Programs & Examples On #Apt

Debian's Advanced Packaging Tool whose main binary is apt-get. Most questions about APT are off topic for Stack Overflow, unless it is clearly related to a programming tool.

Installing SciPy and NumPy using pip

On windows python 3.5, I managed to install scipy by using conda not pip:

conda install scipy

How to check the version before installing a package using apt-get?

OK, I found it.

apt-cache policy <package name> will show the version details.

It also shows which version is currently installed and which versions are available to install.

For example, apt-cache policy hylafax+

Package php5 have no installation candidate (Ubuntu 16.04)

This worked for me.

sudo apt-get update
sudo apt-get install lamp-server^ -y


E: Unable to locate package npm

From the official Node.js documentation:

A Node.js package is also available in the official repo for Debian Sid (unstable), Jessie (testing) and Wheezy (wheezy-backports) as "nodejs". It only installs a nodejs binary.

So, if you only type sudo apt-get install nodejs , it does not install other goodies such as npm.

You need to type:

curl -sL | sudo -E bash -
sudo apt-get install -y nodejs

Optional: install build tools

To compile and install native add-ons from npm you may also need to install build tools:

sudo apt-get install -y build-essential

More info: Docs

How to update-alternatives to Python 3 without breaking apt?

Somehow python 3 came back (after some updates?) and is causing big issues with apt updates, so I've decided to remove python 3 completely from the alternatives:

root:~# python -V
Python 3.5.2

root:~# update-alternatives --config python
There are 2 choices for the alternative python (providing /usr/bin/python).

  Selection    Path                Priority   Status
* 0            /usr/bin/python3.5   3         auto mode
  1            /usr/bin/python2.7   2         manual mode
  2            /usr/bin/python3.5   3         manual mode

root:~# update-alternatives --remove python /usr/bin/python3.5

root:~# update-alternatives --config python
There is 1 choice for the alternative python (providing /usr/bin/python).

    Selection    Path                Priority   Status
  0            /usr/bin/python2.7   2         auto mode
* 1            /usr/bin/python2.7   2         manual mode

Press <enter> to keep the current choice[*], or type selection number: 0

root:~# python -V
Python 2.7.12

root:~# update-alternatives --config python
There is only one alternative in link group python (providing /usr/bin/python): /usr/bin/python2.7
Nothing to configure.

How to install "make" in ubuntu?

I have no idea what linux distribution "ubuntu centOS" is. Ubuntu and CentOS are two different distributions.

To answer the question in the header: To install make in ubuntu you have to install build-essentials

sudo apt-get install build-essential

How do you run `apt-get` in a dockerfile behind a proxy?


You have wrong capitalization of environment variables in ENV. Correct one is http_proxy. Your example should be:

FROM ubuntu:13.10
ENV http_proxy <HTTP_PROXY>
ENV https_proxy <HTTPS_PROXY>
RUN apt-get update && apt-get upgrade


FROM centos
ENV http_proxy <HTTP_PROXY>
ENV https_proxy <HTTPS_PROXY>
RUN yum update 

All variables specified in ENV are prepended to every RUN command. Every RUN command is executed in own container/environment, so it does not inherit variables from previous RUN commands!

Note: There is no need to call docker daemon with proxy for this to work, although if you want to pull images etc. you need to set the proxy for docker deamon too. You can set proxy for daemon in /etc/default/docker in Ubuntu (it does not affect containers setting).

Also, this can happen in case you run your proxy on host (i.e. localhost, Localhost on host differ from localhost in container. In such case, you need to use another IP (like to bind your proxy to or if you bind to, you can use instead of for connection from container during docker build.

You can also look for an example here: How to rebuild dockerfile quick by using cache?

Install MySQL on Ubuntu without a password prompt


sudo DEBIAN_FRONTEND=noninteractive apt-get install -y mysql-server

sudo mysql -h127.0.0.1 -P3306 -uroot -e"UPDATE mysql.user SET password = PASSWORD('yourpassword') WHERE user = 'root'"

Amazon Linux: apt-get: command not found

For openSUSE Linux distribution:

sudo zypper install <package>

For example:

sudo zypper install git

What is the difference/usage of homebrew, macports or other package installation tools?

MacPorts is the way to go.

  1. Like @user475443 pointed, MacPorts has many many more packages. With brew you'll find yourself trapped soon because the formula you need doesn't exist.

  2. MacPorts is a native application: C + TCL. You don't need Ruby at all. To install Ruby on Mac OS X you might need MacPorts, so just go with MacPorts and you'll be happy.

  3. MacPorts is really stable, in 8 years I never had a problem with it, and my entire Unix ecosystem relay on it.

  4. If you are a PHP developer you can install the last version of Apache (Mac OS X uses 2.2), PHP and all the extensions you need, then upgrade all with one command. Forget to do the same with Homebrew.

  5. MacPorts support groups.

    foo@macpro:~/ port select --summary
    Name        Selected      Options
    ====        ========      =======
    db          none          db46 none
    gcc         none          gcc42 llvm-gcc42 mp-gcc48 none
    llvm        none          mp-llvm-3.3 none
    mysql       mysql56       mysql56 none
    php         php55         php55 php56 none
    postgresql  postgresql94  postgresql93 postgresql94 none
    python      none          python24 python25-apple python26-apple python27 python27-apple none

    If you have both PHP55 and PHP56 installed (with many different extensions), you can swap between them with just one command. All the relative extensions are part of the group and they will be activated within the chosen group: php55 or php56. I'm not sure Homebrew has this feature.

  6. Rubists like to rewrite everything in Ruby, because the only thing they are at ease is Ruby itself.

How to trust a apt repository : Debian apt-get update error public key is not available: NO_PUBKEY <id>

I had the same problem of "gpg: keyserver timed out" with a couple of different servers. Finally, it turned out that I didn't need to do that manually at all. On a Debian system, the simple solution which fixed it was just (as root or precede with sudo):

aptitude install debian-archive-keyring

In case it is some other keyring you need, check out

apt-cache search keyring | grep debian

My squeeze system shows all these:

debian-archive-keyring       - GnuPG archive keys of the Debian archive
debian-edu-archive-keyring   - GnuPG archive keys of the Debian Edu archive
debian-keyring               - GnuPG keys of Debian Developers
debian-ports-archive-keyring - GnuPG archive keys of the debian-ports archive
emdebian-archive-keyring     - GnuPG archive keys for the emdebian repository

How can I get a list of repositories 'apt-get' is checking?

It seems the closest is:

apt-cache policy

jQuery event for images loaded

As per this answer, you can use the jQuery load event on the window object instead of the document:

jQuery(window).load(function() {
    console.log("page finished loading now.");

This will be triggered after all content on the page has been loaded. This differs from jQuery(document).load(...) which is triggered after the DOM has finished loading.

How to solve "Unresolved inclusion: <iostream>" in a C++ file in Eclipse CDT?

I'm using Eclipse with Cygwin and this worked for me:

Go to Project > Properties > C/C++ General > Preprocessor Includes... > Providers and select "CDT GCC Built-in Compiler Settings Cygwin [Shared]".

How to compare values which may both be null in T-SQL

I needed a similar comparison when doing a MERGE:

WHEN MATCHED AND (Target.Field1 <> Source.Field1 OR ...)

The additional checks are to avoid updating rows where all the columns are already the same. For my purposes I wanted NULL <> anyValue to be True, and NULL <> NULL to be False.

The solution evolved as follows:

First attempt:

        -- Neither is null, values are not equal
        Target.Field1 IS NOT NULL
            AND Source.Field1 IS NOT NULL
            AND Target.Field1 <> Source.Field1
        -- Target is null but source is not
        Target.Field1 IS NULL
            AND Source.Field1 IS NOT NULL
        -- Source is null but target is not
        Target.Field1 IS NOT NULL
            AND Source.Field1 IS NULL

    -- OR ... Repeat for other columns

Second attempt:

    -- Neither is null, values are not equal
    NOT (Target.Field1 IS NULL OR Source.Field1 IS NULL)
        AND Target.Field1 <> Source.Field1

    -- Source xor target is null
    OR (Target.Field1 IS NULL OR Source.Field1 IS NULL)
        AND NOT (Target.Field1 IS NULL AND Source.Field1 IS NULL)

    -- OR ... Repeat for other columns

Third attempt (inspired by @THEn's answer):


        NULLIF(Target.Field1, Source.Field1),
        NULLIF(Source.Field1, Target.Field1)

    -- OR ... Repeat for other columns

The same ISNULL/NULLIF logic can be used to test equality and inequality:


Here is an SQL-Fiddle demonstrating how it works!3/471d60/1

Creating a ZIP archive in memory using System.IO.Compression

This is the way to convert a entity to XML File and then compress it:

private  void downloadFile(EntityXML xml) {

string nameDownloadXml = "File_1.xml";
string nameDownloadZip = "";

var serializer = new XmlSerializer(typeof(EntityXML));

Response.AddHeader("content-disposition", "attachment;filename=" + nameDownloadZip);

using (var memoryStream = new MemoryStream())
    using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
        var demoFile = archive.CreateEntry(nameDownloadXml);
        using (var entryStream = demoFile.Open())
        using (StreamWriter writer = new StreamWriter(entryStream, System.Text.Encoding.UTF8))
            serializer.Serialize(writer, xml);

    using (var fileStream = Response.OutputStream)
        memoryStream.Seek(0, SeekOrigin.Begin);



Extract value of attribute node via XPath

As answered above:


will only output the name attribute of the 4 child nodes belonging to the Parent specified by its predicate [@id=1]. You'll then need to change the predicate to [@id=2] to get the set of child nodes for the next Parent.

However, if you ignore the Parent node altogether and use:


you can select name attribute of all child nodes in one go.



Have a look at <openssl/pem.h>. It gives possible BEGIN markers.

Copying the content from the above link for quick reference:

#define PEM_STRING_X509_CRL "X509 CRL"
#define PEM_STRING_PKCS7    "PKCS7"
#define PEM_STRING_CMS      "CMS"

Uncaught TypeError: Cannot read property 'toLowerCase' of undefined

This Works For me !!!

Call a Function without Parameter

$("#CourseSelect").change(function(e1) {

Call a Function with Parameter

$("#CourseSelect").change(function(e1) {

How to execute command stored in a variable?

If you just do eval $cmd when we do cmd="ls -l" (interactively and in a script) we get the desired result. In your case, you have a pipe with a grep without a pattern, so the grep part will fail with an error message. Just $cmd will generate a "command not found" (or some such) message. So try use eval and use a finished command, not one that generates an error message.

How to create a HashMap with two keys (Key-Pair, Value)?

There are several options:

2 dimensions

Map of maps

Map<Integer, Map<Integer, V>> map = //...


Wrapper key object

public class Key {

    private final int x;
    private final int y;

    public Key(int x, int y) {
        this.x = x;
        this.y = y;

    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Key)) return false;
        Key key = (Key) o;
        return x == key.x && y == key.y;

    public int hashCode() {
        int result = x;
        result = 31 * result + y;
        return result;


Implementing equals() and hashCode() is crucial here. Then you simply use:

Map<Key, V> map = //...


map.get(new Key(2, 5));

Table from Guava

Table<Integer, Integer, V> table = HashBasedTable.create();

table.get(2, 5);

Table uses map of maps underneath.

N dimensions

Notice that special Key class is the only approach that scales to n-dimensions. You might also consider:

Map<List<Integer>, V> map = //...

but that's terrible from performance perspective, as well as readability and correctness (no easy way to enforce list size).

Maybe take a look at Scala where you have tuples and case classes (replacing whole Key class with one-liner).

How do I run Visual Studio as an administrator by default?

Right click on the application, Props -> Compatibility -> Check the Run the program as administrator

curl posting with header application/x-www-form-urlencoded

// A very simple PHP example that sends a HTTP POST to a remote site

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL,"");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded'));

// receive server response ...
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$server_output = curl_exec ($ch);

curl_close ($ch);

// further processing ....
if ($server_output == "OK") { ... } else { ... }


When is layoutSubviews called?

A rather obscure, yet potentially important case when layoutSubviews never gets called is:

import UIKit

class View: UIView {

    override class var layerClass: AnyClass { return Layer.self }

    class Layer: CALayer {
        override func layoutSublayers() {
            // if we don't call super.layoutSublayers()...
            print(type(of: self), #function)

    override func layoutSubviews() {
        // ... this method never gets called by the OS!
        print(type(of: self), #function)

let view = View(frame: CGRect(x: 0, y: 0, width: 100, height: 100))

How to inject Javascript in WebBrowser control?

I believe the most simple method to inject Javascript in a WebBrowser Control HTML Document from c# is to invoke the "execScript" method with the code to be injected as argument.

In this example the javascript code is injected and executed at global scope:

var jsCode="alert('hello world from injected code');";
WebBrowser.Document.InvokeScript("execScript", new Object[] { jsCode, "JavaScript" });

If you want to delay execution, inject functions and call them after:

var jsCode="function greet(msg){alert(msg);};";
WebBrowser.Document.InvokeScript("execScript", new Object[] { jsCode, "JavaScript" });
WebBrowser.Document.InvokeScript("greet",new object[] {"hello world"});

This is valid for Windows Forms and WPF WebBrowser controls.

This solution is not cross browser because "execScript" is defined only in IE and Chrome. But the question is about Microsoft WebBrowser controls and IE is the only one supported.

For a valid cross browser method to inject javascript code, create a Function object with the new Keyword. This example creates an anonymous function with injected code and executes it (javascript implements closures and the function has access to global space without local variable pollution).

var jsCode="alert('hello world');";
(new Function(code))();

Of course, you can delay execution:

var jsCode="alert('hello world');";
var inserted=new Function(code);

Hope it helps

How to convert CSV file to multiline JSON?

import csv
import json
csvfile = csv.DictReader('filename.csv', 'r'))
output =[]
for each in csvfile:
    row ={}
    row['FirstName'] = each['FirstName']
    row['LastName']  = each['LastName']
    row['IDNumber']  = each ['IDNumber']
    row['Message']   = each['Message']

Is there a concise way to iterate over a stream with indices in Java 8?

If you are trying to get an index based on a predicate, try this:

If you only care about the first index:

OptionalInt index = IntStream.range(0, list.size())
    .filter(i -> list.get(i) == 3)

Or if you want to find multiple indexes:

IntStream.range(0, list.size())
   .filter(i -> list.get(i) == 3)

Add .orElse(-1); in case you want to return a value if it doesn't find it.

