Programs & Examples On #Space efficiency

How do I change the title of the "back" button on a Navigation Bar

I know, the question is very old, but I found a nice solution.

UIBarButtonItem *barButton = [[UIBarButtonItem alloc] init];
barButton.title = @"Custom Title";
self.navigationController.navigationBar.topItem.backBarButtonItem = barButton;

Works from childView! Tested with iOS 7.

Is there a way to change the spacing between legend items in ggplot2?

ggplot2 v3.0.0 released in July 2018 has working options to modify legend.spacing.x, legend.spacing.y and legend.text.

Example: Increase horizontal spacing between legend keys


ggplot(mtcars, aes(factor(cyl), fill = factor(cyl))) + 
  geom_bar() +
  coord_flip() +
  scale_fill_brewer("Cyl", palette = "Dark2") +
  theme_minimal(base_size = 14) +
  theme(legend.position = 'top', 
        legend.spacing.x = unit(1.0, 'cm'))

Note: If you only want to expand the spacing to the right of the legend text, use stringr::str_pad()

Example: Move the legend key labels to the bottom and increase vertical spacing

ggplot(mtcars, aes(factor(cyl), fill = factor(cyl))) + 
  geom_bar() +
  coord_flip() +
  scale_fill_brewer("Cyl", palette = "Dark2") +
  theme_minimal(base_size = 14) +
  theme(legend.position = 'top', 
        legend.spacing.x = unit(1.0, 'cm'),
        legend.text = element_text(margin = margin(t = 10))) +
  guides(fill = guide_legend(title = "Cyl",
                             label.position = "bottom",
                             title.position = "left", title.vjust = 1)) 

Example: for scale_fill_xxx & guide_colorbar

ggplot(mtcars, aes(mpg, wt)) +
  geom_point(aes(fill = hp), pch = I(21), size = 5)+
  scale_fill_viridis_c(guide = FALSE) +
  theme_classic(base_size = 14) +
  theme(legend.position = 'top', 
        legend.spacing.x = unit(0.5, 'cm'),
        legend.text = element_text(margin = margin(t = 10))) +
  guides(fill = guide_colorbar(title = "HP",
                               label.position = "bottom",
                               title.position = "left", title.vjust = 1,
                               # draw border around the legend
                               frame.colour = "black",
                               barwidth = 15,
                               barheight = 1.5)) 

For vertical legends, settinglegend.key.size only increases the size of the legend keys, not the vertical space between them

ggplot(mtcars) +
  aes(x = cyl, fill = factor(cyl)) +
  geom_bar() +
  scale_fill_brewer("Cyl", palette = "Dark2") +
  theme_minimal(base_size = 14) +
  theme(legend.key.size = unit(1, "cm"))

In order to increase the distance between legend keys, modification of the legend-draw.r function is needed. See this issue for more info

# function to increase vertical spacing between legend keys
# @clauswilke
draw_key_polygon3 <- function(data, params, size) {
  lwd <- min(data$size, min(size) / 4)
    width = grid::unit(0.6, "npc"),
    height = grid::unit(0.6, "npc"),
    gp = grid::gpar(
      col = data$colour,
      fill = alpha(data$fill, data$alpha),
      lty = data$linetype,
      lwd = lwd * .pt,
      linejoin = "mitre"

### this step is not needed anymore per tjebo's comment below
### see also:
# register new key drawing function, 
# the effect is global & persistent throughout the R session
# GeomBar$draw_key = draw_key_polygon3

ggplot(mtcars) +
  aes(x = cyl, fill = factor(cyl)) +
  geom_bar(key_glyph = "polygon3") +
  scale_fill_brewer("Cyl", palette = "Dark2") +
  theme_minimal(base_size = 14) +
  theme(legend.key = element_rect(color = NA, fill = NA),
        legend.key.size = unit(1.5, "cm")) +
  theme(legend.title.align = 0.5)

System.Collections.Generic.IEnumerable' does not contain any definition for 'ToList'

You're missing a reference to System.Linq.


using System.Linq

to get access to the ToList() function on the current code file.

To give a little bit of information over why this is necessary, Enumerable.ToList<TSource> is an extension method. Extension methods are defined outside the original class that it targets. In this case, the extension method is defined on System.Linq namespace.

Access a URL and read Data with R

In the simplest case, just do

X <- read.csv(url(""))

plus which ever options read.csv() may need.

Edit in Sep 2020 or 9 years later:

For a few years now R also supports directly passing the URL to read.csv:

X <- read.csv("")

End of 2020 edit. Original post continutes.

Long answer: Yes this can be done and many packages have use that feature for years. E.g. the tseries packages uses exactly this feature to download stock prices from Yahoo! for almost a decade:

R> library(tseries)
Loading required package: quadprog
Loading required package: zoo

    ‘tseries’ version: 0.10-24

    ‘tseries’ is a package for time series analysis and computational finance.

    See ‘library(help="tseries")’ for details.

R> get.hist.quote("IBM")
trying URL '    ## manual linebreak here
Content type 'text/csv' length unknown
opened URL
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
downloaded 258 Kb

             Open   High    Low  Close
1991-01-02 112.87 113.75 112.12 112.12
1991-01-03 112.37 113.87 112.25 112.50
1991-01-04 112.75 113.00 111.87 112.12
1991-01-07 111.37 111.87 110.00 110.25
1991-01-08 110.37 110.37 108.75 109.00
1991-01-09 109.75 110.75 106.75 106.87

This is all exceedingly well documented in the manual pages for help(connection) and help(url). Also see the manul on 'Data Import/Export' that came with R.

how can I connect to a remote mongo server from Mac OS terminal

You are probably connecting fine but don't have sufficient privileges to run show dbs.

You don't need to run the db.auth if you pass the auth in the command line:

mongo -u username -p password

Once you connect are you able to see collections?

> show collections

If so all is well and you just don't have admin privileges to the database and can't run the show dbs

Editing the git commit message in GitHub

For intellij users: If you want to make changes in interactive way for past commits, which are not pushed follow below steps in Intellij:

  • Select Version Control
  • Select Log
  • Right click the commit for which you want to amend comment
  • Click reword
  • Done

Hope it helps

What is an .axd file?

from Google

An .axd file is a HTTP Handler file. There are two types of .axd files.

  1. ScriptResource.axd
  2. WebResource.axd

These are files which are generated at runtime whenever you use ScriptManager in your Web app. This is being generated only once when you deploy it on the server.

Simply put the ScriptResource.AXD contains all of the clientside javascript routines for Ajax. Just because you include a scriptmanager that loads a script file it will never appear as a ScriptResource.AXD - instead it will be merely passed as the .js file you send if you reference a external script file. If you embed it in code then it may merely appear as part of the html as a tag and code but depending if you code according to how the ToolKit handles it - may or may not appear as as a ScriptResource.axd. ScriptResource.axd is only introduced with AJAX and you will never see it elsewhere

And ofcourse it is necessary

Hiding the address bar of a browser (popup)

What is the truth?

Microsoft's documentation describing the behaviour of their browser is correct.

Is there any solution to hide the addressbar?

No. If you could hide it, then you could use HTML/CSS to make something that looked like a common address bar. You could then put a different address in it. You could then trick people into thinking they were on a different site and entering their password for it.

It is impossible to conceal the user's location from them because it is essential for security that they know what their location is.

Jquery to get the id of selected value from dropdown

First set a custom attribute into your option for example nameid (you can set non-standardized attribute of an HTML element, it's allowed):

'<option nameid= "' + + "' value="' + i + '">' + n.names + '</option>'

then you can easily get attribute value using jquery .attr() :


For Example:

<select id="jobSel" class="longcombo" onchange="GetNameId">
    <option nameid="32" value="1">test1</option>
    <option nameid="67" value="1">test2</option>
    <option nameid="45" value="1">test3</option>    


function GetNameId(){
   alert($('#jobSel option:selected').attr("nameid"));

Python exit commands - why so many and when should each be used?

Different Means of Exiting


  • Exit the process without calling the cleanup handlers.


  • a clean exit without any errors / problems.


  • There was some issue / error / problem and that is why the program is exiting.


  • When the system and python shuts down; it means less memory is being used after the program is run.


  • Closes the python file.


Basically they all do the same thing, however, it also depends on what you are doing it for.

I don't think you left anything out and I would recommend getting used to quit() or exit().

You would use sys.exit() and os._exit() mainly if you are using big files or are using python to control terminal.

Otherwise mainly use exit() or quit().

Returning a boolean value in a JavaScript function

An old thread, sure, but a popular one apparently. It's 2020 now and none of these answers have addressed the issue of unreadable code. @pimvdb's answer takes up less lines, but it's also pretty complicated to follow. For easier debugging and better readability, I should suggest refactoring the OP's code to something like this, and adopting an early return pattern, as this is likely the main reason you were unsure of why the were getting undefined:

function validatePassword() {
   const password = document.getElementById("password");
   const confirm_password = document.getElementById("password_confirm");

   if (password.value.length === 0) {
      return false;

   if (password.value !== confirm_password.value) {
      return false;
   return true;

How to delete session cookie in Postman?

into Chrome, right click -> Inspect Element. Go to the tab active tracking of resources and if you have not already. Now the left hand sidebar thingy down until you see "Cookies", click below your domain name and to remove a cookie just right-click on it and "Delete"

How to get 'System.Web.Http, Version=

Install-Package Microsoft.AspNet.WebApi.Core -version 5.2.3

Then in the project Add Reference -> Browse. Push the browse button and go to the C:\Users\UserName\Documents\Visual Studio 2015\Projects\ProjectName\packages\Microsoft.AspNet.Mvc.5.2.3\lib\net45 and add the needed .dll file

Select a date from date picker using Selenium webdriver

I tried this code, it may work for you also:

            DateFormat dateFormat2 = new SimpleDateFormat("dd"); 
            Date date2 = new Date();

            String today = dateFormat2.format(date2); 

            //find the calendar
            WebElement dateWidget = driver.findElement("dp-calendar"));  
            List<WebElement> columns=dateWidget.findElements(By.tagName("td"));  

            //comparing the text of cell with today's date and clicking it.
            for (WebElement cell : columns)
               if (cell.getText().equals(today))

Change SVN repository URL

Given that the Apache Subversion server will be moved to this new DNS alias:

  • With Subversion 1.7 or higher, use svn relocate. Relocate is used when the SVN server's location changes. switch is only used if you want to change your local working copy to another branch or another path. If using TortoiseSVN, you may follow instructions from the TortoiseSVN Manual. If using the SVN command line interface, refer to this section of SVN's documentation. The command should look like this:

    svn relocate svn://

  • Keep using /project given that the actual contents of your repository probably won't change.

Note: svn relocate is not available before version 1.7 (thanks to ColinM for the info). In older versions you would use:

    svn switch --relocate OLD NEW

Returning string from C function

word is on the stack and goes out of scope as soon as getStr() returns. You are invoking undefined behavior.

html script src="" triggering redirection with button

First you are linking the file that is here:

<script src="../Script/login.js"> 

Which would lead the website to a file in the Folder Script, but then in the second paragraph you are saying that the folder name is

and also i have onother folder named scripts that contains the the following login.js file

So, this won't work! Because you are not accessing the correct file. To do that please write the code as

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

Try removing the .. from the beginning of the code too.

This way, you'll reach the js file where the function would run!

Just to make sure:

Just to make sure that the files are attached the HTML DOM, then please open Developer Tools (F12) and in the network workspace note each request that the browser makes to the server. This way you will learn which files were loaded and which weren't, and also why they were not!

Good luck.

How to use Sublime over SSH

This is the easiest way to locally edit files which live on remote host where you have previously setup ssh to remote IP

# issue on local box

sudo apt-get install sshfs   # on local host install sshfs ( linux )

# on local box create secure mount of remote directory

export REMOTE_IP= # remote host IP

sshfs myremoteuserid@${REMOTE_IP}:/your/remote/dir  /your/local/dir # for example

Done !!!

