution is to apply Python str function to the column you are trying to loop through.

If you are using pandas, this can be implemented as:


Count length of array and return 1 if it only contains one element

Instead of writing echo $cars.length write echo @($cars).length

Correct use of transactions in SQL Server

At the beginning of stored procedure one should put SET XACT_ABORT ON to instruct Sql Server to automatically rollback transaction in case of error. If ommited or set to OFF one needs to test @@ERROR after each statement or use TRY ... CATCH rollback block.

Numpy converting array from float to strings

If the main problem is the loss of precision when converting from a float to a string, one possible way to go is to convert the floats to the decimalS:

In python 2.7 and higher you can directly convert a float to a decimal object.

minimum double value in C/C++

Floating point numbers (IEEE 754) are symmetrical, so if you can represent the greatest value (DBL_MAX or numeric_limits<double>::max()), just prepend a minus sign.

And then is the cool way:

double f;
(*((long long*)&f))= ~(1LL<<52);

Closing Twitter Bootstrap Modal From Angular Controller

**just fire bootstrap modal close button click event**
var app = angular.module('myApp', []);
  $('#btnClose').click();// this is bootstrap modal close button id that fire click event


<div class="modal fade" id="myModal" role="dialog">
    <div class="modal-dialog">
      <div class="modal-content">
        <div class="modal-header">
        <div class="modal-body">
          <p>Some text in the modal.</p>
        <div class="modal-footer">
          <button type="button" id="btnClose" class="btn btn-default" data-dismiss="modal">Close</button>

just set modal 'close button' id as i set btnClose, for closing modal in angular you have to just fire that close button click event as i did $('#btnClose').click()

CSS: Responsive way to center a fluid div (without px width) while limiting the maximum width?

This might sound really simplistic...

But this will center the div inside the div, exactly in the center in relation to left and right margin or parent container, but you can adjust percentage symmetrically on left and right.

margin-right: 10%;
margin-left: 10%;

Then you can adjust % to make it as wide as you want it.

How to capture a backspace on the onkeydown event

event.key === "Backspace" or "Delete"

More recent and much cleaner: use event.key. No more arbitrary number codes!

input.addEventListener('keydown', function(event) {
    const key = event.key; // const {key} = event; ES6+
    if (key === "Backspace" || key === "Delete") {
        return false;

Mozilla Docs

Supported Browsers

How to decrypt a password from SQL server?

You realise that you may be making a rod for your own back for the future. The pwdencrypt() and pwdcompare() are undocumented functions and may not behave the same in future versions of SQL Server.

Why not hash the password using a predictable algorithm such as SHA-2 or better before hitting the DB?

How do I check out a remote Git branch?

Just run these two commands and you should be good to go.

git checkout <branch-name>
git pull origin <branch-name>

How to implement "confirmation" dialog in Jquery UI dialog?

I've created a my own function for a jquery ui confirm dialog. Here is the code

function myConfirm(dialogText, okFunc, cancelFunc, dialogTitle) {
  $('<div style="padding: 10px; max-width: 500px; word-wrap: break-word;">' + dialogText + '</div>').dialog({
    draggable: false,
    modal: true,
    resizable: false,
    width: 'auto',
    title: dialogTitle || 'Confirm',
    minHeight: 75,
    buttons: {
      OK: function () {
        if (typeof (okFunc) == 'function') {
          setTimeout(okFunc, 50);
      Cancel: function () {
        if (typeof (cancelFunc) == 'function') {
          setTimeout(cancelFunc, 50);

Now to use this in your code, simply write following

myConfirm('Do you want to delete this record ?', function () {
    alert('You clicked OK');
  }, function () {
    alert('You clicked Cancel');
  'Confirm Delete'

Go on.

Preventing HTML and Script injections in Javascript

From here

var string="<script>...</script>";
string=encodeURIComponent(string); // %3Cscript%3E...%3C/script%3

Converting from IEnumerable to List

You can do this very simply using LINQ.

Make sure this using is at the top of your C# file:

using System.Linq;

Then use the ToList extension method.


IEnumerable<int> enumerable = Enumerable.Range(1, 300);
List<int> asList = enumerable.ToList();

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

Look at You have to use cors.


$ npm install cors
const cors = require('cors');

You have to put this code in your node server.

Reading CSV file and storing values into an array

You can use Microsoft.VisualBasic.FileIO.TextFieldParser dll in C# for better performance

get below code example from above article

static void Main()
    string csv_file_path=@"C:\Users\Administrator\Desktop\test.csv";

    DataTable csvData = GetDataTabletFromCSVFile(csv_file_path);

    Console.WriteLine("Rows count:" + csvData.Rows.Count);


private static DataTable GetDataTabletFromCSVFile(string csv_file_path)
    DataTable csvData = new DataTable();


    using(TextFieldParser csvReader = new TextFieldParser(csv_file_path))
            csvReader.SetDelimiters(new string[] { "," });
            csvReader.HasFieldsEnclosedInQuotes = true;
            string[] colFields = csvReader.ReadFields();
            foreach (string column in colFields)
                DataColumn datecolumn = new DataColumn(column);
                datecolumn.AllowDBNull = true;

            while (!csvReader.EndOfData)
                string[] fieldData = csvReader.ReadFields();
                //Making empty value as null
                for (int i = 0; i < fieldData.Length; i++)
                    if (fieldData[i] == "")
                        fieldData[i] = null;
    catch (Exception ex)
    return csvData;

Combining multiple commits before pushing in Git

I came up with


message=`git log --format=%B origin..HEAD | sort | uniq | grep -v '^$'`
git reset --soft origin
git commit -m "$message"

Combines, sorts, unifies and remove empty lines from the commit message. I use this for local changes to a github wiki (using gollum)

Java converting Image to BufferedImage

One way to handle this is to create a new BufferedImage, and tell it's graphics object to draw your scaled image into the new BufferedImage:

final float FACTOR  = 4f;
BufferedImage img = File("graphic.png"));
int scaleX = (int) (img.getWidth() * FACTOR);
int scaleY = (int) (img.getHeight() * FACTOR);
Image image = img.getScaledInstance(scaleX, scaleY, Image.SCALE_SMOOTH);
BufferedImage buffered = new BufferedImage(scaleX, scaleY, TYPE);
buffered.getGraphics().drawImage(image, 0, 0 , null);

That should do the trick without casting.

MSIE and addEventListener Problem in Javascript?

Using <meta http-equiv="X-UA-Compatible" content="IE=9">, IE9+ does support addEventListener by removing the "on" in the event name, like this:

 var btn1 = document.getElementById('btn1');
 btn1.addEventListener('mousedown', function() {

Round number to nearest integer

If you need (for example) a two digit approximation for A, then int(A*100+0.5)/100.0 will do what you are looking for.

If you need three digit approximation multiply and divide by 1000 and so on.

"Specified argument was out of the range of valid values"

It seems that you are trying to get 5 items out of a collection with 5 items. Looking at your code, it seems you're starting at the second value in your collection at position 1. Collections are zero-based, so you should start with the item at index 0. Try this:

TextBox box1 = (TextBox)Gridview1.Rows[i].Cells[0].FindControl("txt_type");
TextBox box2 = (TextBox)Gridview1.Rows[i].Cells[1].FindControl("txt_total");
TextBox box3 = (TextBox)Gridview1.Rows[i].Cells[2].FindControl("txt_max");
TextBox box4 = (TextBox)Gridview1.Rows[i].Cells[3].FindControl("txt_min");
TextBox box5 = (TextBox)Gridview1.Rows[i].Cells[4].FindControl("txt_rate");

cannot open shared object file: No such file or directory

When working on a supercomputer, I received this error when I ran:

module load python/3.4.0

To resolve the error, I simply needed to reload the module in the screen terminal:

module load python/3.4.0

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

Make a

class PassMeByRef { public int theValue; }

then pass a reference to an instance of it. Note that a method that mutates state through its arguments is best avoided, especially in parallel code.

How to get "GET" request parameters in JavaScript?

Today I needed to get the page's request parameters into a associative array so I put together the following, with a little help from my friends. It also handles parameters without an = as true.

With an example:

// URL:

var _GET = (function() {
    var _get = {};
    var re = /[?&]([^=&]+)(=?)([^&]*)/g;
    while (m = re.exec(
        _get[decodeURIComponent(m[1])] = (m[2] == '=' ? decodeURIComponent(m[3]) : true);
    return _get;

> Object {abc: "123", def: true, xyz: "", something else: true}
console.log(_GET['something else']);
> true
> 123

Check number of arguments passed to a Bash script

Here a simple one liners to check if only one parameter is given otherwise exit the script:

[ "$#" -ne 1 ] && echo "USAGE $0 <PARAMETER>" && exit

How do I POST XML data with curl

-H "text/xml" isn't a valid header. You need to provide the full header:

-H "Content-Type: text/xml" 

Does Python have a toString() equivalent, and can I convert a db.Model element to String?

In Python we can use the __str__() method.

We can override it in our class like this:

class User: 

    firstName = ''
    lastName = ''

    def __str__(self):
        return self.firstName + " " + self.lastName

and when running


it will call the function __str__(self) and print the firstName and lastName

How to write log file in c#?

Add log to file with Static Class

 public static class LogWriter
            private static string m_exePath = string.Empty;
            public static void LogWrite(string logMessage)
                m_exePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
                if (!File.Exists(m_exePath + "\\" + "log.txt"))
                    File.Create(m_exePath + "\\" + "log.txt");

                    using (StreamWriter w = File.AppendText(m_exePath + "\\" + "log.txt"))
                        AppendLog(logMessage, w);
                catch (Exception ex)


            private static void AppendLog(string logMessage, TextWriter txtWriter)
                    txtWriter.Write("\r\nLog Entry : ");
                    txtWriter.WriteLine("{0} {1}", DateTime.Now.ToLongTimeString(),DateTime.Now.ToLongDateString());
                    txtWriter.WriteLine("  :");
                    txtWriter.WriteLine("  :{0}", logMessage);
                catch (Exception ex)

How would I find the second largest salary from the employee table?

select * from emp 
where sal=(select min(sal) from 
(select sal from(select distinct sal from emp order by sal desc)
where rownum<=n));

n can be the value you want to see......

you can see all the fields of that person who having nth highest salary*strong text*

Twitter Bootstrap Use collapse.js on table cells [Almost Done]

If you're using Angular's ng-repeat to populate the table hackel's jquery snippet will not work by placing it in the document load event. You'll need to run the snippet after angular has finished rendering the table.