Generic type conversion FROM string

Yet another variation. Handles Nullables, as well as situations where the string is null and T is not nullable.

public class TypedProperty<T> : Property where T : IConvertible
    public T TypedValue
            if (base.Value == null) return default(T);
            var type = Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T);
            return (T)Convert.ChangeType(base.Value, type);
        set { base.Value = value.ToString(); }

How do I tell Spring Boot which main class to use for the executable jar?

For those using Gradle (instead of Maven) :

springBoot {
    mainClass = "com.example.Main"

Change project name on Android Studio

  1. Close Android Studio.

  2. Rename the folder of the root of the project. For example, change "MyApplication" to "Myblablabla".

  3. Delete the '.idea' folder.

  4. Open Android Studio, and import the updated project.

Cross Browser Flash Detection in Javascript

I agree with Max Stewart. SWFObject is the way to go. I'd like to supplement his answer with a code example. This ought to to get you started:

Make sure you have included the swfobject.js file (get it here):

<script type="text/javascript" src="swfobject.js"></script>

Then use it like so:

    alert("You have the minimum required flash version (or newer)");
    alert("You do not have the minimum required flash version");

Replace "9.0.115" with whatever minimum flash version you need. I chose 9.0.115 as an example because that's the version that added h.264 support.

If the visitor does not have flash, it will report a flash version of "0.0.0", so if you just want to know if they have flash at all, use:

    alert("You have flash!");
    alert("You do not flash :-(");

What is SOA "in plain english"?

SOA is acronym for Service Oriented Architecture.

SOA is designing and writing software applications in such a way that distinct software modules can be integrated seamlessly with high degree of re-usability.

Most of the people restrict SOA as writing client/server software-web-services. But it is too small context of SOA. SOA is much larger than that and over the past few years web-services have been primary medium of communcation which is probably the reason why people think of SOA as web-services in general restricting the boundaries and meaning of SOA.

You can think of writing a database-access module which is so independent that it can work on its own without any dependencies. This module can expose classes which can be used by any host-software that needs database access. There's no start-up configuration in host-application. Whatever is needed or required is communicated through classes exposes by database-access module. We can call these classes as services and consider the module as service-enabled.

Practicing SOA gives high degree of re-usability by enforcing DRY [Don't repeat your self] which results into highly maintainable software. Maintainability is the first thing any software architecture thinks of - SOA gives you that.

How to get full REST request body using Jersey?

It does seem you would have to use a MessageBodyReader here. Here's an example, using jdom:

import org.jdom.Document;
import java.lang.reflect.Type;
import java.lang.annotation.Annotation;

@Provider // this annotation is necessary!
@ConsumeMime("application/xml") // this is a hint to the system to only consume xml mime types
public class XMLMessageBodyReader implements MessageBodyReader<Document> {
  private SAXBuilder builder = new SAXBuilder();

  public boolean isReadable(Class type, Type genericType, Annotation[] annotations, MediaType mediaType) {
    // check if we're requesting a jdom Document
    return Document.class.isAssignableFrom(type);

  public Document readFrom(Class type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, String> httpHeaders, InputStream entityStream) {
    try {
    catch (Exception e) {
      // handle error somehow

Add this class to the list of resources your jersey deployment will process (usually configured via web.xml, I think). You can then use this reader in one of your regular resource classes like this:

@Path("/somepath") @POST
public void handleXMLData(Document doc) {
  // do something with the document

I haven't verified that this works exactly as typed, but that's the gist of it. More reading here:

How to index into a dictionary?

If you need an ordered dictionary, you can use odict.

Equivalent to 'app.config' for a library (DLL)

If you add Settings to a Class Library project in Visual Studio (Project Properties, Settings), it will add an app.config file to your project with the relevant userSettings/applicatioNSettings sections, and the default values for these settings from your Settings.settings file.

However this configuration file will not be used at runtime - instead the class library uses the configuration file of its hosting application.

I believe the main reason for generating this file is so that you can copy/paste the settings into the host application's configuration file.

Query to list all users of a certain group

For Active Directory users, an alternative way to do this would be -- assuming all your groups are stored in OU=Groups,DC=CorpDir,DC=QA,DC=CorpName -- to use the query (&(objectCategory=group)(CN=GroupCN)). This will work well for all groups with less than 1500 members. If you want to list all members of a large AD group, the same query will work, but you'll have to use ranged retrieval to fetch all the members, 1500 records at a time.

The key to performing ranged retrievals is to specify the range in the attributes using this syntax: attribute;range=low-high. So to fetch all members of an AD Group with 3000 members, first run the above query asking for the member;range=0-1499 attribute to be returned, then for the member;range=1500-2999 attribute.

A formula to copy the values from a formula to another column

you can use those functions together with iferror as a work around.


iOS: How to store username/password within an app?

try this one:

 KeychainItemWrapper *keychainItem = [[KeychainItemWrapper alloc] initWithIdentifier:@"YourAppLogin" accessGroup:nil];
[keychainItem setObject:@"password you are saving" forKey:kSecValueData]; 
[keychainItem setObject:@"username you are saving" forKey:kSecAttrAccount];

may it will help.

angularjs ng-style: background-image isn't working

Correct syntax for background-image is:

background-image: url("path_to_image");

Correct syntax for ng-style is:


How to get selected path and name of the file opened with file dialog?

I think you want this:

Dim filename As String
filename = Application.GetOpenFilename

Dim cell As Range
cell = Application.Range("A1")
cell.Value = filename

Adding default parameter value with type hint in Python

If you're using typing (introduced in Python 3.5) you can use typing.Optional, where Optional[X] is equivalent to Union[X, None]. It is used to signal that the explicit value of None is allowed . From typing.Optional:

def foo(arg: Optional[int] = None) -> None:

HTML5 form validation pattern alphanumeric with spaces?

My solution is to cover all the range of diacritics:


A-z - this is for all latin characters

0-9 - this is for all digits

À-ž - this is for all diacritics

\s - this is for spaces

{2,} - string needs to be at least 2 characters long

How to remove entry from $PATH on mac

If you're removing the path for Python 3 specifically, I found it in ~/.zprofile and ~/.zshrc.

.gitignore after commit

I had to remove .idea and target folders and after reading all comments this worked for me:

git rm -r .idea
git rm -r target
git commit -m 'removed .idea folder'

and then push to master

What is the most efficient way to create HTML elements using jQuery?

This is not the correct answer for the question but still I would like to share this...

Using just document.createElement('div') and skipping JQuery will improve the performance a lot when you want to make lot of elements on the fly and append to DOM.

drop down list value in

You can add an empty value such as:

ddlmonths.Items.Insert(0, new ListItem("Select Month", ""))

And just add a validation to prevent chosing empty option such as asp:RequiredFieldValidator.

Make the current Git branch a master branch

For me, i wanted my devl to be back to the master after it was ahead.

While on develop:

git checkout master
git pull

git checkout develop
git pull

git reset --hard origin/master
git push -f

Populating a ListView using an ArrayList?

Here's an example of how you could implement a list view:

protected void onCreate(Bundle savedInstanceState) {

    //We have our list view
    final ListView dynamic = findViewById(;

    //Create an array of elements
    final ArrayList<String> classes = new ArrayList<>();
    classes.add("Data Structures");
    classes.add("Assembly Language");
    classes.add("Calculus 3");
    classes.add("Switching Systems");
    classes.add("Analysis Tools");

    //Create adapter for ArrayList
    final ArrayAdapter<String> adapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1, classes);

    //Insert Adapter into List

    //set click functionality for each list item
    dynamic.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Log.i("User clicked ", classes.get(position));


PHP function to build query string from array

Implode will combine an array into a string for you, but to make an SQL query out a kay/value pair you'll have to write your own function.

Equal height rows in CSS Grid Layout

The short answer is that setting grid-auto-rows: 1fr; on the grid container solves what was asked.

$(this).serialize() -- How to add a value?

Instead of

 data: $(this).serialize() + '&=NonFormValue' + NonFormValue,

you probably want

 data: $(this).serialize() + '&NonFormValue=' + NonFormValue,

You should be careful to URL-encode the value of NonFormValue if it might contain any special characters.

Error: "Adb connection Error:An existing connection was forcibly closed by the remote host"

In my case, resetting ADB didn't make a difference. I also needed to delete my existing virtual devices, which were pretty old, and create new ones.

Find records from one table which don't exist in another

SELECT t1.ColumnID,
    WHEN NOT EXISTS( SELECT t2.FieldText  
                     FROM Table t2 
                     WHERE t2.ColumnID = t1.ColumnID) 
    THEN t1.FieldText
    ELSE t2.FieldText
END FieldText       
FROM Table1 t1, Table2 t2

geom_smooth() what are the methods available?

The method argument specifies the parameter of the smooth statistic. You can see stat_smooth for the list of all possible arguments to the method argument.

Singular matrix issue with Numpy

As it was already mentioned in previous answers, your matrix cannot be inverted, because its determinant is 0. But if you still want to get inverse matrix, you can use np.linalg.pinv, which leverages SVD to approximate initial matrix.

Android: Access child views from a ListView

A quick search of the docs for the ListView class has turned up getChildCount() and getChildAt() methods inherited from ViewGroup. Can you iterate through them using these? I'm not sure but it's worth a try.

Found it here

XML Schema minOccurs / maxOccurs default values

New, expanded answer to an old, commonly asked question...

Default Values

  • Occurrence constraints minOccurs and maxOccurs default to 1.

Common Cases Explained

<xsd:element name="A"/>

means A is required and must appear exactly once.

<xsd:element name="A" minOccurs="0"/>

means A is optional and may appear at most once.

 <xsd:element name="A" maxOccurs="unbounded"/>

means A is required and may repeat an unlimited number of times.

 <xsd:element name="A" minOccurs="0" maxOccurs="unbounded"/>

means A is optional and may repeat an unlimited number of times.

See Also

  • W3C XML Schema Part 0: Primer

    In general, an element is required to appear when the value of minOccurs is 1 or more. The maximum number of times an element may appear is determined by the value of a maxOccurs attribute in its declaration. This value may be a positive integer such as 41, or the term unbounded to indicate there is no maximum number of occurrences. The default value for both the minOccurs and the maxOccurs attributes is 1. Thus, when an element such as comment is declared without a maxOccurs attribute, the element may not occur more than once. Be sure that if you specify a value for only the minOccurs attribute, it is less than or equal to the default value of maxOccurs, i.e. it is 0 or 1. Similarly, if you specify a value for only the maxOccurs attribute, it must be greater than or equal to the default value of minOccurs, i.e. 1 or more. If both attributes are omitted, the element must appear exactly once.

  • W3C XML Schema Part 1: Structures Second Edition

      maxOccurs = (nonNegativeInteger | unbounded)  : 1
      minOccurs = nonNegativeInteger : 1

JQuery Validate Dropdown list

var HoursEntry = $(#HoursEntry option:selected).val();
if(HoursEntry == "")
$("#HoursEntry").html("Please select");
return false;

Setting the default active profile in Spring-boot



java -jar file.jar

How to check that a string is parseable to a double?

All answers are OK, depending on how academic you want to be. If you wish to follow the Java specifications accurately, use the following:

private static final Pattern DOUBLE_PATTERN = Pattern.compile(
    "[\\x00-\\x20]*[+-]?(NaN|Infinity|((((\\p{Digit}+)(\\.)?((\\p{Digit}+)?)" +
    "([eE][+-]?(\\p{Digit}+))?)|(\\.((\\p{Digit}+))([eE][+-]?(\\p{Digit}+))?)|" +
    "(((0[xX](\\p{XDigit}+)(\\.)?)|(0[xX](\\p{XDigit}+)?(\\.)(\\p{XDigit}+)))" +

public static boolean isFloat(String s)
    return DOUBLE_PATTERN.matcher(s).matches();

This code is based on the JavaDocs at Double.

Make error: missing separator

For me, the problem was that I had some end-of-line # ... comments embedded within a define ... endef multi-line variable definition. Removing the comments made the problem go away.

Using reflection in Java to create a new instance with the reference variable type set to the new instance class name?

//====Single Class Reference used to retrieve object for fields and initial values. Performance enhancing only====          
Class<?>    reference           =   vector.get(0).getClass();
Object      obj                 =   reference.newInstance();
Field[]     objFields           =   obj.getClass().getFields(); 

Compute elapsed time

Hope this will help:

<!doctype html public "-//w3c//dtd html 3.2//en">
        <title>compute elapsed time in JavaScript</title>

        <script type="text/javascript">

            function display_c (start) {
                window.start = parseFloat(start);
                var end = 0 // change this to stop the counter at a higher value
                var refresh = 1000; // Refresh rate in milli seconds
                if( window.start >= end ) {
                    mytime = setTimeout( 'display_ct()',refresh )
                } else {
                    alert("Time Over ");

            function display_ct () {
                // Calculate the number of days left
                var days = Math.floor(window.start / 86400);
                // After deducting the days calculate the number of hours left
                var hours = Math.floor((window.start - (days * 86400 ))/3600)
                // After days and hours , how many minutes are left
                var minutes = Math.floor((window.start - (days * 86400 ) - (hours *3600 ))/60)
                // Finally how many seconds left after removing days, hours and minutes.
                var secs = Math.floor((window.start - (days * 86400 ) - (hours *3600 ) - (minutes*60)))

                var x = window.start + "(" + days + " Days " + hours + " Hours " + minutes + " Minutes and " + secs + " Secondes " + ")";

                document.getElementById('ct').innerHTML = x;
                window.start = window.start - 1;

                tt = display_c(window.start);

            function stop() {




        <input type="button" value="Start Timer" onclick="display_c(86501);"/> | <input type="button" value="End Timer" onclick="stop();"/>
        <span id='ct' style="background-color: #FFFF00"></span>


How can I overwrite file contents with new content in PHP?

MY PREFERRED METHOD is using fopen,fwrite and fclose [it will cost less CPU]

fwrite($f,'new content');

Warning for those using file_put_contents

It'll affect a lot in performance, for example [on the same class/situation] file_get_contents too: if you have a BIG FILE, it'll read the whole content in one shot and that operation could take a long waiting time

Are there bookmarks in Visual Studio Code?