Now on local host just start editing files ... when you list dir locally it may not list anything until you cd into subdir or list a specific file ... lazy loading ... this does not impact editing files

subl /your/local/dir/magnum_opus.go # local file edit using sublime text

so above is actually editing remote file at

/your/remote/dir/magnum_opus.go  # remote file on box $REMOTE_IP

For OSX or Windows see this tut from the kind folk over on Digital Ocean

rotate image with css

The trouble looks like the image isn't square and the browser adjusts as such. After rotation ensure the dimensions are retained by changing the image margin.

.imagetest img {
  transform: rotate(270deg);
  margin: 10px 0px;

The amount will depend on the difference in height x width of the image. You may also need to add display:inline-block; or display:block to get it to recognize the margin parameter.

Android: How to set password property in an edit text?

See this link text view android:password

This applies for EditText as well, as it is a known direct subclass of TextView.

IOError: [Errno 2] No such file or directory trying to open a file


with open(os.path.join(src_dir, f)) as fin:
    for line in fin:

Also, you never output to a new file.

How to build a Horizontal ListView with RecyclerView?

Trying to build a horizontal ListView is taking too much time. I have resolved it in two ways.

1.By using a ViewPager whose adapter extends from PagerAdapter.

2.By using RecyclerView just as above. Need to apply LayoutManager as in the following code:

LinearLayoutManager layoutManager
    = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);

RecyclerView myList = (RecyclerView) findViewById(;

Simple regular expression for a decimal with a precision of 2

I tried one with my project. This allows numbers with + | - signs as well.


addEventListener, "change" and option selection

You need a click listener which calls addActivityItem if less than 2 options exist:

var activities = document.getElementById("activitySelector");

activities.addEventListener("click", function() {
    var options = activities.querySelectorAll("option");
    var count = options.length;
    if(typeof(count) === "undefined" || count < 2)

activities.addEventListener("change", function() {
    if(activities.value == "addNew")

function addActivityItem() {
    // ... Code to add item here

A live demo is here on JSfiddle.

What is NODE_ENV and how to use it in Express?

Typically, you'd use the NODE_ENV variable to take special actions when you develop, test and debug your code. For example to produce detailed logging and debug output which you don't want in production. Express itself behaves differently depending on whether NODE_ENV is set to production or not. You can see this if you put these lines in an Express app, and then make a HTTP GET request to /error:

app.get('/error', function(req, res) {
  if ('production' !== app.get('env')) {
    console.log("Forcing an error!");
  throw new Error('TestError');

app.use(function (req, res, next) {

Note that the latter app.use() must be last, after all other method handlers!

If you set NODE_ENV to production before you start your server, and then send a GET /error request to it, you should not see the text Forcing an error! in the console, and the response should not contain a stack trace in the HTML body (which origins from Express). If, instead, you set NODE_ENV to something else before starting your server, the opposite should happen.

In Linux, set the environment variable NODE_ENV like this:

export NODE_ENV='value'

SQL Server convert select a column and convert it to a string

You can use the following method:

        select ', ' + CONVERT(varchar(10), ID) FROM @temp
        where ID<50
group by ID for xml path('')
        ), 1, 2, '') as IDs


Declare @temp Table(
ID int
insert into @temp
insert into @temp
insert into @temp
insert into @temp

        select ', ' + CONVERT(varchar(10), ID) FROM @temp
        where ID<50
group by ID for xml path('')
        ), 1, 2, '') as IDs

Result will be:

enter image description here

What is the difference between new/delete and malloc/free?

new / delete

  • Allocate / release memory
    1. Memory allocated from 'Free Store'.
    2. Returns a fully typed pointer.
    3. new (standard version) never returns a NULL (will throw on failure).
    4. Are called with Type-ID (compiler calculates the size).
    5. Has a version explicitly to handle arrays.
    6. Reallocating (to get more space) not handled intuitively (because of copy constructor).
    7. Whether they call malloc / free is implementation defined.
    8. Can add a new memory allocator to deal with low memory (std::set_new_handler).
    9. operator new / operator delete can be overridden legally.
    10. Constructor / destructor used to initialize / destroy the object.

malloc / free

  • Allocate / release memory
    1. Memory allocated from 'Heap'.
    2. Returns a void*.
    3. Returns NULL on failure.
    4. Must specify the size required in bytes.
    5. Allocating array requires manual calculation of space.
    6. Reallocating larger chunk of memory simple (no copy constructor to worry about).
    7. They will NOT call new / delete.
    8. No way to splice user code into the allocation sequence to help with low memory.
    9. malloc / free can NOT be overridden legally.

Table comparison of the features:

Feature new / delete malloc / free
Memory allocated from 'Free Store' 'Heap'
Returns Fully typed pointer void*
On failure Throws (never returns NULL) Returns NULL
Required size Calculated by compiler Must be specified in bytes
Handling arrays Has an explicit version Requires manual calculations
Reallocating Not handled intuitively Simple (no copy constructor)
Call of reverse Implementation defined No
Low memory cases Can add a new memory allocator Not handled by user code
Overridable Yes No
Use of constructor / destructor Yes No

Technically, memory allocated by new comes from the 'Free Store' while memory allocated by malloc comes from the 'Heap'. Whether these two areas are the same is an implementation detail, which is another reason that malloc and new cannot be mixed.

Twitter Bootstrap Datepicker within modal window

This solutions worked perfectly for me to render the datepicker on top of bootstrap modal.


<div class="wrapper">
Some content goes here<br />
Some more content.
<div class="row">
<div class="col-xs-4">

<!-- padding for jsfiddle -->
<div class="input-group date" id="dtp">
<input type="text" class="form-control" />  
<span class="input-group-addon">
  <span class="glyphicon-calendar glyphicon"></span>


format: 'MMM D, YYYY',
widgetParent: 'body'});

$('#dtp').on('', function() {
      var datepicker = $('body').find('.bootstrap-datetimepicker-widget:last');
      if (datepicker.hasClass('bottom')) {
        var top = $(this).offset().top + $(this).outerHeight();
        var left = $(this).offset().left;
          'top': top + 'px',
          'bottom': 'auto',
          'left': left + 'px'
      else if (datepicker.hasClass('top')) {
        var top = $(this).offset().top - datepicker.outerHeight();
        var left = $(this).offset().left;
          'top': top + 'px',
          'bottom': 'auto',
          'left': left + 'px'


.wrapper {
height: 100px;
overflow: auto;}
body {
position: relative;

MySQL select where column is not empty

select phone, phone2 from jewishyellow.users 
where phone like '813%' and phone2 is not null

What is and how to fix System.TypeInitializationException error?

System.TypeInitializationException happens when the code that gets executed during the process of loading the type throws an exception.

When .NET loads the type, it must prepare all its static fields before the first time that you use the type. Sometimes, initialization requires running code. It is when that code fails that you get a System.TypeInitializationException.

In your specific case, the following three static fields run some code:

private static string s_bstCommonAppData = Path.Combine(s_commonAppData, "XXXX");
private static string s_bstUserDataDir = Path.Combine(s_bstCommonAppData, "UserData");
private static string s_commonAppData = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);

Note that s_bstCommonAppData depends on s_commonAppData, but it is declared ahead of its dependency. Therefore, the value of s_commonAppData is null at the time that the Path.Combine is called, resulting in ArgumentNullException. Same goes for the s_bstUserDataDir and s_bstCommonAppData: they are declared in reverse order to the desired order of initialization.

Re-order the lines to fix this problem:

private static string s_commonAppData = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);
private static string s_bstCommonAppData = Path.Combine(s_commonAppData, "XXXX");
private static string s_bstUserDataDir = Path.Combine(s_bstCommonAppData, "UserData");

Can you break from a Groovy "each" closure?

Replace each loop with any closure.

def list = [1, 2, 3, 4, 5]
list.any { element ->
    if (element == 2)
        return // continue

    println element

    if (element == 3)
        return true // break



How to edit binary file on Unix systems

You can also try ghex2 GNOME utilities. This give you the automated hex-to-ASCII on the side, as well as the various character/integer decodes at the bottom. ghex2

Angular-cli from css to scss

A quick and easy way to perform the migration is to use the schematic NPM package schematics-scss-migrate. this package rename all css to scss file :

ng add schematics-scss-migrate mvc @Html.CheckBoxFor

Html.CheckBoxFor expects a Func<TModel, bool> as the first parameter. Therefore your lambda must return a bool, you are currently returning an instance of List<Checkboxes>:

model => model.EmploymentType

You need to iterate over the List<Checkboxes> to output each checkbox:

@for (int i = 0; i < Model.EmploymentType.Count; i++)
    @Html.HiddenFor(m => m.EmploymentType[i].Text)
    @Html.CheckBoxFor(m => m.EmploymentType[i].Checked, 
              new { id = string.Format("employmentType_{0}", i) })

JPA & Criteria API - Select only specific columns

First of all, I don't really see why you would want an object having only ID and Version, and all other props to be nulls. However, here is some code which will do that for you (which doesn't use JPA Em, but normal Hibernate. I assume you can find the equivalence in JPA or simply obtain the Hibernate Session obj from the em delegate Accessing Hibernate Session from EJB using EntityManager ):

List<T> results = session.createCriteria(entityClazz)
    .setProjection( Projections.projectionList()
        .add( Property.forName("ID") )
        .add( Property.forName("VERSION") )

This will return a list of Objects having their ID and Version set and all other props to null, as the aliasToBean transformer won't be able to find them. Again, I am uncertain I can think of a situation where I would want to do that.

How to create a timeline with LaTeX?

Also the package chronosys provides a nice solution. Here's an example from the user manual:

enter image description here

How to DROP multiple columns with a single ALTER TABLE statement in SQL Server?

create table test (a int, b int , c int, d int);
alter table test drop column b, d;

Be aware that DROP COLUMN does not physically remove the data, and for fixed length types (int, numeric, float, datetime, uniqueidentifier etc) the space is consumed even for records added after the columns were dropped. To get rid of the wasted space do ALTER TABLE ... REBUILD.

Changing precision of numeric column in Oracle

If the table is compressed this will work:

alter table EVAPP_FEES add AMOUNT_TEMP NUMBER(14,2);


update EVAPP_FEES set AMOUNT = null;

alter table EVAPP_FEES modify AMOUNT NUMBER(14,2);


alter table EVAPP_FEES move nocompress;

alter table EVAPP_FEES drop column AMOUNT_TEMP;

alter table EVAPP_FEES compress;

How to find all serial devices (ttyS, ttyUSB, ..) on Linux without opening them?

In recent kernels (not sure since when) you can list the contents of /dev/serial to get a list of the serial ports on your system. They are actually symlinks pointing to the correct /dev/ node:

flu0@laptop:~$ ls /dev/serial/
total 0
drwxr-xr-x 2 root root 60 2011-07-20 17:12 by-id/
drwxr-xr-x 2 root root 60 2011-07-20 17:12 by-path/
flu0@laptop:~$ ls /dev/serial/by-id/
total 0
lrwxrwxrwx 1 root root 13 2011-07-20 17:12 usb-Prolific_Technology_Inc._USB-Serial_Controller-if00-port0 -> ../../ttyUSB0
flu0@laptop:~$ ls /dev/serial/by-path/
total 0
lrwxrwxrwx 1 root root 13 2011-07-20 17:12 pci-0000:00:0b.0-usb-0:3:1.0-port0 -> ../../ttyUSB0

This is a USB-Serial adapter, as you can see. Note that when there are no serial ports on the system, the /dev/serial/ directory does not exists. Hope this helps :).

Encoding as Base64 in Java

In Java 7 I coded this method

import javax.xml.bind.DatatypeConverter;

public static String toBase64(String data) {
    return DatatypeConverter.printBase64Binary(data.getBytes());

Maven 3 Archetype for Project With Spring, Spring MVC, Hibernate, JPA

Possible duplicate: Is there a maven 2 archetype for spring 3 MVC applications?

That said, I would encourage you to think about making your own archetype. The reason is, no matter what you end up getting from someone else's, you can do better in not that much time, and a decent sized Java project is going to end up making a lot of jar projects.

How to terminate a Python script

I've just found out that when writing a multithreadded app, raise SystemExit and sys.exit() both kills only the running thread. On the other hand, os._exit() exits the whole process. This was discussed in "Why does sys.exit() not exit when called inside a thread in Python?".