To trigger an event after ng-repeat has rendered try this directive:

var app = angular.module('myapp', [])
.directive('onFinishRender', function ($timeout) {
return {
    restrict: 'A',
    link: function (scope, element, attr) {
        if (scope.$last === true) {
            $timeout(function () {

Complete example in angular:

I got the directive from here: Use AngularJS just for routing purposes

Multiple SQL joins

You can use something like this :

FROM Books
INNER JOIN Categories_Books ON Categories_Books._Books_ISBN = Books._ISBN
INNER JOIN Categories ON Categories._CategoryID = Categories_Books._Categories_Category_ID
INNER JOIN Publishers ON Publishers._Publisherid = Books.PublisherID
INNER JOIN Writers_Books ON Writers_Books._Books_ISBN = Books._ISBN
INNER JOIN Writers ON Writers.Writers_Books = _Writers_WriterID.

If conditions in a Makefile, inside a target

You can simply use shell commands. If you want to suppress echoing the output, use the "@" sign. For example:

    @if [ "test" = "test" ]; then\
        echo "Hello world";\

Note that the closing ";" and "\" are necessary.

Simple http post example in Objective-C?

Thanks a lot it worked , please note I did a typo in php as it should be mysqli_query( $con2, $sql )

How to playback MKV video in web browser?

You can use this following code. work just on chrome browser.

 function failed(e) {_x000D_
   // video playback failed - show a message saying why_x000D_
   switch ( {_x000D_
       alert('You aborted the video playback.');_x000D_
       alert('A network error caused the video download to fail part-way.');_x000D_
       alert('The video playback was aborted due to a corruption problem or because the video used features your browser did not support.');_x000D_
       alert('The video could not be loaded, either because the server or network failed or because the format is not supported.');_x000D_
       alert('An unknown error occurred.');_x000D_
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">_x000D_
<html xmlns="" xml:lang="en" lang="en">_x000D_
 <meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />_x000D_
 <meta name="author" content="Amin Developer!" />_x000D_
 <title>Untitled 1</title>_x000D_
<p><video src="" type='video/x-matroska; codecs="theora, vorbis"' autoplay controls onerror="failed(event)" ></video></p>_x000D_
<p><a href="YOU mkv FILE LINK GOES HERE TO DOWNLOAD">Download the video file</a>.</p>_x000D_

Check if PHP session has already started

This is what I use to determine if a session has started. By using empty and isset as follows:

if (empty($_SESSION)  && !isset($_SESSION))  {

Access Database opens as read only

on my pc I had the same problem and it was because in properties -> security I didn't have the ownership of the file...

How to do a redirect to another route with react-router?

For the simple answer, you can use Link component from react-router, instead of button. There is ways to change the route in JS, but seems you don't need that here.

<span className="input-group-btn">
  <Link to="/login" />Click to login</Link>

To do it programmatically in 1.0.x, you do like this, inside your clickHandler function:

this.history.pushState(null, 'login');

Taken from upgrade doc here

You should have this.history placed on your route handler component by react-router. If it child component beneath that mentioned in routes definition, you may need pass that down further

Change Text Color of Selected Option in a Select Box


<select id="sel" onclick="document.getElementById('sel').style.color='green';">
 <option>Select Your Option</option>
 <option value="">INDIA</option>
 <option value="">USA</option>

The above code will change the colour of text on click of the select box.

and if you want every option different colour, give separate class or id to all options.

What are the differences in die() and exit() in PHP?

Functionally, they are identical. So to choose which one to use is totally a personal preference. Semantically in English, they are different. Die sounds negative. When I have a function which returns JSON data to the client and terminate the program, it can be awful if I call this function jsonDie(), and it is more appropriate to call it jsonExit(). For that reason, I always use exit instead of die.

Java Map equivalent in C#

You can index Dictionary, you didn't need 'get'.

Dictionary<string,string> example = new Dictionary<string,string>();

An efficient way to test/get values is TryGetValue (thanx to Earwicker):

if (otherExample.TryGetValue("key", out value))
    otherExample["key"] = value + 1;

With this method you can fast and exception-less get values (if present).



Try Get Value

TypeError: unhashable type: 'list' when using built-in set function

Sets remove duplicate items. In order to do that, the item can't change while in the set. Lists can change after being created, and are termed 'mutable'. You cannot put mutable things in a set.

Lists have an unmutable equivalent, called a 'tuple'. This is how you would write a piece of code that took a list of lists, removed duplicate lists, then sorted it in reverse.

result = sorted(set(map(tuple, my_list)), reverse=True)

Additional note: If a tuple contains a list, the tuple is still considered mutable.

Some examples:

>>> hash( tuple() )
>>> hash( dict() )

Traceback (most recent call last):
  File "<pyshell#5>", line 1, in <module>
    hash( dict() )
TypeError: unhashable type: 'dict'
>>> hash( list() )

Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    hash( list() )
TypeError: unhashable type: 'list'

Finding the index of an item in a list

All of the proposed functions here reproduce inherent language behavior but obscure what's going on.

[i for i in range(len(mylist)) if mylist[i]==myterm]  # get the indices

[each for each in mylist if each==myterm]             # get the items

mylist.index(myterm) if myterm in mylist else None    # get the first index and fail quietly

Why write a function with exception handling if the language provides the methods to do what you want itself?

add image to uitableview cell

Swift 4 solution:

    cell.imageView?.image = UIImage(named: "yourImageName")

height: calc(100%) not working correctly in CSS

You need to ensure the html and body are set to 100% and also be sure to add vendor prefixes for calc, so -moz-calc, -webkit-calc.

Following CSS works:

html,body {
    background: blue;
header {
    background: red;
    height: 20px;
h1 {
    height: 30px;
    font-weight: bold;
#theCalcDiv {
    height: -moz-calc(100% - (20px + 30px));
    height: -webkit-calc(100% - (20px + 30px));
    height: calc(100% - (20px + 30px));

I also set your margin/padding to 0 on html and body, otherwise there would be a scrollbar when this is added on.

Here's an updated fiddle

Browser support is: IE9+, Firefox 16+ and with vendor prefix Firefox 4+, Chrome 19+, Safari 6+

PHP Warning: PHP Startup: Unable to load dynamic library

In my case I got this error because I downloaded a thread-safe version of the dll (infixed with -ts-), but my php installation of php was a non-thread-safe (infixed with -nts-). Downloading the right version of the dll, exactly matching my php installation version fixed the issue.

Select From all tables - MySQL

As Suhel Meman said in the comments:

SELECT column1, column2, column3 FROM table 1
SELECT column1, column2, column3 FROM table 2

would work.

But all your SELECTS would have to consist of the same amount of columns. And because you are displaying it in one resulting table they should contain the same information.

What you might want to do, is a JOIN on Product ID or something like that. This way you would get more columns, which makes more sense most of the time.

When to use RDLC over RDL reports?

if you want to use report in then use .rdl if you want to use /view in report builder / report server then use .rdlc just by converting format manually it works

How to add a form load event (currently not working)

Three ways you can do this - from the form designer, select the form, and where you normally see the list of properties, just above it there should be a little lightning symbol - this shows you all the events of the form. Find the form load event in the list, and you should be able to pick ProgramViwer_Load from the dropdown.

A second way to do it is programmatically - somewhere (constructor maybe) you'd need to add it, something like: ProgramViwer.Load += new EventHandler(ProgramViwer_Load);

A third way using the designer (probably the quickest) - when you create a new form, double click on the middle of it on it in design mode. It'll create a Form load event for you, hook it in, and take you to the event handler code. Then you can just add your two lines and you're good to go!

jquery change style of a div on click

If I understand correctly you want to change the CSS style of an element by clicking an item in a ul list. Am I right?


<div class="results" style="background-color:Red;">

 <ul class="colors-list">


$('.colors-list li').click(function(e){
    var color = $(this).text();

Note that jquery can use addClass, removeClass and toggleClass if you want to use classes rather than inline styling. This means that you can do something like that:


And define the 'selected' styling in the CSS.

Working example:

What is the best way to concatenate two vectors?

In the direction of Bradgonesurfing's answer, many times one doesn't really need to concatenate two vectors (O(n)), but instead just work with them as if they were concatenated (O(1)). If this is your case, it can be done without the need of Boost libraries.

The trick is to create a vector proxy: a wrapper class which manipulates references to both vectors, externally seen as a single, contiguous one.


std::vector<int> A{ 1, 2, 3, 4, 5};
std::vector<int> B{ 10, 20, 30 };

VecProxy<int> AB(A, B);  // ----> O(1). No copies performed.

for (size_t i = 0; i < AB.size(); ++i)
    std::cout << AB[i] << " ";  // 1 2 3 4 5 10 20 30


template <class T>
class VecProxy {
    std::vector<T>& v1, v2;
    VecProxy(std::vector<T>& ref1, std::vector<T>& ref2) : v1(ref1), v2(ref2) {}
    const T& operator[](const size_t& i) const;
    const size_t size() const;

template <class T>
const T& VecProxy<T>::operator[](const size_t& i) const{
    return (i < v1.size()) ? v1[i] : v2[i - v1.size()];

template <class T>
const size_t VecProxy<T>::size() const { return v1.size() + v2.size(); };


It's O(1) (constant time) to create it, and with minimal extra memory allocation.


  • You should only go for it if you really know what you're doing when dealing with references. This solution is intended for the specific purpose of the question made, for which it works pretty well. To employ it in any other context may lead to unexpected behavior if you are not sure on how references work.
  • In this example, AB does not provide a non-const access operator ([ ]). Feel free to include it, but keep in mind: since AB contains references, to assign it values will also affect the original elements within A and/or B. Whether or not this is a desirable feature, it's an application-specific question one should carefully consider.
  • Any changes directly made to either A or B (like assigning values, sorting, etc.) will also "modify" AB. This is not necessarily bad (actually, it can be very handy: AB does never need to be explicitly updated to keep itself synchronized to both A and B), but it's certainly a behavior one must be aware of. Important exception: to resize A and/or B to sth bigger may lead these to be reallocated in memory (for the need of contiguous space), and this would in turn invalidate AB.
  • Because every access to an element is preceded by a test (namely, "i < v1.size()"), VecProxy access time, although constant, is also a bit slower than that of vectors.
  • This approach can be generalized to n vectors. I haven't tried, but it shouldn't be a big deal.

Use a JSON array with objects with javascript

By 'JSON array containing objects' I guess you mean a string containing JSON?

If so you can use the safe var myArray = JSON.parse(myJSON) method (either native or included using JSON2), or the usafe var myArray = eval("(" + myJSON + ")"). eval should normally be avoided, but if you are certain that the content is safe, then there is no problem.

After that you just iterate over the array as normal.

for (var i = 0; i < myArray.length; i++) {

OnChange event using React JS for drop down

React Hooks (16.8+):

const Dropdown = ({
}) => {
  const [selectedOption, setSelectedOption] = useState(options[0].value);
  return (
        onChange={e => setSelectedOption(}>
        { => (
          <option key={o.value} value={o.value}>{o.label}</option>

Avoid dropdown menu close on click inside

This helped me,

$('.dropdown-menu').on('click', function (e) {
     if ($(this).parent().is(".open")) {
         var target = $(;
         if (target.hasClass("keepopen") || target.parents(".keepopen").length){
                    return false; 
                    return true;

Your drop down menu element needs to be like this, (take a note of the classes dropdown-menu and keepopen.