You need to do this via an extension as of the version 1.8.1.

  1. Go to View ? Extensions. This will open Extensions Panel.

  2. Type bookmark to list all related extensions.

  3. Install

I personally like "Numbered Bookmarks" - it is pretty simple and powerful.

Go to the line you need to create a bookmark.

Click Ctrl + Shift + [some number]

Ex: Ctrl + Shift + 2

Now you can jump to this line from anywhere by pressing Ctrl + number

Ex: Ctrl + 2

change <audio> src with javascript

with jQuery:

 $("#playerSource").attr("src", "new_src");

    var audio = $("#player");      

    audio[0].load();//suspends and restores all audio element

    if (isAutoplay) 

How to get first and last day of the current week in JavaScript

You could do something like this

var today = new Date();
var startDay = 0; 
var weekStart = new Date(today.getDate() - (7 + today.getDay() - startDay) % 7);
var weekEnd = new Date(today.getDate() + (7 - today.getDay() - startDay) % 7);

Where startDay is a number from 0 to 6 where 0 stands for Sunday (ie 1 = Monday, 2 = Tuesday, etc).

fs.writeFile in a promise, asynchronous-synchronous stuff

What worked for me was fs.promises.

Example One:

const fs = require("fs")

  .writeFile(__dirname + '/test.json', "data", { encoding: 'utf8' })
  .then(() => {
    // Do whatever you want to do.

Example Two. Using Async-Await:

const fs = require("fs")

async function writeToFile() {
  await fs.promises.writeFile(__dirname + '/test-22.json', "data", {
    encoding: 'utf8'



.NET obfuscation tools/strategy

For the past two days I've been experimenting with Dotfuscator Community Edition advanced (a free download after registering the basic CE that comes bundled with Visual Studio).

I think the reason more people don't use obfuscation as a default option is that it's a serious hassle compared to the risk. On smaller test projects I could get the obfuscated code running with a lot of effort. Deploying a simple project via ClickOnce was troublesome, but achievable after manually signing the manifests with mage. The only problem was that on error the stack trace came back obfuscated and the CE doesn't have a deobfuscator or clarifier packaged.

I tried to obfuscate a real project which is VSTO based in Excel, with Virtual Earth integration, lots of webservice calls and an IOC container and lot's of reflection. It was impossible.

If obfuscation is really a critical requirement, you should design your application with that in mind from the start, testing the obfuscated builds as you progress. Otherwise, if it's a fairly complex project, you're going to end up with a serious amount of pain.

Can you have a <span> within a <span>?

Yes. You can have a span within a span. Your problem stems from something else.

How do you test a public/private DSA keypair?

If you are in Windows and want use a GUI, with puttygen you can import your private key into it:

enter image description here

Once imported, you can save its public key and compare it to yours.

"Multiple definition", "first defined here" errors

The problem here is that you are including commands.c in commands.h before the function prototype. Therefore, the C pre-processor inserts the content of commands.c into commands.h before the function prototype. commands.c contains the function definition. As a result, the function definition ends up before than the function declaration causing the error.

The content of commands.h after the pre-processor phase looks like this:

#ifndef COMMANDS_H_
#define COMMANDS_H_

// function definition
void f123(){


// function declaration
void f123();

#endif /* COMMANDS_H_ */

This is an error because you can't declare a function after its definition in C. If you swapped #include "commands.c" and the function declaration the error shouldn't happen because, now, the function prototype comes before the function declaration.

However, including a .c file is a bad practice and should be avoided. A better solution for this problem would be to include commands.h in commands.c and link the compiled version of command to the main file. For example:


#ifndef COMMANDS_H_
#define COMMANDS_H_

void f123(); // function declaration



#include "commands.h"

void f123(){} // function definition

Why should you use strncpy instead of strcpy?

This may be used in many other scenarios, where you need to copy only a portion of your original string to the destination. Using strncpy() you can copy a limited portion of the original string as opposed by strcpy(). I see the code you have put up comes from

How to read text file in JavaScript

Yeah it is possible with FileReader, I have already done an example of this, here's the code:

<!DOCTYPE html>
    <title>Read File (via User Input selection)</title>
    <script type="text/javascript">
    var reader; //GLOBAL File Reader object for demo purpose only

     * Check for the various File API support.
    function checkFileAPI() {
        if (window.File && window.FileReader && window.FileList && window.Blob) {
            reader = new FileReader();
            return true; 
        } else {
            alert('The File APIs are not fully supported by your browser. Fallback required.');
            return false;

     * read text input
    function readText(filePath) {
        var output = ""; //placeholder for text output
        if(filePath.files && filePath.files[0]) {           
            reader.onload = function (e) {
                output =;
            };//end onload()
        }//end if html5 filelist support
        else if(ActiveXObject && filePath) { //fallback to IE 6-8 support via ActiveX
            try {
                reader = new ActiveXObject("Scripting.FileSystemObject");
                var file = reader.OpenTextFile(filePath, 1); //ActiveX File Object
                output = file.ReadAll(); //text contents of file
                file.Close(); //close file "input stream"
            } catch (e) {
                if (e.number == -2146827859) {
                    alert('Unable to access local files due to browser security settings. ' + 
                     'To overcome this, go to Tools->Internet Options->Security->Custom Level. ' + 
                     'Find the setting for "Initialize and script ActiveX controls not marked as safe" and change it to "Enable" or "Prompt"'); 
        else { //this is where you could fallback to Java Applet, Flash or similar
            return false;
        return true;

     * display content using a basic HTML replacement
    function displayContents(txt) {
        var el = document.getElementById('main'); 
        el.innerHTML = txt; //display output in DOM
<body onload="checkFileAPI();">
    <div id="container">    
        <input type="file" onchange='readText(this)' />
        <h3>Contents of the Text file:</h3>
        <div id="main">

It's also possible to do the same thing to support some older versions of IE (I think 6-8) using the ActiveX Object, I had some old code which does that too but its been a while so I'll have to dig it up I've found a solution similar to the one I used courtesy of Jacky Cui's blog and edited this answer (also cleaned up code a bit). Hope it helps.

Lastly, I just read some other answers that beat me to the draw, but as they suggest, you might be looking for code that lets you load a text file from the server (or device) where the JavaScript file is sitting. If that's the case then you want AJAX code to load the document dynamically which would be something as follows:

<!DOCTYPE html>
<head><meta charset="utf-8" />
<title>Read File (via AJAX)</title>
<script type="text/javascript">
var reader = new XMLHttpRequest() || new ActiveXObject('MSXML2.XMLHTTP');

function loadFile() {'get', 'test.txt', true); 
    reader.onreadystatechange = displayContents;

function displayContents() {
    if(reader.readyState==4) {
        var el = document.getElementById('main');
        el.innerHTML = reader.responseText;

<div id="container">
    <input type="button" value="test.txt"  onclick="loadFile()" />
    <div id="main">

How to detect the end of loading of UITableView

Here is what I would do.

  1. In your base class (can be rootVC BaseVc etc),

    A. Write a Protocol to send the "DidFinishReloading" callback.

    @protocol ReloadComplition <NSObject>
    - (void)didEndReloading:(UITableView *)tableView;

    B. Write a generic method to reload the table view.

    -(void)reloadTableView:(UITableView *)tableView withOwner:(UIViewController *)aViewController;
  2. In the base class method implementation, call reloadData followed by delegateMethod with delay.

    -(void)reloadTableView:(UITableView *)tableView withOwner:(UIViewController *)aViewController{
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            [tableView reloadData];
            if(aViewController && [aViewController respondsToSelector:@selector(didEndReloading:)]){
                [aViewController performSelector:@selector(didEndReloading:) withObject:tableView afterDelay:0];
  3. Confirm to the reload completion protocol in all the view controllers where you need the callback.

    -(void)didEndReloading:(UITableView *)tableView{
        //do your stuff.


WCF on IIS8; *.svc handler mapping doesn't work

Windows 8 with IIS8

  • Hit Windows+X
  • Select Programs and Features (first item on list)
  • Select Turn Windows Features on or off on the left
  • Expand .NET Framework 4.5 Advanced Services
  • Expand WCF Services
  • Enable HTTP Activation

read word by word from file in C++

First of all, don't loop while (!eof()), it will not work as you expect it to because the eofbit will not be set until after a failed read due to end of file.

Secondly, the normal input operator >> separates on whitespace and so can be used to read "words":

std::string word;
while (file >> word)

When use ResponseEntity<T> and @RestController for Spring RESTful applications

According to official documentation: Creating REST Controllers with the @RestController annotation

@RestController is a stereotype annotation that combines @ResponseBody and @Controller. More than that, it gives more meaning to your Controller and also may carry additional semantics in future releases of the framework.

It seems that it's best to use @RestController for clarity, but you can also combine it with ResponseEntity for flexibility when needed (According to official tutorial and the code here and my question to confirm that).

For example:

public class MyController {

    @GetMapping(path = "/test")
    public User test() {
        User user = new User();
        user.setName("Name 1");

        return user;


is the same as:

public class MyController {

    @GetMapping(path = "/test")
    public ResponseEntity<User> test() {
        User user = new User();
        user.setName("Name 1");

        HttpHeaders responseHeaders = new HttpHeaders();
        // ...
        return new ResponseEntity<>(user, responseHeaders, HttpStatus.OK);


This way, you can define ResponseEntity only when needed.


You can use this:

    return ResponseEntity.ok().headers(responseHeaders).body(user);

How to post JSON to a server using C#?

var data = Encoding.ASCII.GetBytes(json);

byte[] postBytes = Encoding.UTF8.GetBytes(json);

Use ASCII instead of UFT8

Not equal <> != operator on NULL

I just don't see the functional and seamless reason for nulls not to be comparable to other values or other nulls, cause we can clearly compare it and say they are the same or not in our context. It's funny. Just because of some logical conclusions and consistency we need to bother constantly with it. It's not functional, make it more functional and leave it to philosophers and scientists to conclude if it's consistent or not and does it hold "universal logic". :) Someone may say that it's because of indexes or something else, I doubt that those things couldn't be made to support nulls same as values. It's same as comparing two empty glasses, one is vine glass and other is beer glass, we are not comparing the types of objects but values they contain, same as you could compare int and varchar, with null it's even easier, it's nothing and what two nothingness have in common, they are the same, clearly comparable by me and by everyone else that write sql, because we are constantly breaking that logic by comparing them in weird ways because of some ANSI standards. Why not use computer power to do it for us and I doubt it would slow things down if everything related is constructed with that in mind. "It's not null it's nothing", it's not apple it's apfel, come on... Functionally is your friend and there is also logic here. In the end only thing that matter is functionality and does using nulls in that way brings more or less functionality and ease of use. Is it more useful?

Consider this code:

SELECT CASE WHEN NOT (1 = null or (1 is null and null is null)) THEN 1 ELSE 0 end

How many of you knows what will this code return? With or without NOT it returns 0. To me that is not functional and it's confusing. In c# it's all as it should be, comparison operations return value, logically this too produces value, because if it didn't there is nothing to compare (except. nothing :) ). They just "said": anything compared to null "returns" 0 and that creates many workarounds and headaches.

This is the code that brought me here:

where a != b OR (a is null and b IS not null) OR (a IS not null and b IS null)

I just need to compare if two fields (in where) have different values, I could use function, but...

React navigation goBack() and update parent state

I would also use navigation.navigate. If someone has the same problem and also uses nested navigators, this is how it would work:

onPress={() =>
        navigation.navigate('MyStackScreen', {
          // Passing params to NESTED navigator screen:
          screen: 'goToScreenA',
          params: { Data: data.item },

How do I center a window onscreen in C#?

A single line:

this.Location = new Point((Screen.PrimaryScreen.WorkingArea.Width - this.Width) / 2,
                          (Screen.PrimaryScreen.WorkingArea.Height - this.Height) / 2);

ValueError: could not broadcast input array from shape (224,224,3) into shape (224,224)

@aravk33 's answer is absolutely correct.

I was going through the same problem. I had a data set of 2450 images. I just could not figure out why I was facing this issue.

Check the dimensions of all the images in your training data.

Add the following snippet while appending your image into your list:

if image.shape==(1,512,512):

Line break in SSRS expression

If your placeholder is in html enabled mode then "<br />" will work as a newline

How to remove empty cells in UITableView?

In the Storyboard, select the UITableView, and modify the property Style from Plain to Grouped.

How to concatenate text from multiple rows into a single text string in SQL server?

One method not yet shown via the XML data() command in MS SQL Server is:

Assume table called NameList with one column called FName,

SELECT FName + ', ' AS 'data()' 
FROM NameList 


"Peter, Paul, Mary, "

Only the extra comma must be dealt with.

Edit: As adopted from @NReilingh's comment, you can use the following method to remove the trailing comma. Assuming the same table and column names:

FOR XML PATH('')),' #!',', '), 1, 2, '') as Brands

Matching an optional substring in a regex

You can do this:

([0-9]+) (\([^)]+\))? Z

This will not work with nested parens for Y, however. Nesting requires recursion which isn't strictly regular any more (but context-free). Modern regexp engines can still handle it, albeit with some difficulties (back-references).

Could not find 3.2.25 4.0.30 4.1.32 4.2.40 4.2.42 4.3.23 4.4.52 5.0.77 5.0.89 5.2.08 6.1.11 6.1.71 6.5.87

Check if you also installed the "Google Repository". If not, you also have to install the "Google Repository" in your SDK Manager.

Also be aware that there might be 2 SDK installations - one coming from AndroidStudio and one you might have installed. Better consolidate this to one installation - this is a common pitfall - that you have it installed in one installation but it fails when you build with the other installation.

Example of how to access SDK Manager for Google Repository

Difference between no-cache and must-revalidate

max-age=0, must-revalidate and no-cache aren't exactly identical. With must-revalidate, if the server doesn't respond to a revalidation request, the browser/proxy is supposed to return a 504 error. With no-cache, it would just show the cached content, which would be probably preferred by the user (better to have something stale than nothing at all). This is why must-revalidate is intended for critical transactions only.

Best way to implement keyboard shortcuts in a Windows Forms application?