The example below has 2 threads. Kenny and Cartman. Cartman is supposed to live forever, but Kenny is called recursively and should die after 3 seconds. (recursive calling is not the best way, but I had other reasons)

If we also want Cartman to die when Kenny dies, Kenny should go away with os._exit, otherwise, only Kenny will die and Cartman will live forever.

import threading
import time
import sys
import os

def kenny(num=0):
    if num > 3:
        # print("Kenny dies now...")
        # raise SystemExit #Kenny will die, but Cartman will live forever
        # sys.exit(1) #Same as above

        print("Kenny dies and also kills Cartman!")
    while True:
        print("Kenny lives: {0}".format(num))
        num += 1

def cartman():
    i = 0
    while True:
        print("Cartman lives: {0}".format(i))
        i += 1

if __name__ == '__main__':
    daemon_kenny = threading.Thread(name='kenny', target=kenny)
    daemon_cartman = threading.Thread(name='cartman', target=cartman)


How can I view live MySQL queries?

Even though an answer has already been accepted, I would like to present what might even be the simplest option:

$ mysqladmin -u bob -p -i 1 processlist

This will print the current queries on your screen every second.

  • -u The mysql user you want to execute the command as
  • -p Prompt for your password (so you don't have to save it in a file or have the command appear in your command history)
  • i The interval in seconds.
  • Use the --verbose flag to show the full process list, displaying the entire query for each process. (Thanks, nmat)

There is a possible downside: fast queries might not show up if they run between the interval that you set up. IE: My interval is set at one second and if there is a query that takes .02 seconds to run and is ran between intervals, you won't see it.

Use this option preferably when you quickly want to check on running queries without having to set up a listener or anything else.

Can you overload controller methods in ASP.NET MVC?

You can use the attribute if you want your code to do overloading.


But, you'll have to use a different action name for the same http method (as others have said). So it's just semantics at that point. Would you rather have the name in your code or your attribute?

Phil has an article related to this:

Get the Highlighted/Selected text

This solution works if you're using chrome (can't verify other browsers) and if the text is located in the same DOM Element:


How to make a node.js application run permanently?

You could simply use this

nohup node /srv/www/MyUserAccount/server/server.js &

This will keep the application running and to shut it down you will have to kill it.

For that you could install htop and then search for node and then kill it

collapse cell in jupyter notebook

You can create a cell and put the following code in it:

div.input {

Running this cell will hide all input cells. To show them back, you can use the menu to clear all outputs.

Otherwise you can try notebook extensions like below:

SQL: capitalize first letter only

Please check the query without using a function:

declare @T table(Insurance varchar(max))

insert into @T values ('wezembeek-oppem')
insert into @T values ('roeselare')
insert into @T values ('BRUGGE')
insert into @T values ('louvain-la-neuve')

select (
       select upper(T.N.value('.', 'char(1)'))+
                lower(stuff(T.N.value('.', 'varchar(max)'), 1, 1, ''))+(CASE WHEN RIGHT(T.N.value('.', 'varchar(max)'), 1)='-' THEN '' ELSE ' ' END)
       from X.InsXML.nodes('/N') as T(N)
       for xml path(''), type
       ).value('.', 'varchar(max)') as Insurance
  select cast('<N>'+replace(
                ' ', '</N><N>'),
            '-', '-</N><N>')+'</N>' as xml) as InsXML
  from @T
  ) as X

The ResourceConfig instance does not contain any root resource classes

Basically I corrected it like below and everything worked fine.

    <servlet-name >MyWebApplication</servlet-name>


Electron: jQuery is not defined

This works for me.

<script languange="JavaScript">
     if (typeof module === 'object') {window.module = module; module = undefined;}

Things to consider:

1) Put this in section right before </head>

2) Include Jquery.min.js or Jquery.js right before the </body> tag

How can I backup a remote SQL Server database to a local drive?

First, grant full control permissions to a local path on your machine (as shown below) with Everyone. (Or alternatively grant permissions specifically to the SQL Server Agent account).

Second, execute the following:

BACKUP DATABASE [dev] TO  DISK = N'\\myMachine\c\dev.bak' WITH COPY_ONLY, INIT;

comparing elements of the same array in java

Try this or purpose will solve with lesser no of steps

for (int i = 0; i < a.length; i++) 
    for (int k = i+1; k < a.length; k++) 
        if (a[i] != a[k]) 
            System.out.println(a[i]+"not the same with"+a[k]+"\n");

When to use reinterpret_cast?

One case when reinterpret_cast is necessary is when interfacing with opaque data types. This occurs frequently in vendor APIs over which the programmer has no control. Here's a contrived example where a vendor provides an API for storing and retrieving arbitrary global data:

// vendor.hpp
typedef struct _Opaque * VendorGlobalUserData;
void VendorSetUserData(VendorGlobalUserData p);
VendorGlobalUserData VendorGetUserData();

To use this API, the programmer must cast their data to VendorGlobalUserData and back again. static_cast won't work, one must use reinterpret_cast:

// main.cpp
#include "vendor.hpp"
#include <iostream>
using namespace std;

struct MyUserData {
    MyUserData() : m(42) {}
    int m;

int main() {
    MyUserData u;

        // store global data
    VendorGlobalUserData d1;
//  d1 = &u;                                          // compile error
//  d1 = static_cast<VendorGlobalUserData>(&u);       // compile error
    d1 = reinterpret_cast<VendorGlobalUserData>(&u);  // ok

        // do other stuff...

        // retrieve global data
    VendorGlobalUserData d2 = VendorGetUserData();
    MyUserData * p = 0;
//  p = d2;                                           // compile error
//  p = static_cast<MyUserData *>(d2);                // compile error
    p = reinterpret_cast<MyUserData *>(d2);           // ok

    if (p) { cout << p->m << endl; }
    return 0;

Below is a contrived implementation of the sample API:

// vendor.cpp
static VendorGlobalUserData g = 0;
void VendorSetUserData(VendorGlobalUserData p) { g = p; }
VendorGlobalUserData VendorGetUserData() { return g; }

'Java' is not recognized as an internal or external command

I corrected my path variable but command prompt need to Restart otherwise, it won't be able to verify the change to the path variable. May be helpful for someone like me. so "restart command prompt"

how to know status of currently running jobs

I found a better answer by Kenneth Fisher. The following query returns only currently running jobs:

    ja.job_id, AS job_name,
    ISNULL(last_executed_step_id,0)+1 AS current_executed_step_id,
FROM msdb.dbo.sysjobactivity ja 
LEFT JOIN msdb.dbo.sysjobhistory jh ON ja.job_history_id = jh.instance_id
JOIN msdb.dbo.sysjobs j ON ja.job_id = j.job_id
JOIN msdb.dbo.sysjobsteps js
    ON ja.job_id = js.job_id
    AND ISNULL(ja.last_executed_step_id,0)+1 = js.step_id
  ja.session_id = (
    SELECT TOP 1 session_id FROM msdb.dbo.syssessions ORDER BY agent_start_date DESC
AND start_execution_date is not null
AND stop_execution_date is null;

You can get more information about a job by adding more columns from msdb.dbo.sysjobactivity table in select clause.

How do I kill the process currently using a port on localhost in Windows?

Step 1:

Open up cmd.exe (note: you may need to run it as an administrator, but this isn't always necessary), then run the below command:

netstat -ano | findstr :<PORT>

(Replace <PORT> with the port number you want, but keep the colon)

The area circled in red shows the PID (process identifier). Locate the PID of the process that's using the port you want.

Step 2:

Next, run the following command:

taskkill /PID <PID> /F

(No colon this time)

Lastly, you can check whether the operation succeeded or not by re-running the command in "Step 1". If it was successful you shouldn't see any more search results for that port number.

Add a fragment to the URL without causing a redirect?

window.location.hash = 'something';

That is just plain JavaScript.

Your comment...

Hi, what I really need is to add only the hash... something like this: window.location.hash = '#'; but in this way nothing is added.

Try this...

window.location = '#';

Also, don't forget about the window.location.replace() method.

How do you programmatically update query params in react-router?

It can also be written this way


What is the difference between Digest and Basic Authentication?

Digest Authentication communicates credentials in an encrypted form by applying a hash function to: the username, the password, a server supplied nonce value, the HTTP method and the requested URI.

Whereas Basic Authentication uses non-encrypted base64 encoding.

Therefore, Basic Authentication should generally only be used where transport layer security is provided such as https.

See RFC-2617 for all the gory details.

What does "-ne" mean in bash?

"not equal" So in this case, $RESULT is tested to not be equal to zero.

However, the test is done numerically, not alphabetically:

n1 -ne n2     True if the integers n1 and n2 are not algebraically equal.

compared to:

s1 != s2      True if the strings s1 and s2 are not identical.

Negative matching using grep (match lines that do not contain foo)

In your case, you presumably don't want to use grep, but add instead a negative clause to the find command, e.g.

find /home/baumerf/public_html/ -mmin -60 -not -name error_log

If you want to include wildcards in the name, you'll have to escape them, e.g. to exclude files with suffix .log:

find /home/baumerf/public_html/ -mmin -60 -not -name \*.log

Ruby value of a hash key?

I didn't understand your problem clearly but I think this is what you're looking for(Based on my understanding)

  person =   {"name"=>"BillGates", "company_name"=>"Microsoft", "position"=>"Chairman"}

  person.delete_if {|key, value| key == "name"} #doing something if the key == "something"

  Output: {"company_name"=>"Microsoft", "position"=>"Chairman"}

OS X Sprite Kit Game Optimal Default Window Size

You should target the smallest, not the largest, supported pixel resolution by the devices your app can run on.

Say if there's an actual Mac computer that can run OS X 10.9 and has a native screen resolution of only 1280x720 then that's the resolution you should focus on. Any higher and your game won't correctly run on this device and you could as well remove that device from your supported devices list.

You can rely on upscaling to match larger screen sizes, but you can't rely on downscaling to preserve possibly important image details such as text or smaller game objects.

The next most important step is to pick a fitting aspect ratio, be it 4:3 or 16:9 or 16:10, that ideally is the native aspect ratio on most of the supported devices. Make sure your game only scales to fit on devices with a different aspect ratio.

You could scale to fill but then you must ensure that on all devices the cropped areas will not negatively impact gameplay or the use of the app in general (ie text or buttons outside the visible screen area). This will be harder to test as you'd actually have to have one of those devices or create a custom build that crops the view accordingly.

Alternatively you can design multiple versions of your game for specific and very common screen resolutions to provide the best game experience from 13" through 27" displays. Optimized designs for iMac (desktop) and a Macbook (notebook) devices make the most sense, it'll be harder to justify making optimized versions for 13" and 15" plus 21" and 27" screens.

But of course this depends a lot on the game. For example a tile-based world game could simply provide a larger viewing area onto the world on larger screen resolutions rather than scaling the view up. Provided that this does not alter gameplay, like giving the player an unfair advantage (specifically in multiplayer).

You should provide @2x images for the Retina Macbook Pro and future Retina Macs.



  FROM TableName

Oracle & DB2

     , LISTAGG(FieldB, ',') WITHIN GROUP (ORDER BY FieldB) AS FieldBs
  FROM TableName


     , STRING_AGG(FieldB, ',' ORDER BY FieldB) AS FieldBs
  FROM TableName

SQL Server

SQL Server ≥ 2017 & Azure SQL

     , STRING_AGG(FieldB, ',') WITHIN GROUP (ORDER BY FieldB) AS FieldBs
  FROM TableName

SQL Server ≤ 2016 (CTE included to encourage the DRY principle)

  WITH CTE_TableName AS (
       SELECT FieldA, FieldB
         FROM TableName)
SELECT t0.FieldA
     , STUFF((
       SELECT ',' + t1.FieldB
         FROM CTE_TableName t1
        WHERE t1.FieldA = t0.FieldA
        ORDER BY t1.FieldB
          FOR XML PATH('')), 1, LEN(','), '') AS FieldBs
  FROM CTE_TableName t0
 GROUP BY t0.FieldA


Ordering requires a CTE or subquery

  WITH CTE_TableName AS (
       SELECT FieldA, FieldB
         FROM TableName
        ORDER BY FieldA, FieldB)
     , GROUP_CONCAT(FieldB, ',') AS FieldBs
  FROM CTE_TableName

Without ordering

     , GROUP_CONCAT(FieldB, ',') AS FieldBs
  FROM TableName

Trusting all certificates with okHttp

SSLSocketFactory does not expose its X509TrustManager, which is a field that OkHttp needs to build a clean certificate chain. This method instead must use reflection to extract the trust manager. Applications should prefer to call sslSocketFactory(SSLSocketFactory, X509TrustManager), which avoids such reflection.

