Programs & Examples On #Gsm

GSM is an abbreviation for "Global System for Mobile Communication"

What is meaning of negative dbm in signal strength?

I think it is confusing to think of it in terms of negative numbers. Since it is a logarithm think of the negative values the same way you think of powers of ten. 10^3 = 1000 while 10^-3 = 0.001.

With this in mind and using the formulas from S Lists's answer (and assuming our base power is 1mW in all these cases) we can build a little table:

| P(dBm) |        P(mW)      |
|    50  |  100000           |    
|    40  |   10000           |    strong transmitter
|    30  |    1000           |             ^  
|    20  |     100           |             |
|    10  |      10           |             |
|     0  |       1           |
|   -10  |       0.1         |
|   -20  |       0.01        |
|   -30  |       0.001       |
|   -40  |       0.0001      |
|   -50  |       0.00001     |             |
|   -60  |       0.000001    |             |
|   -70  |       0.0000001   |             v
|   -80  |       0.00000001  |    sensitive receiver
|   -90  |       0.000000001 |

When I think of it like this I find that it's easier to see that the more negative the dBm value then the farther to the right of the decimal the actual power value is.

When it comes to mobile networks, it not so much that they aren't powerful enough, rather it is that they are more sensitive. When you see receivers specs with dBm far into the negative values, then what you are seeing is more sensitive equipment.

Normally you would want your transmitter to be powerful (further in to the positives) and your receiver to be sensitive (further in to the negatives).

Get gateway ip address in android

On Android 7 works it:

 ip route get

output will be: via gateway...

Determine if Python is running inside virtualenv

  • Updated Nov 2019 (appended).

I routinely use several Anaconda-installed virtual environments (venv). This code snippet/examples enables you to determine whether or not you are in a venv (or your system environment), and to also require a specific venv for your script.

Add to Python script (code snippet):

# ----------------------------------------------------------------------------
# Want script to run in Python 3.5 (has required installed OpenCV, imutils, ... packages):
import os

# First, see if we are in a conda venv { py27: Python 2.7 | py35: Python 3.5 | tf: TensorFlow | thee : Theano }
except KeyError:
   print("\tPlease set the py35 { p3 | Python 3.5 } environment!\n")

# If we are in a conda venv, require the p3 venv:
if os.environ['CONDA_DEFAULT_ENV'] != "py35":
    print("\tPlease set the py35 { p3 | Python 3.5 } environment!\n")

# See also:
# Python: Determine if running inside virtualenv
# [ ... SNIP! ... ]


$ p2
  [Anaconda Python 2.7 venv (source activate py27)]

(py27) $ python
    Please set the py35 { p3 | Python 3.5 } environment!

(py27) $ p3
  [Anaconda Python 3.5 venv (source activate py35)]

(py35) $ python -n50

    current env: py35
    processing (live): found 2 faces and 4 eyes in this frame
    threaded OpenCV implementation
    num_frames: 50
    webcam -- approx. FPS: 18.59
    Found 2 faces and 4 eyes!
(py35) $

Update 1 -- use in bash scripts:

You can also use this approach in bash scripts (e.g., those that must run in a specific virtual environment). Example (added to bash script):

if [ $CONDA_DEFAULT_ENV ]        ## << note the spaces (important in BASH)!
        printf 'venv: operating in tf-env, proceed ...'
        printf 'Note: must run this script in tf-env venv'

Update 2 [Nov 2019]

Since my original post I've moved on from Anaconda venv (and Python itself has evolved viz-a-viz virtual environments).

Reexamining this issue, here is some updated Python code that you can insert to test that you are operating in a specific Python virtual environment (venv).

import os, re
    if'py37', os.environ['VIRTUAL_ENV']):
except KeyError:
    print("\n\tPlease set the Python3 venv [alias: p3]!\n")

Here is some explanatory code.

[victoria@victoria ~]$ date; python --version
  Thu 14 Nov 2019 11:27:02 AM PST
  Python 3.8.0

[victoria@victoria ~]$ python
  Python 3.8.0 (default, Oct 23 2019, 18:51:26) 
  [GCC 9.2.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.

>>> import os, re

>>>'py37', os.environ['VIRTUAL_ENV'])
<re.Match object; span=(20, 24), match='py37'>

>>> try:
...     if'py37', os.environ['VIRTUAL_ENV']):
...       print('\n\tOperating in Python3 venv, please proceed!  :-)')
... except KeyError:
...     print("\n\tPlease set the Python3 venv [alias: p3]!\n")

    Please set the Python3 venv [alias: p3]!

>>> [Ctrl-d]
  now exiting EditableBufferInteractiveConsole...

[victoria@victoria ~]$ p3
  [Python 3.7 venv (source activate py37)]

(py37) [victoria@victoria ~]$ python --version
  Python 3.8.0

(py37) [victoria@victoria ~]$ env | grep -i virtual

(py37) [victoria@victoria ~]$ python
  Python 3.8.0 (default, Oct 23 2019, 18:51:26) 
  [GCC 9.2.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.

>>> import os, re
>>> try:
...     if'py37', os.environ['VIRTUAL_ENV']):
...       print('\n\tOperating in Python3 venv, please proceed!  :-)')
... except KeyError:
...     print("\n\tPlease set the Python3 venv [alias: p3]!\n")

    Operating in Python3 venv, please proceed!  :-)

C# 4.0: Convert pdf to byte[] and vice versa

Easiest way:

byte[] buffer;
using (Stream stream = new IO.FileStream("file.pdf"))
   buffer = new byte[stream.Length - 1];
   stream.Read(buffer, 0, buffer.Length);

using (Stream stream = new IO.FileStream("newFile.pdf"))
   stream.Write(buffer, 0, buffer.Length);

Or something along these lines...

Simple tool to 'accept theirs' or 'accept mine' on a whole file using git

Try this:

To accept theirs changes: git merge --strategy-option theirs

To accept yours: git merge --strategy-option ours

UIView frame, bounds and center

There are very good answers with detailed explanation to this post. I just would like to refer that there is another explanation with visual representation for the meaning of Frame, Bounds, Center, Transform, Bounds Origin in WWDC 2011 video Understanding UIKit Rendering starting from @4:22 till 20:10

jQuery UI DatePicker to show year only

Try this piece of code, it worked for me:

    format: "yyyy",
    viewMode: "years",
    minViewMode: "years"

I hope it will do magic also for you.

Is if(document.getElementById('something')!=null) identical to if(document.getElementById('something'))?

jquery will provide you with this and more ...

if($("#something").val()){ //do stuff}

It took me a couple of days to pick it up, but it provides you with you with so much more functionality. An example below.

jQuery(document).ready(function() {
    /* finds closest element with class divright/left and 
    makes all checkboxs inside that div class the same as selectAll...
        $("#selectAll").click(function() {
        $(this).closest('.divright').find(':checkbox').attr('checked', this.checked);

How to see indexes for a database or table in MySQL?

Why not show create table myTable ?

Someone told me this but I didn't see anyone mention here, anything bad?

It's neat if you just want to take a glance at the indexes along with column infomations.

Java Error opening registry key

I followed multiple answers from above and got my issue resolved.


Javac was on 13 from jdk but java was using 1.8 from jre so java threw incompatible runtime error


  1. Under Control Panel -> Programs: I uninstalled 1.8 (named Java 8 runtime) and DID NOT touch the other one (named Java (TM) SE Development Kit 13)

  2. Deleted java.exe, javac.exe and javawc.exe files from: a. C:\Windows\system32 b. C:\Windows\SysWOW64 c. C:\ProgramData\Oracle\Java\javapath

  3. The environment variable JDK_HOME was pointing to 13 but JAVA_HOME was pointing to 1.8 so i pointed JAVA_HOME to also use 13 which was C:\Program Files\Java\jdk-13.0.1

  4. There was a Path variable under both User variables and system variables sections. For the one in user variables section, i added the string %JDK_HOME% - which translated automatically to the physical path. For the one under system variables, I deleted the path C:\ProgramData\Oracle\Java\javapath and added C:\Program Files\Java\jdk-13.0.1\bin

All good now! Thanks to all the people who answered, you rock!

Accessing Imap in C#

MailSystem.NET contains all your need for IMAP4. It's free & open source.

(I'm involved in the project)

Hash table runtime complexity (insert, search and delete)

Some hash tables (cuckoo hashing) have guaranteed O(1) lookup

What is the equivalent of "none" in django templates?

isoperator : New in Django 1.10

{% if somevar is None %}
  This appears if somevar is None, or if somevar is not found in the context.
{% endif %}

HashSet vs LinkedHashSet

All Methods and constructors are same but only one difference is LinkedHashset will maintain insertion order but it will not allow duplicates.

Hashset will not maintain any insertion order. It is combination of List and Set simple :)

What is a Java String's default initial value?

It's initialized to null if you do nothing, as are all reference types.

Check if value exists in enum in TypeScript

For anyone who comes here looking to validate if a string is one of the values of an enum and type convert it, I wrote this function that returns the proper type and returns undefined if the string is not in the enum.

function keepIfInEnum<T>(
  value: string,
  enumObject: { [key: string]: T }
) {
  if (Object.values(enumObject).includes((value as unknown) as T)) {
    return (value as unknown) as T;
  } else {
    return undefined;

As an example:

enum StringEnum {
  value1 = 'FirstValue',
  value2 = 'SecondValue',
keepIfInEnum<StringEnum>('FirstValue', StringEnum)  // 'FirstValue'
keepIfInEnum<StringEnum>('OtherValue', StringEnum)  // undefined

JSON response parsing in Javascript to get key/value pair

Try the JSON Parser by Douglas Crockford at github. You can then simply create a JSON object out of your String variable as shown below:

var JSONText = '{"c":{"a":[{"name":"cable - black","value":2},{"name":"case","value":2}]},"o":{"v":[{"name":"over the ear headphones - white/purple","value":1}]},"l":{"e":[{"name":"lens cleaner","value":1}]},"h":{"d":[{"name":"hdmi cable","value":1},{"name":"hdtv essentials (hdtv cable setup)","value":1},{"name":"hd dvd \u0026 blue-ray disc lens cleaner","value":1}]}'

var JSONObject = JSON.parse(JSONText);
var c = JSONObject["c"];
var o = JSONObject["o"];

Regex, every non-alphanumeric character except white space or colon

In JavaScript:


^ negation, i.e. select anything not in the following set

\w any word character (i.e. any alphanumeric character, plus underscore)

_ negate the underscore, as it's considered a 'word' character

Usage example - const nonAlphaNumericChars = /[^\w_]/g;

UL list style not applying

This problem was caused by the li display attribute being set to block in a parent class. Overriding with list-item solved the problem.

android: how to align image in the horizontal center of an imageview?

Try this code :


                android:src="@drawable/back_detail" />

Get week number (in the year) from a date PHP

Becomes more difficult when you need year and week.
Try to find out which week is 01.01.2017.
(It is the 52nd week of 2016, which is from Mon 26.12.2016 - Sun 01.01.2017).

After a longer search I found


Result: 2016-52
ISO-8601:1988 week number of the given year, starting with the first week of the year with at least 4 weekdays, with Monday being the start of the week. (01 through 53)

The equivalent in mysql is DATE_FORMAT(date, '%x-%v')
Week where Monday is the first day of the week (01 to 53).

Could not find a corresponding solution with date() or DateTime.
At least not without solutions like "+1day, last monday".

adb shell command to make Android package uninstall dialog appear

While the above answers work but in case you have multiple devices connected to your computer then the following command can be used to remove the app from one of them:

adb -s <device-serial> shell pm uninstall <app-package-name>

If you want to find out the device serial then use the following command:

adb devices -l

This will give you a list of devices attached. The left column shows the device serials.

In Java, can you modify a List while iterating through it?