You probably forgot to set the form's KeyPreview property to True. Overriding the ProcessCmdKey() method is the generic solution:

protected override bool ProcessCmdKey(ref Message msg, Keys keyData) {
  if (keyData == (Keys.Control | Keys.F)) {
    MessageBox.Show("What the Ctrl+F?");
    return true;
  return base.ProcessCmdKey(ref msg, keyData);

Android setOnClickListener method - How does it work?

That what manual says about setOnClickListener method is:

public void setOnClickListener (View.OnClickListener l)

Added in API level 1 Register a callback to be invoked when this view is clicked. If this view is not clickable, it becomes clickable.


l View.OnClickListener: The callback that will run

And normally you have to use it like this

public class ExampleActivity extends Activity implements OnClickListener {
    protected void onCreate(Bundle savedValues) {
        Button button = (Button)findViewById(;

    // Implement the OnClickListener callback
    public void onClick(View v) {
      // do something when the button is clicked

Take a look at this lesson as well Building a Simple Calculator using Android Studio.

How can I parse a string with a comma thousand separator to a number?

Replace the comma with an empty string:

var x = parseFloat("2,299.00".replace(",",""))_x000D_

Android - Spacing between CheckBox and text

I don't know guys, but I tested

<CheckBox android:paddingLeft="8mm" and only moves the text to the right, not entire control.

It suits me fine.

What is the difference between varchar and nvarchar?

Jeffrey L Whitledge with ~47000 reputation score recommends usage of nvarchar

Solomon Rutzky with with ~33200 reputation score recommends: Do NOT always use NVARCHAR. That is a very dangerous, and often costly, attitude / approach.

What are the main performance differences between varchar and nvarchar SQL Server data types?

Both persons of such a high reputation, what does a learning sql server database developer choose?

There are many warnings in answers and comments about performance issues if you are not consistent in choices.

There are comments pro/con nvarchar for performance.

There are comments pro/con varchar for performance.

I have a particular requirement for a table with many hundreds of columns, which in itself is probably unusual ?

I'm choosing varchar to avoid going close to the 8060 byte table record size limit of SQL*server 2012.

Use of nvarchar, for me, goes over this 8060 byte limit.

I'm also thinking that I should match the data types of the related code tables to the data types of the primary central table.

I have seen use of varchar column at this place of work, South Australian Government, by previous experienced database developers, where the table row count is going to be several millions or more (and very few nvarchar columns, if any, in these very large tables), so perhaps the expected data row volumes becomes part of this decision.

Add CSS3 transition expand/collapse

this should work, had to try a while too.. :D

function showHide(shID) {_x000D_
  if (document.getElementById(shID)) {_x000D_
    if (document.getElementById(shID + '-show').style.display != 'none') {_x000D_
      document.getElementById(shID + '-show').style.display = 'none';_x000D_
      document.getElementById(shID + '-hide').style.display = 'inline';_x000D_
      document.getElementById(shID).style.height = '100px';_x000D_
    } else {_x000D_
      document.getElementById(shID + '-show').style.display = 'inline';_x000D_
      document.getElementById(shID + '-hide').style.display = 'none';_x000D_
      document.getElementById(shID).style.height = '0px';_x000D_
#example {_x000D_
  background: red;_x000D_
  height: 0px;_x000D_
  overflow: hidden;_x000D_
  transition: height 2s;_x000D_
  -moz-transition: height 2s;_x000D_
  /* Firefox 4 */_x000D_
  -webkit-transition: height 2s;_x000D_
  /* Safari and Chrome */_x000D_
  -o-transition: height 2s;_x000D_
  /* Opera */_x000D_
a.hideLink {_x000D_
  text-decoration: none;_x000D_
  background: transparent url('down.gif') no-repeat left;_x000D_
a.hideLink {_x000D_
  background: transparent url('up.gif') no-repeat left;_x000D_
Here is some text._x000D_
<div class="readmore">_x000D_
  <a href="#" id="example-show" class="showLink" onclick="showHide('example');return false;">Read more</a>_x000D_
  <div id="example" class="more">_x000D_
    <div class="text">_x000D_
      Here is some more text: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum vitae urna nulla. Vivamus a purus mi. In hac habitasse platea dictumst. In ac tempor quam. Vestibulum eleifend vehicula ligula, et cursus nisl gravida sit amet._x000D_
      Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas._x000D_
      <a href="#" id="example-hide" class="hideLink" onclick="showHide('example');return false;">Hide</a>_x000D_

Export table from database to csv file

Dead horse perhaps, but a while back I was trying to do the same and came across a script to create a STP that tried to do what I was looking for, but it had a few quirks that needed some attention. In an attempt to track down where I found the script to post an update, I came across this thread and it seemed like a good spot to share it.

This STP (Which for the most part I take no credit for, and I can't find the site I found it on), takes a schema name, table name, and Y or N [to include or exclude headers] as input parameters and queries the supplied table, outputting each row in comma-separated, quoted, csv format.

I've made numerous fixes/changes to the original script, but the bones of it are from the OP, whoever that was.

Here is the script:

IF OBJECT_ID('get_csvFormat', 'P') IS NOT NULL
    DROP PROCEDURE get_csvFormat

CREATE PROCEDURE get_csvFormat(@schemaname VARCHAR(20), @tablename VARCHAR(30),@header char(1))
    IF ISNULL(@tablename, '') = ''
        DECLARE @cols VARCHAR(MAX), @sqlstrs VARCHAR(MAX), @heading VARCHAR(MAX), @schemaid int

        --if no schemaname provided, default to dbo
        IF ISNULL(@schemaname, '') = ''
            SELECT @schemaname = 'dbo'

        --if no header provided, default to Y
        IF ISNULL(@header, '') = ''
            SELECT @header = 'Y'

        SELECT @schemaid = (SELECT schema_id FROM sys.schemas WHERE [name] = @schemaname)
        @cols = (
            SELECT ' , CAST([', + '] AS VARCHAR(50)) '  
            FROM sys.objects a 
            INNER JOIN sys.columns b ON a.object_id=b.object_id 
            WHERE = @tablename AND a.schema_id = @schemaid
            FOR XML PATH('')
        @heading = (
            SELECT ',"' + + '"' FROM sys.objects a 
            INNER JOIN sys.columns b ON a.object_id=b.object_id 
            WHERE @tablename AND a.schema_id = @schemaid
            FOR XML PATH('')

        SET @tablename = @schemaname + '.' + @tablename
        SET @heading =  'SELECT ''' + right(@heading,len(@heading)-1) + ''' AS CSV, 0 AS Sort'  + CHAR(13)
        SET @cols =  '''"'',' + replace(right(@cols,len(@cols)-1),',', ',''","'',') + ',''"''' + CHAR(13)

        IF @header = 'Y'
            SET @sqlstrs =  'SELECT CSV FROM (' + CHAR(13) + @heading + ' UNION SELECT CONCAT(' + @cols + ') CSV, 1 AS Sort FROM ' + @tablename + CHAR(13) + ') X ORDER BY Sort, CSV ASC'
            SET @sqlstrs =  'SELECT CONCAT(' + @cols + ') CSV FROM ' + @tablename 

        IF @schemaid IS NOT NULL 



--EXEC get_csvFormat @schemaname='dbo', @tablename='TradeUnion', @header='Y'

How to update a claim in ASP.NET Identity?

You can update claims for the current user by implementing a CookieAuthenticationEvents class and overriding ValidatePrincipal. There you can remove the old claim, add the new one, and then replace the principal using CookieValidatePrincipalContext.ReplacePrincipal. This does not affect any claims stored in the database. This is using ASP.NET Core Identity 2.2.

public class MyCookieAuthenticationEvents : CookieAuthenticationEvents
    string newAccountNo = "102";

    public override Task ValidatePrincipal(CookieValidatePrincipalContext context)
        // first remove the old claim
        var claim = context.Principal.FindFirst(ClaimTypes.UserData);
        if (claim != null)

        // add the new claim
        ((ClaimsIdentity)context.Principal.Identity).AddClaim(new Claim(ClaimTypes.UserData, newAccountNo));

        // replace the claims
        context.ShouldRenew = true;

        return Task.CompletedTask;

You need to register the events class in Startup.cs:

public IServiceProvider ConfigureServices(IServiceCollection services)

    services.ConfigureApplicationCookie(o =>
        o.EventsType = typeof(MyCookieAuthenticationEvents);

You can inject services into the events class to access the new AccountNo value but as per the warning on this page you should avoid doing anything too expensive:


The approach described here is triggered on every request. Validating authentication cookies for all users on every request can result in a large performance penalty for the app.

add an element to int [] array in java

The length of an array is immutable in java. This means you can't change the size of an array once you have created it. If you initialised it with 2 elements, its length is 2. You can however use a different collection.

List<Integer> myList = new ArrayList<Integer>();

And with a wrapper method

public void addMember(Integer x) {

How to add a color overlay to a background image?

background-image takes multiple values.

so a combination of just 1 color linear-gradient and css blend modes will do the trick.

.testclass {
    background-image: url("../images/image.jpg"), linear-gradient(rgba(0,0,0,0.5),rgba(0,0,0,0.5));
    background-blend-mode: overlay;

note that there is no support on IE/Edge for CSS blend-modes at all.

Redirect pages in JSP?

This answer also contains a standard solution using only the jstl redirect tag:

<c:redirect url="/home.html"/>

Formula px to dp, dp to px android

px to dp:

int valueInpx = ...;
int valueInDp= (int) TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_DIP, valueInpx , getResources()

Failed to load resource: the server responded with a status of 404 (Not Found)

I have added app.UseStaticFiles(); this code in my startup.cs than it is fixed

What is the difference between a mutable and immutable string in C#?

in implementation detail.

CLR2's System.String is mutable. StringBuilder.Append calling String.AppendInplace (private method)

CLR4's System.String is immutable. StringBuilder have Char array with chunking.

Get source jar files attached to Eclipse for Maven-managed dependencies

For Indigo (and probably Helios) the checkboxes mentioned above are located here:

Window -> Preferences -> Maven

How to fire an event when v-model changes?

This happens because your click handler fires before the value of the radio button changes. You need to listen to the change event instead:

  v-on:change="foo"> //here

Also, make sure you really want to call foo() on ready... seems like maybe you don't actually want to do that.


adding 1 day to a DATETIME format value

If you want to do this in PHP:

// replace time() with the time stamp you want to add one day to
$startDate = time();
date('Y-m-d H:i:s', strtotime('+1 day', $startDate));

If you want to add the date in MySQL:

-- replace CURRENT_DATE with the date you want to add one day to

How to get ERD diagram for an existing database?

Our team use Visual Paradigm to generate ER diagram from database in many of our projects. While we mainly work on MS SQL and Oracle, as I know they also support some other DBMS like PostgreSQL, MySQL, Sybase, DB2 and SQLite.


  1. Select Tools > DB > Reverse Database... from the toolbar of Visual Paradigm
  2. Keep the settings as is and click Next Select PostgreSQL as driver and provide the driver file there. You can simply click on the download link there to get the driver.
  3. Enter the hostname, database name, user and password, and then click Next
  4. They will then study your database and lists out the tables in it.
  5. Select the table to form an ERD and continue, and that's it. An ERD will be generated with the tables you selected presented.

BTW they also support generating and updating database schema from ERD.

Hope this helps. :-)

More information about generating ERD from PostgreSQL database

what is the use of $this->uri->segment(3) in codeigniter pagination

By default the function returns FALSE (boolean) if the segment does not exist. There is an optional second parameter that permits you to set your own default value if the segment is missing. For example, this would tell the function to return the number zero in the event of failure: $product_id = $this->uri->segment(3, 0);

It helps avoid having to write code like this:

[if ($this->uri->segment(3) === FALSE)
    $product_id = 0;
    $product_id = $this->uri->segment(3);

Run/install/debug Android applications over Wi-Fi?

If you want to enable wireless adb on the device without connecting with a USB cable at all (root required):

  1. Install a terminal app on the device (like Android Terminal Emulator) Type the following
  2. su
  3. setprop service.adb.tcp.port 5555
  4. stop adbd
  5. start adbd

Since you already have the terminal opened, you can find the IP address of the device:

ip addr show

Then in your debugging environment run command:

adb connect ip.of.the.device

This will make the device to be listed as any other emulators you might have. Note that the TCP will stay opened until you reset the device. You might also want to install a Wi-Fi Keep Alive app if you often experience disconnects.

Remember to close the TCP when connecting to public networks if you want to feel safe. You can do the following or simply restart the device:

  1. su
  2. setprop service.adb.tcp.port -1
  3. stop adbd
  4. start adbd

Best way to incorporate Volley (or other library) into Android Studio project


dependencies {
    compile ''

A lot of different ways to do it back in the day (original answer)

  • Use the source files from git (a rather manual/general way described here)

    1. Download / install the git client (if you don't have it on your system yet): (or via git clone ... sry bad one, but couldn't resist ^^)
    2. Execute git clone
    3. Copy the com folder from within [path_where_you_typed_git_clone]/volley/src to your projects app/src/main/java folder (Integrate it instead, if you already have a com folder there!! ;-))

    The files show up immediately in Android Studio. For Eclipse you will have to right-click on the src folder and press refresh (or F5) first.

  • Use gradle via the "unofficial" maven mirror

    1. In your project's src/build.gradle file add following volley dependency:

      dependencies {
          compile fileTree(dir: 'libs', include: ['*.jar'])
          // ...
          compile 'com.mcxiaoke.volley:library:1.+'
    2. Click on Try Again which should right away appear on the top of the file, or just Build it if not

    The main "advantage" here is, that this will keep the version up to date for you, whereas in the other two cases you would have to manually update volley.

    On the "downside" it is not officially from google, but a third party weekly mirror.

    But both of these points, are really relative to what you would need/want. Also if you don't want updates, just put the desired version there instead e.g. compile 'com.mcxiaoke.volley:library:1.0.7'.

PHP list of specific files in a directory

$it = new RegexIterator(new DirectoryIterator("."), "/\\.xml\$/i"));

foreach ($it as $filename) {

You can also use the recursive variants of the iterators to traverse an entire directory hierarchy.

Configuring Hibernate logging using Log4j XML config file?