Source: OkHttp documentation

OkHttpClient.Builder builder = new OkHttpClient.Builder();

    new X509TrustManager() {
        public void checkClientTrusted([] chain, String authType) throws CertificateException {

        public void checkServerTrusted([] chain, String authType) throws CertificateException {

        public[] getAcceptedIssuers() {
            return new[]{};

How to convert hex strings to byte values in Java

String str[] = {"aa", "55"};

byte b[] = new byte[str.length];

for (int i = 0; i < str.length; i++) {
    b[i] = (byte) Integer.parseInt(str[i], 16);

Integer.parseInt(string, radix) converts a string into an integer, the radix paramter specifies the numeral system.

Use a radix of 16 if the string represents a hexadecimal number.
Use a radix of 2 if the string represents a binary number.
Use a radix of 10 (or omit the radix paramter) if the string represents a decimal number.

For further details check the Java docs:,%20int)

Pick a random value from an enum?

The only thing I would suggest is caching the result of values() because each call copies an array. Also, don't create a Random every time. Keep one. Other than that what you're doing is fine. So:

public enum Letter {

  private static final List<Letter> VALUES =
  private static final int SIZE = VALUES.size();
  private static final Random RANDOM = new Random();

  public static Letter randomLetter()  {
    return VALUES.get(RANDOM.nextInt(SIZE));

How can I use String substring in Swift 4? 'substring(to:)' is deprecated: Please use String slicing subscript with a 'partial range from' operator

When programming I often have strings with just plain A-Za-z and 0-9. No need for difficult Index actions. This extension is based on the plain old left / mid / right functions.

extension String {

    // LEFT
    // Returns the specified number of chars from the left of the string
    // let str = "Hello"
    // print(str.left(3))         // Hel
    func left(_ to: Int) -> String {
        return "\(self[..<self.index(startIndex, offsetBy: to)])"

    // RIGHT
    // Returns the specified number of chars from the right of the string
    // let str = "Hello"
    // print(str.left(3))         // llo
    func right(_ from: Int) -> String {
        return "\(self[self.index(startIndex, offsetBy: self.length-from)...])"

    // MID
    // Returns the specified number of chars from the startpoint of the string
    // let str = "Hello"
    // print(str.left(2,amount: 2))         // ll
    func mid(_ from: Int, amount: Int) -> String {
        let x = "\(self[self.index(startIndex, offsetBy: from)...])"
        return x.left(amount)

What's the net::ERR_HTTP2_PROTOCOL_ERROR about?

We experienced this problem on pages with long Base64 strings. The problem occurs because we use CloudFlare.


Key section from the forum post:

After further testing on Incognito tabs on multiple browsers, then doing the changes on the code from a BASE64 to a real .png image, the issue never happened again, in ANY browser. The .png had around 500kb before becoming a base64,so CloudFlare has issues with huge lines of text on same line (since base64 is a long string) as a proxy between the domain and the heroku. As mentioned before, directly hitting Heroku url also never happened the issue.

The temporary hack is to disable HTTP/2 on CloudFlare.

Hope someone else can produce a better solution that doesn't require disabling HTTP/2 on CloudFlare.

Difference between adjustResize and adjustPan in android?

I was also a bit confused between adjustResize and adjustPan when I was a beginner. The definitions given above are correct.
AdjustResize : Main activity's content is resized to make room for soft input i.e keyboard
AdjustPan : Instead of resizing overall contents of the window, it only pans the content so that the user can always see what is he typing
AdjustNothing : As the name suggests nothing is resized or panned. Keyboard is opened as it is irrespective of whether it is hiding the contents or not.

I have a created a example for better understanding
Below is my xml file:

<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""

        android:hint="Type Here"




Here is the design view of the xml
original view

AdjustResize Example below:
adjustResize example

AdjustPan Example below:
adjustPan example

AdjustNothing Example below:
adjustNothing example

Array as session variable

Yes, you can put arrays in sessions, example:

$_SESSION['name_here'] = $your_array;

Now you can use the $_SESSION['name_here'] on any page you want but make sure that you put the session_start() line before using any session functions, so you code should look something like this:

 $_SESSION['name_here'] = $your_array;

Possible Example:

 $_SESSION['name_here'] = $_POST;

Now you can get field values on any page like this:

 echo $_SESSION['name_here']['field_name'];

As for the second part of your question, the session variables remain there unless you assign different array data:

 $_SESSION['name_here'] = $your_array;

Session life time is set into php.ini file.

More Info Here

Java decimal formatting using String.format?

java.text.NumberFormat is probably what you want.

ShowAllData method of Worksheet class failed

The error ShowAllData method of Worksheet class failed usually occurs when you try to remove an applied filter when there is not one applied.

I am not certain if you are trying to remove the whole AutoFilter, or just remove any applied filter, but there are different approaches for each.

To remove an applied filter but leave AutoFilter on:

If ActiveSheet.AutoFilterMode Or ActiveSheet.FilterMode Then
End If

The rationale behind the above code is to test that there is an AutoFilter or whether a filter has been applied (this will also remove advanced filters).

To completely remove the AutoFilter:

ActiveSheet.AutoFilterMode = False

In the above case, you are simply disabling the AutoFilter completely.

react-native - Fit Image in containing View, not the whole screen size

Set the dimensions to the View and make sure your Image is styled with height and width set to 'undefined' like the example below :

    <View style={{width: 10, height:10 }} >
      <Image style= {{flex:1 , width: undefined, height: undefined}}    

This will make sure your image scales and fits perfectly into your view.

byte[] to hex string

Hex, Linq-fu:

string.Concat(ba.Select(b => b.ToString("X2")).ToArray())

UPDATE with the times

As noted by @RubenBartelink, the code that don't have a conversion of IEnumerable<string> to an array: ba.Select(b => b.ToString("X2")) does not work prior to 4.0, the same code is now working on 4.0.

This code...

byte[] ba = { 1, 2, 4, 8, 16, 32 };

string s = string.Concat(ba.Select(b => b.ToString("X2")));
string t = string.Concat(ba.Select(b => b.ToString("X2")).ToArray());

Console.WriteLine (s);
Console.WriteLine (t);

...prior to .NET 4.0, the output is:


On .NET 4.0 onwards, string.Concat has an overload that accepts IEnumerable. Hence on 4.0, the above code will have same output for both variables s and t


Prior to 4.0, ba.Select(b => b.ToString("X2")) goes to overload (object arg0), the way for the IEnumerable<string> to go to a proper overload, i.e. (params string[] values), is we need to convert the IEnumerable<string> to string array. Prior to 4.0, string.Concat has 10 overload functions, on 4.0 it is now 12

Overriding !important style has a setProperty method that can take the priority as a third parameter:"display", "inline", "important")

It didn't work in old IEs but it should be fine in current browsers.

qmake: could not find a Qt installation of ''

I have qt4 installed. I found that using the following path worked for me, despite 'which qmake' returning /usr/bin/qmake, which is just a link to qtchooser anyway.

The following path works for me, on a 64 bit system. Running from the full path of:


nil detection in Go

You can also check like struct_var == (struct{}). This does not allow you to compare to nil but it does check if it is initialized or not. Be careful while using this method. If your struct can have zero values for all of its fields you won't have great time.

package main

import "fmt"

type A struct {
    Name string

func main() {
    a := A{"Hello"}
    var b A

    if a == (A{}) {
        fmt.Println("A is empty") // Does not print

    if b == (A{}) {
        fmt.Println("B is empty") // Prints

find difference between two text files with one item per line



>awk 'NR == FNR {file1[$0]++; next} !($0 in file1)' file1 file2

>awk 'NR == FNR {file1[$0]++; next} ($0 in file1)' file1 file2

> What's awk command to get 'm1 and m3' ??  as in file1 and not in file2? 

How to convert DataSet to DataTable

A DataSet already contains DataTables. You can just use:

DataTable firstTable = dataSet.Tables[0];

or by name:

DataTable customerTable = dataSet.Tables["Customer"];

Note that you should have using statements for your SQL code, to ensure the connection is disposed properly:

using (SqlConnection conn = ...)
    // Code here...

Foreach Control in form, how can I do something to all the TextBoxes in my Form?

A lot of the above work. Just to add. If your textboxes are not directly on the form but are on other container objects like a GroupBox, you will have to get the GroupBox object and then iterate through the GroupBox to access the textboxes contained therein.

foreach(Control t in this.Controls.OfType<GroupBox>())
   foreach (Control tt in t.Controls.OfType<TextBox>())
        // do stuff

Is mathematics necessary for programming?

See also Is Programmng == Math? from stackoverflow.

While I don't think it's required for programming, I can't tell you how many times I've been able to use linear algebra concepts to write a clear and short solution to replace a convoluted (and sometimes incorrect) one. When dong any graphics or geometry (and even some solver) work, knowledge of matrices and how to work with them has also been extremely useful.

What does <> mean?

could be a shorthand for React.Fragment

How to convert Javascript datetime to C# datetime?

JavaScript (HTML5)

function TimeHelper_GetDateAndFormat() {
    var date = new Date();

    return MakeValid(date.getDate()).concat(
        MakeValid(date.getMonth() + 1),

function MakeValid(timeRegion) {
    return timeRegion !== undefined && timeRegion < 10 ? ("0" + timeRegion).toString() : timeRegion.toString();


private const string DATE_FORMAT = "dd/MM/yyyy HH:mm:ss";

public DateTime? JavaScriptDateParse(string dateString)
    DateTime date;
    return DateTime.TryParseExact(dateString, DATE_FORMAT, CultureInfo.InvariantCulture, DateTimeStyles.None, out date) ? date : null;

Auto-increment primary key in SQL tables

Right-click on the table in SSMS, 'Design' it, and click on the id column. In the properties, set the identity to be seeded @ e.g. 1 and to have increment of 1 - save and you're done.

Adding devices to team provisioning profile

All answers I've seen above assumed that the developer owns an iPhone. No one knows the right answer. As far as I know, you need:

  • a physical iPhone that you own
  • or UDID of someone else's iPhone. But it is a must to have an iPhone before you publish your app. Correct me if I am wrong.

Simple way to get element by id within a div tag?

In HTML ids should be unique. I suggest you change your code to something like this:

<div id="div1" >
    <input type="text" name="edit1" id="edit1" />
    <input type="text" name="edit2" id="edit2" />
<div id="div2" >
    <input type="text" name="edit1" id="edit3" />
    <input type="text" name="edit2" id="edit4" />

How do I launch the Android emulator from the command line?

I think the best way to reach it via terminal is :

cd ~/Library/Android/sdk/emulator

To run a certain AVD directly:

./emulator -avd {AVD_NAME}

To list your AVDs use :

./emulator -list-avds

how to convert rgb color to int in java

Use getRGB(), it helps ( no complicated programs )

Returns an array of integer pixels in the default RGB color model (TYPE_INT_ARGB) and default sRGB color space, from a portion of the image data.

Getting the textarea value of a ckeditor textarea with javascript

Well. You asked about get value from textarea but in your example you are using a input. Anyways, here we go:

$("#CampaignTitle").bind("keyup", function()

If you really wanted a textarea change your input type text to this

<textarea id="CampaignTitle"></textarea>

Hope it helps.

How to initialize a static array?