Use CopyOnWriteArrayList
and if you want to remove it, do the following:

for (Iterator<String> it = userList.iterator(); it.hasNext() ;)
    if (wordsToRemove.contains(word))

JAX-WS - Adding SOAP Headers

I'm adding this answer because none of the others worked for me.

I had to add a Header Handler to the Proxy:

import java.util.Set;
import java.util.TreeSet;

import javax.xml.namespace.QName;
import javax.xml.soap.SOAPElement;
import javax.xml.soap.SOAPEnvelope;
import javax.xml.soap.SOAPFactory;
import javax.xml.soap.SOAPHeader;

public class SOAPHeaderHandler implements SOAPHandler<SOAPMessageContext> {

    private final String authenticatedToken;

    public SOAPHeaderHandler(String authenticatedToken) {
        this.authenticatedToken = authenticatedToken;

    public boolean handleMessage(SOAPMessageContext context) {
        Boolean outboundProperty =
                (Boolean) context.get(MessageContext.MESSAGE_OUTBOUND_PROPERTY);
        if (outboundProperty.booleanValue()) {
            try {
                SOAPEnvelope envelope = context.getMessage().getSOAPPart().getEnvelope();
                SOAPFactory factory = SOAPFactory.newInstance();
                String prefix = "urn";
                String uri = "urn:xxxx";
                SOAPElement securityElem =
                        factory.createElement("Element", prefix, uri);
                SOAPElement tokenElem =
                        factory.createElement("Element2", prefix, uri);
                SOAPHeader header = envelope.addHeader();
            } catch (Exception e) {
        } else {
            // inbound
        return true;

    public Set<QName> getHeaders() {
        return new TreeSet();

    public boolean handleFault(SOAPMessageContext context) {
        return false;

    public void close(MessageContext context) {

In the proxy, I just add the Handler:

BindingProvider bp =(BindingProvider)basicHttpBindingAuthentication;
bp.getBinding().getHandlerChain().add(new SOAPHeaderHandler(authenticatedToken));
bp.getBinding().getHandlerChain().add(new SOAPLoggingHandler());

No value accessor for form control with name: 'recipient'

Make sure you import MaterialModule as well since you are using md-input which does not belong to FormsModule

How to get height of entire document with JavaScript?

To get the width in a cross browser/device way use:

function getActualWidth() {
    var actualWidth = window.innerWidth ||
                      document.documentElement.clientWidth ||
                      document.body.clientWidth ||

    return actualWidth;

python pip on Windows - command 'cl.exe' failed

  1. Install Microsoft visual c++ 14.0 build tool.(Windows 7)
  2. create a virtual environment using conda.
  3. Activate the environment and use conda to install the necessary package.

For example: conda install -c conda-forge spacy

How change default SVN username and password to commit changes?

To use alternate credentials for a single operation, use the --username and --password switches for svn.

To clear previously-saved credentials, delete ~/.subversion/auth. You'll be prompted for credentials the next time they're needed.

These settings are saved in the user's home directory, so if you're using a shared account on "this laptop", be careful - if you allow the client to save your credentials, someone can impersonate you. The first option I provided is the better way to go in this case. At least until you stop using shared accounts on computers, which you shouldn't be doing.

To change credentials you need to do:

  • rm -rf ~/.subversion/auth
  • svn up ( it'll ask you for new username & password )

Hadoop: «ERROR : JAVA_HOME is not set»

  • hadoop ERROR : JAVA_HOME is not set

Above error is because of the space in between two words.

Eg: Java located in C:\Program Files\Java --> Space in between Program and files would cause the above problem. If you remove the space, it would not show any error.

How to read pickle file?

I developed a software tool that opens (most) Pickle files directly in your browser (nothing is transferred so it's 100% private):

What should I use to open a url instead of urlopen in urllib3

urllib3 is a different library from urllib and urllib2. It has lots of additional features to the urllibs in the standard library, if you need them, things like re-using connections. The documentation is here:

If you'd like to use urllib3, you'll need to pip install urllib3. A basic example looks like this:

from bs4 import BeautifulSoup
import urllib3

http = urllib3.PoolManager()

url = ''
response = http.request('GET', url)
soup = BeautifulSoup(

How to disable button in React.js

I have had a similar problem, turns out we don't need hooks to do these, we can make an conditional render and it will still work fine.

        name === "" || email === "" || password === "" ? true : false

Replace tabs with spaces in vim

If you want to keep your \t equal to 8 spaces then consider setting:

   set softtabstop=2 tabstop=8 shiftwidth=2

This will give you two spaces per <TAB> press, but actual \t in your code will still be viewed as 8 characters.

Two constructors

Let's, just as example:

public class Test {     public Test() {         System.out.println("NO ARGS");     }      public Test(String s) {         this();         System.out.println("1 ARG");     }      public static void main(String args[])     {         Test t = new Test("s");     } } 

It will print

>>> NO ARGS >>> 1 ARG 

The correct way to call the constructor is by:


How do I get the name of the active user via the command line in OS X?

The question has not been completely answered, IMHO. I will try to explain: I have a crontab entry that schedules a bash shell command procedure, that in turn does some cleanup of my files; and, when done, sends a notification to me using the OS X notification center (with the command osascript -e 'display notification ...). If someone (e.g. my wife or my daughter) switches the current user of the computer to her, leaving me in the background, the cron script fails when sending the notification.

So, Who is the current user means Has some other people become the effective user leaving me in the background? Do stat -f "%Su" /dev/console returns the current active user name?

The answer is yes; so, now my crontab shell script has been modified in the following way:

if [ "$(/usr/bin/stat -f ""%Su"" /dev/console)" = "loreti" ]
then /usr/bin/osascript -e \
  'display notification "Cleanup done" sound name "sosumi" with title "myCleanup"'

Can I use git diff on untracked files?

Not 100% to the point, but if for some reason you don't want to add your files to the index as suggested by the accepted answer, here is another option:

If the files are untracked, obviously the diff is the whole file, so you can just view them with less:

less $(git ls-files --others --exclude-standard)

Navigate between them with :n and :p for next and previous..

Update from the comments: If you need a patch format you can also combine it with git diff:

git ls-files --others --exclude-standard | xargs -n 1 git --no-pager diff /dev/null | less

You can also redirect the output to a file or use an other diff command in this case.

Recursion in Python? RuntimeError: maximum recursion depth exceeded while calling a Python object

Python lacks the tail recursion optimizations common in functional languages like lisp. In Python, recursion is limited to 999 calls (see sys.getrecursionlimit).

If 999 depth is more than you are expecting, check if the implementation lacks a condition that stops recursion, or if this test may be wrong for some cases.

I dare to say that in Python, pure recursive algorithm implementations are not correct/safe. A fib() implementation limited to 999 is not really correct. It is always possible to convert recursive into iterative, and doing so is trivial.

It is not reached often because in many recursive algorithms the depth tend to be logarithmic. If it is not the case with your algorithm and you expect recursion deeper than 999 calls you have two options:

1) You can change the recursion limit with sys.setrecursionlimit(n) until the maximum allowed for your platform:


Set the maximum depth of the Python interpreter stack to limit. This limit prevents infinite recursion from causing an overflow of the C stack and crashing Python.

The highest possible limit is platform-dependent. A user may need to set the limit higher when she has a program that requires deep recursion and a platform that supports a higher limit. This should be done with care, because a too-high limit can lead to a crash.

2) You can try to convert the algorithm from recursive to iterative. If recursion depth is bigger than allowed by your platform, it is the only way to fix the problem. There are step by step instructions on the Internet and it should be a straightforward operation for someone with some CS education. If you are having trouble with that, post a new question so we can help.

JSP : JSTL's <c:out> tag

c:out escapes HTML characters so that you can avoid cross-site scripting.

if = <script>alert("Yo")</script>

the script will be executed in the second case, but not when using c:out

How can I open a URL in Android's web browser from my application?

Just like the solutions other have written (that work fine), I would like to answer the same thing, but with a tip that I think most would prefer to use.

In case you wish the app you start to open in a new task, indepandant of your own, instead of staying on the same stack, you can use this code:

final Intent intent=new Intent(Intent.ACTION_VIEW,Uri.parse(url));

There is also a way to open the URL in Chrome Custom Tabs . Example in Kotlin :

fun openWebsite(activity: Activity, websiteUrl: String, useWebBrowserAppAsFallbackIfPossible: Boolean) {
    var websiteUrl = websiteUrl
    if (TextUtils.isEmpty(websiteUrl))
    if (websiteUrl.startsWith("www"))
        websiteUrl = "http://$websiteUrl"
    else if (!websiteUrl.startsWith("http"))
        websiteUrl = "http://www.$websiteUrl"
    val finalWebsiteUrl = websiteUrl
    val webviewFallback = object : CustomTabActivityHelper.CustomTabFallback {
        override fun openUri(activity: Activity, uri: Uri?) {
            var intent: Intent
            if (useWebBrowserAppAsFallbackIfPossible) {
                intent = Intent(Intent.ACTION_VIEW, Uri.parse(finalWebsiteUrl))
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_NO_HISTORY
                if (!CollectionUtil.isEmpty(activity.packageManager.queryIntentActivities(intent, 0))) {
            // open our own Activity to show the URL
            intent = Intent(activity,
            WebViewActivity.prepareIntent(intent, finalWebsiteUrl)
    val uri = Uri.parse(finalWebsiteUrl)
    val intentBuilder = CustomTabsIntent.Builder()
    val customTabsIntent =
    customTabsIntent.intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_NO_HISTORY
    CustomTabActivityHelper.openCustomTab(activity, customTabsIntent, uri, webviewFallback)

Java Embedded Databases Comparison

Java DB (Sun's distribution of Apache Derby) now ships in JDK 6!

I've been wanted to do something like Jason Cohen and have been thinking this looks like the easiest way being in the JDK distro (which of last week is now a requirement for my app). Or maybe I am just lazy that way.

Installation of SQL Server Business Intelligence Development Studio

This worked for me:

Start /wait setup.exe /qb  ADDLOCAL=SQL_DTS,Client_Components,Connectivity,SQL_Tools90,SQL_WarehouseDevWorkbench,SQLXML,Tools_Legacy,SQL_Documentation,SQL_BooksOnline

Based off this TechNet Article:

for or while loop to do something n times

but on the other hand it creates a completely useless list of integers just to loop over them. Isn't it a waste of memory, especially as far as big numbers of iterations are concerned?

That is what xrange(n) is for. It avoids creating a list of numbers, and instead just provides an iterator object.

In Python 3, xrange() was renamed to range() - if you want a list, you have to specifically request it via list(range(n)).

How often should you use git-gc?

If you're using Git-Gui, it tells you when you should worry:

This repository currently has approximately 1500 loose objects.

The following command will bring a similar number:

$ git count-objects

Except, from its source, git-gui will do the math by itself, actually counting something at .git/objects folder and probably brings an approximation (I don't know tcl to properly read that!).

In any case, it seems to give the warning based on an arbitrary number around 300 loose objects.

JavaScript and getElementById for multiple elements with the same ID

you can use document.document.querySelectorAll("#divId")

Get a random boolean in python?

Found a faster method:

$ python -m timeit -s "from random import getrandbits" "not getrandbits(1)"
10000000 loops, best of 3: 0.222 usec per loop
$ python -m timeit -s "from random import random" "True if random() > 0.5 else False"
10000000 loops, best of 3: 0.0786 usec per loop
$ python -m timeit -s "from random import random" "random() > 0.5"
10000000 loops, best of 3: 0.0579 usec per loop

xsl: how to split strings?