<ul role="menu" class="dropdown-menu topmenu-menu eserv_top_notifications keepopen">

The above code prevents biding on the whole <body>, instead to the specfic element with the class dropdown-menu.

Hope this helps someone.


HTTPS connections over proxy servers

You can accomplish this using man-in-the-middle techniques with dynamic SSL generation. Take a look at mitmproxy - it's a Python based, SSL-capable MITM proxy.

"Strict Standards: Only variables should be passed by reference" error

Instead of parsing it manually it's better to use pathinfo function:

$path_parts = pathinfo($value);
$extension = strtolower($path_parts['extension']);
$fileName = $path_parts['filename'];

Is floating point math broken?

A Hardware Designer's Perspective

I believe I should add a hardware designer’s perspective to this since I design and build floating point hardware. Knowing the origin of the error may help in understanding what is happening in the software, and ultimately, I hope this helps explain the reasons for why floating point errors happen and seem to accumulate over time.

1. Overview

From an engineering perspective, most floating point operations will have some element of error since the hardware that does the floating point computations is only required to have an error of less than one half of one unit in the last place. Therefore, much hardware will stop at a precision that's only necessary to yield an error of less than one half of one unit in the last place for a single operation which is especially problematic in floating point division. What constitutes a single operation depends upon how many operands the unit takes. For most, it is two, but some units take 3 or more operands. Because of this, there is no guarantee that repeated operations will result in a desirable error since the errors add up over time.

2. Standards

Most processors follow the IEEE-754 standard but some use denormalized, or different standards . For example, there is a denormalized mode in IEEE-754 which allows representation of very small floating point numbers at the expense of precision. The following, however, will cover the normalized mode of IEEE-754 which is the typical mode of operation.

In the IEEE-754 standard, hardware designers are allowed any value of error/epsilon as long as it's less than one half of one unit in the last place, and the result only has to be less than one half of one unit in the last place for one operation. This explains why when there are repeated operations, the errors add up. For IEEE-754 double precision, this is the 54th bit, since 53 bits are used to represent the numeric part (normalized), also called the mantissa, of the floating point number (e.g. the 5.3 in 5.3e5). The next sections go into more detail on the causes of hardware error on various floating point operations.

3. Cause of Rounding Error in Division

The main cause of the error in floating point division is the division algorithms used to calculate the quotient. Most computer systems calculate division using multiplication by an inverse, mainly in Z=X/Y, Z = X * (1/Y). A division is computed iteratively i.e. each cycle computes some bits of the quotient until the desired precision is reached, which for IEEE-754 is anything with an error of less than one unit in the last place. The table of reciprocals of Y (1/Y) is known as the quotient selection table (QST) in the slow division, and the size in bits of the quotient selection table is usually the width of the radix, or a number of bits of the quotient computed in each iteration, plus a few guard bits. For the IEEE-754 standard, double precision (64-bit), it would be the size of the radix of the divider, plus a few guard bits k, where k>=2. So for example, a typical Quotient Selection Table for a divider that computes 2 bits of the quotient at a time (radix 4) would be 2+2= 4 bits (plus a few optional bits).

3.1 Division Rounding Error: Approximation of Reciprocal

What reciprocals are in the quotient selection table depend on the division method: slow division such as SRT division, or fast division such as Goldschmidt division; each entry is modified according to the division algorithm in an attempt to yield the lowest possible error. In any case, though, all reciprocals are approximations of the actual reciprocal and introduce some element of error. Both slow division and fast division methods calculate the quotient iteratively, i.e. some number of bits of the quotient are calculated each step, then the result is subtracted from the dividend, and the divider repeats the steps until the error is less than one half of one unit in the last place. Slow division methods calculate a fixed number of digits of the quotient in each step and are usually less expensive to build, and fast division methods calculate a variable number of digits per step and are usually more expensive to build. The most important part of the division methods is that most of them rely upon repeated multiplication by an approximation of a reciprocal, so they are prone to error.

4. Rounding Errors in Other Operations: Truncation

Another cause of the rounding errors in all operations are the different modes of truncation of the final answer that IEEE-754 allows. There's truncate, round-towards-zero, round-to-nearest (default), round-down, and round-up. All methods introduce an element of error of less than one unit in the last place for a single operation. Over time and repeated operations, truncation also adds cumulatively to the resultant error. This truncation error is especially problematic in exponentiation, which involves some form of repeated multiplication.

5. Repeated Operations

Since the hardware that does the floating point calculations only needs to yield a result with an error of less than one half of one unit in the last place for a single operation, the error will grow over repeated operations if not watched. This is the reason that in computations that require a bounded error, mathematicians use methods such as using the round-to-nearest even digit in the last place of IEEE-754, because, over time, the errors are more likely to cancel each other out, and Interval Arithmetic combined with variations of the IEEE 754 rounding modes to predict rounding errors, and correct them. Because of its low relative error compared to other rounding modes, round to nearest even digit (in the last place), is the default rounding mode of IEEE-754.

Note that the default rounding mode, round-to-nearest even digit in the last place, guarantees an error of less than one half of one unit in the last place for one operation. Using the truncation, round-up, and round down alone may result in an error that is greater than one half of one unit in the last place, but less than one unit in the last place, so these modes are not recommended unless they are used in Interval Arithmetic.

6. Summary

In short, the fundamental reason for the errors in floating point operations is a combination of the truncation in hardware, and the truncation of a reciprocal in the case of division. Since the IEEE-754 standard only requires an error of less than one half of one unit in the last place for a single operation, the floating point errors over repeated operations will add up unless corrected.

Arduino error: does not name a type?

I found the solution to this problem in a "}". I did some changes to my sketch and forgot to check for "}" and I had an extra one. As soon as I deleted it and compiled everything was fine.

Center a column using Twitter Bootstrap 3

With Bootstrap v4, this can be accomplished just by adding .justify-content-center to the .row <div>

<div class="row justify-content-center">
    <div class="col-1">centered 1 column</div>

Calling a Function defined inside another function in Javascript

You are not calling the function inner, just defining it.

function outer() { 
    function inner() {

    inner(); //Call the inner function


CSS Pseudo-classes with inline styles

or you can simply try this in inline css

<textarea style="::placeholder{color:white}"/>

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

You have to load jdbc driver. Consider below Code.

try {

            // connect way #1
            String url1 = "jdbc:mysql://localhost:3306/aavikme";
            String user = "root";
            String password = "aa";

            conn1 = DriverManager.getConnection(url1, user, password);
            if (conn1 != null) {
                System.out.println("Connected to the database test1");

            // connect way #2
            String url2 = "jdbc:mysql://localhost:3306/aavikme?user=root&password=aa";
            conn2 = DriverManager.getConnection(url2);
            if (conn2 != null) {
                System.out.println("Connected to the database test2");

            // connect way #3
            String url3 = "jdbc:mysql://localhost:3306/aavikme";
            Properties info = new Properties();
            info.put("user", "root");
            info.put("password", "aa");

            conn3 = DriverManager.getConnection(url3, info);
            if (conn3 != null) {
                System.out.println("Connected to the database test3");
   } catch (SQLException ex) {
            System.out.println("An error occurred. Maybe user/password is invalid");
   } catch (ClassNotFoundException e) {
    // TODO Auto-generated catch block

How to compare two java objects

1) == evaluates reference equality in this case
2) im not too sure about the equals, but why not simply overriding the compare method and plant it inside MyClass?

What is the default lifetime of a session?

But watch out, on most xampp/ampp/...-setups and some linux destributions it's 0, which means the file will never get deleted until you do it within your script (or dirty via shell)


; Lifetime in seconds of cookie or, if 0, until browser is restarted.
session.cookie_lifetime = 0

Adding an image to a project in Visual Studio

Click on the Project in Visual Studio and then click on the button titled "Show all files" on the Solution Explorer toolbar. That will show files that aren't in the project. Now you'll see that image, right click in it, and select "Include in project" and that will add the image to the project!

jQuery $.cookie is not a function

Check that you included the script in header and not in footer of the page. Particularly in WordPress this one didn't work:

wp_register_script('cookie', get_template_directory_uri() . '/js/jquery.cookie.js', array(), false, true);

The last parameter indicates including the script in footer and needed to be changed to false (default). The way it worked:

wp_register_script('cookie', get_template_directory_uri() . '/js/jquery.cookie.js');

Stacked Bar Plot in R

The dataset:

dat <- read.table(text = "A   B   C   D   E   F    G
1 480 780 431 295 670 360  190
2 720 350 377 255 340 615  345
3 460 480 179 560  60 735 1260
4 220 240 876 789 820 100   75", header = TRUE)

Now you can convert the data frame into a matrix and use the barplot function.


enter image description here

how to add background image to activity?

Place the Image in the folder drawable. drawable folder is in res. drawable have 5 variants drawable-hdpi drawable-ldpi drawable-mdpi drawable-xhdpi drawable-xxhdpi

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

On the command prompt, do:

netstat -nb

Take a full page screenshot with Firefox on the command-line

Update 2018-07-23

As was just pointed out in the comments, this question was about getting a screenshot from the command line. Sorry, I just read over that. So here is the correct answer:

As of Firefox 57 you can create a screenshot in headless mode like this:

firefox -screenshot

Read more in the documentation.

Update 2017-06-15

As of Firefox 55 there is Firefox Screenshots as a more flexible alternative. As of Firefox 57 Screenshots can capture a full page, too.

Original answer

Since Firefox 32 there is also a full page screenshot button in the developer tools (F12). If it is not enabled go to the developer tools settings (gear button) and choose "Take a fullpage screenshot" at the "Available Toolbox Buttons" section.

developer tools toolbar source:

By default the screenshots are saved in the download directory. This works similar to screenshot --fullpage in the toolbar.

Sending string via socket (python)

import socket

s = socket.socket()
while True:
    str = raw_input("S: ")
    if(str == "Bye" or str == "bye"):
    print "N:",s.recv(1024).decode()

import socket

s = socket.socket()
port = 12345
s.bind(('', port))
c, addr = s.accept()
print "Socket Up and running with a connection from",addr
while True:
    rcvdData = c.recv(1024).decode()
    print "S:",rcvdData
    sendData = raw_input("N: ")
    if(sendData == "Bye" or sendData == "bye"):

This should be the code for a small prototype for the chatting app you wanted. Run both of them in separate terminals but then just check for the ports.