Nope, no difference. It's just syntactic sugar. Arrays.asList(..) creates an additional list.

jquery fill dropdown with json data

In most of the companies they required a common functionality for multiple dropdownlist for all the pages. Just call the functions or pass your (DropDownID,JsonData,KeyValue,textValue)




        var data = [{"stateid" : "1","statename" : "Mumbai"},
                    {"stateid" : "2","statename" : "Panjab"},
                    {"stateid" : "3","statename" : "Pune"},
                     {"stateid" : "4","statename" : "Nagpur"},
                     {"stateid" : "5","statename" : "kanpur"}];

        var Did=document.getElementById("DLState");

        function GetData(Did,data,valkey,textkey){
          var str= "";
          for (var i = 0; i <data.length ; i++){


            str+= "<option value='" + data[i][valkey] + "'>" + data[i][textkey] + "</option>";

        };    </script>

  <select id="DLState">

Combine two tables for one output

You'll need to use UNION to combine the results of two queries. In your case:

SELECT ChargeNum, CategoryID, SUM(Hours)
FROM KnownHours
GROUP BY ChargeNum, CategoryID
SELECT ChargeNum, 'Unknown' AS CategoryID, SUM(Hours)
FROM UnknownHours
GROUP BY ChargeNum

Note - If you use UNION ALL as in above, it's no slower than running the two queries separately as it does no duplicate-checking.

What does elementFormDefault do in XSD?

Consider the following ComplexType AuthorType used by author element

<xsd:complexType name="AuthorType">
  <!-- compositor goes here -->
     <xsd:element name="name" type="xsd:string"/>
     <xsd:element name="phone" type="tns:Phone"/>
  <xsd:attribute name="id" type="tns:AuthorId"/>
<xsd:element name="author" type="tns:AuthorType"/>

If elementFormDefault="unqualified"

then following XML Instance is valid

<x:author xmlns:x="">
   <name>Aaron Skonnard</name>

the authors's name attribute is allowed without specifying the namespace(unqualified). Any elements which are a part of <xsd:complexType> are considered as local to complexType.

if elementFormDefault="qualified"

then the instance should have the local elements qualified

<x:author xmlns:x="">
   <x:name>Aaron Skonnard</name>

please refer this link for more details

Responsive font size in CSS

We can use calc() from css

font-size: calc(48px + (56 - 48) * ((100vw - 300px) / (1600 - 300))) !important;

The mathematical formula is calc(minsize + (maxsize - minsize) * (100vm - minviewportwidth) / (maxwidthviewoport - minviewportwidth)))


Get current application physical path within Application_Start

use below code

server.mappath() in

application.startuppath in c# windows application

Using SQL LOADER in Oracle to import CSV file

Sqlldr wants to write a log file in the same directory where the control file is. But obviously it can't. It probably doesn't have the required permission.

If you're on Linux or Unix, try to run the following command the same way you run sqldr:

touch Billing.log

It will show whether you have the permissions.


The proper command line is:

sqlldr myusername/mypassword control=Billing.ctl

Prevent flex items from stretching

You don't want to stretch the span in height?
You have the possiblity to affect one or more flex-items to don't stretch the full height of the container.

To affect all flex-items of the container, choose this:
You have to set align-items: flex-start; to div and all flex-items of this container get the height of their content.

div {_x000D_
  align-items: flex-start;_x000D_
  background: tan;_x000D_
  display: flex;_x000D_
  height: 200px;_x000D_
span {_x000D_
  background: red;_x000D_
  <span>This is some text.</span>_x000D_

To affect only a single flex-item, choose this:
If you want to unstretch a single flex-item on the container, you have to set align-self: flex-start; to this flex-item. All other flex-items of the container aren't affected.

div {_x000D_
  display: flex;_x000D_
  height: 200px;_x000D_
  background: tan;_x000D_
span.only {_x000D_
  background: red;_x000D_
span {_x000D_
  <span class="only">This is some text.</span>_x000D_
  <span>This is more text.</span>_x000D_

Why is this happening to the span?
The default value of the property align-items is stretch. This is the reason why the span fill the height of the div.

Difference between baseline and flex-start?
If you have some text on the flex-items, with different font-sizes, you can use the baseline of the first line to place the flex-item vertically. A flex-item with a smaller font-size have some space between the container and itself at top. With flex-start the flex-item will be set to the top of the container (without space).

div {_x000D_
  align-items: baseline;_x000D_
  background: tan;_x000D_
  display: flex;_x000D_
  height: 200px;_x000D_
span {_x000D_
  background: red;_x000D_
span.fontsize {_x000D_
  <span class="fontsize">This is some text.</span>_x000D_
  <span>This is more text.</span>_x000D_

You can find more information about the difference between baseline and flex-start here:
What's the difference between flex-start and baseline?

How to remove provisioning profiles from Xcode

. Simple Steps:

1:Click finder

2:Right click on Finder
3:click on goto folder

4: Paste in Search : ~/Library/MobileDevice/Provisioning Profiles

5:Click on Go

6:List of the Profiles .you can delete any one


You'll want to restart XCode to refresh the list.

Connection refused to MongoDB errno 111

I Didn't have a /data/db directory. I created one and gave a chmod 777 permission and it worked for me

Convert command line argument to string

It's already an array of C-style strings:

#include <iostream>
#include <string>
#include <vector>

int main(int argc, char *argv[]) // Don't forget first integral argument 'argc'
  std::string current_exec_name = argv[0]; // Name of the current exec program
  std::vector<std::string> all_args;

  if (argc > 1) {
    all_args.assign(argv + 1, argv + argc);

Argument argc is count of arguments plus the current exec file.

Add php variable inside echo statement as href link address?

This worked much better in my case.

HTML in PHP: <a href=".$link_address.">Link</a>

How to display image from database using php

$sqlimage  = "SELECT image FROM userdetail where `id` = $id1";
    $imageresult1 = mysqli_query($link, $sqlimage);


    echo "<img src = 'Image/".$row['image'].'" />';


How do I release memory used by a pandas dataframe?

This solves the problem of releasing the memory for me!!!

import gc
import pandas as pd

del [[df_1,df_2]]

the data-frame will be explicitly set to null

in the above statements

Firstly, the self reference of the dataframe is deleted meaning the dataframe is no longer available to python there after all the references of the dataframe is collected by garbage collector (gc.collect()) and then explicitly set all the references to empty dataframe.

more on the working of garbage collector is well explained in

How to output numbers with leading zeros in JavaScript?

NOTE: Potentially outdated. ECMAScript 2017 includes String.prototype.padStart.

You'll have to convert the number to a string since numbers don't make sense with leading zeros. Something like this:

function pad(num, size) {
    num = num.toString();
    while (num.length < size) num = "0" + num;
    return num;

Or, if you know you'd never be using more than X number of zeros, this might be better. This assumes you'd never want more than 10 digits.

function pad(num, size) {
    var s = "000000000" + num;
    return s.substr(s.length-size);

If you care about negative numbers you'll have to strip the - and read it.

Split string with delimiters in C

This optimized method create (or update an existing) array of pointers in *result and returns the number of elements in *count.

Use "max" to indicate the maximum number of strings you expect (when you specify an existing array or any other reaseon), else set it to 0

To compare against a list of delimiters, define delim as a char* and replace the line:

if (str[i]==delim) {

with the two following lines:

 char *c=delim; while(*c && *c!=str[i]) c++;
 if (*c) {


#include <stdlib.h>
#include <string.h>

char **split(char *str, size_t len, char delim, char ***result, unsigned long *count, unsigned long max) {
  size_t i;
  char **_result;

  // there is at least one string returned

  _result= *result;

  // when the result array is specified, fill it during the first pass
  if (_result) {

  // scan the string for delimiter, up to specified length
  for (i=0; i<len; ++i) {

    // to compare against a list of delimiters,
    // define delim as a string and replace 
    // the next line:
    //     if (str[i]==delim) {
    // with the two following lines:
    //     char *c=delim; while(*c && *c!=str[i]) c++;
    //     if (*c) {
    if (str[i]==delim) {

      // replace delimiter with zero

      // when result array is specified, fill it during the first pass
      if (_result) {

      // increment count for each separator found

      // if max is specified, dont go further
      if (max && *count==max)  {


  // when result array is specified, we are done here
  if (_result) {
    return _result;

  // else allocate memory for result
  // and fill the result array                                                                                    

  if (!*result) {
    return NULL;

  // add first string to result

  // if theres more strings
  for (i=1; i<*count; ++i) {

    // find next string
    while(*str) ++str;

    // add next string to result


  return _result;

Usage example:

#include <stdio.h>

int main(int argc, char **argv) {
  char **result=malloc(6*sizeof(char*));
  char **result2=0;
  unsigned long count;
  unsigned long count2;
  unsigned long i;


  if (result)
  for (i=0; i<count; ++i) {


  if (result2)
  for (i=0; i<count2; ++i) {
    printf("%s\n", result2[i]);

  return 0;


Android Relative Layout Align Center

You can use gravity with aligning top and bottom.


How to Correctly Use Lists in R?

You say:

For another, lists can be returned from functions even though you never passed in a List when you called the function, and even though the function doesn't contain a List constructor, e.g.,

x = strsplit(LETTERS[1:10], "") # passing in an object of type 'character'
# => 'list'

And I guess you suggest that this is a problem(?). I'm here to tell you why it's not a problem :-). Your example is a bit simple, in that when you do the string-split, you have a list with elements that are 1 element long, so you know that x[[1]] is the same as unlist(x)[1]. But what if the result of strsplit returned results of different length in each bin. Simply returning a vector (vs. a list) won't do at all.

For instance:

stuff <- c("You, me, and dupree",  "You me, and dupree",
           "He ran away, but not very far, and not very fast")
x <- strsplit(stuff, ",")
xx <- unlist(strsplit(stuff, ","))

In the first case (x : which returns a list), you can tell what the 2nd "part" of the 3rd string was, eg: x[[3]][2]. How could you do the same using xx now that the results have been "unraveled" (unlist-ed)?

How do I ignore all files in a folder with a Git repository in Sourcetree?

As mentioned by others: git doesn't track folders, only files.

You can ensure a folder exists with these commands (or equivalent logic):

echo "*" > keepthisfolder/.gitignore
git add --force keepthisfolder/.gitignore
git commit -m "adding git ignore file to keepthisfolder"

The existence of the file will mean anyone checking out the repository will have the folder.

The contents of the gitignore file will mean anything in it are ignored

You do not need to not-ignore the .gitignore file itself. It is a rule which would serve no purpose at all once committed.


if you prefer to keep all your ignore definitions in the same place, you can create .gitignore in the root of your project with contents like so:

*.tmp # example, ignore all .tmp files in any folder

and to ensure the folders exist

touch path/to/keepthisfolder/anything
git add --force path/to/keepthisfolder/anything
git commit -m "ensure keepthisfolder exists when checked out"

"anything" can literally be anything. Common used names are .gitignore, .gitkeep, empty.

Count(*) vs Count(1) - SQL Server

There is an article showing that the COUNT(1) on Oracle is just an alias to COUNT(*), with a proof about that.

I will quote some parts:

There is a part of the database software that is called “The Optimizer”, which is defined in the official documentation as “Built-in database software that determines the most efficient way to execute a SQL statement“.

One of the components of the optimizer is called “the transformer”, whose role is to determine whether it is advantageous to rewrite the original SQL statement into a semantically equivalent SQL statement that could be more efficient.

Would you like to see what the optimizer does when you write a query using COUNT(1)?

With a user with ALTER SESSION privilege, you can put a tracefile_identifier, enable the optimizer tracing and run the COUNT(1) select, like: SELECT /* test-1 */ COUNT(1) FROM employees;.

After that, you need to localize the trace files, what can be done with SELECT VALUE FROM V$DIAG_INFO WHERE NAME = 'Diag Trace';. Later on the file, you will find:


As you can see, it's just an alias for COUNT(*).

Another important comment: the COUNT(*) was really faster two decades ago on Oracle, before Oracle 7.3:

Count(1) has been rewritten in count(*) since 7.3 because Oracle like to Auto-tune mythic statements. In earlier Oracle7, oracle had to evaluate (1) for each row, as a function, before DETERMINISTIC and NON-DETERMINISTIC exist.

So two decades ago, count(*) was faster

For another databases as Sql Server, it should be researched individually for each one.

I know that this question is specific for Sql Server, but the other questions on SO about the same subject, without mention the database, was closed and marked as duplicated from this answer.