I. Plain XSLT 1.0 solution:

This transformation:

<xsl:stylesheet version="1.0"
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="text()" name="split">
  <xsl:param name="pText" select="."/>
  <xsl:if test="string-length($pText)">
   <xsl:if test="not($pText=.)">
    <br />
   <xsl:value-of select=
   <xsl:call-template name="split">
    <xsl:with-param name="pText" select=
     "substring-after($pText, ';')"/>

when applied on this XML document:

<t>123 Elm Street;PO Box 222;c/o James Jones</t>

produces the wanted, corrected result:

123 Elm Street<br />PO Box 222<br />c/o James Jones

II. FXSL 1 (for XSLT 1.0):

Here we just use the FXSL template str-map (and do not have to write recursive template for the 999th time):

<xsl:stylesheet version="1.0" 
exclude-result-prefixes="xsl f testmap"
   <xsl:import href="str-dvc-map.xsl"/>


   <xsl:output omit-xml-declaration="yes" indent="yes"/>

   <xsl:template match="/">
     <xsl:variable name="vTestMap" select="document('')/*/testmap:*[1]"/>
     <xsl:call-template name="str-map">
       <xsl:with-param name="pFun" select="$vTestMap"/>
       <xsl:with-param name="pStr" select=
       "'123 Elm Street;PO Box 222;c/o James Jones'"/>

    <xsl:template name="replace" mode="f:FXSL"
         match="*[namespace-uri() = 'testmap']">
      <xsl:param name="arg1"/>

       <xsl:when test="not($arg1=';')">
        <xsl:value-of select="$arg1"/>
       <xsl:otherwise><br /></xsl:otherwise>

when this transformation is applied on any XML document (not used), the same, wanted correct result is produced:

123 Elm Street<br/>PO Box 222<br/>c/o James Jones

III. Using XSLT 2.0

<xsl:stylesheet version="2.0"
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="text()">
  <xsl:for-each select="tokenize(.,';')">
   <xsl:sequence select="."/>
   <xsl:if test="not(position() eq last())"><br /></xsl:if>

when this transformation is applied on this XML document:

<t>123 Elm Street;PO Box 222;c/o James Jones</t>

the wanted, correct result is produced:

123 Elm Street<br />PO Box 222<br />c/o James Jones

"SELECT ... IN (SELECT ...)" query in CodeIgniter

I think you can create a simple SQL query:

$sql="select username from user where id in (select id from idtables)";

and then you can use it normally.

Removing an activity from the history stack

I use this way.

Intent i = new Intent(MyOldActivity.this, MyNewActivity.class);

Error:Execution failed for task ':app:dexDebug'.

I solved the same issue by removing:

compile fileTree(include: ['*.jar'], dir: 'libs')

and adding for each jar file:

compile files('libs/yourjarfile.jar')

How can I iterate over files in a given directory?

I really like using the scandir directive that is built into the os library. Here is a working example:

import os

i = 0
with os.scandir('/usr/local/bin') as root_dir:
    for path in root_dir:
        if path.is_file():
            i += 1
            print(f"Full path is: {path} and just the name is: {}")
print(f"{i} files scanned successfully.")

How to connect to SQL Server from another computer?

all of above answers would help you but you have to add three ports in the firewall of PC on which SQL Server is installed.

  1. Add new TCP Local port in Windows firewall at port no. 1434

  2. Add new program for SQL Server and select sql server.exe Path: C:\ProgramFiles\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\Binn\sqlservr.exe

  3. Add new program for SQL Browser and select sqlbrowser.exe Path: C:\ProgramFiles\Microsoft SQL Server\90\Shared\sqlbrowser.exe

Set up Python 3 build system with Sublime Text 3

And to add on to the already solved problem, I had installed Portable Scientific Python on my flash drive E: which on another computer changed to D:, I would get the error "The system cannot find the file specified". So I used parent directory to define the path, like this:

From this:

    "cmd": ["E:/WPy64-3720/python-3.7.2.amd64/python.exe", "$file"],
    "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)",
    "selector": "source.python"

To this:

    "cmd": ["../../../../WPy64-3720/python-3.7.2.amd64/python.exe","$file"],
    "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)",
    "selector": "source.python"

You can modify depending on where your python is installed your python.

Constructing pandas DataFrame from values in variables gives "ValueError: If using all scalar values, you must pass an index"

You could try:

df2 = pd.DataFrame.from_dict({'a':a,'b':b}, orient = 'index')

From the documentation on the 'orient' argument: If the keys of the passed dict should be the columns of the resulting DataFrame, pass ‘columns’ (default). Otherwise if the keys should be rows, pass ‘index’.

Why aren't python nested functions called closures?

I had a situation where I needed a separate but persistent name space. I used classes. I don't otherwise. Segregated but persistent names are closures.

>>> class f2:
...     def __init__(self):
...         self.a = 0
...     def __call__(self, arg):
...         self.a += arg
...         return(self.a)
>>> f=f2()
>>> f(2)
>>> f(2)
>>> f(4)
>>> f(8)

# **OR**
>>> f=f2() # **re-initialize**
>>> f(f(f(f(2)))) # **nested**

# handy in list comprehensions to accumulate values
>>> [f(i) for f in [f2()] for i in [2,2,4,8]][-1] 

Python NLTK: SyntaxError: Non-ASCII character '\xc3' in file (Sentiment Analysis -NLP)

Add the following to the top of your file # coding=utf-8

If you go to the link in the error you can seen the reason why:

Defining the Encoding

Python will default to ASCII as standard encoding if no other encoding hints are given. To define a source code encoding, a magic comment must be placed into the source files either as first or second line in the file, such as: # coding=

Google Chrome "" workaround?

Why is this still so complicated in 2021? For me I wanted to open in a new chrome window fullscreen so I used the below:"", "", "fullscreen=yes");

This worked as exepected opening a new chrome window. Without the options at the end it will only open a new tab

Difference between 'cls' and 'self' in Python classes?

The distinction between "self" and "cls" is defined in PEP 8 . As Adrien said, this is not a mandatory. It's a coding style. PEP 8 says:

Function and method arguments:

Always use self for the first argument to instance methods.

Always use cls for the first argument to class methods.

What is a Memory Heap?

Heap is just an area where memory is allocated or deallocated without any order. This happens when one creates an object using the new operator or something similar. This is opposed to stack where memory is deallocated on the first in last out basis.

Convert Uppercase Letter to Lowercase and First Uppercase in Sentence using CSS

Just Simply use

use css code: text-transform: uppercase;

How to get a random number in Ruby

you can do rand(range)

x = rand(1..5)

Check if value is in select list with JQuery

Here is another similar option. In my case, I'm checking values in another box as I build a select list. I kept running into undefined values when I would compare, so I set my check this way:

if ( $("#select-box option[value='" + thevalue + "']").val() === undefined) { //do stuff }

I've no idea if this approach is more expensive.

Make an image responsive - the simplest way

I'm using this technique to keep the logo as responsive for mobile devices as a simple way. The logo will resize automatically.


<div id="logo_wrapper">
  <a href="" target="_blank">
    <img src="" border="0" alt="logo" />


#logo_wrapper img {
  max-width: 100%;
  height: auto;

Can constructors throw exceptions in Java?

Yes, it can throw an exception and you can declare that in the signature of the constructor too as shown in the example below:

public class ConstructorTest
    public ConstructorTest() throws InterruptedException
        System.out.println("Preparing object....");
        System.out.println("Object ready");

    public static void main(String ... args)
            ConstructorTest test = new ConstructorTest();
        catch (InterruptedException e)
            System.out.println("Got interrupted...");

text-align: right; not working for <label>

Label is an inline element - so, unless a width is defined, its width is exact the same which the letters span. Your div element is a block element so its width is by default 100%.

You will have to place the text-align: right; on the div element in your case, or applying display: block; to your label

Another option is to set a width for each label and then use text-align. The display: block method will not be necessary using this.

How do I fetch lines before/after the grep result in bash?

The way to do this is near the top of the man page

grep -i -A 10 'error data'

jQuery selector regular expressions

Add a jQuery function,

    $.fn.regex = function(pattern, fn, fn_a){
        var fn = fn || $.fn.text;
        return this.filter(function() {
            return pattern.test(fn.apply($(this), fn_a));



will select all span elements with text matches /Sent/.

$('span').regex(/tooltip.year/, $.fn.attr, ['class'])

will select all span elements with their classes match /tooltip.year/.

Undefined symbols for architecture x86_64 on Xcode 6.1

Apparently, your class "Format" is involved in the problem. Check your declaration of this class, especially if you did it inside another class you probably forgot the @implementation or something similar.

How do I do an initial push to a remote repository with Git?

@Josh Lindsey already answered perfectly fine. But I want to add some information since I often use ssh.

Therefore just change:

git remote add origin [email protected]:/path/to/my_project.git


git remote add origin ssh://[email protected]/path/to/my_project

Note that the colon between domain and path isn't there anymore.

Is there an API to get bank transaction and bank balance?

I use GNU Cash and it uses Open Financial Exchange (ofx) to download complete transactions and balances from each account of each bank.

Let me emphasize that again, you get a huge list of transactions with OFX into the GNU Cash. Depending on the account type these transactions can be very detailed description of your transactions (purchases+paycheques), investments, interests, etc.

In my case, even though I have Chase debit card I had to choose Chase Credit to make it work. But Chase wants you to enable this OFX feature by logging into your online banking and enable Quicken/MS Money/etc. somewhere in your profile or preferences. Don't call Chase customer support because they know nothing about it.

This service for OFX and GNU Cash is free. I have heard that they charge $10 a month for other platforms.

OFX can download transactions from 348 banks so far.

Actualy, OFX also supports making bill payments, stop a check, intrabank and interbank transfers etc. It is quite extensive. See it here:

Using .otf fonts on web browsers

You can implement your OTF font using @font-face like:

@font-face {
    font-family: GraublauWeb;
    src: url("path/GraublauWeb.otf") format("opentype");

@font-face {
    font-family: GraublauWeb;
    font-weight: bold;
    src: url("path/GraublauWebBold.otf") format("opentype");

// Edit: OTF now works in most browsers, see comments

However if you want to support a wide variety of browsers i would recommend you to switch to WOFF and TTF font types. WOFF type is implemented by every major desktop browser, while the TTF type is a fallback for older Safari, Android and iOS browsers. If your font is a free font, you could convert your font using for example a transfonter.

@font-face {
    font-family: GraublauWeb;
    src: url("path/GraublauWebBold.woff") format("woff"), url("path/GraublauWebBold.ttf")  format("truetype");

If you want to support nearly every browser that is still out there (not necessary anymore IMHO), you should add some more font-types like:

@font-face {
    font-family: GraublauWeb;
    src: url("webfont.eot"); /* IE9 Compat Modes */
    src: url("webfont.eot?#iefix") format("embedded-opentype"), /* IE6-IE8 */
         url("webfont.woff") format("woff"), /* Modern Browsers */
         url("webfont.ttf")  format("truetype"), /* Safari, Android, iOS */
         url("webfont.svg#svgFontName") format("svg"); /* Legacy iOS */

You can read more about why all these types are implemented and their hacks here. To get a detailed view of which file-types are supported by which browsers, see:

@font-face Browser Support

EOT Browser Support

WOFF Browser Support

TTF Browser Support

SVG-Fonts Browser Support

hope this helps

PHP - check if variable is undefined

You can use -

$isTouch = isset($variable);

It will return true if the $variable is defined. if the variable is not defined it will return false.

Note : Returns TRUE if var exists and has value other than NULL, FALSE otherwise.

If you want to check for false, 0 etc You can then use empty() -

$isTouch = empty($variable);

empty() works for -

  • "" (an empty string)
  • 0 (0 as an integer)
  • 0.0 (0 as a float)
  • "0" (0 as a string)
  • NULL
  • array() (an empty array)
  • $var; (a variable declared, but without a value)

[Vue warn]: Property or method is not defined on the instance but referenced during render

It's probably caused by spelling error

I got a typo at script closing tag


Where is Java's Array indexOf?

Arrays themselves do not have that method. A List, however, does: indexOf

How to use PHP string in mySQL LIKE query?