You can configure your log4j file with the category tag like this (with a console appender for the example):

<appender name="console" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yy-MM-dd HH:mm:ss} %p %c - %m%n" />
<category name="org.hibernate">
    <priority value="WARN" />
    <priority value="INFO" />
    <appender-ref ref="console" />

So every warning, error or fatal message from hibernate will be displayed, nothing more. Also, your code and library code will be in info level (so info, warn, error and fatal)

To change log level of a library, just add a category, for example, to desactive spring info log:

<category name="org.springframework">
    <priority value="WARN" />

Or with another appender, break the additivity (additivity default value is true)

<category name="org.springframework" additivity="false">
    <priority value="WARN" />
    <appender-ref ref="anotherAppender" />

And if you don't want that hibernate log every query, set the hibernate property show_sql to false.

Simple UDP example to send and receive data from same socket

I'll try to keep this short, I've done this a few months ago for a game I was trying to build, it does a UDP "Client-Server" connection that acts like TCP, you can send (message) (message + object) using this. I've done some testing with it and it works just fine, feel free to modify it if needed.

How to store Node.js deployment settings/configuration files?

You can require JSON files as of Node v0.5.x (referencing this answer)


    "username" : "root",
    "password" : "foot"


var config = require('./config.json');
log_in(config.username, config.password);

What operator is <> in VBA

Not Equal To

Before C came along and popularized !=, languages tended to use <> for not equal to.

At least, the various dialects of Basic did, and they predate C.

An even older and more unusual case is Fortran, which uses .NE., as in X .NE. Y.

Object does not support item assignment error

Another way would be adding __getitem__, __setitem__ function

def __getitem__(self, key):
    return getattr(self, key)

You can use self[key] to access now.

How to get Linux console window width in Python

Many of the Python 2 implementations here will fail if there is no controlling terminal when you call this script. You can check sys.stdout.isatty() to determine if this is in fact a terminal, but that will exclude a bunch of cases, so I believe the most pythonic way to figure out the terminal size is to use the builtin curses package.

import curses
w = curses.initscr()
height, width = w.getmaxyx()

DateTime.Compare how to check if a date is less than 30 days old?

No you are not using it correctly.

See here for details.

DateTime t1 = new DateTime(100);
DateTime t2 = new DateTime(20);

if (DateTime.Compare(t1, t2) >  0) Console.WriteLine("t1 > t2"); 
if (DateTime.Compare(t1, t2) == 0) Console.WriteLine("t1 == t2"); 
if (DateTime.Compare(t1, t2) <  0) Console.WriteLine("t1 < t2");

What does the "undefined reference to varName" in C mean?

An initial reaction to this would be to ask and ensure that the two object files are being linked together. This is done at the compile stage by compiling both files at the same time:

gcc -o programName a.c b.c

Or if you want to compile separately, it would be:

gcc -c a.c
gcc -c b.c
gcc -o programName a.o b.o

Find Facebook user (url to profile page) by known email address

Maybe things changed, but I recall rapleaf had a service where you enter an email address and you could receive a facebook id.

If something was not in there, one could "sign up" with the email, and it should have a chance to get the data after a while.

I came across this when using a search tool called Maltego a few years back.
The app uses many types of "transforms", and a few where related to facebook and twitter etc..

..or find some new sqli's on fb and fb apps, hehe. :)

How to set a DateTime variable in SQL Server 2008?

You need to enclose the date time value in quotes:


SET @Test = '2011-02-15'


ComboBox- SelectionChanged event has old value, not new value

This should work for you ...

int myInt= ((data)(((object[])(e.AddedItems))[0])).kid;

Transport security has blocked a cleartext HTTP

NOTE: The exception domain in your plist should be in LOWER-CASE.

Example: you have named your machine "MyAwesomeMacbook" under Settings->Sharing; your server (for test purposes) is running on MyAwesomeMacbook.local:3000, and your app needs to send a request to http://MyAwesomeMacbook.local:3000/files..., your plist you will need to specify "myawesomemacbook.local" as the exception domain.


Your info.plist would contain...

      <!--Include to allow subdomains-->
      <!--Include to allow HTTP requests-->

Why can't I define my workbook as an object?

It's actually a sensible question. Here's the answer from Excel 2010 help:

"The Workbook object is a member of the Workbooks collection. The Workbooks collection contains all the Workbook objects currently open in Microsoft Excel."

So, since that workbook isn't open - at least I assume it isn't - it can't be set as a workbook object. If it was open you'd just set it like:

Set wbk = workbooks("Master Benchmark Data Sheet.xlsx")

How to iterate over each string in a list of strings and operate on it's elements

The following code outputs the number of words whose first and last letters are equal. Tested and verified using a python online compiler:

words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']  
count = 0  
for i in words:  
     if i[0]==i[-1]:
        count = count + 1  



Convert java.time.LocalDate into java.util.Date type

public static Date convertToTimeZone(Date date, String tzFrom, String tzTo) {
    return Date.from(LocalDateTime.ofInstant(date.toInstant(), ZoneId.of(tzTo)).atZone(ZoneId.of(tzFrom)).toInstant());

Yahoo Finance API

You may use YQL however* tables are not the core yahoo tables. It is an open data table which uses the 'csv api' and converts it to json or xml format. It is more convenient to use but it's not always reliable. I could not use it just a while ago because it the table hits its storage limit or something...

You may use this php library to get historical data / quotes using YQL

Disable F5 and browser refresh using JavaScript

If you want to disable ctrl+f5 , ctrl+R , f5 ,backspace then you can use this simple code. This code is working in Mozila as well as Chrome . Add this code inside your body tag:

<body onkeydown="return (event.keyCode == 154)">

What is the size of column of int(11) in mysql in bytes?

I think max value of int(11) is 4294967295

typecast string to integer - Postgres

Common issue

Naively type casting any string into an integer like so

SELECT ''::integer

Often results to the famous error:

Query failed: ERROR: invalid input syntax for integer: ""


PostgreSQL has no pre-defined function for safely type casting any string into an integer.


Create a user-defined function inspired by PHP's intval() function.

CREATE FUNCTION intval(character varying) RETURNS integer AS $$

    WHEN length(btrim(regexp_replace($1, '[^0-9]', '','g')))>0 THEN btrim(regexp_replace($1, '[^0-9]', '','g'))::integer
    ELSE 0
END AS intval;



/* Example 1 */
SELECT intval('9000');
-- output: 9000

/* Example 2 */
SELECT intval('9gag');
-- output: 9

/* Example 3 */
SELECT intval('the quick brown fox jumps over the lazy dog');
-- output: 0

LDAP server which is my base dn

The base dn is dc=example,dc=com.

I don't know about openca, but I will try this answer since you got very little traffic so far.

A base dn is the point from where a server will search for users. So I would try to simply use admin as a login name.

If openca behaves like most ldap aware applications, this is what is going to happen :

  1. An ldap search for the user admin will be done by the server starting at the base dn (dc=example,dc=com).
  2. When the user is found, the full dn (cn=admin,dc=example,dc=com) will be used to bind with the supplied password.
  3. The ldap server will hash the password and compare with the stored hash value. If it matches, you're in.

Getting step 1 right is the hardest part, but mostly because we don't get to do it often. Things you have to look out for in your configuraiton file are :

  • The dn your application will use to bind to the ldap server. This happens at application startup, before any user comes to authenticate. You will have to supply a full dn, maybe something like cn=admin,dc=example,dc=com.
  • The authentication method. It is usually a "simple bind".
  • The user search filter. Look at the attribute named objectClass for your admin user. It will be either inetOrgPerson or user. There will be others like top, you can ignore them. In your openca configuration, there should be a string like (objectClass=inetOrgPerson). Whatever it is, make sure it matches your admin user's object Class. You can specify two object class with this search filter (|(objectClass=inetOrgPerson)(objectClass=user)).

Download an LDAP Browser, such as Apache's Directory Studio. Connect using your application's credentials, so you will see what your application sees.

Forms authentication timeout vs sessionState timeout

The slidingExpiration=true value is basically saying that after every request made, the timer is reset and as long as the user makes a request within the timeout value, he will continue to be authenticated.

This is not correct. The authentication cookie timeout will only be reset if half the time of the timeout has passed.

See for example or

Adding a column to a dataframe in R

That is a pretty standard use case for apply():

R> vec <- 1:10
R> DF <- data.frame(start=c(1,3,5,7), end=c(2,6,7,9))
R> DF$newcol <- apply(DF,1,function(row) mean(vec[ row[1] : row[2] ] ))
  start end newcol
1     1   2    1.5
2     3   6    4.5
3     5   7    6.0
4     7   9    8.0

You can also use plyr if you prefer but here is no real need to go beyond functions from base R.

How to redirect 'print' output to a file using python?

If you are using Linux I suggest you to use the tee command. The implementation goes like this:

python | tee any_file_name.txt

If you don't want to change anything in the code, I think this might be the best possible solution. You can also implement logger but you need do some changes in the code.

Setting Timeout Value For .NET Web Service

After creating your client specifying the binding and endpoint address, you can assign an OperationTimeout,

client.InnerChannel.OperationTimeout = new TimeSpan(0, 5, 0);

How do I vertically align text in a div?

<!DOCTYPE html>

      .container {
        height: 250px;
        background: #f8f8f8;
        display: -ms-flexbox;
        display: -webkit-flex;
        display: flex;
        -ms-flex-align: center;
        align-items: center;
        -webkit-box-align: center;
        justify-content: center;
        font-size: 24px;

    <div class="container">
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>


How do you check whether a number is divisible by another number (Python)?

You do this using the modulus operator, %

n % k == 0

evaluates true if and only if n is an exact multiple of k. In elementary maths this is known as the remainder from a division.

In your current approach you perform a division and the result will be either

  • always an integer if you use integer division, or
  • always a float if you use floating point division.

It's just the wrong way to go about testing divisibility.

How can strings be concatenated?

you can also do this:

section = "C_type"
new_section = "Sec_%s" % section

This allows you not only append, but also insert wherever in the string:

section = "C_type"
new_section = "Sec_%s_blah" % section

How to insert image in mysql database(table)?

This is on mysql workbench -- give the image file path:

INSERT INTO XX_SAMPLE(id,image) VALUES(3,'/home/ganesan-pc/Documents/aios_database/confe.jpg');

How to return the output of stored procedure into a variable in sql server

Use this code, Working properly

CREATE PROCEDURE [dbo].[sp_delete_item]
@ItemId int = 0
@status bit OUT

 DECLARE @cnt int;
 DECLARE @status int =0;
 SELECT @cnt =COUNT(Id) from ItemTransaction where ItemId = @ItemId
 if(@cnt = 1)
     return @status;
   SET @status =1;
    return @status;

Execute SP

DECLARE @statuss bit;
EXECUTE  [dbo].[sp_delete_item] 6, @statuss output;
PRINT @statuss;

what does the __file__ variable mean/do?

When a module is loaded from a file in Python, __file__ is set to its path. You can then use that with other functions to find the directory that the file is located in.

Taking your examples one at a time:

A = os.path.join(os.path.dirname(__file__), '..')
# A is the parent directory of the directory where program resides.

B = os.path.dirname(os.path.realpath(__file__))
# B is the canonicalised (?) directory where the program resides.

C = os.path.abspath(os.path.dirname(__file__))
# C is the absolute path of the directory where the program resides.

You can see the various values returned from these here:

import os
print(os.path.join(os.path.dirname(__file__), '..'))

and make sure you run it from different locations (such as ./, ~/python/ and so forth) to see what difference that makes.

I just want to address some confusion first. __file__ is not a wildcard it is an attribute. Double underscore attributes and methods are considered to be "special" by convention and serve a special purpose. shows many of the special methods and attributes, if not all of them.

In this case __file__ is an attribute of a module (a module object). In Python a .py file is a module. So import amodule will have an attribute of __file__ which means different things under difference circumstances.

Taken from the docs:

__file__ is the pathname of the file from which the module was loaded, if it was loaded from a file. The __file__ attribute is not present for C modules that are statically linked into the interpreter; for extension modules loaded dynamically from a shared library, it is the pathname of the shared library file.

In your case the module is accessing it's own __file__ attribute in the global namespace.

To see this in action try:

# file:

print globals()
print __file__

And run:


{'__builtins__': <module '__builtin__' (built-in)>, '__name__': '__main__', '__file__':
 '', '__doc__': None, '__package__': None}

How do I show the changes which have been staged?

Note that git status -v also shows the staged changes! (meaning you need to have staged -- git add -- some changes. No staged changes, no diff with git status -v.
It does that since Git 1.2.0, February 2006)

In its long form (default), git status has an undocumented "verbose" option which actually display the diff between HEAD and index.

And it is about to become even more complete: see "Show both staged & working tree in git diff?" (git 2.3.4+, Q2 2015):

git status -v -v

'module' has no attribute 'urlencode'

You use the Python 2 docs but write your program in Python 3.

How do I skip an iteration of a `foreach` loop?

You can use the continue statement.

For example:

foreach(int number in numbers)
    if(number < 0)

Unmarshaling nested JSON objects

I was working on something like this. But is working only with structures generated from proto.

in your proto

message Msg {
  Firstname string = 1 [(gogoproto.jsontag) = "name.firstname"];
  PseudoFirstname string = 2 [(gogoproto.jsontag) = "lastname"];
  EmbedMsg = 3  [(gogoproto.nullable) = false, (gogoproto.embed) = true];
  Lastname string = 4 [(gogoproto.jsontag) = "name.lastname"];
  Inside string  = 5 [(gogoproto.jsontag) = "name.inside.a.b.c"];

message EmbedMsg{
   Opt1 string = 1 [(gogoproto.jsontag) = "opt1"];

Then your output will be

"lastname": "Three",
"name": {
    "firstname": "One",
    "inside": {
        "a": {
            "b": {
                "c": "goo"
    "lastname": "Two"
"opt1": "var"

How do I find out what version of Sybase is running

There are two ways to know the about Sybase version,

1) Using this System procedure to get the information about Sybase version

> sp_version
> go

2) Using this command to get Sybase version

> select @@version
> go

How to create an installer for a .net Windows Service using Visual Studio

Nor Kelsey, nor Brendan solutions does not works for me in Visual Studio 2015 Community.