Getting Image from API in Angular 4/5+?

You should set responseType: ResponseContentType.Blob in your GET-Request settings, because so you can get your image as blob and convert it later da base64-encoded source. You code above is not good. If you would like to do this correctly, then create separate service to get images from API. Beacuse it ism't good to call HTTP-Request in components.

Here is an working example:

Create image.service.ts and put following code:

Angular 4:

getImage(imageUrl: string): Observable<File> {
    return this.http
        .get(imageUrl, { responseType: ResponseContentType.Blob })
        .map((res: Response) => res.blob());

Angular 5+:

getImage(imageUrl: string): Observable<Blob> {
  return this.httpClient.get(imageUrl, { responseType: 'blob' });

Important: Since Angular 5+ you should use the new HttpClient.

The new HttpClient returns JSON by default. If you need other response type, so you can specify that by setting responseType: 'blob'. Read more about that here.

Now you need to create some function in your image.component.ts to get image and show it in html.

For creating an image from Blob you need to use JavaScript's FileReader. Here is function which creates new FileReader and listen to FileReader's load-Event. As result this function returns base64-encoded image, which you can use in img src-attribute:

imageToShow: any;

createImageFromBlob(image: Blob) {
   let reader = new FileReader();
   reader.addEventListener("load", () => {
      this.imageToShow = reader.result;
   }, false);

   if (image) {

Now you should use your created ImageService to get image from api. You should to subscribe to data and give this data to createImageFromBlob-function. Here is an example function:

getImageFromService() {
      this.isImageLoading = true;
      this.imageService.getImage(yourImageUrl).subscribe(data => {
        this.isImageLoading = false;
      }, error => {
        this.isImageLoading = false;

Now you can use your imageToShow-variable in HTML template like this:

<img [src]="imageToShow"
     alt="Place image title"
     *ngIf="!isImageLoading; else noImageFound">
<ng-template #noImageFound>
     <img src="fallbackImage.png" alt="Fallbackimage">

I hope this description is clear to understand and you can use it in your project.

See the working example for Angular 5+ here.

Leader Not Available Kafka in Console Producer

What solved it for me is to set listeners like so:

advertised.listeners = PLAINTEXT://my.public.ip:9092
listeners = PLAINTEXT://

This makes KAFKA broker listen to all interfaces.

How can I display an image from a file in Jupyter Notebook?

When using GenomeDiagram with Jupyter (iPython), the easiest way to display images is by converting the GenomeDiagram to a PNG image. This can be wrapped using an IPython.display.Image object to make it display in the notebook.

from Bio.Graphics import GenomeDiagram
from Bio.SeqFeature import SeqFeature, FeatureLocation
from IPython.display import display, Image
gd_diagram = GenomeDiagram.Diagram("Test diagram")
gd_track_for_features = gd_diagram.new_track(1, name="Annotated Features")
gd_feature_set = gd_track_for_features.new_set()
gd_feature_set.add_feature(SeqFeature(FeatureLocation(25, 75), strand=+1))
gd_diagram.draw(format="linear", orientation="landscape", pagesize='A4',
                fragments=1, start=0, end=100)

[See Notebook]

Copy table without copying data





How do I run Selenium in Xvfb?

You can use PyVirtualDisplay (a Python wrapper for Xvfb) to run headless WebDriver tests.

#!/usr/bin/env python

from pyvirtualdisplay import Display
from selenium import webdriver

display = Display(visible=0, size=(800, 600))

# now Firefox will run in a virtual display. 
# you will not see the browser.
browser = webdriver.Firefox()
print browser.title


more info

You can also use xvfbwrapper, which is a similar module (but has no external dependencies):

from xvfbwrapper import Xvfb

vdisplay = Xvfb()

# launch stuff inside virtual display here


or better yet, use it as a context manager:

from xvfbwrapper import Xvfb

with Xvfb() as xvfb:
    # launch stuff inside virtual display here.
    # It starts/stops in this code block.

How to correct TypeError: Unicode-objects must be encoded before hashing?

If it's a single line string. wrapt it with b or B. e.g:

variable = b"This is a variable"


variable2 = B"This is also a variable"

How is a JavaScript hash map implemented?

I was running into the problem where i had the json with some common keys. I wanted to group all the values having the same key. After some surfing I found hashmap package. Which is really helpful.

To group the element with the same key, I used multi(key:*, value:*, key2:*, value2:*, ...).

This package is somewhat similar to Java Hashmap collection, but not as powerful as Java Hashmap.

Select columns in PySpark dataframe

First two columns and 5 rows[:2]).take(5)

PHP Warning: PHP Startup: ????????: Unable to initialize module

Looks like you haven't upgraded PHP modules, they are not compatible.

Check extension_dir directive in your php.ini. It should point to folder with 5.2 modules.

Create and open a phpinfo file and search for extension_dir to find the path.

Since you did upgrade, there is a chance that you are using old php.ini that is pointing to 5.1 modules

calling a java servlet from javascript

   function callServlet()

 document.getElementById("adminForm").method = "GET";


<button type="submit"  onclick="callServlet()" align="center"> Register</button>

How to change button background image on mouseOver?

You can create a class based on a Button with specific images for MouseHover and MouseDown like this:

public class AdvancedImageButton : Button {

public Image HoverImage { get; set; }
public Image PlainImage { get; set; }
public Image PressedImage { get; set; }

protected override void OnMouseEnter(System.EventArgs e)
  if (HoverImage == null) return;
  if (PlainImage == null) PlainImage = base.Image;
  base.Image = HoverImage;

protected override void OnMouseLeave(System.EventArgs e)
  if (HoverImage == null) return;
  base.Image = PlainImage;

protected override void OnMouseDown(MouseEventArgs e)
  if (PressedImage == null) return;
  if (PlainImage == null) PlainImage = base.Image;
  base.Image = PressedImage;


This solution has a small drawback that I am sure can be fixed: when you need for some reason change the Image property, you will also have to change the PlainImage property also.

PHP append one array to another (not array_push or +)

Following on from answer's by bstoney and Snark I did some tests on the various methods:

// Test 1 (array_merge)
$array1 = $array2 = array_fill(0, 50000, 'aa');
$start = microtime(true);
$array1 = array_merge($array1, $array2);
echo sprintf("Test 1: %.06f\n", microtime(true) - $start);

// Test2 (foreach)
$array1 = $array2 = array_fill(0, 50000, 'aa');
$start = microtime(true);
foreach ($array2 as $v) {
    $array1[] = $v;
echo sprintf("Test 2: %.06f\n", microtime(true) - $start);

// Test 3 (... token)
// PHP 5.6+ and produces error if $array2 is empty
$array1 = $array2 = array_fill(0, 50000, 'aa');
$start = microtime(true);
array_push($array1, ...$array2);
echo sprintf("Test 3: %.06f\n", microtime(true) - $start);

Which produces:

Test 1: 0.002717 
Test 2: 0.006922 
Test 3: 0.004744

ORIGINAL: I believe as of PHP 7, method 3 is a significantly better alternative due to the way foreach loops now act, which is to make a copy of the array being iterated over.

Whilst method 3 isn't strictly an answer to the criteria of 'not array_push' in the question, it is one line and the most high performance in all respects, I think the question was asked before the ... syntax was an option.

UPDATE 25/03/2020: I've updated the test which was flawed as the variables weren't reset. Interestingly (or confusingly) the results now show as test 1 being the fastest, where it was the slowest, having gone from 0.008392 to 0.002717! This can only be down to PHP updates, as this wouldn't have been affected by the testing flaw.

So, the saga continues, I will start using array_merge from now on!

How to embed a PDF?

do you know about it is a project by mozila to render pdf inside of your html using canvas. it is super simple to use.

twitter bootstrap autocomplete dropdown / combobox with Knockoutjs

Have a look at Select2 for Bootstrap. It should be able to do everything you need.

Another good option is Selectize.js. It feels a bit more native to Bootstrap.

How to create a private class method?

ExiRe wrote:

Such behavior of ruby is really frustrating. I mean if you move to private section self.method then it is NOT private. But if you move it to class << self then it suddenly works. It is just disgusting.

Confusing it probably is, frustrating it may well be, but disgusting it is definitely not.

It makes perfect sense once you understand Ruby's object model and the corresponding method lookup flow, especially when taking into consideration that private is NOT an access/visibility modifier, but actually a method call (with the class as its recipient) as discussed here... there's no such thing as "a private section" in Ruby.

To define private instance methods, you call private on the instance's class to set the default visibility for subsequently defined methods to private... and hence it makes perfect sense to define private class methods by calling private on the class's class, ie. its metaclass.

Other mainstream, self-proclaimed OO languages may give you a less confusing syntax, but you definitely trade that off against a confusing and less consistent (inconsistent?) object model without the power of Ruby's metaprogramming facilities.

Converting JSON to XLS/CSV in Java

You could only convert a JSON array into a CSV file.

Lets say, you have a JSON like the following :

{"infile": [{"field1": 11,"field2": 12,"field3": 13},
            {"field1": 21,"field2": 22,"field3": 23},
            {"field1": 31,"field2": 32,"field3": 33}]}

Lets see the code for converting it to csv :


import org.json.CDL;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class JSON2CSV {
    public static void main(String myHelpers[]){
        String jsonString = "{\"infile\": [{\"field1\": 11,\"field2\": 12,\"field3\": 13},{\"field1\": 21,\"field2\": 22,\"field3\": 23},{\"field1\": 31,\"field2\": 32,\"field3\": 33}]}";

        JSONObject output;
        try {
            output = new JSONObject(jsonString);

            JSONArray docs = output.getJSONArray("infile");

            File file=new File("/tmp2/fromJSON.csv");
            String csv = CDL.toString(docs);
            FileUtils.writeStringToFile(file, csv);
        } catch (JSONException e) {
        } catch (IOException e) {
            // TODO Auto-generated catch block


Now you got the CSV generated from JSON.

It should look like this:


The maven dependency was like,


Update Dec 13, 2019:

Updating the answer, since now we can support complex JSON Arrays as well.

import java.nio.file.Files;
import java.nio.file.Paths;

import com.github.opendevl.JFlat;

public class FlattenJson {

    public static void main(String[] args) throws Exception {
        String str = new String(Files.readAllBytes(Paths.get("path_to_imput.json")));

        JFlat flatMe = new JFlat(str);

        //get the 2D representation of JSON document

        //write the 2D representation in csv format


dependency and docs details are in link

BigDecimal setScale and round

One important point that is alluded to but not directly addressed is the difference between "precision" and "scale" and how they are used in the two statements. "precision" is the total number of significant digits in a number. "scale" is the number of digits to the right of the decimal point.

The MathContext constructor only accepts precision and RoundingMode as arguments, and therefore scale is never specified in the first statement.

setScale() obviously accepts scale as an argument, as well as RoundingMode, however precision is never specified in the second statement.

If you move the decimal point one place to the right, the difference will become clear:

// 1.
new BigDecimal("35.3456").round(new MathContext(4, RoundingMode.HALF_UP));
//result = 35.35
// 2.
new BigDecimal("35.3456").setScale(4, RoundingMode.HALF_UP);
// result = 35.3456

How do I add FTP support to Eclipse?

I'm not sure if this works for you, but when I do small solo PHP projects with Eclipse, the first thing I set up is an Ant script for deploying the project to a remote testing environment. I code away locally, and whenever I want to test it, I just hit the shortcut which updates the remote site.

Eclipse has good Ant support out of the box, and the scripts aren't hard to make.

How to convert an array of key-value tuples into an object

In my case, all other solutions didn't work, but this one did:

obj = {...arr}

my arr is in a form: [name: "the name", email: "[email protected]"]

UICollectionView - dynamic cell height?

It worked for me, hope you too.

*Note: I have used auto layout in Nib, remember add top and bottom contraints for subviews in contentView

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
           let cell = YourCollectionViewCell.instantiateFromNib()
           cell.frame.size.width = collectionView.frame.width
           let resizing = cell.systemLayoutSizeFitting(UILayoutFittingCompressedSize, withHorizontalFittingPriority: UILayoutPriority.required, verticalFittingPriority: UILayoutPriority.fittingSizeLevel)
           return resizing

When is the init() function run?