Run ScrollTop with offset of element by ID

var top = ($(".apps_intro_wrapper_inner").offset() || { "top": NaN }).top;   
if (!isNaN(top)) {
$("#app_scroler").click(function () {   
$('html, body').animate({
            scrollTop: top
        }, 100);

if you want to scroll a little above or below from specific div that add value to the top like I add 800

var top = ($(".apps_intro_wrapper_inner").offset() || { "top": NaN }).top + 800;

How to check if a column exists in a datatable


Show SOME invisible/whitespace characters in Eclipse

Unfortunately, you can only turn on all invisible (whitespace) characters at the same time. I suggest you file an enhancement request but I doubt they will pick it up.

The text component in Eclipse is very complicated as it is and they are not keen on making them even worse.

[UPDATE] This has been fixed in Eclipse 3.7: Go to Window > Preferences > General > Editors > Text Editors

Click on the link "whitespace characters" to fine tune what should be shown.

Kudos go to John Isaacks

What is tail recursion?

Many people have already explained recursion here. I would like to cite a couple of thoughts about some advantages that recursion gives from the book “Concurrency in .NET, Modern patterns of concurrent and parallel programming” by Riccardo Terrell:

“Functional recursion is the natural way to iterate in FP because it avoids mutation of state. During each iteration, a new value is passed into the loop constructor instead to be updated (mutated). In addition, a recursive function can be composed, making your program more modular, as well as introducing opportunities to exploit parallelization."

Here also are some interesting notes from the same book about tail recursion:

Tail-call recursion is a technique that converts a regular recursive function into an optimized version that can handle large inputs without any risks and side effects.

NOTE The primary reason for a tail call as an optimization is to improve data locality, memory usage, and cache usage. By doing a tail call, the callee uses the same stack space as the caller. This reduces memory pressure. It marginally improves the cache because the same memory is reused for subsequent callers and can stay in the cache, rather than evicting an older cache line to make room for a new cache line.

LINQ query to select top five

The solution:

var list = (from t in ctn.Items
           where t.DeliverySelection == true && t.Delivery.SentForDelivery == null
           orderby t.Delivery.SubmissionDate
           select t).Take(5);

How to create a custom string representation for a class object?

class foo(object):
    def __str__(self):
        return "representation"
    def __unicode__(self):
        return u"representation"

Any way to clear python's IDLE window?

"command + L" for MAC OS X.

"control + L" for Ubuntu

Clears the last line on the interactive session

C# LINQ select from list

Execute the GetEventIdsByEventDate() method and save the results in a variable, and then you can use the .Contains() method

How to resolve Unable to load authentication plugin 'caching_sha2_password' issue

Another cause might be the fact that you're pointing to the wrong port.

Make sure you are actually pointing to the right SQL server. You may have a default installation of MySQL running on 3306 but you may actually be needing a different MySQL instance.

Check the ports and run some query against the db.

How to order citations by appearance using BibTeX?

There are three good answers to this question.

  • Use the unsrt bibliography style, if you're happy with its formatting otherwise
  • Use the makebst (link) tool to design your own bibliography style

And my personal recommendation:

  • Use the biblatex package (link). It's the most complete and flexible bibliography tool in the LaTeX world.

Using biblatex, you'd write something like

\bibliography{journals,phd-references} % Where journals.bib and phd-references.bib are BibTeX databases

How do I query using fields inside the new PostgreSQL JSON datatype?

With Postgres 9.3+, just use the -> operator. For example,

SELECT data->'images'->'thumbnail'->'url' AS thumb FROM instagram;

see for some nice examples and a tutorial.

Checking for the correct number of arguments


    if [ "$#" -eq 2 ]
            if [ -d $var1 ]
            echo directory ${var1} exist
            echo Directory ${var1} Does not exists
            if [ -d $var2 ]
            echo directory ${var2} exist
            echo Directory ${var2} Does not exists
    echo "Arguments are not equals to 2"
    exit 1

execute it like below -

./ directory1 directory2

Output will be like -

directory1 exit
directory2 Does not exists

.NET Core vs Mono

.Net Core does not require mono in the sense of the mono framework. .Net Core is a framework that will work on multiple platforms including Linux. Reference

However the .Net core can use the mono framework. Reference (note rc1 documentatiopn no rc2 available), however mono is not a Microsoft supported framework and would recommend using a supported framework

Now entity framework 7 is now called Entity Framework Core and is available on multiple platforms including Linux. Reference (review the road map)

I am currently using both of these frameworks however you must understand that it is still in release candidate stage (RC2 is the current version) and over the beta & release candidates there have been massive changes that usually end up with you scratching your head.

Here is a tutorial on how to install MVC .Net Core into Linux.

Finally you have a choice of Web Servers (where I am assuming the fast cgi reference came from) to host your application on Linux. Here is a reference point for installing to a Linux enviroment.

I realise this post ends up being mostly links to documentation but at this point those are your best sources of information. .Net core is still relatively new in the .Net community and until its fully released I would be hesitant to use it in a product environment given the breaking changes between released version.

No signing certificate "iOS Distribution" found

I had the same issue and I have gone through all these solutions given, but none of them worked for me. But then I realised my stupid mistake. I forgot to change Code signing identity to iOS Distribution from iOS Developer, under build settings tab. Please make sure you have selected 'iOS Distribution' there.

Refused to display in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'

Little late, but this error can also be caused if you use a native application Client ID instead of a web application Client ID.

What is the difference between response.sendRedirect() and request.getRequestDispatcher().forward(request,response)

Redirect and Request dispatcher are two different methods to move form one page to another. if we are using redirect to a new page actually a new request is happening from the client side itself to the new page. so we can see the change in the URL. Since redirection is a new request the old request values are not available here.

How do you access the value of an SQL count () query in a Java program

Use aliases:


and then


SQL Server Linked Server Example Query

Following Query is work best.

Try this Query:


It Very helps to link MySQL to MS SQL

Python 3.2 Unable to import urllib2 (ImportError: No module named urllib2)

    import urllib2

Traceback (most recent call last):

File "", line 1, in

    import urllib2

ImportError: No module named 'urllib2' So urllib2 has been been replaced by the package : urllib.request.

Here is the PEP link (Python Enhancement Proposals )

so instead of urllib2 you can now import urllib.request and then use it like this:

    >>>import urllib.request


Original Link :

Changing Tint / Background color of UITabBar

iOS 5 has added some new appearance methods for customising the look of most UI elements.

You can target every instance of a UITabBar in your app by using the appearance proxy.

For iOS 5 + 6:

[[UITabBar appearance] setTintColor:[UIColor redColor]];

For iOS 7 and above, please use the following:

[[UITabBar appearance] setBarTintColor:[UIColor redColor]];

Using the appearance proxy will change any tab bar instance throughout the app. For a specific instance, use one of the new properties on that class:

UIColor *tintColor; // iOS 5+6
UIColor *barTintColor; // iOS 7+
UIColor *selectedImageTintColor;
UIImage *backgroundImage;
UIImage *selectionIndicatorImage;

Set title background color

This code helps to change the background of the title bar programmatically in Android. Change the color to any color you want.

public void onCreate(Bundle savedInstanceState) 
    getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#1c2833")));


How to check the multiple permission at single request in Android M?

I faced the same problem and below is the workaround I came up with:

public boolean checkForPermission(final String[] permissions, final int permRequestCode, int msgResourceId) {
        final List<String> permissionsNeeded = new ArrayList<>();
        for (int i = 0; i < permissions.length; i++) {
            final String perm = permissions[i];
            if (ContextCompat.checkSelfPermission(getActivity(), permissions[i]) != PackageManager.PERMISSION_GRANTED) {
                if (shouldShowRequestPermissionRationale(permissions[i])) {
                    final AlertDialog dialog = AlertDialog.newInstance( getResources().getString(R.string.permission_title), getResources().getString(msgResourceId) );
                    dialog.setPositiveButton("OK", new View.OnClickListener() {
                        public void onClick(View view) {
                            // add the request.
           getActivity().getSupportFragmentManager(), "HCFAlertDialog" );
                } else {
                    // add the request.

        if (permissionsNeeded.size() > 0) {
            // go ahead and request permissions
            requestPermissions(permissionsNeeded.toArray(new String[permissionsNeeded.size()]), permRequestCode);
            return false;
        } else {
            // no permission need to be asked so all good...we have them all.
            return true;

And you call the above method like this:

if ( checkForPermission( new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, 
Manifest.permission.CAMERA}, REQUEST_PERMISSION_EXTERNAL_STORAGE_RESULT, R.string.permission_image) ) {
                        // DO YOUR STUFF


How to deny access to a file in .htaccess

Well you could use the <Directory> tag for example:

<Directory /inscription>
  <Files log.txt>
    Order allow,deny
    Deny from all

Do not use ./ because if you just use / it looks at the root directory of your site.

For a more detailed example visit

how to bypass Access-Control-Allow-Origin?

I have fixed this problem when calling a MVC3 Controller. I added:

Response.AddHeader("Access-Control-Allow-Origin", "*"); 

before my

return Json(model, JsonRequestBehavior.AllowGet);

And also my $.ajax was complaining that it does not accept Content-type header in my ajax call, so I commented it out as I know its JSON being passed to the Action.

Hope that helps.

How to extract filename.tar.gz file

Check to make sure that the file is complete. This error message can occur if you only partially downloaded a file or if it has major issues. Check the MD5sum.

Sending SMS from PHP

Clickatell is a popular SMS gateway. It works in 200+ countries.

Their API offers a choice of connection options via: HTTP/S, SMPP, SMTP, FTP, XML, SOAP. Any of these options can be used from php.

The HTTP/S method is as simple as this:

The SMTP method consists of sending a plain-text e-mail to: [email protected], with the following body:

user: xxxxx
password: xxxxx
api_id: xxxxx
to: 448311234567
text: Meet me at home

You can also test the gateway (incoming and outgoing) for free from your browser

Toolbar Navigation Hamburger Icon missing

Use this constructor in MyActionBarDrawerToggle :

    public MyActionBarDrawerToggle(AppCompatActivity host, DrawerLayout drawerlayout, SupportToolbar toolbar, int openedResource, int closedResource)
        : base(host, drawerlayout, toolbar, openedResource, closedResource)
        mHostActivity = host;
        mOpenedResource = openedResource;
        mClosedResource = closedResource;

and Call this method in teh mainActivity (Using AppCompatActivity)

        mDrawerToggle = new MyActionBarDrawerToggle(
            this,                           //Host Activity
            mDrawerLayout,                  //DrawerLayout
            mToolbar,                       //Toolbar
            Resource.String.openDrawer,     //Opened Message
            Resource.String.closeDrawer     //Closed Message

        mDrawerToggle.DrawerIndicatorEnabled = true;

Find the division remainder of a number

you can define a function and call it remainder with 2 values like rem(number1,number2) that returns number1%number2 then create a while and set it to true then print out two inputs for your function holding number 1 and 2 then print(rem(number1,number2)

How to delete only the content of file in python

I think the easiest is to simply open the file in write mode and then close it. For example, if your file myfile.dat contains:

"This is the original content"

Then you can simply write:

f = open('myfile.dat', 'w')

This would erase all the content. Then you can write the new content to the file:

f = open('myfile.dat', 'w')
f.write('This is the new content!')