DO it like

$query = mysql_query("SELECT * FROM table WHERE the_number LIKE '$yourPHPVAR%'");

Do not forget the % at the end

SSRS custom number format

am assuming that you want to know how to format numbers in SSRS

Just right click the TextBox on which you want to apply formatting, go to its expression.

suppose its expression is something like below


then do this




difference between the two is that former one would make 4 as 4 and later one would make 4 as 04.00

this should give you an idea.

also: you might have to convert your field into a numerical one. i.e.


so: 0 in format expression means, when no number is present, place a 0 there and # means when no number is present, leave it. Both of them works same when numbers are present ie. 45.6567 would be 45.65 for both of them:


if you want to apply variable formatting on the same column based on row values i.e. you want myField to have no formatting when it has no decimal value but formatting with double precision when it has decimal then you can do it through logic. (though you should not be doing so)

Go to the appropriate textbox and go to its expression and do this:

=IIF((Fields!myField.Value - CInt(Fields!myField.Value)) > 0, 
    Format(Fields!myField.Value, "##.##"),Fields!myField.Value)

so basically you are using IIF(condition, true,false) operator of SSRS, ur condition is to check whether the number has decimal value, if it has, you apply the formatting and if no, you let it as it is.

this should give you an idea, how to handle variable formatting.

Disable submit button when form invalid with AngularJS

To add to this answer. I just found out that it will also break down if you use a hyphen in your form name (Angular 1.3):

So this will not work:

<form name="my-form">
    <input name="myText" type="text" ng-model="mytext" required />
    <button ng-disabled="my-form.$invalid">Save</button>

Show div when radio button selected

$('input[name=test]').click(function () {
    if ( == "watch-me") {
    } else {

How do you produce a .d.ts "typings" definition file from an existing JavaScript library?

I would look for an existing mapping of your 3rd party JS libraries that support Script# or SharpKit. Users of these C# to .js cross compilers will have faced the problem you now face and might have published an open source program to scan your 3rd party lib and convert into skeleton C# classes. If so hack the scanner program to generate TypeScript in place of C#.

Failing that, translating a C# public interface for your 3rd party lib into TypeScript definitions might be simpler than doing the same by reading the source JavaScript.

My special interest is Sencha's ExtJS RIA framework and I know there have been projects published to generate a C# interpretation for Script# or SharpKit

What do >> and << mean in Python?

12 << 2


Actual binary value of 12 is "00 1100" when we execute the above statement Left shift ( 2 places shifted left) returns the value 48 its binary value is "11 0000".

48 >> 2


The binary value of 48 is "11 0000", after executing above statement Right shift ( 2 places shifted right) returns the value 12 its binary value is "00 1100".

Sqlite: CURRENT_TIMESTAMP is in GMT, not the timezone of the machine

In the (admitted rare) case that a local datatime is wanted (I, for example, store local time in one of my database since all I care is what time in the day is was and I don't keep track of where I was in term of time zones...), you can define the column as

"timestamp" TEXT DEFAULT (strftime('%Y-%m-%dT%H:%M','now', 'localtime'))

The %Y-%m-%dT%H:%M part is of course optional; it is just how I like my time to be stored. [Also, if my impression is correct, there is no "DATETIME" datatype in sqlite, so it does not really matter whether TEXT or DATETIME is used as data type in column declaration.]

How to connect to mysql with laravel?

I spent a lot of time trying to figure this one out. Finally, I tried shutting down my development server and booting it up again. Frustratingly, this worked for me. I came to the conclusion, that after editing the .env file in Laravel 5, you have to exit the server, and run php artisan serve again.

How to check if Location Services are enabled?

To check for network provider you just need to change the string passed to isProviderEnabled to LocationManager.NETWORK_PROVIDER if you check the return values for both GPS provider and NETwork provider - both false means no location services

How to make lists contain only distinct element in Python?

one-liner and preserve order


although you'll need

from collections import OrderedDict

To get specific part of a string in c#

If you want to get the strings separated by the , you can use

string b = a.Split(',')[0];

How to use Session attributes in Spring-mvc

Isn't it easiest and shortest that way? I knew it and just tested it - working perfect here:

public String hello(HttpSession session) {
    return "hello";

p.s. I came here searching for an answer of "How to use Session attributes in Spring-mvc", but read so many without seeing the most obvious that I had written in my code. I didn't see it, so I thought its wrong, but no it was not. So lets share that knowledge with the easiest solution for the main question.

jQuery: How to get the event object in an event handler function without passing it as an argument?

in IE you can get the event object by window.event in other browsers with no 'use strict' directive, it is possible to get by arguments.callee.caller.arguments[0].

function myFunc(p1, p2, p3) {
    var evt = window.event || arguments.callee.caller.arguments[0];

Get first day of week in PHP?

Here is what I am using...

$day = date('w');
$week_start = date('m-d-Y', strtotime('-'.$day.' days'));
$week_end = date('m-d-Y', strtotime('+'.(6-$day).' days'));

$day contains a number from 0 to 6 representing the day of the week (Sunday = 0, Monday = 1, etc.).
$week_start contains the date for Sunday of the current week as mm-dd-yyyy.
$week_end contains the date for the Saturday of the current week as mm-dd-yyyy.

SSIS - Text was truncated or one or more characters had no match in the target code page - Special Characters

If you go to the Flat file connection manager under Advanced and Look at the "OutputColumnWidth" description's ToolTip It will tell you that Composit characters may use more spaces. So the "é" in "Société" most likely occupies more than one character.

EDIT: Here's something about it:

What are good grep tools for Windows?

PowerShell's select-string is similar, it's not the same options and semantics, but it's still powerful.

MVC Redirect to View from jQuery with parameters

This would also work I believe:

$('#results').on('click', '.item', function () {
            var NestId = $(this).data('id');
            var url = '@Html.Raw(Url.Action("Artists", new { NestId = @NestId }))';
            window.location.href = url; 

Execute a shell function with timeout

You can create a function which would allow you to do the same as timeout but also for other functions:

function run_cmd { 
    cmd="$1"; timeout="$2";
    grep -qP '^\d+$' <<< $timeout || timeout=10

        eval "$cmd" &
        trap -- "" SIGTERM 
                sleep $timeout
                kill $child 2> /dev/null 
        ) &     
        wait $child

And could run as below:

run_cmd "echoFooBar" 10

Note: The solution came from one of my questions: Elegant solution to implement timeout for bash commands and functions

Convert float to std::string in C++

You can use std::to_string in C++11

float val = 2.5;
std::string my_val = std::to_string(val);

How to get height of Keyboard?

Swift 4 .

Simplest Method

override func viewDidLoad() {
      NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: .UIKeyboardWillShow, object: nil)

func keyboardWillShow(notification: NSNotification) {  

      if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
             let keyboardHeight : Int = Int(keyboardSize.height)


Reading PDF content with itextsharp dll in VB.NET or C#

LGPL / FOSS iTextSharp 4.x

var pdfReader = new PdfReader(path); //other filestream etc
byte[] pageContent = _pdfReader .GetPageContent(pageNum); //not zero based
byte[] utf8 = Encoding.Convert(Encoding.Default, Encoding.UTF8, pageContent);
string textFromPage = Encoding.UTF8.GetString(utf8);

None of the other answers were useful to me, they all seem to target the AGPL v5 of iTextSharp. I could never find any reference to SimpleTextExtractionStrategy or LocationTextExtractionStrategy in the FOSS version.

Something else that might be very useful in conjunction with this:

const string PdfTableFormat = @"\(.*\)Tj";
Regex PdfTableRegex = new Regex(PdfTableFormat, RegexOptions.Compiled);

List<string> ExtractPdfContent(string rawPdfContent)
    var matches = PdfTableRegex.Matches(rawPdfContent);

    var list = matches.Cast<Match>()
        .Select(m => m.Value
            .Substring(1) //remove leading (
            .Remove(m.Value.Length - 4) //remove trailing )Tj
            .Replace(@"\)", ")") //unencode parens
            .Replace(@"\(", "(")
    return list;

This will extract the text-only data from the PDF if the text displayed is Foo(bar) it will be encoded in the PDF as (Foo\(bar\))Tj, this method would return Foo(bar) as expected. This method will strip out lots of additional information such as location coordinates from the raw pdf content.

How to encrypt a large file in openssl using public key

Solution for safe and high secured encode anyone file in OpenSSL and command-line:

You should have ready some X.509 certificate for encrypt files in PEM format.

Encrypt file:

openssl smime -encrypt -binary -aes-256-cbc -in -out -outform DER yourSslCertificate.pem

What is what:

  • smime - ssl command for S/MIME utility (smime(1))
  • -encrypt - chosen method for file process
  • -binary - use safe file process. Normally the input message is converted to "canonical" format as required by the S/MIME specification, this switch disable it. It is necessary for all binary files (like a images, sounds, ZIP archives).
  • -aes-256-cbc - chosen cipher AES in 256 bit for encryption (strong). If not specified 40 bit RC2 is used (very weak). (Supported ciphers)
  • -in - input file name
  • -out - output file name
  • -outform DER - encode output file as binary. If is not specified, file is encoded by base64 and file size will be increased by 30%.
  • yourSslCertificate.pem - file name of your certificate's. That should be in PEM format.

That command can very effectively a strongly encrypt big files regardless of its format.
Known issue: Something wrong happens when you try encrypt huge file (>600MB). No error thrown, but encrypted file will be corrupted. Always verify each file! (or use PGP - that has bigger support for files encryption with public key)

Decrypt file:

openssl smime -decrypt -binary -in -inform DER -out -inkey private.key -passin pass:your_password

What is what:

  • -inform DER - same as -outform above
  • -inkey private.key - file name of your private key. That should be in PEM format and can be encrypted by password.
  • -passin pass:your_password - your password for private key encrypt. (passphrase arguments)

How to check if a variable is an integer or a string?

The isdigit method of the str type returns True iff the given string is nothing but one or more digits. If it's not, you know the string should be treated as just a string.

Netbeans installation doesn't find JDK

I also had the same problem. So I tried by installing a lesser version say jdk1.5 and running the netbeans installation from command prompt as: Linux: netbeans-5_5-linux.bin -is:javahome /usr/jdk/jdk1.5.0_06 Windows: netbeans-5_5-windows.exe -is:javahome "C:\Program Files\Java\jdk1.5.0_06"

Hope it helps


Finaly I found another answer for this problem. and this is working for me. Just add below datas to the your webconfig file.

    <verbs allowUnlisted="true">
     <add verb="OPTIONS" allowed="false" />

Form more information, you can visit this web site:

if you want to test your web site, is it working or not... You can use "HttpRequester" mozilla firefox plugin. for this plugin:

How to prevent ENTER keypress to submit a web form?

Simply add this attribute to your FORM tag:

onsubmit="return gbCanSubmit;"

Then, in your SCRIPT tag, add this:

var gbCanSubmit = false;

Then, when you make a button or for any other reason (like in a function) you finally permit a submit, simply flip the global boolean and do a .submit() call, similar to this example:

function submitClick(){

  // error handler code goes here and return false if bad data

  // okay, proceed...
  gbCanSubmit = true;
  $('#myform').submit(); // jQuery example


Copying files using rsync from remote server to local machine

From your local machine:

rsync -chavzP --stats [email protected]:/path/to/copy /path/to/local/storage

From your local machine with a non standard ssh port:

rsync -chavzP -e "ssh -p $portNumber" [email protected]:/path/to/copy /local/path

Or from the remote host, assuming you really want to work this way and your local machine is listening on SSH:

rsync -chavzP --stats /path/to/copy [email protected]:/path/to/local/storage

See man rsync for an explanation of my usual switches.

Convert String to Calendar Object in Java

SimpleDateFormat is great, just note that HH is different from hh when working with hours. HH will return 24 hour based hours and hh will return 12 hour based hours.