Here is my brief steps how to create service with installer:

  1. Run Visual Studio, Go to File->New->Project
  2. Select .NET Framework 4, in 'Search Installed Templates' type 'Service'
  3. Select 'Windows Service'. Type Name and Location. Press OK.
  4. Double click Service1.cs, right click in designer and select 'Add Installer'
  5. Double click ProjectInstaller.cs. For serviceProcessInstaller1 open Properties tab and change 'Account' property value to 'LocalService'. For serviceInstaller1 change 'ServiceName' and set 'StartType' to 'Automatic'.
  6. Double click serviceInstaller1. Visual Studio creates serviceInstaller1_AfterInstall event. Write code:

    private void serviceInstaller1_AfterInstall(object sender, InstallEventArgs e)
        using (System.ServiceProcess.ServiceController sc = new 
  7. Build solution. Right click on project and select 'Open Folder in File Explorer'. Go to bin\Debug.

  8. Create install.bat with below script:

    :: Automatically check & get admin rights
    @echo off
    ECHO =============================
    ECHO Running Admin shell
    ECHO =============================
    if '%errorlevel%' == '0' ( goto gotPrivileges ) else ( goto getPrivileges ) 
    if '%1'=='ELEV' (shift & goto gotPrivileges)  
    ECHO **************************************
    ECHO Invoking UAC for Privilege Escalation 
    ECHO **************************************
    setlocal DisableDelayedExpansion
    set "batchPath=%~0"
    setlocal EnableDelayedExpansion
    ECHO Set UAC = CreateObject^("Shell.Application"^) > "%temp%\OEgetPrivileges.vbs" 
    ECHO UAC.ShellExecute "!batchPath!", "ELEV", "", "runas", 1 >> "%temp%\OEgetPrivileges.vbs" 
    exit /B 
    setlocal & pushd .
    cd /d %~dp0
    %windir%\Microsoft.NET\Framework\v4.0.30319\InstallUtil /i "WindowsService1.exe"
  9. Create uninstall.bat file (change in pen-ult line /i to /u)
  10. To install and start service run install.bat, to stop and uninstall run uninstall.bat

Showing all session data at once?

echo "<pre>";
echo "</pre>";

Display yet formatting then you can view properly.

malloc for struct and pointer in C

You could actually do this in a single malloc by allocating for the Vector and the array at the same time. Eg:

struct Vector y = (struct Vector*)malloc(sizeof(struct Vector) + 10*sizeof(double));
y->x = (double*)((char*)y + sizeof(struct Vector));
y->n = 10;

This allocates Vector 'y', then makes y->x point to the extra allocated data immediate after the Vector struct (but in the same memory block).

If resizing the vector is required, you should do it with the two allocations as recommended. The internal y->x array would then be able to be resized while keeping the vector struct 'y' intact.

How to use Tomcat 8 in Eclipse?

In addition to @Jason's answer I had to do a bit more to get my app to run.

Matplotlib connect scatterplot points with line - Python

In addition to what provided in the other answers, the keyword "zorder" allows one to decide the order in which different objects are plotted vertically. E.g.:


plots the scatter symbols on top of the line, while


plots the line over the scatter symbols.

See, e.g., the zorder demo

Applications are expected to have a root view controller at the end of application launch

for ARC change:

change to

@synthesize window;

instead of

@synthesize window=_window;

Current date and time - Default in MVC razor

You could initialize ReturnDate on the model before sending it to the view.

In the controller:

public ActionResult SomeAction()
    var viewModel = new MyActionViewModel
        ReturnDate = System.DateTime.Now

    return View(viewModel);

"cannot be used as a function error"

Modify your estimated population function to take a growth argument of type float. Then you can call the growthRate function with your birthRate and deathRate and use the return value as the input for grown into estimatedPopulation.

float growthRate (float birthRate, float deathRate)     
    return ((birthRate) - (deathRate));    

int estimatedPopulation (int currentPopulation, float growth)
    return ((currentPopulation) + (currentPopulation) * (growth / 100);

// main.cpp
int currentPopulation = 100;
int births = 50;
int deaths = 25;
int population = estimatedPopulation(currentPopulation, growthRate(births, deaths));

how to copy only the columns in a DataTable to another DataTable?

The DataTable.Clone() method works great when you want to create a completely new DataTable, but there might be cases where you would want to add the schema columns from one DataTable to another existing DataTable.

For example, if you've derived a new subclass from DataTable, and want to import schema information into it, you couldn't use Clone().


public class CoolNewTable : DataTable {
   public void FillFromReader(DbDataReader reader) {
       // We want to get the schema information (i.e. columns) from the 
       // DbDataReader and 
       // import it into *this* DataTable, NOT a new one.
       DataTable schema = reader.GetSchemaTable(); 
       //GetSchemaTable() returns a DataTable with the columns we want.

       ImportSchema(this, schema); // <--- how do we do this?

The answer is just to create new DataColumns in the existing DataTable using the schema table's columns as templates.

I.e. the code for ImportSchema would be something like this:

void ImportSchema(DataTable dest, DataTable source) {
    foreach(var c in source.Columns)

or, if you're using Linq:

void ImportSchema(DataTable dest, DataTable source) {
    var cols = source.Columns.Cast<DataColumn>().ToArray();

This was just one example of a situation where you might want to copy schema/columns from one DataTable into another one without using Clone() to create a completely new DataTable. I'm sure I've come across several others as well.

How to use NSURLConnection to connect with SSL for an untrusted cert?

The category workaround posted by Nathan de Vries will pass the AppStore private API checks, and is useful in cases where you do not have control of the NSUrlConnection object. One example is NSXMLParser which will open the URL you supply, but does not expose the NSURLRequest or NSURLConnection.

In iOS 4 the workaround still seems to work, but only on the device, the Simulator does not invoke the allowsAnyHTTPSCertificateForHost: method anymore.

Save multiple sheets to .pdf

Similar to Tim's answer - but with a check for 2007 (where the PDF export is not installed by default):

Public Sub subCreatePDF()

    If Not IsPDFLibraryInstalled Then
        'Better show this as a userform with a proper link:
        MsgBox "Please install the Addin to export to PDF. You can find it at". 
        Exit Sub
    End If

    ActiveSheet.ExportAsFixedFormat Type:=xlTypePDF, _
        Filename:=ActiveWorkbook.Path & Application.PathSeparator & _
        ActiveSheet.Name & " für " & Range("SelectedName").Value & ".pdf", _
        Quality:=xlQualityStandard, IncludeDocProperties:=True, _
        IgnorePrintAreas:=False, OpenAfterPublish:=True
End Sub

Private Function IsPDFLibraryInstalled() As Boolean
'Credits go to Ron DeBruin (
    IsPDFLibraryInstalled = _
        (Dir(Environ("commonprogramfiles") & _
        "\Microsoft Shared\OFFICE" & _
        Format(Val(Application.Version), "00") & _
        "\EXP_PDF.DLL") <> "")
End Function

How to force a web browser NOT to cache images

I'm a NEW Coder, but here's what I came up with, to stop the Browser from caching and holding onto my webcam views:

<meta Http-Equiv="Cache" content="no-cache">
<meta Http-Equiv="Pragma-Control" content="no-cache">
<meta Http-Equiv="Cache-directive" Content="no-cache">
<meta Http-Equiv="Pragma-directive" Content="no-cache">
<meta Http-Equiv="Cache-Control" Content="no-cache">
<meta Http-Equiv="Pragma" Content="no-cache">
<meta Http-Equiv="Expires" Content="0">
<meta Http-Equiv="Pragma-directive: no-cache">
<meta Http-Equiv="Cache-directive: no-cache">

Not sure what works on what Browser, but it does work for some: IE: Works when webpage is refreshed and when website is revisited (without a refresh). CHROME: Works only when webpage is refreshed (even after a revisit). SAFARI and iPad: Doesn't work, I have to clear the History & Web Data.

Any Ideas on SAFARI/ iPad?

Jquery how to find an Object by attribute in an Array

Use the Underscore.js findWhere function (

var purposeObjects = [
    {purpose: "daily"},
    {purpose: "weekly"},
    {purpose: "monthly"}

var daily = _.findWhere(purposeObjects, {purpose: 'daily'});

daily would equal:


Here's a fiddle:

To return more than one (if you had more in your array) you could use _.where(...)

UICollectionView Self Sizing Cells with Auto Layout

Updated for Swift 5

preferredLayoutAttributesFittingAttributes renamed to preferredLayoutAttributesFitting and use auto sizing

Updated for Swift 4

systemLayoutSizeFittingSize renamed to systemLayoutSizeFitting

Updated for iOS 9

After seeing my GitHub solution break under iOS 9 I finally got the time to investigate the issue fully. I have now updated the repo to include several examples of different configurations for self sizing cells. My conclusion is that self sizing cells are great in theory but messy in practice. A word of caution when proceeding with self sizing cells.


Check out my GitHub project

Self sizing cells are only supported with flow layout so make sure thats what you are using.

There are two things you need to setup for self sizing cells to work.

1. Set estimatedItemSize on UICollectionViewFlowLayout

Flow layout will become dynamic in nature once you set the estimatedItemSize property.

self.flowLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize

2. Add support for sizing on your cell subclass

This comes in 2 flavours; Auto-Layout or custom override of preferredLayoutAttributesFittingAttributes.

Create and configure cells with Auto Layout

I won't go to in to detail about this as there's a brilliant SO post about configuring constraints for a cell. Just be wary that Xcode 6 broke a bunch of stuff with iOS 7 so, if you support iOS 7, you will need to do stuff like ensure the autoresizingMask is set on the cell's contentView and that the contentView's bounds is set as the cell's bounds when the cell is loaded (i.e. awakeFromNib).

Things you do need to be aware of is that your cell needs to be more seriously constrained than a Table View Cell. For instance, if you want your width to be dynamic then your cell needs a height constraint. Likewise, if you want the height to be dynamic then you will need a width constraint to your cell.

Implement preferredLayoutAttributesFittingAttributes in your custom cell

When this function is called your view has already been configured with content (i.e. cellForItem has been called). Assuming your constraints have been appropriately set you could have an implementation like this:

//forces the system to do one layout pass
var isHeightCalculated: Bool = false

override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
    //Exhibit A - We need to cache our calculation to prevent a crash.
    if !isHeightCalculated {
        let size = contentView.systemLayoutSizeFitting(layoutAttributes.size)
        var newFrame = layoutAttributes.frame
        newFrame.size.width = CGFloat(ceilf(Float(size.width)))
        layoutAttributes.frame = newFrame
        isHeightCalculated = true
    return layoutAttributes

NOTE On iOS 9 the behaviour changed a bit that could cause crashes on your implementation if you are not careful (See more here). When you implement preferredLayoutAttributesFittingAttributes you need to ensure that you only change the frame of your layout attributes once. If you don't do this the layout will call your implementation indefinitely and eventually crash. One solution is to cache the calculated size in your cell and invalidate this anytime you reuse the cell or change its content as I have done with the isHeightCalculated property.

Experience your layout

At this point you should have 'functioning' dynamic cells in your collectionView. I haven't yet found the out-of-the box solution sufficient during my tests so feel free to comment if you have. It still feels like UITableView wins the battle for dynamic sizing IMHO.


Be very mindful that if you are using prototype cells to calculate the estimatedItemSize - this will break if your XIB uses size classes. The reason for this is that when you load your cell from a XIB its size class will be configured with Undefined. This will only be broken on iOS 8 and up since on iOS 7 the size class will be loaded based on the device (iPad = Regular-Any, iPhone = Compact-Any). You can either set the estimatedItemSize without loading the XIB, or you can load the cell from the XIB, add it to the collectionView (this will set the traitCollection), perform the layout, and then remove it from the superview. Alternatively you could also make your cell override the traitCollection getter and return the appropriate traits. It's up to you.

Let me know if I missed anything, hope I helped and good luck coding

How can I check if a MySQL table exists with PHP?

It was already posted but here it is with PDO (same query)...

$connection = new PDO ( "mysql:host=host_db; dbname=name_db", user_db, pass_db );

if ($connection->query ("DESCRIBE table_name"  )) {
    echo "exist";
} else {
    echo "doesn't exist";

Works like a charm for me....

And here's another approach (i think it is slower)...

if ($connection->query ( "SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE table_schema = 'db_name' AND table_name ='tbl_name'" )->fetch ()) {
    echo "exist";
} else {
    echo "doesn't exist";

You can also play with this query:

SHOW TABLE STATUS FROM db_name LIKE 'tbl_name'

I think this was suggested to use in the mysql page.

How to compile for Windows on Linux with gcc/g++?

One option of compiling for Windows in Linux is via mingw. I found a very helpful tutorial here.

To install mingw32 on Debian based systems, run the following command:
sudo apt-get install mingw32

To compile your code, you can use something like:
i586-mingw32msvc-g++ -o myApp.exe myApp.cpp

You'll sometimes want to test the new Windows application directly in Linux. You can use wine for that, although you should always keep in mind that wine could have bugs. This means that you might not be sure that a bug is in wine, your program, or both, so only use wine for general testing.

To install wine, run:
sudo apt-get install wine

What is the maximum float in Python?

sys.maxint is not the largest integer supported by python. It's the largest integer supported by python's regular integer type.

SQL Server: Invalid Column Name

If you are going to ALTER Table column and immediate UPDATE the table including the new column in the same script. Make sure that use GO command to after line of code of alter table as below.


UPDATE Location SET TransitionType =  4


Node.js Web Application examples/tutorials

DailyJS has a good tutorial (long series of 24 posts) that walks you through all the aspects of building a notepad app (including all the possible extras).

Heres an overview of the tutorial:

And heres a link to all the posts:

Regex to check if valid URL that ends in .jpg, .png, or .gif


Why are you checking the URL? That's no guarantee what you're going to get is an image, and no guarantee that the things you're rejecting aren't images. Try performing a HEAD request on it, and see what content-type it actually is.

Conversion of Char to Binary in C

We show up two functions that prints a SINGLE character to binary.

void printbinchar(char character)
    char output[9];
    itoa(character, output, 2);
    printf("%s\n", output);

printbinchar(10) will write into the console


itoa is a library function that converts a single integer value to a string with the specified base. For example... itoa(1341, output, 10) will write in output string "1341". And of course itoa(9, output, 2) will write in the output string "1001".