CSS: Fix row height

HTML Table row heights will typically change proportionally to the table height, if the table height is larger than the height of your rows. Since the table is forcing the height of your rows, you can remove the table height to resolve the issue. If this is not acceptable, you can also give the rows explicit height, and add a third row that will auto size to the remaining table height.

Another option in CSS2 is the Max-Height Property, although it may lead to strange behavior in a table.


How to add content to html body using JS?

You can use

document.getElementById("parentID").appendChild(/*..your content created using DOM methods..*/)


document.getElementById("parentID").innerHTML+= "new content"

What is an 'undeclared identifier' error and how do I fix it?

A C++ identifier is a name used to identify a variable, function, class, module, or any other user-defined item. In C++ all names have to be declared before they are used. If you try to use the name of a such that hasn't been declared you will get an "undeclared identifier" compile-error.

According to the documentation, the declaration of printf() is in cstdio i.e. you have to include it, before using the function.

Python, Pandas : write content of DataFrame into text File

I used a slightly modified version:

with open(file_name, 'w', encoding = 'utf-8') as f:
    for rec_index, rec in df.iterrows():
        f.write(rec['<field>'] + '\n')

I had to write the contents of a dataframe field (that was delimited) as a text file.

Find an element in a list of tuples

The filter function can also provide an interesting solution:

result = list(filter(lambda x: x.count(1) > 0, a))

which searches the tuples in the list a for any occurrences of 1. If the search is limited to the first element, the solution can be modified into:

result = list(filter(lambda x: x[0] == 1, a))

How do I "Add Existing Item" an entire directory structure in Visual Studio?

I just want to point out that two of the solutions offered previously,

  • Drag and drop from Windows Explorer
  • Show All Files and then include in project.

do not do what the question asked for:

Include in project while preserving the directory structure.

At least not in my case (C++/CLI project Visual Studio 2013 on Windows 7).

In Visual Studio, once you are back in the normal view (not Show All Files), the files you added are all listed at the top level of the project.

Yes, on disk they still reside where they were, but in Solution Explorer they are loose.

I did not find a way around it except recreating the directory structure in Solution Explorer and then doing Add Existing Items at the right location.

Determine distance from the top of a div to top of window with javascript

I used this:

                              myElement = document.getElemenById("xyz");
Get_Offset_From_Start       ( myElement );  // returns positions from website's start position
Get_Offset_From_CurrentView ( myElement );  // returns positions from current scrolled view's TOP and LEFT


function Get_Offset_From_Start (object, offset) { 
    offset = offset || {x : 0, y : 0};
    offset.x += object.offsetLeft;       offset.y += object.offsetTop;
    if(object.offsetParent) {
        offset = Get_Offset_From_Start (object.offsetParent, offset);
    return offset;

function Get_Offset_From_CurrentView (myElement) {
    if (!myElement) return;
    var offset = Get_Offset_From_Start (myElement);
    var scrolled = GetScrolled (myElement.parentNode);
    var posX = offset.x - scrolled.x;   var posY = offset.y - scrolled.y;
    return {lefttt: posX , toppp: posY };
function GetScrolled (object, scrolled) {
    scrolled = scrolled || {x : 0, y : 0};
    scrolled.x += object.scrollLeft;    scrolled.y += object.scrollTop;
    if (object.tagName.toLowerCase () != "html" && object.parentNode) { scrolled=GetScrolled (object.parentNode, scrolled); }
    return scrolled;

    // live monitoring
    window.addEventListener('scroll', function (evt) {
        var Positionsss =  Get_Offset_From_CurrentView(myElement);  

How to manually include external aar package using new Gradle Android Build System

Unfortunately none of the solutions here worked for me (I get unresolved dependencies). What finally worked and is the easiest way IMHO is: Highlight the project name from Android Studio then File -> New Module -> Import JAR or AAR Package. Credit goes to the solution in this post

Freeze screen in chrome debugger / DevTools panel for popover inspection?

To be able to inspect any element do the following. This should work even if it's hard to duplicate the hover state:

  • Run the following javascript in the console. This will break into the debugger in 5 seconds.

    setTimeout(function(){debugger;}, 5000)

  • Go show your element (by hovering or however) and wait until Chrome breaks into the Debugger.

  • Now click on the Elements tab in the Chrome Inspector, and you can look for your element there.
  • You may also be able to click on the Find Element icon (looks like a magnifying glass) and Chrome will let you go and inspect and find your element on the page by right clicking on it, then choosing Inspect Element

Note that this approach is a slight variation to this other great answer on this page.

How to display both icon and title of action inside ActionBar?

Using app:showAsAction="always|withText". I am using Android 4.1.1, but it should applicable anyway. Mine look like below


jQuery function to open link in new window

Try this,

$('.popup').click(function(event) {
    event.preventDefault();$(this).attr("href"), "popupWindow", "width=600,height=600,scrollbars=yes");

You have to include jQuery reference to work this, here is the working sampe

How to force table cell <td> content to wrap?

If you want fix the column you should set width. For example:

<td style="width:100px;">some data</td>

How can I get the last 7 characters of a PHP string?

for last 7 characters

$newstring = substr($dynamicstring, -7);

$newstring : 5409els

for first 7 characters

$newstring = substr($dynamicstring, 0, 7);

$newstring : 2490slk

check for null date in CASE statement, where have I gone wrong?


    THEN 'Awaiting'
    ELSE 'Approved' END AS StartDateStatus
FROM myTable

You code would have been doing a When StartDate = NULL, I think.

NULL is never equal to NULL (as NULL is the absence of a value). NULL is also never not equal to NULL. The syntax noted above is ANSI SQL standard and the converse would be StartDate IS NOT NULL.

You can run the following:


And this returns:

EqualityCheck = 0
InEqualityCheck = 0
NullComparison = 1

For completeness, in SQL Server you can:


Which would result in your equals comparisons working differently:



Which returns:

EqualityCheck = 1
InEqualityCheck = 0
NullComparison = 1

But I would highly recommend against doing this. People subsequently maintaining your code might be compelled to hunt you down and hurt you...

Also, it will no longer work in upcoming versions of SQL server:

Is there a Java equivalent or methodology for the typedef keyword in C++?

If this is what you mean, you can simply extend the class you would like to typedef, e.g.:

public class MyMap extends HashMap<String, String> {}

How to make connection to Postgres via Node.js

A modern and simple approach: pg-promise:

const pgp = require('pg-promise')(/* initialization options */);

const cn = {
    host: 'localhost', // server name or IP address;
    port: 5432,
    database: 'myDatabase',
    user: 'myUser',
    password: 'myPassword'

// alternative:
// var cn = 'postgres://username:password@host:port/database';

const db = pgp(cn); // database instance;

// select and return a single user name from id:'SELECT name FROM users WHERE id = $1', [123])
    .then(user => {
        console.log(; // print user name;
    .catch(error => {
        console.log(error); // print the error;

// alternative - new ES7 syntax with 'await':
// await'SELECT name FROM users WHERE id = $1', [123]);

See also: How to correctly declare your database module.

How to check if a column exists in a SQL Server table?

A temp table version of the accepted answer:

if (exists(select 1 
             from tempdb.sys.columns  
            where Name = 'columnName'
              and Object_ID = object_id('tempdb..#tableName')))

Checking if a SQL Server login already exists

You can use the built-in function:

SUSER_ID ( [ 'myUsername' ] )


IF [value] IS NULL [statement]


IF SUSER_ID (N'myUsername') IS NULL
CREATE LOGIN [myUsername] WITH PASSWORD=N'myPassword', 

Angular JS update input field after change

I wrote a directive you can use to bind an ng-model to any expression you want. Whenever the expression changes the model is set to the new value.

 module.directive('boundModel', function() {
      return {
        require: 'ngModel',
        link: function(scope, elem, attrs, ngModel) {
          var boundModel$watcher = scope.$watch(attrs.boundModel, function(newValue, oldValue) {
            if(newValue != oldValue) {

          // When $destroy is fired stop watching the change.
          // If you don't, and you come back on your state
          // you'll have two watcher watching the same properties
          scope.$on('$destroy', function() {

You can use it in your templates like this:

 <li>Total<input type="text" ng-model="total" bound-model="one * two"></li>      

How to loop backwards in python?

def reverse(text):
    reversed = ''
    for i in range(len(text)-1, -1, -1):
        reversed += text[i]
    return reversed

print("reverse({}): {}".format("abcd", reverse("abcd")))

IIS7 - The request filtering module is configured to deny a request that exceeds the request content length

The following example Web.config file will configure IIS to deny access for HTTP requests where the length of the "Content-type" header is greater than 100 bytes.

                  <add header="Content-type" sizeLimit="100" />


mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource

This error message is displayed when you have an error in your query which caused it to fail. It will manifest itself when using:

  • mysql_fetch_array/mysqli_fetch_array()
  • mysql_fetch_assoc()/mysqli_fetch_assoc()
  • mysql_num_rows()/mysqli_num_rows()

Note: This error does not appear if no rows are affected by your query. Only a query with an invalid syntax will generate this error.

Troubleshooting Steps

  • Make sure you have your development server configured to display all errors. You can do this by placing this at the top of your files or in your config file: error_reporting(-1);. If you have any syntax errors this will point them out to you.

  • Use mysql_error(). mysql_error() will report any errors MySQL encountered while performing your query.

    Sample usage:

    mysql_connect($host, $username, $password) or die("cannot connect"); 
    mysql_select_db($db_name) or die("cannot select DB");
    $sql = "SELECT * FROM table_name";
    $result = mysql_query($sql);
    if (false === $result) {
        echo mysql_error();
  • Run your query from the MySQL command line or a tool like phpMyAdmin. If you have a syntax error in your query this will tell you what it is.

  • Make sure your quotes are correct. A missing quote around the query or a value can cause a query to fail.

  • Make sure you are escaping your values. Quotes in your query can cause a query to fail (and also leave you open to SQL injections). Use mysql_real_escape_string() to escape your input.

  • Make sure you are not mixing mysqli_* and mysql_* functions. They are not the same thing and cannot be used together. (If you're going to choose one or the other stick with mysqli_*. See below for why.)

Other tips

mysql_* functions should not be used for new code. They are no longer maintained and the community has begun the deprecation process. Instead you should learn about prepared statements and use either PDO or MySQLi. If you can't decide, this article will help to choose. If you care to learn, here is good PDO tutorial.

Any way to exit bash script, but not quitting the terminal

Also make sure to return with expected return value. Else if you use exit when you will encounter an exit it will exit from your base shell since source does not create another process (instance).