For example, the following will return 12 hour time:

SimpleDateFormat sdf = new SimpleDateFormat("hh:mm aa");

While this will return 24 hour time:

SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");

Java Compare Two Lists

Simple solution :-

    List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "d", "c"));
    List<String> list2 = new ArrayList<String>(Arrays.asList("b", "f", "c"));

    System.out.println("similiar " + list);
    System.out.println("different " + list2);

Output :-

similiar [b, c]
different [f]

How to duplicate a whole line in Vim?

I like: Shift+v (to select the whole line immediately and let you select other lines if you want), y, p

Sending email with PHP from an SMTP server

In cases where you are hosting a Wordpress site on Linux and have server access you can save some headaches by installing msmtp which allows you to send via smtp from the standard php mail() function. msmtp is a simpler alternative to postfix which requires a bit more configuration.

Here are the steps:

Install msmtp

sudo apt-get install msmtp-mta ca-certificates

Create a new configuration file:

sudo nano /etc/msmtprc

...with the following configuration information:

# Set defaults.    

# Enable or disable TLS/SSL encryption.
tls on
tls_starttls on
tls_trust_file /etc/ssl/certs/ca-certificates.crt

# Set up a default account's settings.
account default
host <>
port 587
auth on
user <[email protected]>
password <password>
from <[email protected]>
syslog LOG_MAIL

You need to replace the configuration data represented by everything within "<" and ">" (inclusive, remove these). For host/username/password, use your normal credentials for sending mail through your mail provider.

Tell PHP to use it

sudo nano /etc/php5/apache2/php.ini

Add this single line:

sendmail_path = /usr/bin/msmtp -t

Complete documention can be found here:

How to download PDF automatically using js?

Use the download attribute.

var link = document.createElement('a');
link.href = url; = 'file.pdf';
link.dispatchEvent(new MouseEvent('click'));

How do I remove a MySQL database?

If you are using an SQL script when you are creating your database and have any users created by your script, you need to drop them too. Lastly you need to flush the users; i.e., force MySQL to read the user's privileges again.


drop schema <database_name>;
-- Same as `drop database <database_name>`

drop user <a_user_name>;
-- You may need to add a hostname e.g `drop user bob@localhost`


Good luck!

Use awk to find average of a column

awk '{ sum += $2; n++ } END { if (n > 0) print sum / n; }'

Add the numbers in $2 (second column) in sum (variables are auto-initialized to zero by awk) and increment the number of rows (which could also be handled via built-in variable NR). At the end, if there was at least one value read, print the average.

awk '{ sum += $2 } END { if (NR > 0) print sum / NR }'

If you want to use the shebang notation, you could write:


{ sum += $2 }
END { if (NR > 0) print sum / NR }

You can also control the format of the average with printf() and a suitable format ("%13.6e\n", for example).

You can also generalize the code to average the Nth column (with N=2 in this sample) using:

awk -v N=2 '{ sum += $N } END { if (NR > 0) print sum / NR }'

Best Practice: Access form elements by HTML id or name attribute?

[1] document.forms[0].elements[0];

"No-omg-never!" comes to mind when I see this method of element access. The problem with this is that it assumes that the DOM is a normal data structure (e.g.: an array) wherein the element order is static, consistent or reliable in anyway. We know that 99.9999% of the time, that this is not the case. Reordering or input elements within the form, adding another form to the page before the form in question, or moving the form in question are all cases where this code breaks. Short story: this is very fragile. As soon as you add or move something, it's going to break.


I'm with Sergey ILinsky on this:

  • Access arbitrary elements by referring to their id attribute: document.getElementById("myform");
  • Access named form elements by name, relative to their parent form element: document.getElementById("myform").foo;

My main issue with this method is that the name attribute is useless when applied to a form. The name is not passed to the server as part of the POST/GET and doesn't work for hash style bookmarks.

[3] document.getElementById('foo');

In my opinion, this is the most preferable method. Direct access is the most concise and clear method.

[4] document.getElementById('myForm').foo;

In my opinion, this is acceptable, but more verbose than necessary. Method #3 is preferable.

I just so happened to be watch a video from Douglas Crockford and he weighed in on this very subject. The point of interest is at -12:00. To summarize:

  • Document collections (document.anchor, document.form, etc) are obsolete and irrelevant (method 1).
  • The name attribute is used to name things, not to access them. It is for naming things like windows, input fields, and anchor tags.
  • "ID is the thing that you should use to uniquely identify an element so that you can get access to it. They (name and ID) used to be interchangeable, but they aren't anymore."

So there you have it. Semantically, this makes the most sense.

Dropdownlist width in IE

The jquery BalusC's solution improved by me. Used also: Brad Robertson's comment here.

Just put this in a .js, use the wide class for your desired combos and don't forge to give it an Id. Call the function in the onload (or documentReady or whatever).
As simple ass that :)
It will use the width that you defined for the combo as minimun length.

function fixIeCombos() {
    if ($.browser.msie && $.browser.version < 9) {
    var style = $('<style>select.expand { width: auto; }</style>');
    $('html > head').append(style);

    var defaultWidth = "200";

    // get predefined combo's widths.
    var widths = new Array();
    $('select.wide').each(function() {
        var width = $(this).width();
        if (!width) {
        width = defaultWidth;
        widths[$(this).attr('id')] = width;

    .bind('focus mouseover', function() {
        // We're going to do the expansion only if the resultant size is bigger
        // than the original size of the combo.
        // In order to find out the resultant size, we first clon the combo as
        // a hidden element, add to the dom, and then test the width.
        var originalWidth = widths[$(this).attr('id')];

        var $selectClone = $(this).clone();
        $(this).after( $selectClone );
        var expandedWidth = $selectClone.width()
        if (expandedWidth > originalWidth) {
    .bind('click', function() {
    .bind('mouseout', function() {
        if (!$(this).hasClass('clicked')) {
    .bind('blur', function() {
        $(this).removeClass('expand clicked');

Change DIV content using ajax, php and jQuery


$('#summary').load('ajax.php', function() {

Interactive shell using Docker Compose

You need to include the following lines in your docker-compose.yml:

version: "3"
    image: app:1.2.3
    stdin_open: true # docker run -i
    tty: true        # docker run -t

The first corresponds to -i in docker run and the second to -t.

Getting JSONObject from JSONArray

Make use of Android Volly library as much as possible. It maps your JSON reponse in respective class objects. You can add getter setter for that response model objects. And then you can access these JSON values/parameter using .operator like normal JAVA Object. It makes response handling very simple.

Execute a shell script in current shell with sudo permission

Easiest method is to type:

sudo /bin/sh

Select from one table matching criteria in another?

The simplest solution would be a correlated sub select:

    table_A A
where in (
        select from table_B B where B.tag = 'chair'

Alternatively you could join the tables and filter the rows you want:

    table_A A
inner join table_B B
    on =
    B.tag = 'chair'

You should profile both and see which is faster on your dataset.

Explaining the 'find -mtime' command

The POSIX specification for find says:

-mtimen The primary shall evaluate as true if the file modification time subtracted from the initialization time, divided by 86400 (with any remainder discarded), is n.

Interestingly, the description of find does not further specify 'initialization time'. It is probably, though, the time when find is initialized (run).

In the descriptions, wherever n is used as a primary argument, it shall be interpreted as a decimal integer optionally preceded by a plus ( '+' ) or minus-sign ( '-' ) sign, as follows:

+n More than n.
  n Exactly n.
-n Less than n.

At the given time (2014-09-01 00:53:44 -4:00, where I'm deducing that AST is Atlantic Standard Time, and therefore the time zone offset from UTC is -4:00 in ISO 8601 but +4:00 in ISO 9945 (POSIX), but it doesn't matter all that much):

1409547224 = 2014-09-01 00:53:44 -04:00
1409457540 = 2014-08-30 23:59:00 -04:00


1409547224 - 1409457540 = 89684
89684 / 86400 = 1

Even if the 'seconds since the epoch' values are wrong, the relative values are correct (for some time zone somewhere in the world, they are correct).

The n value calculated for the 2014-08-30 log file therefore is exactly 1 (the calculation is done with integer arithmetic), and the +1 rejects it because it is strictly a > 1 comparison (and not >= 1).

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin '...' is therefore not allowed access

Solved with below entry in httpd.conf

#CORS Issue
Header set X-Content-Type-Options "nosniff"
Header always set Access-Control-Max-Age 1728000
Header always set Access-Control-Allow-Origin: "*"
Header always set Access-Control-Allow-Methods: "GET,POST,OPTIONS,DELETE,PUT,PATCH"
Header always set Access-Control-Allow-Headers: "DNT,X-CustomHeader,Keep-Alive,Content-Type,Origin,Authentication,Authorization,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control"
Header always set Access-Control-Allow-Credentials true

RewriteEngine On                  
#RewriteRule ^(.*)$ $1 [R=200,L]
RewriteRule ^(.*)$ $1 [R=200,L,E=HTTP_ORIGIN:%{HTTP:ORIGIN}]]

How to select option in drop down protractorjs e2e tests

Another way to set an option element:

var select = element(by.model('organization.parent_id'));

Do while loop in SQL Server 2008

I am not sure about DO-WHILE IN MS SQL Server 2008 but you can change your WHILE loop logic, so as to USE like DO-WHILE loop.

Examples are taken from here:

  1. Example of WHILE Loop

    DECLARE @intFlag INT
    SET @intFlag = 1
    WHILE (@intFlag <=5)
        PRINT @intFlag
        SET @intFlag = @intFlag + 1


  2. Example of WHILE Loop with BREAK keyword

    DECLARE @intFlag INT
    SET @intFlag = 1
    WHILE (@intFlag <=5)
        PRINT @intFlag
        SET @intFlag = @intFlag + 1
        IF @intFlag = 4


  3. Example of WHILE Loop with CONTINUE and BREAK keywords

    DECLARE @intFlag INT
    SET @intFlag = 1
    WHILE (@intFlag <=5)
        PRINT @intFlag
        SET @intFlag = @intFlag + 1
        IF @intFlag = 4 -- This will never executed



But try to avoid loops at database level. Reference.

Error: No default engine was specified and no extension was provided

If all that's needed is to send html code inline in the code, we can use below

var app = express();
app.get('/test.html', function (req, res) {
   res.header('Content-Type', 'text/html').send("<html>my html code</html>");

Getting TypeError: __init__() missing 1 required positional argument: 'on_delete' when trying to add parent table after child table with entries

Here are available options if it helps anyone for on_delete


jQuery function to get all unique elements from an array?

    // for numbers
    a = [1,3,2,4,5,6,7,8, 1,1,4,5,6]
    [7, 6, 1, 8, 3, 2, 5, 4]

    // for string
    a = ["a", "a", "b"]
    ["b", "a"]

And for dom elements there is no example is needed here I guess because you already know that!

Here is the jsfiddle link of live example:

Can table columns with a Foreign Key be NULL?

Yes, the value can be NULL, but you must be explicit. I have experienced this same situation before, and it's easy to forget WHY this happens, and so it takes a little bit to remember what needs to be done.

If the data submitted is cast or interpreted as an empty string, it will fail. However, by explicitly setting the value to NULL when INSERTING or UPDATING, you're good to go.

But this is the fun of programming, isn't it? Creating our own problems and then fixing them! Cheers!

Create an ArrayList with multiple object types?

You can make it like :

List<Object> sections = new ArrayList <Object>();

(Recommended) Another possible solution would be to make a custom model class with two parameters one Integer and other String. Then using an ArrayList of that object.

How do I check if a given Python string is a substring of another one?

string.find("substring") will help you. This function returns -1 when there is no substring.

How to reference a file for variables using Bash?