The next function will print into the standard output the full binary representation of a character, that is, it will print all 8 bits, also if the higher bits are zero.

void printbincharpad(char c)
    for (int i = 7; i >= 0; --i)
        putchar( (c & (1 << i)) ? '1' : '0' );

printbincharpad(10) will write into the console


Now i present a function that prints out an entire string (without last null character).

void printstringasbinary(char* s)
    // A small 9 characters buffer we use to perform the conversion
    char output[9];

    // Until the first character pointed by s is not a null character
    // that indicates end of string...
    while (*s)
        // Convert the first character of the string to binary using itoa.
        // Characters in c are just 8 bit integers, at least, in noawdays computers.
        itoa(*s, output, 2);

        // print out our string and let's write a new line.

        // we advance our string by one character,
        // If our original string was "ABC" now we are pointing at "BC".

Consider however that itoa don't adds padding zeroes, so printstringasbinary("AB1") will print something like:


Unable to create migrations after upgrading to ASP.NET Core 2.0

Solution 1: (Find the problem in 99% of cases)

Set Web Application project as Startup Project

Run the following commands with -verbose option.

Add-Migration Init -Verbose

-verbose option helps to actually uncover the real problem, It contains detailed errors.

Solution 2:

Rename BuildWebHost() to CreateWebHostBuilder(), because Entity Framework Core tools expect to find a CreateHostBuilder method that configures the host without running the app.

.NET Core 2.2

public class Program
    public static void Main(string[] args)

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>

.NET Core 3.1

Rename BuildWebHost() to CreateHostBuilder()

public class Program
    public static void Main(string[] args)

    public static IHostBuilder CreateHostBuilder(string[] args) =>
            .ConfigureWebHostDefaults(webBuilder =>

Solution 3:

Make sure you added Dbcontext to dependency injection: AddDbContext<TContext> will make both your DbContext type, TContext, and the corresponding DbContextOptions<TContext> available for injection from the service container. This requires adding a constructor argument to your DbContext type that accepts DbContextOptions<TContext>.

Example: In Startup.cs

public void ConfigureServices(IServiceCollection services)
    services.AddDbContext<AppDbContext>(options => options.UseSqlServer(connectionString));

AppDbContext code:

public class AppDbContext: DbContext
    public AppDbContext(DbContextOptions<AppDbContext> options)
    { }


The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly

In your example, the compiler has no way of knowing what type should TModel be. You could do something close to what you are probably trying to do with an extension method.

static class ModelExtensions
   public static IDictionary<string, object> GetHtmlAttributes<TModel, TProperty>
      (this TModel model, Expression<Func<TModel, TProperty>> propertyExpression)
       return new Dictionary<string, object>();

But you wouldn't be able to have anything similar to virtual, I think.


Actually, you can do virtual, using self-referential generics:

class ModelBase<TModel>
    public virtual IDictionary<string, object> GetHtmlAttributes<TProperty>
        (Expression<Func<TModel, TProperty>> propertyExpression)
        return new Dictionary<string, object>();

class FooModel : ModelBase<FooModel>
    public override IDictionary<string, object> GetHtmlAttributes<TProperty>
        (Expression<Func<FooModel, TProperty>> propertyExpression)
        return new Dictionary<string, object> { { "foo", "bar" } };

Can a for loop increment/decrement by more than one?

for (var i = 0; i < myVar.length; i+=3) {
   //every three


Operator   Example    Same As
  ++       X ++        x = x + 1
  --       X --        x = x - 1
  +=       x += y      x = x + y
  -=       x -= y      x = x - y
  *=       x *= y      x = x * y
  /=       x /= y      x = x / y
  %=       x %= y      x = x % y

How to get the first five character of a String

string str = "GoodMorning"

string strModified = str.Substring(0,5);

C# Reflection: How to get class reference from string?

You will want to use the Type.GetType method.

Here is a very simple example:

using System;
using System.Reflection;

class Program
    static void Main()
        Type t = Type.GetType("Foo");
        MethodInfo method 
             = t.GetMethod("Bar", BindingFlags.Static | BindingFlags.Public);

        method.Invoke(null, null);

class Foo
    public static void Bar()

I say simple because it is very easy to find a type this way that is internal to the same assembly. Please see Jon's answer for a more thorough explanation as to what you will need to know about that. Once you have retrieved the type my example shows you how to invoke the method.

Laravel 4: Redirect to a given url

This worked for me in Laravel 5.8

return \Redirect::to('');

Or instead of / you can use

use Redirect;

Android RecyclerView addition & removal of items

  String str = arrayList.get(position);

error: (-215) !empty() in function detectMultiScale

the error may be due to, the required xml files has not been loaded properly. Search for the file haarcascade_frontalface_default.xml by using the search engine of ur OS get the full path and put it as the argument to cv2.CascadeClassifier as string

count files in specific folder and display the number into 1 cel

Try below code :

Assign the path of the folder to variable FolderPath before running the below code.

Sub sample()

    Dim FolderPath As String, path As String, count As Integer
    FolderPath = "C:\Documents and Settings\Santosh\Desktop"

    path = FolderPath & "\*.xls"

    Filename = Dir(path)

    Do While Filename <> ""
       count = count + 1
        Filename = Dir()

    Range("Q8").Value = count
    'MsgBox count & " : files found in folder"
End Sub

How to make a JSON call to a url?

DickFeynman's answer is a workable solution for any circumstance in which JQuery is not a good fit, or isn't otherwise necessary. As ComFreek notes, this requires setting the CORS headers on the server-side. If it's your service, and you have a handle on the bigger question of security, then that's entirely feasible.

Here's a listing of a Flask service, setting the CORS headers, grabbing data from a database, responding with JSON, and working happily with DickFeynman's approach on the client-side:

#!/usr/bin/env python 
from __future__ import unicode_literals
from flask      import Flask, Response, jsonify, redirect, request, url_for
from your_model import *
import os
    import simplejson as json;
except ImportError:
    import json
    from flask.ext.cors import *
    from flask_cors import *

app = Flask(__name__)

def before_request():
    # Provided by an object in your_model
    app.session = SessionManager.connect()
    print "Database connection failed."

def shutdown_session(exception=None):

# A route with a CORS header, to enable your javascript client to access 
# JSON created from a database query.
@app.route('/whatever-data/', methods=['GET', 'OPTIONS'])
def json_data():
    whatever_list = []
    results_json  = None
        # Use SQL Alchemy to select all Whatevers, WHERE size > 0.
        whatevers = app.session.query(Whatever).filter(Whatever.size > 0).all()
        if whatevers and len(whatevers) > 0:
            for whatever in whatevers:
                # Each whatever is able to return a serialized version of itself. 
                # Refer to your_model.
             # Convert a list to JSON. 
             results_json = json.dumps(whatever_list)
    except SQLAlchemyError as e:
        print 'Error {0}'.format(e)

    if len(whatevers) < 1 or not results_json:
        # Because we used json.dumps(), rather than jsonify(), 
        # we need to create a Flask Response object, here.
        return Response(response=str(results_json), mimetype='application/json')

if __name__ == '__main__':
    #@NOTE Not suitable for production. As configured, 
    #      your Flask service is in debug mode and publicly accessible., host='', port=5001) # http://localhost:5001/

your_model contains the serialization method for your whatever, as well as the database connection manager (which could stand a little refactoring, but suffices to centralize the creation of database sessions, in bigger systems or Model/View/Control architectures). This happens to use postgreSQL, but could just as easily use any server side data store:

#!/usr/bin/env python 
# Filename:
import time
import psycopg2
import psycopg2.pool
import psycopg2.extras
from   psycopg2.extensions        import adapt, register_adapter, AsIs
from   sqlalchemy                 import update
from   sqlalchemy.orm             import *
from   sqlalchemy.exc             import *
from   sqlalchemy.dialects        import postgresql
from   sqlalchemy                 import Table, Column, Integer, ForeignKey
from   sqlalchemy.ext.declarative import declarative_base

class SessionManager(object):
    def connect():
        engine = create_engine('postgresql://id:passwd@localhost/mydatabase', 
                                echo = True)
        Session = sessionmaker(bind = engine, 
                               autoflush = True, 
                               expire_on_commit = False, 
                               autocommit = False)
    session = Session()
    return session

  def declareBase():
      engine = create_engine('postgresql://id:passwd@localhost/mydatabase', echo=True)
      whatever_metadata = MetaData(engine, schema ='public')
      Base = declarative_base(metadata=whatever_metadata)
      return Base

Base = SessionManager.declareBase()

class Whatever(Base):
    """Create, supply information about, and manage the state of one or more whatever.
    __tablename__         = 'whatever'
    id                    = Column(Integer, primary_key=True)
    whatever_digest       = Column(VARCHAR, unique=True)
    best_name             = Column(VARCHAR, nullable = True)
    whatever_timestamp    = Column(BigInteger, default = time.time())
    whatever_raw          = Column(Numeric(precision = 1000, scale = 0), default = 0.0)
    whatever_label        = Column(postgresql.VARCHAR, nullable = True)
    size                  = Column(BigInteger, default = 0)

    def __init__(self, 
                 whatever_digest = '', 
                 best_name = '', 
                 whatever_timestamp = 0, 
                 whatever_raw = 0, 
                 whatever_label = '', 
                 size = 0):
        self.whatever_digest         = whatever_digest
        self.best_name               = best_name
        self.whatever_timestamp      = whatever_timestamp
        self.whatever_raw            = whatever_raw
        self.whatever_label          = whatever_label

    # Serialize one way or another, just handle appropriately in the client.  
    def serialize(self):
        return {
            'best_name'     :self.best_name,
            'size'          :self.size,

In retrospect, I might have serialized the whatever objects as lists, rather than a Python dict, which might have simplified their processing in the Flask service, and I might have separated concerns better in the Flask implementation (The database call probably shouldn't be built-in the the route handler), but you can improve on this, once you have a working solution in your own development environment.

Also, I'm not suggesting people avoid JQuery. But, if JQuery's not in the picture, for one reason or another, this approach seems like a reasonable alternative.

It works, in any case.

Here's my implementation of DickFeynman's approach, in the the client:

<script type="text/javascript">
    var addr = "dev.yourserver.yourorg.tld"
    var port = "5001"

    function Get(whateverUrl){
        var Httpreq = new XMLHttpRequest(); // a new request"GET",whateverUrl,false);
        return Httpreq.responseText;          

    var whatever_list_obj = JSON.parse(Get("http://" + addr + ":" + port + "/whatever-data/"));
    whatever_qty = whatever_list_obj.length;
    for (var i = 0; i < whatever_qty; i++) {

I'm not going to list my console output, but I'm looking at a long list of whatever.best_name strings.

More to the point: The whatever_list_obj is available for use in my javascript namespace, for whatever I care to do with it, ...which might include generating graphics with D3.js, mapping with OpenLayers or CesiumJS, or calculating some intermediate values which have no particular need to live in my DOM.

How to connect to MySQL Database?

Looking at the code below, I tried it and found: Instead of writing DBCon = DBConnection.Instance(); you should put DBConnection DBCon - new DBConnection(); (That worked for me)

and instead of MySqlComman cmd = new MySqlComman(query, DBCon.GetConnection()); you should put MySqlCommand cmd = new MySqlCommand(query, DBCon.GetConnection()); (it's missing the d)

What issues should be considered when overriding equals and hashCode in Java?

There are two methods in super class as java.lang.Object. We need to override them to custom object.

public boolean equals(Object obj)
public int hashCode()

Equal objects must produce the same hash code as long as they are equal, however unequal objects need not produce distinct hash codes.

public class Test
    private int num;
    private String data;
    public boolean equals(Object obj)
        if(this == obj)
            return true;
        if((obj == null) || (obj.getClass() != this.getClass()))
            return false;
        // object must be Test at this point
        Test test = (Test)obj;
        return num == test.num &&
        (data == || (data != null && data.equals(;

    public int hashCode()
        int hash = 7;
        hash = 31 * hash + num;
        hash = 31 * hash + (null == data ? 0 : data.hashCode());
        return hash;

    // other methods

If you want get more, please check this link as

This is another example,

Have Fun! @.@

Select SQL results grouped by weeks

This should do it for you:

Declare @DatePeriod datetime

Set @DatePeriod = '2011-05-30'

Select  ProductName,
        IsNull([1],0) as 'Week 1',
        IsNull([2],0) as 'Week 2',
        IsNull([3],0) as 'Week 3',
        IsNull([4],0) as 'Week 4',
        IsNull([5], 0) as 'Week 5'

Select  ProductName,
        DATEDIFF(week, DATEADD(MONTH, DATEDIFF(MONTH, 0, InputDate), 0), InputDate) +1 as [Weeks],
        Sale as 'Sale'

From dbo.YourTable
-- Only get rows where the date is the same as the DatePeriod
-- i.e DatePeriod is 30th May 2011 then only the weeks of May will be calculated
Where DatePart(Month, InputDate)= DatePart(Month, @DatePeriod)
Pivot (Sum(Sale) for Weeks in ([1],[2],[3],[4],[5])) as pv

It will calculate the week number relative to the month. So instead of week 20 for the year it will be week 2. The @DatePeriod variable is used to fetch only rows relative to the month (in this example only for the month of May)

Output using my sample data:

enter image description here

How to create a Rectangle object in Java using g.fillRect method

Try this:

public void paint (Graphics g) {    
    Rectangle r = new Rectangle(xPos,yPos,width,height);
    g.fillRect(r.getX(), r.getY(), r.getWidth(), r.getHeight());  


// With explicit casting
public void paint (Graphics g) {    
        Rectangle r = new Rectangle(xPos, yPos, width, height);

Printing one character at a time from a string, using the while loop

   # make a list out of text - ['h','e','l','l','o']
   text = list('hello') 

   while text:
       print text.pop()


In python empty object are evaluated as false. The .pop() removes and returns the last item on a list. And that's why it prints on reverse !

But can be fixed by using:

text.pop( 0 )

Origin null is not allowed by Access-Control-Allow-Origin

Just wanted to add that the "run a webserver" answer seems quite daunting, but if you have python on your system (installed by default at least on MacOS and any Linux distribution) it's as easy as:

python -m http.server  # with python3


python -m SimpleHTTPServer  # with python2

So if you have your html file myfile.html in a folder, say mydir, all you have to do is:

cd /path/to/mydir
python -m http.server  # or the python2 alternative above

Then point your browser to:


And you are done! Works on all browsers, without disabling web security, allowing local files, or even restarting the browser with command line options.