Mapping US zip code to time zone

Google has a specific API for this:


  dstOffset: 0,
  rawOffset: -18000,
  status: "OK",
  timeZoneId: "America/New_York",
  timeZoneName: "Eastern Standard Time"

They require a unix timestamp on the querystring. From the response returned it appears that timeZoneName takes into account daylight savings, based on the timestamp, while timeZoneId is a DST-independent name for the timezone.

For my use, in Python, I am just passing timestamp=0 and using the timeZoneId value to get a tz_info object from pytz, I can then use that to localize any particular datetime in my own code.

I believe for PHP similarly you can find "America/New_York" in

Storyboard doesn't contain a view controller with identifier

I tried all of the above solutions and none worked.

What I did was:

  • Project clean
  • Delete derived data
  • Restart Xcode
  • Re-enter the StoryboardID shown in previous answers (inside IB).

And then it worked. The shocking thing was that I had entered the Storyboar ID in interface builder and it got removed/deleted after opening Xcode again.

Hope this helps someone.

What are C++ functors and their uses?

Here's an actual situation where I was forced to use a Functor to solve my problem:

I have a set of functions (say, 20 of them), and they are all identical, except each calls a different specific function in 3 specific spots.

This is incredible waste, and code duplication. Normally I would just pass in a function pointer, and just call that in the 3 spots. (So the code only needs to appear once, instead of twenty times.)

But then I realized, in each case, the specific function required a completely different parameter profile! Sometimes 2 parameters, sometimes 5 parameters, etc.

Another solution would be to have a base class, where the specific function is an overridden method in a derived class. But do I really want to build all of this INHERITANCE, just so I can pass a function pointer????

SOLUTION: So what I did was, I made a wrapper class (a "Functor") which is able to call any of the functions I needed called. I set it up in advance (with its parameters, etc) and then I pass it in instead of a function pointer. Now the called code can trigger the Functor, without knowing what is happening on the inside. It can even call it multiple times (I needed it to call 3 times.)

That's it -- a practical example where a Functor turned out to be the obvious and easy solution, which allowed me to reduce code duplication from 20 functions to 1.

Converting ISO 8601-compliant String to java.util.Date

A little test that shows how to parse a date in ISO8601 and that LocalDateTime does not handle DSTs.

    public void shouldHandleDaylightSavingTimes() throws ParseException {

        //ISO8601 UTC date format
        SimpleDateFormat utcFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");

        // 1 hour of difference between 2 dates in UTC happening at the Daylight Saving Time
        Date d1 = utcFormat.parse("2019-10-27T00:30:00.000Z");
        Date d2 = utcFormat.parse("2019-10-27T01:30:00.000Z");

        //Date 2 is before date 2
        Assert.assertTrue(d1.getTime() < d2.getTime());
        // And there is 1 hour difference between the 2 dates
        Assert.assertEquals(1000*60*60, d2.getTime() - d1.getTime());

        //Print the dates in local time
        SimpleDateFormat localFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm z Z", Locale.forLanguageTag("fr_CH"));

        //Both dates are at 02h30 local time (because of DST), but one is CEST +0200 and the other CET +0100 (clock goes backwards)
        Assert.assertEquals("2019-10-27 02:30 CEST +0200", localFormat.format(d1));
        Assert.assertEquals("2019-10-27 02:30 CET +0100", localFormat.format(d2));

        //Small test that shows that LocalDateTime does not handle DST (and should not be used for storing timeseries data)
        LocalDateTime ld1 = LocalDateTime.ofInstant(d1.toInstant(), ZoneId.of("Europe/Zurich"));
        LocalDateTime ld2 = LocalDateTime.ofInstant(d2.toInstant(), ZoneId.of("Europe/Zurich"));

        //Note that a localdatetime does not handle DST, therefore the 2 dates are the same
        Assert.assertEquals(ld1, ld2);

        //They both have the following local values
        Assert.assertEquals(2019, ld1.getYear());
        Assert.assertEquals(27, ld1.getDayOfMonth());
        Assert.assertEquals(10, ld1.getMonthValue());
        Assert.assertEquals(2, ld1.getHour());
        Assert.assertEquals(30, ld1.getMinute());
        Assert.assertEquals(0, ld1.getSecond());


How to properly add include directories with CMake

This worked for me:

set(SOURCE main.cpp)
add_executable(${PROJECT_NAME} ${SOURCE})

# target_include_directories must be added AFTER add_executable
target_include_directories(${PROJECT_NAME} PUBLIC ${INTERNAL_INCLUDES})

How to add text inside the doughnut chart using Chart.js?

First of all, kudos on choosing Chart.js! I'm using it on one of my current projects and I absolutely love it - it does the job perfectly.

Although labels/tooltips are not part of the library yet, you may want to take a look at these three pull requests:

And, as Cracker0dks mentioned, Chart.js uses canvas for rendering so you may as well just implement your own tooltips by interacting with it directly.

Hope this helps.

How can I get query parameters from a URL in Vue.js?

As of this date, the correct way according to the dynamic routing docs is:


instead of


php $_POST array empty upon form submission

same issue here!

i was trying to connect to my local server code via post request in postman, and this problem wasted my time alot!

for anyone who uses local project (e.g. postman): use your IPv4 address (type ipconfig in cmd) instead of the "localhost" keyword. in my case:




Matplotlib-Animation "No MovieWriters Available"

Had the same problem under Linux. By default the method is using ffmpeg but it seems to be deprecated.

Solution: Install some coder, like avconv or mencoder. Provide the alternative coder in the call:'the_movie.mp4', writer = 'mencoder', fps=15)

How to check whether a given string is valid JSON in Java

A wild idea, try parsing it and catch the exception:

import org.json.*;

public boolean isJSONValid(String test) {
    try {
        new JSONObject(test);
    } catch (JSONException ex) {
        // edited, to include @Arthur's comment
        // e.g. in case JSONArray is valid as well...
        try {
            new JSONArray(test);
        } catch (JSONException ex1) {
            return false;
    return true;

This code uses org.json JSON API implementation that is available on github, in maven and partially on Android.

What is the regex pattern for datetime (2008-09-01 12:35:45 )?

A simple version that will work for the format mentioned, but not all the others as per @Espos:

(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}) 

"Insert if not exists" statement in SQLite

If you never want to have duplicates, you should declare this as a table constraint:

CREATE TABLE bookmarks(
    users_id INTEGER,
    lessoninfo_id INTEGER,
    UNIQUE(users_id, lessoninfo_id)

(A primary key over both columns would have the same effect.)

It is then possible to tell the database that you want to silently ignore records that would violate such a constraint:

INSERT OR IGNORE INTO bookmarks(users_id, lessoninfo_id) VALUES(123, 456)

What is a mutex?

To understand MUTEX at first you need to know what is "race condition" and then only you will understand why MUTEX is needed. Suppose you have a multi-threading program and you have two threads. Now, you have one job in the job queue. The first thread will check the job queue and after finding the job it will start executing it. The second thread will also check the job queue and find that there is one job in the queue. So, it will also assign the same job pointer. So, now what happens, both the threads are executing the same job. This will cause a segmentation fault. This is the example of a race condition.

The solution to this problem is MUTEX. MUTEX is a kind of lock which locks one thread at a time. If another thread wants to lock it, the thread simply gets blocked.

The MUTEX topic in this pdf file link is really worth reading.

How to add multiple classes to a ReactJS Component?

It can be done with :

First install it:

npm install --save clsx

Then import it in your component file:

import clsx from  'clsx';

Then use the imported function in your component:

<div className={ clsx(classes.class1, classes.class2)}>

Print "hello world" every X seconds

public class HelloWorld extends TimerTask{

    public void run() {

        System.out.println("Hello World");

public class PrintHelloWorld {
    public static void main(String[] args) {
        Timer timer = new Timer();
        timer.schedule(new HelloWorld(), 0, 5000);

        while (true) {
            try {
            } catch (InterruptedException e) {
                System.out.println("InterruptedException Exception" + e.getMessage());

infinite loop is created ad scheduler task is configured.

android splash screen sizes for ldpi,mdpi, hdpi, xhdpi displays ? - eg : 1024X768 pixels for ldpi

Splash screen sizes for Android

and at the same time for Cordova (a.k.a Phonegap), React-Native and all other development platforms

Format : 9-Patch PNG (recommended)


 - LDPI:
    - Portrait: 200x320px
    - Landscape: 320x200px
 - MDPI:
    - Portrait: 320x480px
    - Landscape: 480x320px
 - HDPI:
    - Portrait: 480x800px
    - Landscape: 800x480px
    - Portrait: 720px1280px
    - Landscape: 1280x720px
    - Portrait: 960x1600px
    - Landscape: 1600x960px
    - Portrait: 1280x1920px
    - Landscape: 1920x1280px

Note: Preparing XXXHDPI is not needed and also maybe XXHDPI size too because of the repeating areas of 9-patch images. On the other hand, if only Portrait sizes are used the App size could be more less. More pictures mean more space is need.

Pay attention

I think there is no an exact size for the all devices. I use Xperia Z 5". If you develop a crossplatform-webview app you should consider a lot of things (whether screen has softkey navigation buttons or not, etc). Therefore, I think there is only one suitable solution. The solution is to prepare a 9-patch splash screen (find How to design a new splash screen heading below).

  1. Create splash screens for the above screen sizes as 9-patch. Give names your files with .9.png suffixes
  2. Add the lines below into your config.xml file
  3. Add the splash screen plugin if it's needed.
  4. Run your project.

That's it!

Cordova specific code
To be added lines into the config.xml for 9-patch splash screens

<preference name="SplashScreen" value="screen" />
<preference name="SplashScreenDelay" value="6000" />
<platform name="android">
    <splash src="res/screen/android/ldpi.9.png" density="ldpi"/>
    <splash src="res/screen/android/mdpi.9.png" density="mdpi"/>
    <splash src="res/screen/android/hdpi.9.png" density="hdpi"/>
    <splash src="res/screen/android/xhdpi.9.png" density="xhdpi"/> 

To be added lines into the config.xml when using non-9-patch splash screens

<platform name="android">
    <splash src="res/screen/android/splash-land-hdpi.png" density="land-hdpi"/>
    <splash src="res/screen/android/splash-land-ldpi.png" density="land-ldpi"/>
    <splash src="res/screen/android/splash-land-mdpi.png" density="land-mdpi"/>
    <splash src="res/screen/android/splash-land-xhdpi.png" density="land-xhdpi"/>

    <splash src="res/screen/android/splash-port-hdpi.png" density="port-hdpi"/>
    <splash src="res/screen/android/splash-port-ldpi.png" density="port-ldpi"/>
    <splash src="res/screen/android/splash-port-mdpi.png" density="port-mdpi"/>
    <splash src="res/screen/android/splash-port-xhdpi.png" density="port-xhdpi"/>

How to design a new splash screen

I would describe a simple way to create proper splash screen using this way. Assume we're designing a 1280dp x 720dp - xhdpi (x-large) screen. I've written for the sake of example the below;

  • In Photoshop: File -> New in new dialog window set your screens

    Width: 720 Pixels Height: 1280 Pixels

    I guess the above sizes mean Resolution is 320 Pixels/Inch. But to ensure you can change resolution value to 320 in your dialog window. In this case Pixels/Inch = DPI

    Congratulations... You have a 720dp x 1280dp splash screen template.