The script containing variables can be executed imported using bash. Consider the


Consider the actual script where the variable will be used :

 bash path/to/
 echo "$scr-var"

VBA Print to PDF and Save with Automatic File Name

Hopefully this is self explanatory enough. Use the comments in the code to help understand what is happening. Pass a single cell to this function. The value of that cell will be the base file name. If the cell contains "AwesomeData" then we will try and create a file in the current users desktop called AwesomeData.pdf. If that already exists then try AwesomeData2.pdf and so on. In your code you could just replace the lines filename = Application..... with filename = GetFileName(Range("A1"))

Function GetFileName(rngNamedCell As Range) As String
    Dim strSaveDirectory As String: strSaveDirectory = ""
    Dim strFileName As String: strFileName = ""
    Dim strTestPath As String: strTestPath = ""
    Dim strFileBaseName As String: strFileBaseName = ""
    Dim strFilePath As String: strFilePath = ""
    Dim intFileCounterIndex As Integer: intFileCounterIndex = 1

    ' Get the users desktop directory.
    strSaveDirectory = Environ("USERPROFILE") & "\Desktop\"
    Debug.Print "Saving to: " & strSaveDirectory

    ' Base file name
    strFileBaseName = Trim(rngNamedCell.Value)
    Debug.Print "File Name will contain: " & strFileBaseName

    ' Loop until we find a free file number
        If intFileCounterIndex > 1 Then
            ' Build test path base on current counter exists.
            strTestPath = strSaveDirectory & strFileBaseName & Trim(Str(intFileCounterIndex)) & ".pdf"
            ' Build test path base just on base name to see if it exists.
            strTestPath = strSaveDirectory & strFileBaseName & ".pdf"
        End If

        If (Dir(strTestPath) = "") Then
            ' This file path does not currently exist. Use that.
            strFileName = strTestPath
            ' Increase the counter as we have not found a free file yet.
            intFileCounterIndex = intFileCounterIndex + 1
        End If

    Loop Until strFileName <> ""

    ' Found useable filename
    Debug.Print "Free file name: " & strFileName
    GetFileName = strFileName

End Function

The debug lines will help you figure out what is happening if you need to step through the code. Remove them as you see fit. I went a little crazy with the variables but it was to make this as clear as possible.

In Action

My cell O1 contained the string "FileName" without the quotes. Used this sub to call my function and it saved a file.

Sub Testing()
    Dim filename As String: filename = GetFileName(Range("o1"))

    ActiveWorkbook.Worksheets("Sheet1").Range("A1:N24").ExportAsFixedFormat Type:=xlTypePDF, _
                                              filename:=filename, _
                                              Quality:=xlQualityStandard, _
                                              IncludeDocProperties:=True, _
                                              IgnorePrintAreas:=False, _
End Sub

Where is your code located in reference to everything else? Perhaps you need to make a module if you have not already and move your existing code into there.

Parsing string as JSON with single quotes?

I know it's an old post, but you can use JSON5 for this purpose.

<script src="json5.js"></script>

What is the difference between range and xrange functions in Python 2.X?

xrange uses an iterator (generates values on the fly), range returns a list.

SVN repository backup strategies

there are 2 main methods to backup a svn server, first is hotcopy that will create a copy of your repository files, the main problem with this approach is that it saves data about the underlying file system, so you may have some difficulties trying to repostore this kind of backup in another svn server kind or another machine. there is another type of backup called dump, this backup wont save any information of the underlying file system and its potable to any kind of SVN server based in subversion.

about the backup tool you can use the svnadmin tool(it is able to do hotcopy and dump) from the command prompt, this console resides in the same directory where your svn server lives or you can google for svn backup tools.

my recommendation is that you do both kinds of backups and get them out of the office to your email acount, amazon s3 service, ftp, or azure services, that way you will have a securityy backup without having to host the svn server somewhere out of your office.

Read CSV with Scanner()

If you absolutely must use Scanner, then you must set its delimiter via its useDelimiter(...) method. Else it will default to using all white space as its delimiter. Better though as has already been stated -- use a CSV library since this is what they do best.

For example, this delimiter will split on commas with or without surrounding whitespace:


Please check out the java.util.Scanner API for more on this.

OS X Bash, 'watch' command

With Homebrew installed:

brew install watch

How to calculate an angle from three points?

Let me give an example in JavaScript, I've fought a lot with that:

 * Calculates the angle (in radians) between two vectors pointing outward from one center
 * @param p0 first point
 * @param p1 second point
 * @param c center point
function find_angle(p0,p1,c) {
    var p0c = Math.sqrt(Math.pow(c.x-p0.x,2)+
                        Math.pow(c.y-p0.y,2)); // p0->c (b)   
    var p1c = Math.sqrt(Math.pow(c.x-p1.x,2)+
                        Math.pow(c.y-p1.y,2)); // p1->c (a)
    var p0p1 = Math.sqrt(Math.pow(p1.x-p0.x,2)+
                         Math.pow(p1.y-p0.y,2)); // p0->p1 (c)
    return Math.acos((p1c*p1c+p0c*p0c-p0p1*p0p1)/(2*p1c*p0c));

Bonus: Example with HTML5-canvas

applying css to specific li class

That's because of the <a> in there and not using the id which you do use a bit further to the top

Change it to:

#sub-navigation-home li.sub-navigation-home-news a 
 color: #C1C1C1;
 font-family: arial;
 font-size: 13.5px;
 text-align: center;
 padding: 0px 90px 0px 0px; 

and it will probably work

I am not able launch JNLP applications using "Java Web Start"?

If javacpl does not open and gives you Could not find the main class:, it could be that Java is confused because of changes in (can be found in C:\Users\<username>\AppData\LocalLow\Sun\Java\Deployment on Win7). Delete that file and everything's fine.

This bug seems to be 6 years old, cf. An app should be able to ignore properties that have become obsolete over time, shouldn't it?

How to compare objects by multiple fields

It is easy to compare two objects with hashcode method in java`

public class Sample{

  String a=null;
  String b=null;

  public Sample(){
  public Sample(String a,String b){
  public static void main(String args[]){
      Sample f=new Sample("b","12");
      Sample s=new Sample("b","12");
      //will return true

      //will return false
      Sample f=new Sample("b","12");
      Sample s=new Sample("b","13");


Must declare the scalar variable

Just FYI, I know this is an old post, but depending on the database COLLATION settings you can get this error on a statement like this,

SET @sql = @Sql + ' WHERE RowNum BETWEEN @RowFrom AND @RowTo;';

if for example you typo the S in the

SET @sql = @***S***ql 

sorry to spin off the answers already posted here, but this is an actual instance of the error reported.

Note also that the error will not display the capital S in the message, I am not sure why, but I think it is because the

Set @sql =

is on the left of the equal sign.

How to allow user to pick the image with Swift?

For Swift 4
This code working for me!!

import UIKit

class ViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {

    @IBOutlet var imageView: UIImageView!
    @IBOutlet var chooseBuuton: UIButton!
    var imagePicker = UIImagePickerController()

    override func viewDidLoad() {
        imagePicker.delegate = self
    @IBAction func btnClicked() {

    if UIImagePickerController.isSourceTypeAvailable(.savedPhotosAlbum) 
        print("Button capture")
        imagePicker.sourceType = .savedPhotosAlbum;
        imagePicker.allowsEditing = false

        self.present(imagePicker, animated: true, completion: nil)

  @objc func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    let chosenImage = info[UIImagePickerControllerOriginalImage] as! UIImage
    imageView.image = chosenImage

    dismiss(animated: true, completion: nil)

Is Safari on iOS 6 caching $.ajax results?

I was able to fix my problem by using a combination of $.ajaxSetup and appending a timestamp to the url of my post (not to the post parameters/body). This based on the recommendations of previous answers

    $.ajaxSetup({ type:'POST', headers: {"cache-control","no-cache"}});

    $('#myForm').submit(function() {
        var data = $('#myForm').serialize();
        var now = new Date();
        var n = now.getTime();
            type: 'POST',
            url: 'myendpoint.cfc?method=login&time='+n,
            data: data,
            success: function(results){
                if(results.success) {
                    window.location = 'app.cfm';
                } else {
                    alert('login failed');

FFmpeg on Android

The most easy to build, easy to use implementation I have found is made by theguardianproject team:

Dynamically replace img src attribute with jQuery

In my case, I replaced the src taq using:

   $('#gmap_canvas').attr('src', newSrc);

Java logical operator short-circuiting

In plain terms, short-circuiting means stopping evaluation once you know that the answer can no longer change. For example, if you are evaluating a chain of logical ANDs and you discover a FALSE in the middle of that chain, you know the result is going to be false, no matter what are the values of the rest of the expressions in the chain. Same goes for a chain of ORs: once you discover a TRUE, you know the answer right away, and so you can skip evaluating the rest of the expressions.

You indicate to Java that you want short-circuiting by using && instead of & and || instead of |. The first set in your post is short-circuiting.

Note that this is more than an attempt at saving a few CPU cycles: in expressions like this

if (mystring != null && mystring.indexOf('+') > 0) {

short-circuiting means a difference between correct operation and a crash (in the case where mystring is null).

len() of a numpy array in python

What is the len of the equivalent nested list?

len([[2,3,1,0], [2,3,1,0], [3,2,1,1]])

With the more general concept of shape, numpy developers choose to implement __len__ as the first dimension. Python maps len(obj) onto obj.__len__.

X.shape returns a tuple, which does have a len - which is the number of dimensions, X.ndim. X.shape[i] selects the ith dimension (a straight forward application of tuple indexing).

Server configuration is missing in Eclipse

In Eclipse Neo
1. Window -> Show view -> Servers
2. Right click on server -> choose Properties
3. From General Tab -> Switch Location

Run a php app using tomcat?

A tad late, but here goes.

How about if you just want to run the real php on tomcat.

Concerning running tomcat on port 80 there's always jsvc, just google jsvc + tomcat.

Set Culture in an ASP.Net MVC app

1: Create a custom attribute and override method like this:

public class CultureAttribute : ActionFilterAttribute
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    // Retreive culture from GET
    string currentCulture = filterContext.HttpContext.Request.QueryString["culture"];

    // Also, you can retreive culture from Cookie like this :
    //string currentCulture = filterContext.HttpContext.Request.Cookies["cookie"].Value;

    // Set culture
    Thread.CurrentThread.CurrentCulture = new CultureInfo(currentCulture);
    Thread.CurrentThread.CurrentUICulture = CultureInfo.CreateSpecificCulture(currentCulture);

2: In App_Start, find FilterConfig.cs, add this attribute. (this works for WHOLE application)

public class FilterConfig
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    // Add custom attribute here
    filters.Add(new CultureAttribute());

That's it !

If you want to define culture for each controller/action in stead of whole application, you can use this attribute like this:

public class StudentsController : Controller


public ActionResult Index()
    return View();

Changing the resolution of a VNC session in linux

I think that depends on your window manager.

I'm a windows user, so this might be a wrong guess, but: Isn't there something called X-Server running on linux machines - at least on ones that might be interesting targets for VNC - that you can connect to with "X-Clients"?

VNC just takes everything that's on the screen and "tunnels it through your network". If I'm not totally wrong then the "X" protocol should give you the chance to use your client's desktop resolution.

Give X-Server on Wikipedia a try, that might give you a rough overview.

What is the best way to check for Internet connectivity using .NET?

I personally find the answer of Anton and moffeltje best, but I added a check to exclude virtual networks set up by VMWare and others.

public static bool IsAvailableNetworkActive()
    // only recognizes changes related to Internet adapters
    if (!System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable()) return false;

    // however, this will include all adapters -- filter by opstatus and activity
    NetworkInterface[] interfaces = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();
    return (from face in interfaces
            where face.OperationalStatus == OperationalStatus.Up
            where (face.NetworkInterfaceType != NetworkInterfaceType.Tunnel) && (face.NetworkInterfaceType != NetworkInterfaceType.Loopback)
            where (!(face.Name.ToLower().Contains("virtual") || face.Description.ToLower().Contains("virtual")))
            select face.GetIPv4Statistics()).Any(statistics => (statistics.BytesReceived > 0) && (statistics.BytesSent > 0));

C# Change A Button's Background Color

this.button2.BaseColor = System.Drawing.Color.FromArgb(((int)(((byte)(29)))), ((int)(((byte)(190)))), ((int)(((byte)(149)))));

Does C# have an equivalent to JavaScript's encodeURIComponent()?