See this picture. :)

import --> const --> var --> init()

  1. If a package imports other packages, the imported packages are initialized first.

  2. Current package's constant initialized then.

  3. Current package's variables are initialized then.

  4. Finally, init() function of current package is called.

A package can have multiple init functions (either in a single file or distributed across multiple files) and they are called in the order in which they are presented to the compiler.

A package will be initialised only once even if it is imported from multiple packages.

How to compare only date components from DateTime in EF?

If you use the Date property for DB Entities you will get exception:

"The specified type member 'Date' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported."

You can use something like this:

  DateTime date = DateTime.Now.Date;

  var result = from client in context.clients
               where client.BirthDate >= date
                     && client.BirthDate < date.AddDays(1)
               select client;

Calculating time difference between 2 dates in minutes

I think you could use TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2) something like

select * from MyTab T where

DateTime.Now.ToShortDateString(); replace month and day

Use DateTime.ToString with the specified format MM.dd.yyyy:

this.TextBox3.Text = DateTime.Now.ToString("MM.dd.yyyy");

Here, MM means the month from 01 to 12, dd means the day from 01 to 31 and yyyy means the year as a four-digit number.

Neither BindingResult nor plain target object for bean name available as request attribute

I had a similar problem in IntelliJ IDEA. My code was 100% correct, but after starting the Tomcat, you receive an exception. java.lang.IllegalStateException: Neither BindingResult

I just removed and added again Tomcat configuration. And it worked for me.

A picture Tomcat configuration

enter image description here

Configuring diff tool with .gitconfig

In Windows we need to run $git difftool --tool-help command to see the various options like:

    'git difftool --tool=<tool>' may be set to one of the following:

    The following tools are valid, but not currently available:
Some of the tools listed above only work in a windowed
environment. If run in a terminal-only session, they will fail.

and we can add any of them(for example winmerge) like

$  git difftool --tool=winmerge

For configuring notepad++ to see files before committing:

 git config --global core.editor "'C:/Program Files/Notepad++/notepad++.exe' -multiInst -notabbar -nosession -noPlugin"

and using $ git commit will open the commit information in notepad++

How to set the initial zoom/width for a webview

//for images and swf videos use width as "100%" and height as "98%"


Html helper for <input type="file" />

You can also use:

@using (Html.BeginForm("Upload", "File", FormMethod.Post, new { enctype = "multipart/form-data" }))
        <input type="file" id="fileUpload" name="fileUpload" size="23" />
        <input type="submit" value="Upload file" /></p> 

Match whitespace but not newlines

Perl versions 5.10 and later support subsidiary vertical and horizontal character classes, \v and \h, as well as the generic whitespace character class \s

The cleanest solution is to use the horizontal whitespace character class \h. This will match tab and space from the ASCII set, non-breaking space from extended ASCII, or any of these Unicode characters

U+0020 SPACE
U+00A0 NO-BREAK SPACE (not matched by \s)

U+2000 EN QUAD
U+2001 EM QUAD

The vertical space pattern \v is less useful, but matches these characters

U+0085 NEXT LINE (not matched by \s)


There are seven vertical whitespace characters which match \v and eighteen horizontal ones which match \h. \s matches twenty-three characters

All whitespace characters are either vertical or horizontal with no overlap, but they are not proper subsets because \h also matches U+00A0 NO-BREAK SPACE, and \v also matches U+0085 NEXT LINE, neither of which are matched by \s

How to set Oracle's Java as the default Java in Ubuntu?

to set Oracle's Java SE Development Kit as the system default Java just download the latest Java SE Development Kit from here then create a directory somewhere you like in your file system for example /usr/java now extract the files you just downloaded in that directory:

$ sudo tar xvzf jdk-8u5-linux-i586.tar.gz -C /usr/java

now to set your JAVA_HOME environment variable:

$ JAVA_HOME=/usr/java/jdk1.8.0_05/
$ sudo update-alternatives --install /usr/bin/java java ${JAVA_HOME%*/}/bin/java 20000
$ sudo update-alternatives --install /usr/bin/javac javac ${JAVA_HOME%*/}/bin/javac 20000

make sure the Oracle's java is set as default java by:

$ update-alternatives --config java

you get something like this:

There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                           Priority   Status
* 0            /opt/java/jdk1.8.0_05/bin/java                  20000     auto mode
  1            /opt/java/jdk1.8.0_05/bin/java                  20000     manual mode
  2            /usr/lib/jvm/java-6-openjdk-i386/jre/bin/java   1061      manual mode

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

pay attention to the asterisk before the numbers on the left and if the correct one is not set choose the correct one by typing the number of it and pressing enter. now test your java:

$ java -version

if you get something like the following, you are good to go:

java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) Server VM (build 25.5-b02, mixed mode)

also note that you might need root permission or be in sudoers group to be able to do this. I've tested this solution on both ubuntu 12.04 and Debian wheezy and it works in both of them.

What does <value optimized out> mean in gdb?

You need to turn off the compiler optimisation.

If you are interested in a particular variable in gdb, you can delare the variable as "volatile" and recompile the code. This will make the compiler turn off compiler optimization for that variable.

volatile int quantity = 0;

Group query results by month and year in postgresql

Take a look at example E of this tutorial ->

You need to call the function on your GROUP BY instead of calling the name of the virtual attribute you created on select. I was doing what all the answers above recommended and I was getting a column 'year_month' does not exist error.

What worked for me was:

    date_trunc('month', created_at), 'MM/YYYY' AS month
    date_trunc('month', created_at)

How to use Greek symbols in ggplot2?

Use expression(delta) where 'delta' for lowercase d and 'Delta' to get capital ?.

Here's full list of Greek characters:

? a alpha
? ß beta
G ? gamma
? d delta
? e epsilon
? ? zeta
? ? eta
T ? theta
? ? iota
? ? kappa
? ? lambda
? µ mu
? ? nu
? ? xi
? ? omicron
? p pi
? ? rho
S s sigma
? t tau
? ? upsilon
F f phi
? ? chi
? ? psi
O ? omega

EDIT: Copied from comments, when using in conjunction with other words use like: expression(Delta*"price")

How can I add a table of contents to a Jupyter / JupyterLab notebook?

There is an ipython nbextension that constructs a table of contents for a notebook. It seems to only provide navigation, not section folding.

Facebook page automatic "like" URL (for QR Code)

For a hyperlink just use ID++/like


To make it work with here's what you do:

Open the Facebook page you're looking for then change the URL to the mobile URL ( which is ).

Now you should see a big version of the mobile Facebook page. Copy the target URL of the like button.

Pop that URL into the QR generator to make a "scan to like" barcode. This will open the m.Facebook page in the browser of most mobiles directly from the QR reader. If they are not logged into Facebook then they will be prompted to log in and then click 'like'. If logged in, it will auto like.

Hope this helps!

Also, definitely include something with a "click here/scan here to like us on Facebook"

Implementation difference between Aggregation and Composition in Java

Aggregation vs Composition

Aggregation implies a relationship where the child can exist independently of the parent. For example, Bank and Employee, delete the Bank and the Employee still exist.

whereas Composition implies a relationship where the child cannot exist independent of the parent. Example: Human and heart, heart don’t exist separate to a Human.

Aggregation relation is “has-a” and composition is “part-of” relation.

Composition is a strong Association whereas Aggregation is a weak Association.

Why aren't python nested functions called closures?

Python has a weak support for closure. To see what I mean take the following example of a counter using closure with JavaScript:

function initCounter(){
    var x = 0;
    function counter  () {
        x += 1;
    return counter;

count = initCounter();

count(); //Prints 1
count(); //Prints 2
count(); //Prints 3

Closure is quite elegant since it gives functions written like this the ability to have "internal memory". As of Python 2.7 this is not possible. If you try

def initCounter():
    x = 0;
    def counter ():
        x += 1 ##Error, x not defined
        print x
    return counter

count = initCounter();

count(); ##Error

You'll get an error saying that x is not defined. But how can that be if it has been shown by others that you can print it? This is because of how Python it manages the functions variable scope. While the inner function can read the outer function's variables, it cannot write them.

This is a shame really. But with just read-only closure you can at least implement the function decorator pattern for which Python offers syntactic sugar.


As its been pointed out, there are ways to deal with python's scope limitations and I'll expose some.

1. Use the global keyword (in general not recommended).

2. In Python 3.x, use the nonlocal keyword (suggested by @unutbu and @leewz)

3. Define a simple modifiable class Object

class Object(object):

and create an Object scope within initCounter to store the variables

def initCounter ():
    scope = Object()
    scope.x = 0
    def counter():
        scope.x += 1
        print scope.x

    return counter

Since scope is really just a reference, actions taken with its fields do not really modify scope itself, so no error arises.

4. An alternative way, as @unutbu pointed out, would be to define each variable as an array (x = [0]) and modify it's first element (x[0] += 1). Again no error arises because x itself is not modified.

5. As suggested by @raxacoricofallapatorius, you could make x a property of counter

def initCounter ():

    def counter():
        counter.x += 1
        print counter.x

    counter.x = 0
    return counter

Laravel Migration table already exists, but I want to add new not the older

You can delete all the tables but it will be not a good practice, instead try this command

php artisan migrate:fresh

Make sure to use the naming convention correctly. I have tested this in version laravel 5.7 It is important to not try this command when your site is on server because it drops all information.

How to check if array is empty or does not exist?

You want to do the check for undefined first. If you do it the other way round, it will generate an error if the array is undefined.

if (array === undefined || array.length == 0) {
    // array empty or does not exist


This answer is getting a fair amount of attention, so I'd like to point out that my original answer, more than anything else, addressed the wrong order of the conditions being evaluated in the question. In this sense, it fails to address several scenarios, such as null values, other types of objects with a length property, etc. It is also not very idiomatic JavaScript.

The foolproof approach
Taking some inspiration from the comments, below is what I currently consider to be the foolproof way to check whether an array is empty or does not exist. It also takes into account that the variable might not refer to an array, but to some other type of object with a length property.

if (!Array.isArray(array) || !array.length) {
  // array does not exist, is not an array, or is empty
  // ? do not attempt to process array

To break it down:

  1. Array.isArray(), unsurprisingly, checks whether its argument is an array. This weeds out values like null, undefined and anything else that is not an array.
    Note that this will also eliminate array-like objects, such as the arguments object and DOM NodeList objects. Depending on your situation, this might not be the behavior you're after.

  2. The array.length condition checks whether the variable's length property evaluates to a truthy value. Because the previous condition already established that we are indeed dealing with an array, more strict comparisons like array.length != 0 or array.length !== 0 are not required here.

The pragmatic approach
In a lot of cases, the above might seem like overkill. Maybe you're using a higher order language like TypeScript that does most of the type-checking for you at compile-time, or you really don't care whether the object is actually an array, or just array-like.

In those cases, I tend to go for the following, more idiomatic JavaScript:

if (!array || !array.length) {
    // array or array.length are falsy
    // ? do not attempt to process array

Or, more frequently, its inverse:

if (array && array.length) {
    // array and array.length are truthy
    // ? probably OK to process array

With the introduction of the optional chaining operator (Elvis operator) in ECMAScript 2020, this can be shortened even further:

if (!array?.length) {
    // array or array.length are falsy
    // ? do not attempt to process array

Or the opposite:

if (array?.length) {
    // array and array.length are truthy
    // ? probably OK to process array

Dataframe to Excel sheet

Or you can do like this:

your_df.to_excel( r'C:\Users\full_path\excel_name.xlsx',
                  sheet_name= 'your_sheet_name'

Use jquery to set value of div tag

When using the .html() method, a htmlString must be the parameter. (source) Put your string inside a HTML tag and it should work or use .text() as suggested by farzad.


<div class="demo-container">
    <div class="demo-box">Demonstration Box</div>

<script type="text/javascript">
$("div.demo-container").html( "<p>All new content. <em>You bet!</em></p>" );

How to detect escape key press with pure JS or jQuery?

pure JS (no JQuery)

document.addEventListener('keydown', function(e) {
    if(e.keyCode == 27){
      //add your code here

How do I specify new lines on Python, when writing on files?