How to generate a 9-patch splash screen

After you designed your splash screen, if you want to design 9-Patch splash screen, you should insert 1 pixel gap for every side. For this reason you should increase +2 pixel your canvas size's width and height ( now your image sizes are 722 x 1282 ).

I've left the blank 1 pixel gap at every side as directed the below.
Changing the canvas size by using Photoshop:
- Open a splash screen png file in Photoshop
- Click onto the lock icon next to the 'Background' name in the Layers field (to leave blank instead of another color like white) if there is like the below:
enter image description here
- Change the canvas size from Image menu ( Width: 720 pixels to 722 pixels and Height: 1280 pixels to 1282 pixels). Now, should see 1 pixel gap at every side of the splash screen image.

Then you can use C:\Program Files (x86)\Android\android-studio\sdk\tools\draw9patch.bat to convert a 9-patch file. For that open your splash screen on draw9patch app. You should define your logo and expandable areas. Notice the black line the following example splash screen. The black line's thickness is just 1 px ;) Left and Top sides black lines define your splash screen's must display area. Exactly as your designed. Right and Bottom lines define the addable and removable area (automatically repeating areas).

Just do that: Zoom your image's top edge on draw9patch application. Click and drag your mouse to draw line. And press shift + click and drag your mouse to erase line.

Sample 9-patch design

If you develop a cross-platform app (like Cordova/PhoneGap) you can find the following address almost all mabile OS splash screen sizes. Click for Windows Phone, WebOS, BlackBerry, Bada-WAC and Bada splash screen sizes.

And if you need IOS, Android etc. app icon sizes you can visit here.


Format : PNG (recommended)


 - Tablet (iPad)
   - Non-Retina (1x)
     - Portrait: 768x1024px
     - Landscape: 1024x768px
   - Retina (2x)
     - Portrait: 1536x2048px
     - Landscape: 2048x1536px
 - Handheld (iPhone, iPod)
   - Non-Retina (1x)
     - Portrait: 320x480px
     - Landscape: 480x320px
   - Retina (2x)
     - Portrait: 640x960px
     - Landscape: 960x640px
 - iPhone 5 Retina (2x)
   - Portrait: 640x1136px
   - Landscape: 1136x640px
 - iPhone 6 (2x)
   - Portrait: 750x1334px
   - Landscape: 1334x750px
 - iPhone 6 Plus (3x)
   - Portrait: 1242x2208px
   - Landscape: 2208x1242px

How to pass an event object to a function in Javascript?

Although this is the accepted answer, toto_tico's answer below is better :)

Try making the onclick js use 'return' to ensure the desired return value gets used...

<button type="button" value="click me" onclick="return check_me();" />

Getting the count of unique values in a column in bash

To see a frequency count for column two (for example):

awk -F '\t' '{print $2}' * | sort | uniq -c | sort -nr


z    z    a
a    b    c
w    d    e


t    r    e
z    d    a
a    g    c


z    r    a
v    d    c
a    m    c


  3 d
  2 r
  1 z
  1 m
  1 g
  1 b

What is the relative performance difference of if/else versus switch statement in Java?

I totally agree with the opinion that premature optimization is something to avoid.

But it's true that the Java VM has special bytecodes which could be used for switch()'s.

See WM Spec (lookupswitch and tableswitch)

So there could be some performance gains, if the code is part of the performance CPU graph.

Make var_dump look pretty

Try xdebug extension for php.


<?php var_dump($_SERVER); ?>


enter image description here

How to add noise (Gaussian/salt and pepper etc) to image in Python with OpenCV

just look at cv2.randu() or cv.randn(), it's all pretty similar to matlab already, i guess.

let's play a bit ;) :

import cv2
import numpy as np

>>> im = np.empty((5,5), np.uint8) # needs preallocated input image
>>> im
array([[248, 168,  58,   2,   1],  # uninitialized memory counts as random, too ?  fun ;) 
       [  0, 100,   2,   0, 101],
       [  0,   0, 106,   2,   0],
       [131,   2,   0,  90,   3],
       [  0, 100,   1,   0,  83]], dtype=uint8)
>>> im = np.zeros((5,5), np.uint8) # seriously now.
>>> im
array([[0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0]], dtype=uint8)
>>> cv2.randn(im,(0),(99))         # normal
array([[  0,  76,   0, 129,   0],
       [  0,   0,   0, 188,  27],
       [  0, 152,   0,   0,   0],
       [  0,   0, 134,  79,   0],
       [  0, 181,  36, 128,   0]], dtype=uint8)
>>> cv2.randu(im,(0),(99))         # uniform
array([[19, 53,  2, 86, 82],
       [86, 73, 40, 64, 78],
       [34, 20, 62, 80,  7],
       [24, 92, 37, 60, 72],
       [40, 12, 27, 33, 18]], dtype=uint8)

to apply it to an existing image, just generate noise in the desired range, and add it:

img = ...
noise = ...

image = img + noise

Excel VBA Run Time Error '424' object required

The first code line, Option Explicit means (in simple terms) that all of your variables have to be explicitly declared by Dim statements. They can be any type, including object, integer, string, or even a variant.

This line: Dim envFrmwrkPath As Range is declaring the variable envFrmwrkPath of type Range. This means that you can only set it to a range.

This line: Set envFrmwrkPath = ActiveSheet.Range("D6").Value is attempting to set the Range type variable to a specific Value that is in cell D6. This could be a integer or a string for example (depends on what you have in that cell) but it's not a range.

I'm assuming you want the value stored in a variable. Try something like this:

Dim MyVariableName As Integer
MyVariableName = ActiveSheet.Range("D6").Value

This assumes you have a number (like 5) in cell D6. Now your variable will have the value.

For simplicity sake of learning, you can remove or comment out the Option Explicit line and VBA will try to determine the type of variables at run time.

Try this to get through this part of your code

Dim envFrmwrkPath As String
Dim ApplicationName As String
Dim TestIterationName As String

Angular HttpClient "Http failure during parsing"

I had the same problem and the cause was That at time of returning a string in your backend (spring) you might be returning as return "spring used"; But this isn't parsed right according to spring. Instead use return "\" spring used \""; -Peace out

Create a button programmatically and set a background image

Try below:

let image = UIImage(named: "ImageName.png") as UIImage
var button   = UIButton.buttonWithType(UIButtonType.System) as UIButton
button.frame = CGRectMake(100, 100, 100, 100)
button .setBackgroundImage(image, forState: UIControlState.Normal)
button.addTarget(self, action: "Action:", forControlEvents:UIControlEvents.TouchUpInside)

Let me know whether if it works or not?

MATLAB error: Undefined function or method X for input arguments of type 'double'

The error code indicates the function definition cannot be found. Make sure you're calling the function from the same workspace as the divrat.m file is stored. And make sure divrat function is not a subfunction, it should be first function declaration in the file. You can also try to call the function from the same divrat.m file in order to see if the problem is with workspace selection or the function.

By the way, why didn't you simply say

s = sqrt(diag(C));

Wouldn't it be the same?

How to bind WPF button to a command in ViewModelBase?

 <Grid >
        <ColumnDefinition Width="*"/>
    <Button Command="{Binding ClickCommand}" Width="100" Height="100" Content="wefwfwef"/>

the code behind for the window:

public partial class MainWindow : Window
    public MainWindow()
        DataContext = new ViewModelBase();

The ViewModel:

public class ViewModelBase
    private ICommand _clickCommand;
    public ICommand ClickCommand
            return _clickCommand ?? (_clickCommand = new CommandHandler(() => MyAction(), ()=> CanExecute));
     public bool CanExecute
            // check if executing is allowed, i.e., validate, check if a process is running, etc. 
            return true/false;

    public void MyAction()


Command Handler:

 public class CommandHandler : ICommand
    private Action _action;
    private Func<bool> _canExecute;

    /// <summary>
    /// Creates instance of the command handler
    /// </summary>
    /// <param name="action">Action to be executed by the command</param>
    /// <param name="canExecute">A bolean property to containing current permissions to execute the command</param>
    public CommandHandler(Action action, Func<bool> canExecute)
        _action = action;
        _canExecute = canExecute;

    /// <summary>
    /// Wires CanExecuteChanged event 
    /// </summary>
    public event EventHandler CanExecuteChanged
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }

    /// <summary>
    /// Forcess checking if execute is allowed
    /// </summary>
    /// <param name="parameter"></param>
    /// <returns></returns>
    public bool CanExecute(object parameter)
        return _canExecute.Invoke();

    public void Execute(object parameter)

I hope this will give you the idea.

How to print a single backslash?

A hacky way of printing a backslash that doesn't involve escaping is to pass its character code to chr:

>>> print(chr(92))

ImportError: No module named mysql.connector using Python2

I used the following command to install python mysql-connector in Mac. it works

pip install mysql-connector-python-rf

How to auto adjust table td width from the content

Remove all widths set using CSS and set white-space to nowrap like so:

.content-loader tr td {
    white-space: nowrap;

I would also remove the fixed width from the container (or add overflow-x: scroll to the container) if you want the fields to display in their entirety without it looking odd...

See more here:

Can anyone explain me StandardScaler?

StandardScaler performs the task of Standardization. Usually a dataset contains variables that are different in scale. For e.g. an Employee dataset will contain AGE column with values on scale 20-70 and SALARY column with values on scale 10000-80000.
As these two columns are different in scale, they are Standardized to have common scale while building machine learning model.

What MIME type should I use for CSV?

You should use "text/csv" according to RFC 4180.

create multiple tag docker image

You can't create tags with Dockerfiles but you can create multiple tags on your images via the command line.

Use this to list your image ids:

$ docker images

Then tag away:

$ docker tag 9f676bd305a4 ubuntu:13.10
$ docker tag 9f676bd305a4 ubuntu:saucy
$ docker tag eb601b8965b8 ubuntu:raring

`React/RCTBridgeModule.h` file not found

I ran into this issue after doing a manual react-native link of a dependency which didn't support auto link on RN 0.59+

The solution was to select the xcodeproj file under the Libraries folder in Xcode and then in Build Settings, change Header Search Paths to add these two (recursive):


MySQL Query - Records between Today and Last 30 Days

You need to apply DATE_FORMAT in the SELECT clause, not the WHERE clause:

SELECT  DATE_FORMAT(create_date, '%m/%d/%Y')
FROM    mytable

Also note that CURDATE() returns only the DATE portion of the date, so if you store create_date as a DATETIME with the time portion filled, this query will not select the today's records.