Try Server.UrlEncode(), or System.Web.HttpUtility.UrlEncode() for instances when you don't have access to the Server object. You can also use System.Uri.EscapeUriString() to avoid adding a reference to the System.Web assembly.

Button background as transparent

To make a background transparent, just do android:background="@android:color/transparent".

However, your problem seems to be a bit deeper, as you're using selectors in a really weird way. The way you're using it seems wrong, although if it actually works, you should be putting the background image in the style as an <item/>.

Take a closer look at how styles are used in the Android source. While they don't change the text styling upon clicking buttons, there are a lot of good ideas on how to accomplish your goals there.

How to disable and then enable onclick event on <div> with javascript

You can use the CSS property pointer-events to disable the click event on any element:

// To disable:    
document.getElementById('id').style.pointerEvents = 'none';
// To re-enable:
document.getElementById('id').style.pointerEvents = 'auto'; 
// Use '' if you want to allow CSS rules to set the value

Here is a JsBin:

excel vba getting the row,cell value from selection.address

Is this what you are looking for ?

Sub getRowCol()

    Range("A1").Select ' example

    Dim col, row
    col = Split(Selection.Address, "$")(1)
    row = Split(Selection.Address, "$")(2)

    MsgBox "Column is : " & col
    MsgBox "Row is : " & row

End Sub

jQuery Change event on an <input> element - any way to retain previous value?

In Russ answer he binds the focus event. I don't think it is necessary.

You can store the old value in the change event.


        var newValue = $('#myInputElement').val();
        var oldValue;

            oldValue = newValue;
            newValue = $(this).val();
<input id="myInputElement" type="text">

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

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

{-# LANGUAGE RankNTypes, TypeOperators #-}

import Control.Monad (join)

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

Quoting Tom Crockett's excellent answer, we have:

A monad is...

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

...satisfying these laws:

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

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

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

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

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

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

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

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

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

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

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

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

newtype Identity a = Identity { runIdentity :: a }

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

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

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

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

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

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

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

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

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

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

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

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

Graphical DIFF programs for linux

I know of two graphical diff programs: Meld and KDiff3. I haven't used KDiff3, but Meld works well for me.

It seems that both are in the standard package repositories for openSUSE 11.0

fatal: git-write-tree: error building trees


git reset --mixed

instead of git reset --hard. You will not lose any changes.

How to pass form input value to php function

you must have read about function call . here i give you example of it.

 funtion pr($n)
echo $n;
<form action="<?php $f=$_POST['input'];pr($f);?>" method="POST">
<input name=input type=text></input>

Adding new files to a subversion repository

Before you can add files in an unversioned directory, you have to add the directory itself to the versioning:

svn add directory_name

will add the directory directory_name and all sub-directories:

How to use order by with union all in sql?

select CONCAT(Name, '(',substr(occupation, 1, 1), ')') AS f1
select temp.str AS f1 from 
(select count(occupation) AS counts, occupation, concat('There are a total of ' ,count(occupation) ,' ', lower(occupation),'s.') As str  from OCCUPATIONS group by occupation order by counts ASC, occupation ASC
 ) As temp
 order by f1

Plot smooth line with PyPlot

You could use scipy.interpolate.spline to smooth out your data yourself:

from scipy.interpolate import spline

# 300 represents number of points to make between T.min and T.max
xnew = np.linspace(T.min(), T.max(), 300)  

power_smooth = spline(T, power, xnew)


spline is deprecated in scipy 0.19.0, use BSpline class instead.

Switching from spline to BSpline isn't a straightforward copy/paste and requires a little tweaking:

from scipy.interpolate import make_interp_spline, BSpline

# 300 represents number of points to make between T.min and T.max
xnew = np.linspace(T.min(), T.max(), 300) 

spl = make_interp_spline(T, power, k=3)  # type: BSpline
power_smooth = spl(xnew)

plt.plot(xnew, power_smooth)

Before: screenshot 1

After: screenshot 2

Convert NaN to 0 in javascript

    var i = [NaN, 1,2,3];

    var j = =>{ return isNaN(i) ? 0 : i});

Rounding a variable to two decimal places C#

Use System.Math.Round to rounds a decimal value to a specified number of fractional digits.

var pay = 200 + bonus;
pay = System.Math.Round(pay, 2);

MSDN References:

Php header location redirect not working

This is likely a problem generated by the headers being already sent.


This occurs if you have echoed anything before deciding to redirect. If so, then the initial (default) headers have been sent and the new headers cannot replace something that's already in the output buffer getting ready to be sent to the browser.

Sometimes it's not even necessary to have echoed something yourself:

  • if an error is being outputted to the browser it's also considered content so the headers must be sent before the error information;
  • if one of your files is encoded in one format (let's say ISO-8859-1) and another is encoded in another (let's say UTF-8 with BOM) the incompatibility between the two encodings may result in a few characters being outputted;

Let's check

To test if this is the case you have to enable error reporting: error_reporting(E_ALL); and set the errors to be displayed ini_set('display_errors', TRUE); after which you will likely see a warning referring to the headers being already sent.

Let's fix

Fixing this kinds of errors:

  • writing your redirect logic somewhere in the code before anything is outputted;
  • using output buffers to trap any outgoing info and only release it at some point when you know all redirect attempts have been run;
  • Using a proper MVC framework they already solve it;


MVC solves it both functionally by ensuring that the logic is in the controller and the controller triggers the display/rendering of a view only at the end of the controllers. This means you can decide to do a redirect somewhere within the action but not withing the view.

Python Pandas iterate over rows and access column names

How to iterate efficiently

If you really have to iterate a Pandas dataframe, you will probably want to avoid using iterrows(). There are different methods and the usual iterrows() is far from being the best. itertuples() can be 100 times faster.

In short:

  • As a general rule, use df.itertuples(name=None). In particular, when you have a fixed number columns and less than 255 columns. See point (3)
  • Otherwise, use df.itertuples() except if your columns have special characters such as spaces or '-'. See point (2)
  • It is possible to use itertuples() even if your dataframe has strange columns by using the last example. See point (4)
  • Only use iterrows() if you cannot the previous solutions. See point (1)

Different methods to iterate over rows in a Pandas dataframe:

Generate a random dataframe with a million rows and 4 columns:

    df = pd.DataFrame(np.random.randint(0, 100, size=(1000000, 4)), columns=list('ABCD'))

1) The usual iterrows() is convenient, but damn slow:

start_time = time.clock()
result = 0
for _, row in df.iterrows():
    result += max(row['B'], row['C'])

total_elapsed_time = round(time.clock() - start_time, 2)
print("1. Iterrows done in {} seconds, result = {}".format(total_elapsed_time, result))

2) The default itertuples() is already much faster, but it doesn't work with column names such as My Col-Name is very Strange (you should avoid this method if your columns are repeated or if a column name cannot be simply converted to a Python variable name).:

start_time = time.clock()
result = 0
for row in df.itertuples(index=False):
    result += max(row.B, row.C)

total_elapsed_time = round(time.clock() - start_time, 2)
print("2. Named Itertuples done in {} seconds, result = {}".format(total_elapsed_time, result))

3) The default itertuples() using name=None is even faster but not really convenient as you have to define a variable per column.

start_time = time.clock()
result = 0
for(_, col1, col2, col3, col4) in df.itertuples(name=None):
    result += max(col2, col3)

total_elapsed_time = round(time.clock() - start_time, 2)
print("3. Itertuples done in {} seconds, result = {}".format(total_elapsed_time, result))

4) Finally, the named itertuples() is slower than the previous point, but you do not have to define a variable per column and it works with column names such as My Col-Name is very Strange.

start_time = time.clock()
result = 0
for row in df.itertuples(index=False):
    result += max(row[df.columns.get_loc('B')], row[df.columns.get_loc('C')])

total_elapsed_time = round(time.clock() - start_time, 2)
print("4. Polyvalent Itertuples working even with special characters in the column name done in {} seconds, result = {}".format(total_elapsed_time, result))


         A   B   C   D
0       41  63  42  23
1       54   9  24  65
2       15  34  10   9
3       39  94  82  97
4        4  88  79  54
...     ..  ..  ..  ..
999995  48  27   4  25
999996  16  51  34  28
999997   1  39  61  14
999998  66  51  27  70
999999  51  53  47  99

[1000000 rows x 4 columns]

1. Iterrows done in 104.96 seconds, result = 66151519
2. Named Itertuples done in 1.26 seconds, result = 66151519
3. Itertuples done in 0.94 seconds, result = 66151519
4. Polyvalent Itertuples working even with special characters in the column name done in 2.94 seconds, result = 66151519

This article is a very interesting comparison between iterrows and itertuples

How can I read a large text file line by line using Java?

The clear way to achieve this,

For example:

If you have dataFile.txt on your current directory

import java.util.Scanner;

public class readByLine
    public readByLine() throws FileNotFoundException
        Scanner linReader = new Scanner(new File("dataFile.txt"));

        while (linReader.hasNext())
            String line = linReader.nextLine();


    public static void main(String args[])  throws FileNotFoundException
        new readByLine();

The output like as below, enter image description here

Convert floating point number to a certain precision, and then copy to string

It's not print that does the formatting, It's a property of strings, so you can just use

newstring = "%.9f" % numvar

Prevent scrolling of parent element when inner element scroll position reaches top/bottom?

Here's a plain JavaScript version:

function scroll(e) {
  var delta = (e.type === "mousewheel") ? e.wheelDelta : e.detail * -40;
  if (delta < 0 && (this.scrollHeight - this.offsetHeight - this.scrollTop) <= 0) {
    this.scrollTop = this.scrollHeight;
  } else if (delta > 0 && delta > this.scrollTop) {
    this.scrollTop = 0;
document.querySelectorAll(".scroller").addEventListener("mousewheel", scroll);
document.querySelectorAll(".scroller").addEventListener("DOMMouseScroll", scroll);

How to instantiate a javascript class in another js file?

// Create Customer class as follows:
export default class Customer {}

// Import the class 
// no need for .js extension in path cos gets inferred automatically
import Customer from './path/to/Customer'; 
// or
const Customer = require('./path/to/Customer') 

// Use the class
var customer = new Customer();
var name = customer.getName();

What is the --save option for npm install?

npm v6.x update ?

now you can be using one of npm i or npm i -S or npm i -P to install and save module as a dependency.

npm i is the alias of npm install

  1. npm i is equal to npm install, means default save module as a dependency;
  2. npm i -S is equal to npm install --save (npm v5-)
  3. npm i -P is equal to npm install --save-prod (npm v5+)

check your npm version

$ npm -v

get npm help

?  ~ npm -h

Usage: npm <command>

where <command> is one of:
    access, adduser, audit, bin, bugs, c, cache, ci, cit,
    clean-install, clean-install-test, completion, config,
    create, ddp, dedupe, deprecate, dist-tag, docs, doctor,
    edit, explore, fund, get, help, help-search, hook, i, init,
    install, install-ci-test, install-test, it, link, list, ln,
    login, logout, ls, org, outdated, owner, pack, ping, prefix,
    profile, prune, publish, rb, rebuild, repo, restart, root,
    run, run-script, s, se, search, set, shrinkwrap, star,
    stars, start, stop, t, team, test, token, tst, un,
    uninstall, unpublish, unstar, up, update, v, version, view,

npm <command> -h  quick help on <command>
npm -l            display full usage info
npm help <term>   search for help on <term>
npm help npm      involved overview

Specify configs in the ini-formatted file:
or on the command line via: npm <command> --key value
Config info can be viewed via: npm help config

[email protected] /Users/xgqfrms-mbp/.nvm/versions/node/v12.18.0/lib/node_modules/npm

get npm install help

npm -h i / npm help install

$ npm -h i  

npm install (with no args, in package dir)
npm install [<@scope>/]<pkg>
npm install [<@scope>/]<pkg>@<tag>
npm install [<@scope>/]<pkg>@<version>
npm install [<@scope>/]<pkg>@<version range>
npm install <alias>@npm:<name>
npm install <folder>
npm install <tarball file>
npm install <tarball url>
npm install <git:// url>
npm install <github username>/<github project>

aliases: i, isntall, add
common options: [--save-prod|--save-dev|--save-optional] [--save-exact] [--no-save]
?  ~ 


enter image description here

Is there an ignore command for git like there is for svn?

for names not present in the working copy or repo:

echo /globpattern >> .gitignore

or for an existing file (sh type command line):

echo /$(ls -1 file) >> .gitignore   # I use tab completion to select the file to be ignored  
git rm -r --cached file             # if already checked in, deletes it on next commit

c++ Read from .csv file

That because your csv file is in invalid format, maybe the line break in your text file is not the \n or \r

and, using c/c++ to parse text is not a good idea. try awk:

 $awk -F"," '{print "ID="$1"\tName="$2"\tAge="$3"\tGender="$4}' 1.csv
 ID=0   Name=Filipe Age=19  Gender=M
 ID=1   Name=Maria  Age=20  Gender=F
 ID=2   Name=Walter Age=60  Gender=M

Java project in Eclipse: The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files

This seems to be an Eclipse bug, though restarting Eclipse worked great for me, hope this helps somebody else too.