Adding values to a C# array

int[] terms = new int[10]; //create 10 empty index in array terms

//fill value = 400 for every index (run) in the array
//terms.Length is the total length of the array, it is equal to 10 in this case 
for (int run = 0; run < terms.Length; run++) 
    terms[run] = 400;

//print value from each of the index
for (int run = 0; run < terms.Length; run++)
    Console.WriteLine("Value in index {0}:\t{1}",run, terms[run]);



Value in index 0: 400
Value in index 1: 400
Value in index 2: 400
Value in index 3: 400
Value in index 4: 400
Value in index 5: 400
Value in index 6: 400
Value in index 7: 400
Value in index 8: 400
Value in index 9: 400

Node.js Port 3000 already in use but it actually isn't?

You can use kill-port. In firstly, kill exist port and in secondly create server and listen.

const kill = require('kill-port')

kill(port, 'tcp')
    .then((d) => {
     * Create HTTP server.
        server = http.createServer(app);

        server.listen(port, () => {
            console.log(`api running on port:${port}`);
    .catch((e) => {

What dependency is missing for org.springframework.web.bind.annotation.RequestMapping?

I was using spring-web version 4.3.7

Changing it to a working 4.1.7 immediately solved it.


Form Google Maps URL that searches for a specific places near specific coordinates

You can use the query parameter ll for your lat and long, and you can use the query parameter q for what you want to search.,-74.86084

Or you can

How to solve npm error "npm ERR! code ELIFECYCLE"

React Application: For me the issue was that after running npm install had some errors.

I've went with the recommendation npm audit fix. This operation broke my package.json and package-lock.json (changed version of packages and and structure of .json).


  • Delete node_modules
  • Run npm install
  • npm start

Hope this will be helpfull for someone.

How do I combine 2 select statements into one?

select Status, * from WorkItems t1
where  exists (select 1 from workitems t2 where t1.TextField01=t2.TextField01 AND (BoolField05=1) )
AND TimeStamp=(select max(t2.TimeStamp) from workitems t2 where t2.TextField01=t1.TextField01) 
AND TimeStamp>'2009-02-12 18:00:00'


select 'DELETED', * from WorkItems t1
where  exists (select 1 from workitems t2 where t1.TextField01=t2.TextField01 AND (BoolField05=1) )
AND TimeStamp=(select max(t2.TimeStamp) from workitems t2 where t2.TextField01=t1.TextField01) 
AND TimeStamp>'2009-02-12 18:00:00'
AND NOT (BoolField05=1)

Perhaps that'd do the trick. I can't test it from here though, and I'm not sure what version of SQL you're working against.

7-zip commandline

Since 7-zip version 9.25 alpha there is a new -spf switch that can be used to store the full file paths including drive letter to the archive.

7zG.exe a -spf c:\BAckup\ @c:\temp\tmpFileList.txt

should be working just fine now.

What is the difference between a "line feed" and a "carriage return"?

A line feed means moving one line forward. The code is \n.
A carriage return means moving the cursor to the beginning of the line. The code is \r.

Windows editors often still use the combination of both as \r\n in text files. Unix uses mostly only the \n.

The separation comes from typewriter times, when you turned the wheel to move the paper to change the line and moved the carriage to restart typing on the beginning of a line. This was two steps.

sql select with column name like

Thank you @Blorgbeard for the genious idea.

By the way Blorgbeard's query was not working for me so I edited it:

DECLARE @Table_Name as VARCHAR(50) SET @Table_Name = 'MyTable'          -- put here you table name
DECLARE @Column_Like as VARCHAR(20) SET @Column_Like = '%something%'    -- put here you element
DECLARE @sql NVARCHAR(MAX) SET @sql = 'select '

SELECT @sql = @sql + '[' + + '],'
FROM sys.columns 
JOIN sys.tables ON sys.columns.object_id = tables.object_id
WHERE like @Column_Like
and = @Table_Name

SET @sql = left(@sql,len(@sql)-1) -- remove trailing comma
SET @sql = @sql + ' from ' + @Table_Name

EXEC sp_executesql @sql

How to convert MySQL time to UNIX timestamp using PHP?

From one of my other posts, getting a unixtimestamp:

$unixTimestamp = time();

Converting to mysql datetime format:

$mysqlTimestamp = date("Y-m-d H:i:s", $unixTimestamp);

Getting some mysql timestamp:

$mysqlTimestamp = '2013-01-10 12:13:37';

Converting it to a unixtimestamp:

$unixTimestamp = strtotime('2010-05-17 19:13:37');

...comparing it with one or a range of times, to see if the user entered a realistic time:

if($unixTimestamp > strtotime("1999-12-15") && $unixTimestamp < strtotime("2025-12-15"))

Unix timestamps are safer too. You can do the following to check if a url passed variable is valid, before checking (for example) the previous range check:


The maximum value for an int type in Go

I originally used the code taken from the discussion thread that @nmichaels used in his answer. I now use a slightly different calculation. I've included some comments in case anyone else has the same query as @Arijoon

const (
    MinUint uint = 0                 // binary: all zeroes

    // Perform a bitwise NOT to change every bit from 0 to 1
    MaxUint      = ^MinUint          // binary: all ones

    // Shift the binary number to the right (i.e. divide by two)
    // to change the high bit to 0
    MaxInt       = int(MaxUint >> 1) // binary: all ones except high bit

    // Perform another bitwise NOT to change the high bit to 1 and
    // all other bits to 0
    MinInt       = ^MaxInt           // binary: all zeroes except high bit

The last two steps work because of how positive and negative numbers are represented in two's complement arithmetic. The Go language specification section on Numeric types refers the reader to the relevant Wikipedia article. I haven't read that, but I did learn about two's complement from the book Code by Charles Petzold, which is a very accessible intro to the fundamentals of computers and coding.

I put the code above (minus most of the comments) in to a little integer math package.

How do I increment a DOS variable in a FOR /F loop?

Or you can do this without using Delay.

set /a "counter=0"

-> your for loop here

do (
   call :increaseby1

set /a "counter+=1"

C++ - Decimal to binary converting


I'm still a beginner, so this code will only use loops and variables xD...

Hope you like it. This can probably be made simpler than it is...

    #include <iostream>
    #include <cmath>
    #include <cstdlib>

    using namespace std;

    int main()
        int i;
        int expoentes; //the sequence > pow(2,i) or 2^i
        int decimal; 
        int extra; //this will be used to add some 0s between the 1s
        int x = 1;

        cout << "\nThis program converts natural numbers into binary code\nPlease enter a Natural number:";
        cout << "\n\nWARNING: Only works until ~1.073 millions\n";
        cout << "     To exit, enter a negative number\n\n";

        while(decimal >= 0){
            cout << "\n----- // -----\n\n";
            cin >> decimal;
            cout << "\n";

            if(decimal == 0){
                cout << "0";
            while(decimal >= 1){
                i = 0;
                expoentes = 1;
                while(decimal >= expoentes){
                    expoentes = pow(2,i);
                x = 1;
                cout << "1";
                decimal -= pow(2,i-x);
                extra = pow(2,i-1-x);
                while(decimal < extra){
                    cout << "0";
                    extra = pow(2,i-1-x);
        return 0;

Node.js EACCES error when listening on most ports

this happens if the port you are trying to locally host on is portfowarded

How to change visibility of layout programmatically

TextView view = (TextView) findViewById(;
view.setText("Add your text here");

Saving images in Python at a very high quality

You can save to a figure that is 1920x1080 (or 1080p) using:

fig = plt.figure(figsize=(19.20,10.80))

You can also go much higher or lower. The above solutions work well for printing, but these days you want the created image to go into a PNG/JPG or appear in a wide screen format.

How to pass multiple values to single parameter in stored procedure

This can not be done easily. There's no way to make an NVARCHAR parameter take "more than one value". What I've done before is - as you do already - make the parameter value like a list with comma-separated values. Then, split this string up into its parts in the stored procedure.

Splitting up can be done using string functions. Add every part to a temporary table. Pseudo-code for this could be:

WHILE LEN(@PortfolioID) > 0
    IF NOT <@PortfolioID contains Comma>
        INSERT INTO #TempTable VALUES CAST(@PortfolioID as INT)
        SET @PortfolioID = ''
         INSERT INTO #Temptable VALUES CAST(<Part until next comma> AS INT)
         SET @PortfolioID = <Everything after the next comma>

Then, change your condition to

WHERE PortfolioId IN (SELECT ID FROM #TempTable)

You may be interested in the documentation for multi value parameters in SSRS, which states:

You can define a multivalue parameter for any report parameter that you create. However, if you want to pass multiple parameter values back to a data source by using the query, the following requirements must be satisfied:

The data source must be SQL Server, Oracle, Analysis Services, SAP BI NetWeaver, or Hyperion Essbase.

The data source cannot be a stored procedure. Reporting Services does not support passing a multivalue parameter array to a stored procedure.

The query must use an IN clause to specify the parameter.

This I found here.

How to get query string parameter from MVC Razor markup?

It was suggested to post this as an answer, because some other answers are giving errors like 'The name Context does not exist in the current context'.

Just using the following works:


Sample usage:

<a href="@Url.Action("Query",new {parm1=Request.Query["queryparm1"]})">GO</a>

How do you properly use namespaces in C++?

Vincent Robert is right in his comment How do you properly use namespaces in C++?.

Using namespace

Namespaces are used at the very least to help avoid name collision. In Java, this is enforced through the "org.domain" idiom (because it is supposed one won't use anything else than his/her own domain name).

In C++, you could give a namespace to all the code in your module. For example, for a module MyModule.dll, you could give its code the namespace MyModule. I've see elsewhere someone using MyCompany::MyProject::MyModule. I guess this is overkill, but all in all, it seems correct to me.

Using "using"

Using should be used with great care because it effectively import one (or all) symbols from a namespace into your current namespace.

This is evil to do it in a header file because your header will pollute every source including it (it reminds me of macros...), and even in a source file, bad style outside a function scope because it will import at global scope the symbols from the namespace.

The most secure way to use "using" is to import select symbols:

void doSomething()
   using std::string ; // string is now "imported", at least,
                       // until the end of the function
   string a("Hello World!") ;
   std::cout << a << std::endl ;

void doSomethingElse()
   using namespace std ; // everything from std is now "imported", at least,
                       // until the end of the function
   string a("Hello World!") ;
   cout << a << endl ;

You'll see a lot of "using namespace std ;" in tutorial or example codes. The reason is to reduce the number of symbols to make the reading easier, not because it is a good idea.

"using namespace std ;" is discouraged by Scott Meyers (I don't remember exactly which book, but I can find it if necessary).

Namespace Composition

Namespaces are more than packages. Another example can be found in Bjarne Stroustrup's "The C++ Programming Language".

In the "Special Edition", at 8.2.8 Namespace Composition, he describes how you can merge two namespaces AAA and BBB into another one called CCC. Thus CCC becomes an alias for both AAA and BBB:

namespace AAA
   void doSomething() ;

namespace BBB
   void doSomethingElse() ;

namespace CCC
   using namespace AAA ;
   using namespace BBB ;

void doSomethingAgain()
   CCC::doSomething() ;
   CCC::doSomethingElse() ;

You could even import select symbols from different namespaces, to build your own custom namespace interface. I have yet to find a practical use of this, but in theory, it is cool.

Call angularjs function using jquery/javascript

Another way is to create functions in global scope. This was necessary for me since it wasn't possible in Angular 1.5 to reach a component's scope.


angular.module("app", []).component("component", {_x000D_
  controller: ["$window", function($window) {_x000D_
    var self = this;_x000D_
    self.logg = function() {_x000D_
    $window.angularControllerLogg = self.logg;_x000D_

Convert normal Java Array or ArrayList to Json Array in android

If you want or need to work with a Java array then you can always use the java.util.Arrays utility classes' static asList() method to convert your array to a List.

Something along those lines should work.

String mStringArray[] = { "String1", "String2" };

JSONArray mJSONArray = new JSONArray(Arrays.asList(mStringArray));

Beware that code is written offhand so consider it pseudo-code.

Convert String XML fragment to Document Node in Java

...and if you're using purely XOM, something like this:

    String xml = "<fakeRoot>" + xml + "</fakeRoot>";
    Document doc = new Builder( false ).build( xml, null );
    Nodes children = doc.getRootElement().removeChildren();
    for( int ix = 0; ix < children.size(); ix++ ) {
        otherDocumentElement.appendChild( children.get( ix ) );

XOM uses fakeRoot internally to do pretty much the same, so it should be safe, if not exactly elegant.

MySQL user DB does not have password columns - Installing MySQL on OSX

It only worked with me when I "flushed" after the commands mentioned here. Here's the full list of commands I used:

Previous answers might not work for later mysql versions. Try these steps if previous answers did not work for you:

1- Click on the wamp icon > mysql > mysql console

2- write following commands, one by one

use mysql;
update user set authentication_string=password('your_password') where user='root';

Most concise way to convert a Set<T> to a List<T>

List<String> l = new ArrayList<String>(listOfTopicAuthors);

Node.js: get path from the request

req.protocol + '://' + req.get('host') + req.originalUrl


req.protocol + '://' + + req.originalUrl // I like this one as it survives from proxy server, getting the original host name

How do you select a particular option in a SELECT element in jQuery?

Exactly it will work try this below methods

For normal select option

    $(document).ready(function() {
    $("#id").val('select value here');

For select 2 option trigger option need to use

        $(document).ready(function() {
        $("#id").val('select value here').trigger('change');

Check synchronously if file/directory exists in Node.js

The path module does not provide a synchronous version of path.exists so you have to trick around with the fs module.

Fastest thing I can imagine is using fs.realpathSync which will throw an error that you have to catch, so you need to make your own wrapper function with a try/catch.

What's the best way to center your HTML email content in the browser window (or email client preview pane)?

table align="center" ... this aligns the table center of page.

Using td align="center" centers the content inside that td, useful for centered aligned text but you will have issues with some email clients centering content in sub level tables so using using td align as a top level method of centering your "container" table on the page is not the way to do it. Use table align instead.

Still use your 100% wrapper table too, purely as a wrapper for the body, as some email clients don't display body background colors but it will show it with the 100% table, so add your body color to both body and the 100% table.

I could go on and on for ages about all the quirks of html email dev. All I can say is test test and test again. is a great tool for testing emails.

The more you do the more you will learn about what works in what email clients.

Hope this helps.