In this case, you'll need to use NOW instead:

SELECT  DATE_FORMAT(create_date, '%m/%d/%Y')
FROM    mytable

Executing a command stored in a variable from PowerShell

Here is yet another way without Invoke-Expression but with two variables (command:string and parameters:array). It works fine for me. Assume 7z.exe is in the system path.

$cmd = '7z.exe'
$prm = 'a', '-tzip', 'c:\temp\with space\', 'C:\TEMP\with space\changelog'

& $cmd $prm

If the command is known (7z.exe) and only parameters are variable then this will do

$prm = 'a', '-tzip', 'c:\temp\with space\', 'C:\TEMP\with space\changelog'

& 7z.exe $prm

BTW, Invoke-Expression with one parameter works for me, too, e.g. this works

$cmd = '& 7z.exe a -tzip "c:\temp\with space\" "C:\TEMP\with space\changelog"'

Invoke-Expression $cmd

P.S. I usually prefer the way with a parameter array because it is easier to compose programmatically than to build an expression for Invoke-Expression.

Matching an optional substring in a regex

This ought to work:


Haven't tested it though, but let me give you the breakdown, so if there are any bugs left they should be pretty straightforward to find:

First the beginning:

^ = beginning of string
\d+ = one or more decimal characters
\s? = one optional whitespace

Then this part:


Is actually:


Which makes the following contents optional, only if it exists fully


\( = an opening bracket
[^\)]+ = a series of at least one character that is not a closing bracket
\) = followed by a closing bracket
\s? = followed by one optional whitespace

And the end is made up of



Z = your constant string
$ = the end of the string

AndroidStudio SDK directory does not exists

Right click your project and select 'Open Module Settings' under SDK Location put your location for your SDK.

paste in /Users/AhmadMusa/Library/Android/sdk

Clean and rebuild your project


Try to delete your file and create a new one, but do not check it into version control.

Right click top level of project and Create new file '' then add: sdk.dir=/Users/AhmadMusa/Library/Android/sdk

Clean and build

Where/How to getIntent().getExtras() in an Android Fragment?

What I tend to do, and I believe this is what Google intended for developers to do too, is to still get the extras from an Intent in an Activity and then pass any extra data to fragments by instantiating them with arguments.

There's actually an example on the Android dev blog that illustrates this concept, and you'll see this in several of the API demos too. Although this specific example is given for API 3.0+ fragments, the same flow applies when using FragmentActivity and Fragment from the support library.

You first retrieve the intent extras as usual in your activity and pass them on as arguments to the fragment:

public static class DetailsActivity extends FragmentActivity {

    protected void onCreate(Bundle savedInstanceState) {

        // (omitted some other stuff)

        if (savedInstanceState == null) {
            // During initial setup, plug in the details fragment.
            DetailsFragment details = new DetailsFragment();
          , details).commit();

In stead of directly invoking the constructor, it's probably easier to use a static method that plugs the arguments into the fragment for you. Such a method is often called newInstance in the examples given by Google. There actually is a newInstance method in DetailsFragment, so I'm unsure why it isn't used in the snippet above...

Anyways, all extras provided as argument upon creating the fragment, will be available by calling getArguments(). Since this returns a Bundle, its usage is similar to that of the extras in an Activity.

public static class DetailsFragment extends Fragment {
     * Create a new instance of DetailsFragment, initialized to
     * show the text at 'index'.
    public static DetailsFragment newInstance(int index) {
        DetailsFragment f = new DetailsFragment();

        // Supply index input as an argument.
        Bundle args = new Bundle();
        args.putInt("index", index);

        return f;

    public int getShownIndex() {
        return getArguments().getInt("index", 0);

    // (other stuff omitted)


Does JavaScript pass by reference?

Primitives are passed by value, and Objects are passed by "copy of a reference".

Specifically, when you pass an object (or array) you are (invisibly) passing a reference to that object, and it is possible to modify the contents of that object, but if you attempt to overwrite the reference it will not affect the copy of the reference held by the caller - i.e. the reference itself is passed by value:

function replace(ref) {
    ref = {};           // this code does _not_ affect the object passed

function update(ref) {
    ref.key = 'newvalue';  // this code _does_ affect the _contents_ of the object

var a = { key: 'value' };
replace(a);  // a still has its original value - it's unmodfied
update(a);   // the _contents_ of 'a' are changed

Single controller with multiple GET methods in ASP.NET Web API

You need to define further routes in global.asax.cs like this:

    name: "Api with action",
    routeTemplate: "api/{controller}/{action}/{id}",
    defaults: new { id = RouteParameter.Optional }

    name: "DefaultApi",
    routeTemplate: "api/{controller}/{id}",
    defaults: new { id = RouteParameter.Optional }

Enabling CORS in Cloud Functions for Firebase

There are two sample functions provided by the Firebase team that demonstrate the use of CORS:

The second sample uses a different way of working with cors than you're currently using.

Consider importing like this, as shown in the samples:

const cors = require('cors')({origin: true});

And the general form of your function will be like this:

exports.fn = functions.https.onRequest((req, res) => {
    cors(req, res, () => {
        // your function body here - use the provided req and res from cors

How to access command line arguments of the caller inside a function?

Ravi's comment is essentially the answer. Functions take their own arguments. If you want them to be the same as the command-line arguments, you must pass them in. Otherwise, you're clearly calling a function without arguments.

That said, you could if you like store the command-line arguments in a global array to use within other functions:

my_function() {
    echo "stored arguments:"
    for arg in "${commandline_args[@]}"; do
        echo "    $arg"



You have to access the command-line arguments through the commandline_args variable, not $@, $1, $2, etc., but they're available. I'm unaware of any way to assign directly to the argument array, but if someone knows one, please enlighten me!

Also, note the way I've used and quoted $@ - this is how you ensure special characters (whitespace) don't get mucked up.

Efficient SQL test query or validation query that will work across all (or most) databases

Assuming the OP wants a Java answer:

As of JDBC3 / Java 6 there's the isValid() method which should be used rather than inventing one's own method.

The implementer of the driver is required to execute some sort of query against the database when this method id called. You - as a mere JDBC user - do not have to know or understand what this query is. All you have to do is to trust that the creator of the JDBC driver has done his/her work properly.

how to display excel sheet in html page

Like you, I cannot get MS Office Web Components to work. I would not consider Google Docs since Google seems to think they own anything that passes through their hands. I have tried MS Publish Objects but the quality of the generated html/css is truely awful.

The secret of converting an Excel worksheet to html that will display correctly on a smartphone is to create clean, lean html/css.

The structure of the HTML is:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
<html xmlns="" xml:lang="en" lang="en">
  <head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>

There are useful html elements that can replace "HEAD" but it is not clear to me how you would generate them from an Excel worksheet. They would need to be added separately.

The obvious output for a worksheet or a range is an html table so the following assumes BODY will be replaced by an html table.

The structure of an html table is:

    More <td>...</td> elements as necessary
  More <tr>...</tr> as necessary

Include as few TABLE-ATTRIBUTES, TABLE-ROW-ATTRIBUTES and TABLE-CELL-ATTRIBUTES as possible. Do not set column widths in pixels. Use css attributes rather than html attributes.

A table attribute worth considering is style = "border-collapse: collapse;". The default is separate with a gap around each cell. With collapse the cells touch as they do with Excel.

Three table attribute worth considering are style="background-color:aliceblue;", style="color:#0000FF;" and style="text-align:right;". With the first, you can specify the background colour to be any of the fifty or so named html colours. With the second, you can specify the font colour to be any of 256*256*256 colours. With the third you can right-align numeric values.

The above covers only a fraction of the formatting information that could be converted from Excel to html/css. I am developing an add-in that will convert as much Excel formatting as possible but I hope the above helps anyone with simple requirements.

Display a loading bar before the entire page is loaded

I've recently made a page loader in vanilla .js for a project, just wanted to share it as all the other answers are jQuery based. It's a plug and play, one-liner.

It automatically creates a <div> tag prepended to the <body>, with a <svg> loader. If you want to customize the color you just have to update the t variable at the beginning of the script.

var t="#106CF6",u=document.querySelector("*"),s=document.createElement("style"),a=document.createElement("aside"),m="",g=document.createElementNS(m,"svg"),c=document.createElementNS(m,"circle");document.head.appendChild(s),(s.innerHTML="#sailor {background:"+t+";color:"+t+";display:flex;align-items:center;justify-content:center;position:fixed;top:0;height:100vh;width:100vw;z-index:2147483647}@keyframes swell{to{transform:rotate(360deg)}}#sailor svg{animation:.3s swell infinite linear}"),a.setAttribute("id","sailor"),document.body.prepend(a),g.setAttribute("height","50"),g.setAttribute("filter","brightness(175%)"),g.setAttribute("viewBox","0 0 100 100"),a.prepend(g),c.setAttribute("cx","50"),c.setAttribute("cy","50"),c.setAttribute("r","35"),c.setAttribute("fill","none"),c.setAttribute("stroke","currentColor"),c.setAttribute("stroke-dasharray","165 57"),c.setAttribute("stroke-width","10"),g.prepend(c),("none"),("none"),("wait"),window.addEventListener("load",function(){setTimeout(function(){(""),(""),("");a.remove()},100)})

You can see the full project and documentation on the GitHub

pros and cons between os.path.exists vs os.path.isdir

Just like it sounds like: if the path exists, but is a file and not a directory, isdir will return False. Meanwhile, exists will return True in both cases.

Copy or rsync command

For a local copy, the only advantage of rsync is that it will avoid copying if the file already exists in the destination directory. The definition of "already exists" is (a) same file name (b) same size (c) same timestamp. (Maybe same owner/group; I am not sure...)

The "rsync algorithm" is great for incremental updates of a file over a slow network link, but it will not buy you much for a local copy, as it needs to read the existing (partial) file to run it's "diff" computation.

So if you are running this sort of command frequently, and the set of changed files is small relative to the total number of files, you should find that rsync is faster than cp. (Also rsync has a --delete option that you might find useful.)

jQuery check/uncheck radio button onclick

-- EDIT --

It sure looks like your code is forcing a radio input to behave like a checkbox input. You might think about just using a checkbox input without the need for jQuery. However, if you want to force, like @manji said, you need to store the value outside the click handler and then set it on each click to the opposite of what it is at that time. @manji's answer is correct, I would just add that you should cache jQuery objects instead of re-querying the DOM:

var $radio = $("#radioinstant"),
    isChecked = $radio.attr("checked");

$ {

    isChecked = !isChecked;
    $(this).attr("checked", isChecked);