Changing the default icon in a Windows Forms application

Once the icon is in a .ICO format in visual studio I use

//This uses the file u give it to make an icon. 

Icon icon = Icon.ExtractAssociatedIcon(String);//pulls icon from .ico and makes it then icon object.

//Assign icon to the icon property of the form

this.Icon = icon;

so in short

Icon icon = Icon.ExtractAssociatedIcon("FILE/Path");

this.Icon = icon; 

Works everytime.

Find document with array that contains a specific value

If you'd want to use something like a "contains" operator through javascript, you can always use a Regular expression for that...

eg. Say you want to retrieve a customer having "Bartolomew" as name

async function getBartolomew() {
    const custStartWith_Bart = await Customers.find({name: /^Bart/ }); // Starts with Bart
    const custEndWith_lomew = await Customers.find({name: /lomew$/ }); // Ends with lomew
    const custContains_rtol = await Customers.find({name: /.*rtol.*/ }); // Contains rtol


'System.Reflection.TargetInvocationException' occurred in PresentationFramework.dll

If the radiobutton-checked event occurs before the content of the window is loaded fully, i.e. the ellipse is loaded fully, such an exception will be thrown. So check if the UI of the window is loaded (probably by Window_ContentRendered event, etc.).

Online PHP syntax checker / validator

In case you're interested, an offline checker that does complicated type analysis: It is not online however.

How do I get the last character of a string?

 public char lastChar(String s) {
     if (s == "" || s == null)
        return ' ';
    char lc = s.charAt(s.length() - 1);
    return lc;

How to find all links / pages on a website

If you have the developer console (JavaScript) in your browser, you can type this code in:

urls = document.querySelectorAll('a'); for (url in urls) console.log(urls[url].href);


n=$$('a');for(u in n)console.log(n[u].href)

Access denied for user 'root'@'localhost' (using password: YES) (Mysql::Error)

Update user table in mysql DB. And set some password where it is blank, i was using root user so i set password for root user.

update mysql.user set password = PASSWORD('123456') where password = '';
flush privileges;

And then again tried from ATG CIM by providing password and it worked fine.

After update

Typescript ReferenceError: exports is not defined

I had the same problem and solved it adding "es5" library to tsconfig.json like this:

    "compilerOptions": {
        "target": "es5", //defines what sort of code ts generates, es5 because it's what most browsers currently UNDERSTANDS.
        "module": "commonjs",
        "moduleResolution": "node",
        "sourceMap": true,
        "emitDecoratorMetadata": true, //for angular to be able to use metadata we specify in our components.
        "experimentalDecorators": true, //angular needs decorators like @Component, @Injectable, etc.
        "removeComments": false,
        "noImplicitAny": false,
        "lib": [

What Are The Best Width Ranges for Media Queries

You can take a look here for a longer list of screen sizes and respective media queries.

Or go for Bootstrap media queries:

/* Large desktop */
@media (min-width: 1200px) { ... }

/* Portrait tablet to landscape and desktop */
@media (min-width: 768px) and (max-width: 979px) { ... }

/* Landscape phone to portrait tablet */
@media (max-width: 767px) { ... }

/* Landscape phones and down */
@media (max-width: 480px) { ... }

Additionally you might wanty to take a look at Foundation's media queries with the following default settings:

// Media Queries

$screenSmall: 768px !default;
$screenMedium: 1279px !default;
$screenXlarge: 1441px !default;

Is there a standardized method to swap two variables in Python?

That is the standard way to swap two variables, yes.

How to find the length of an array list?


Since no elements are in the list

output => 0

myList.add("newString");  // use myList.add() to insert elements to the arraylist

Since one element is added to the list

output => 1

Batch file to copy files from one folder to another folder

@echo off

rem The * at the end of the destination file is to avoid File/Directory Internal Question.

rem You can do this for each especific file. (Make sure you already have permissions to the path)
xcopy /Y "\\Oldeserver\storage\data\MyFile01.txt" "\\New server\storage\data\MyFile01.txt"*

rem You can use "copy" instead of "xcopy "for this example.

HTML code for INR

SPAN class code. Stylesheet:

<link rel="stylesheet" type="text/css" href="">

Now use the below mentioned code to type Indian Rupee symbol,

<span class="WebRupee">Rs.</span>

Once the popular font families will be updated to Unicode 6.0.0, then you will be able to type Indian Rupee Symbol by typing ₹ in HTML editor.

UITableView set to static cells. Is it possible to hide some of the cells programmatically?

For the easiest scenario when you hide cells at the very bottom of table view, you could adjust tableView's contentInset after you hide cell:

- (void)adjustBottomInsetForHiddenSections:(NSInteger)numberOfHiddenSections
    CGFloat bottomInset = numberOfHiddenSections * 44.0; // or any other 'magic number
    self.tableView.contentInset = UIEdgeInsetsMake(, self.tableView.contentInset.left, -bottomInset, self.tableView.contentInset.right);

How can I check the size of a file in a Windows batch script?

Just an idea:

You may get the filesize by running command "dir":

>dir thing

Then again it returns so many things.

Maybe you can get it from there if you look for it.

But I am not sure.

Difference between web reference and service reference?

Another point to take in consideration is that the new UI for Service Interface will give you much more flexibility on how you want to create your proxy class. For example, it will allow you to map data contracts to existing dlls, if they match (actually this is the default behaviour).

Ternary operator in AngularJS templates

For texts in angular template (userType is property of $scope, like $scope.userType):

  {{userType=='admin' ? 'Edit' : 'Show'}}

How do I access command line arguments in Python?

import sys


will give you a list of arguments (not including the name of the python file)

Clicking URLs opens default browser

If you're using a WebView you'll have to intercept the clicks yourself if you don't want the default Android behaviour.

You can monitor events in a WebView using a WebViewClient. The method you want is shouldOverrideUrlLoading(). This allows you to perform your own action when a particular URL is selected.

You set the WebViewClient of your WebView using the setWebViewClient() method.

If you look at the WebView sample in the SDK there's an example which does just what you want. It's as simple as:

private class HelloWebViewClient extends WebViewClient {
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        return true;

Extracting the top 5 maximum values in excel

To my mind the case for a PT (as @Nathan Fisher) is a 'no brainer', but I would add a column to facilitate ordering by rank (up or down):

SO18528624 first example

OPS is entered as VALUES (Sum of) twice so I have renamed the column labels to make clearer which is which. The PT is in a different sheet from the data but could be in the same sheet.

Rank is set with a right click on a data point selected in that column and Show Values As... and Rank Largest to Smallest (there are other options) with the Base field as Player and the filter is a Value Filters, Top 10... one:

SO18528624 second example

Once in a PT the power of that feature can very easily be applied to view the data in many other ways, with no change of formula (there isn't one!).

In the case of a tie for the last position included in the filter both results are included (Top 5 would show six or more results). A tie for top rank between just two players would show as 1 1 3 4 5 for Top 5.

How to highlight a current menu item?

In my case I resolved this problem by creating a simple controller responsible for the navigation

  .controller('NavigationCtrl', ['$scope', '$location', function ($scope, $location) {
    $scope.isCurrentPath = function (path) {
      return $location.path() == path;

And by just adding ng-class to the element like so:

<ul class="nav" ng-controller="NavigationCtrl">
  <li ng-class="{ active: isCurrentPath('/') }"><a href="#/">Home</a></li>
  <li ng-class="{ active: isCurrentPath('/about') }"><a href="#/about">About</a></li>
  <li ng-class="{ active: isCurrentPath('/contact') }"><a href="#/contact">Contact</a></li>

ECMAScript 6 arrow function that returns an object

If the body of the arrow function is wrapped in curly braces, it is not implicitly returned. Wrap the object in parentheses. It would look something like this.

p => ({ foo: 'bar' })

By wrapping the body in parens, the function will return { foo: 'bar }.

Hopefully, that solves your problem. If not, I recently wrote an article about Arrow functions which covers it in more detail. I hope you find it useful. Javascript Arrow Functions

Access denied for user 'root'@'localhost' with PHPMyAdmin

Edit your phpmyadmin file and if you have Password, insert that in front of Password in following code:

$cfg['Servers'][$i]['verbose'] = 'localhost';
$cfg['Servers'][$i]['host'] = 'localhost';
$cfg['Servers'][$i]['port'] = '3306';
$cfg['Servers'][$i]['socket'] = '';
$cfg['Servers'][$i]['connect_type'] = 'tcp';
$cfg['Servers'][$i]['extension'] = 'mysqli';
$cfg['Servers'][$i]['auth_type'] = 'config';
$cfg['Servers'][$i]['user'] = '**your-root-username**';
$cfg['Servers'][$i]['password'] = '**root-password**';
$cfg['Servers'][$i]['AllowNoPassword'] = true;

Nginx no-www to www and www to no-www

if ($host ~* ^$) {
    return 301 $scheme://$request_uri;

How do I resize a Google Map with JavaScript after it has loaded?

First of all, thanks for guiding me and closing this issue. I found a way to fix this issue from your discussions. Yeah, Let's come to the point. The thing is I'm Using GoogleMapHelper v3 helper in CakePHP3. When i tried to open bootstrap modal popup, I got struck with the grey box issue over the map. It's been extended for 2 days. Finally i got a fix over this.

We need to Update the GoogleMapHelper to fix the issue

Need to add the below script in setCenterMap function

google.maps.event.trigger({$id}, \"resize\");

And need the include below code in JavaScript

google.maps.event.addListenerOnce({$id}, 'idle', function(){
   setCenterMap(new google.maps.LatLng({$this->defaultLatitude}, 

How can I convert a .py to .exe for Python?

I can't tell you what's best, but a tool I have used with success in the past was cx_Freeze. They recently updated (on Jan. 7, '17) to version 5.0.1 and it supports Python 3.6.

Here's the pypi

The documentation shows that there is more than one way to do it, depending on your needs.

I have not tried it out yet, so I'm going to point to a post where the simple way of doing it was discussed. Some things may or may not have changed though.

How do I use cx_freeze?

Validation of radio button group using jQuery validation plugin

You can also use this:

<input type="radio" name="myoptions[]" value="blue"> Blue<br />
<input type="radio" name="myoptions[]" value="red"> Red<br />
<input type="radio" name="myoptions[]" value="green"> Green<br />
<label for="myoptions[]" class="error" style="display:none;">Please choose one.</label>

and simply add this rule

rules: {
 'myoptions[]':{ required:true }

Mention how to add rules.