\n separates the lines of a string. In the following example, I keep writing the records in a loop. Each record is separated by \n.

f = open("jsonFile.txt", "w")

for row_index in range(2, sheet.nrows):

  mydict1 = {
    "PowerMeterId" : row_index + 1,
    "Service": "Electricity",
    "Building": "JTC FoodHub",
    "Floor": str(Floor),
    "Location": Location,
    "ReportType": "Electricity",
    "System": System,
    "SubSystem": "",
    "Incomer": "",
    "Category": "",
    "DisplayName": DisplayName,
    "Description": Description,
    "Tag": tag,
    "IsActive": 1,
    "DataProviderType": int(0),
    "DataTable": ""
  mydict1.pop("_id", None)
  f.write(str(mydict1) + '\n')


IE8 crashes when loading website - res://ieframe.dll/acr_error.htm

Try looking for Windows Error Reporting events in the affected machine's Event Viewer, specifically for iexplore.exe. That might give you a pointer for what component is getting loaded in IE that is causing the crash. Even more precise would be to launch IE under a debugger (e.g. windbg), repro the crash and then get a call stack. If you have a bad 3rd party add-on, it should be towards the top of the call stack. Though you said that it "isn't really an option" it will be important for you to identify a possible incompatibility and either reach out to the add-on developer, or workaround the issue on your side.

Bootstrap fullscreen layout with 100% height

Here's an answer using the latest Bootstrap 4.0.0. This layout is easier using the flexbox and sizing utility classes that are all provided in Bootstrap 4. This layout is possible with very little extra CSS.

#mmenu_screen > .row {
    min-height: 100vh;

.flex-fill {
    flex:1 1 auto;

<div id="mmenu_screen" class="container-fluid main_container d-flex">
    <div class="row flex-fill">
        <div class="col-sm-6 h-100">
            <div class="row h-50">
                <div class="col-sm-12" id="mmenu_screen--book">
                    <!-- Button for booking -->
            <div class="row h-50">
                <div class="col-sm-12" id="mmenu_screen--information">
                    <!-- Button for information -->
        <div class="col-sm-6 mmenu_screen--direktaction flex-fill">
            <!-- Button for direktaction -->


The flex-fill and vh-100 classes are included in Bootstrap 4.1 (and later)

Proper way to use AJAX Post in jquery to pass model from strongly typed MVC3 view

You can skip the var declaration and the stringify. Otherwise, that will work just fine.

    url: '/home/check',
    type: 'POST',
    data: {
        Address1: "423 Judy Road",
        Address2: "1001",
        City: "New York",
        State: "NY",
        ZipCode: "10301",
        Country: "USA"
    contentType: 'application/json; charset=utf-8',
    success: function (data) {
    error: function () {

Get all Attributes from a HTML element with Javascript/jQuery

This approach works well if you need to get all the attributes with name and value in objects returned in an array.

Example output:

        name: 'message',
        value: 'test2'

function getElementAttrs(el) {_x000D_
  return [] => {_x000D_
    return {_x000D_
      value: attr.value_x000D_
var allAttrs = getElementAttrs(document.querySelector('span'));_x000D_
<span name="test" message="test2"></span>

If you want only an array of attribute names for that element, you can just map the results:

var onlyAttrNames = =>;
console.log(onlyAttrNames); // ["name", "message"]

How to map calculated properties with JPA and Hibernate

JPA doesn't offer any support for derived property so you'll have to use a provider specific extension. As you mentioned, @Formula is perfect for this when using Hibernate. You can use an SQL fragment:

private float finalPrice;

Or even complex queries on other tables:

@Formula("(select min(o.creation_date) from Orders o where o.customer_id = id)")
private Date firstOrderDate;

Where id is the id of the current entity.

The following blog post is worth the read: Hibernate Derived Properties - Performance and Portability.

Without more details, I can't give a more precise answer but the above link should be helpful.

See also:

Get list from pandas dataframe column or row?

Example conversion:

Numpy Array -> Panda Data Frame -> List from one Panda Column

Numpy Array

data = np.array([[10,20,30], [20,30,60], [30,60,90]])

Convert numpy array into Panda data frame

dataPd = pd.DataFrame(data = data)
0   1   2
0  10  20  30
1  20  30  60
2  30  60  90

Convert one Panda column to list

pdToList = list(dataPd['2'])

How to post an array of complex objects with JSON, jQuery to ASP.NET MVC Controller?

Towards the second half of Create REST API using ASP.NET MVC that speaks both JSON and plain XML, to quote:

Now we need to accept JSON and XML payload, delivered via HTTP POST. Sometimes your client might want to upload a collection of objects in one shot for batch processing. So, they can upload objects using either JSON or XML format. There's no native support in ASP.NET MVC to automatically parse posted JSON or XML and automatically map to Action parameters. So, I wrote a filter that does it."

He then implements an action filter that maps the JSON to C# objects with code shown.

How to ignore PKIX path building failed:

I also faced this issue. I was having JDK 1.8.0_121. I upgraded JDK to 1.8.0_181 and it worked like a charm.

Right way to convert data.frame to a numeric matrix, when df also contains strings?

Edit 2: See @flodel's answer. Much better.


# assuming SFI is your data.frame
as.matrix(sapply(SFI, as.numeric))  

Edit: or as @ CarlWitthoft suggested in the comments:


XPath selecting a node with some attribute value equals to some other node's attribute value

This XPath is specific to the code snippet you've provided. To select <child> with id as #grand you can write //child[@id='#grand'].

To get age //child[@id='#grand']/@age

Hope this helps

What is process.env.PORT in Node.js?

When hosting your application on another service (like Heroku, Nodejitsu, and AWS), your host may independently configure the process.env.PORT variable for you; after all, your script runs in their environment.

Amazon's Elastic Beanstalk does this. If you try to set a static port value like 3000 instead of process.env.PORT || 3000 where 3000 is your static setting, then your application will result in a 500 gateway error because Amazon is configuring the port for you.

This is a minimal Express application that will deploy on Amazon's Elastic Beanstalk:

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('Hello World!');

// use port 3000 unless there exists a preconfigured port
var port = process.env.PORT || 3000;


How to change value of ArrayList element in java

I agree with Duncan ...I have tried it with mutable object but still get the same problem... I got a simple solution to this... use ListIterator instead Iterator and use set method of ListIterator

ListIterator<Integer> i = a.listIterator();
//changed the value of first element in List
Integer x =null;
        if(i.hasNext()) {
            x =;
            x = Integer.valueOf(9);
    //set method sets the recent iterated element in ArrayList
        //initialized the iterator again and print all the elements
        i = a.listIterator();

But this constraints me to use this only for ArrayList only which can use ListIterator...i will have same problem with any other Collection

Setting transparent images background in IrfanView

If you are using the batch conversion, in the window click "options" in the "Batch conversion settings-output format" and tick the two boxes "save transparent color" (one under "PNG" and the other under "ICO").

Ajax Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource

add these in php file where your ajax url call

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Credentials: true ");
header("Access-Control-Allow-Methods: OPTIONS, GET, POST");
header("Access-Control-Allow-Headers: Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control");

Compute row average in pandas

We can find the the mean of a row using the range function, i.e in your case, from the Y1961 column to the Y1965

df['mean'] = df.iloc[:, 0:4].mean(axis=1)

And if you want to select individual columns

df['mean'] = df.iloc[:, [0,1,2,3,4].mean(axis=1)

sweet-alert display HTML code in text

A feature to allow HTML for title and text parameters has been added with a recent merge into the master branch on GitHub

Simply use JSON configuration and set 'html' to true, eg:

swal({ html:true, title:'<i>TITLE</i>', text:'<b>TEXT</b>'});

This was merged less than a week ago and is hinted at in the (html is set to false in one of the examples although not explicitly described) however it is not yet documented on the marketing page

How to get HTML 5 input type="date" working in Firefox and/or IE 10

While this doesn't allow you to get a datepicker ui, Mozilla does allow the use of pattern, so you can at least get date validation with something like this:


Ultimately I agree with @SuperUberDuper in that Mozilla is way behind on including this natively.

How to convert string to Title Case in Python?

Why not write one? Something like this may satisfy your requirements:

def FixCase(st):
    return ' '.join(''.join([w[0].upper(), w[1:].lower()]) for w in st.split())

Print time in a batch file (milliseconds)

To time task in CMD is as simple as

echo %TIME% && your_command && cmd /v:on /c echo !TIME!

What is the best way to implement nested dictionaries?

I like the idea of wrapping this in a class and implementing __getitem__ and __setitem__ such that they implemented a simple query language:

>>> d['new jersey/mercer county/plumbers'] = 3
>>> d['new jersey/mercer county/programmers'] = 81
>>> d['new jersey/mercer county/programmers']
>>> d['new jersey/mercer country']
<view which implicitly adds 'new jersey/mercer county' to queries/mutations>

If you wanted to get fancy you could also implement something like:

>>> d['*/*/programmers']
<view which would contain 'programmers' entries>

but mostly I think such a thing would be really fun to implement :D

Get class name of object as string in Swift

If you don't like the mangled name, you can dictate your own name:

@objc(CalendarViewController) class CalendarViewController : UIViewController {
    // ...

However, it would be better in the long run to learn to parse the mangled name. The format is standard and meaningful and won't change.

Delete all but the most recent X files in bash

Ignoring newlines is ignoring security and good coding. wnoise had the only good answer. Here is a variation on his that puts the filenames in an array $x

while IFS= read -rd ''; do 
    x+=("${REPLY#* }"); 
done < <(find . -maxdepth 1 -printf '%T@ %p\0' | sort -r -z -n )

How can I find the dimensions of a matrix in Python?

The correct answer is the following:

import numpy 

Passing multiple values for a single parameter in Reporting Services

As of MSSQL 2016 - with compatibility level 130, you can utilize String_Split() to parse your joined parameter from SSRS. Say you wanted to populate a parameter from a query in SSRS and then pass that param to a stored proc or SSRS Shared Dataset:

  1. Add two datasets to your SSRS report, one that returns a list of values and labels to display in your parameter and one that has the actual data you're looking to filter. Each of these datasets can be a stored proc or shared dataset or embedded query.
  2. Create a parameter in SSRS that is NOT on the dataset you want to filter. Let's call it Customer
  3. Set Customer param to allow multiple values and set up Available Values tab with the dataset, labels, and values you want to display from the query.
  4. Right click the dataset you're looking to filter and add a parameter that IS defined in the stored procedure. Let's call it CustomerList.
  5. Click the expression button next to the value field for this parameter and do Join(Parameters!Customer.Value, ",")
  6. In your stored proc or shared dataset, utilize string_split to break the comma-delimited @CustomerList param into an array: Customer.CustID in (select value from string_split(@CustomerList, ',') where value = Customer.CustID)

Any way to clear python's IDLE window?

I got it with:

import console 

if you want to do it in your script, or if you are in the console just tap clear() and press enter. That works on Pyto on iPhone. It may depend on the console though.

How can I view the source code for a function?

UseMethod("t") is telling you that t() is a (S3) generic function that has methods for different object classes.

The S3 method dispatch system

For S3 classes, you can use the methods function to list the methods for a particular generic function or class.

> methods(t)
[1] t.default    t.ts*       

   Non-visible functions are asterisked
> methods(class="ts")
 [1] aggregate.ts cbind.ts*        cycle.ts*       
 [5] diffinv.ts*      diff.ts          kernapply.ts*    lines.ts        
 [9] monthplot.ts*    na.omit.ts*      Ops.ts*          plot.ts         
[13] print.ts         time.ts*         [<-.ts*          [.ts*           
[17] t.ts*            window<-.ts*     window.ts*      

   Non-visible functions are asterisked

"Non-visible functions are asterisked" means the function is not exported from its package's namespace. You can still view its source code via the ::: function (i.e. stats:::t.ts), or by using getAnywhere(). getAnywhere() is useful because you don't have to know which package the function came from.

> getAnywhere(t.ts)
A single object matching ‘t.ts’ was found
It was found in the following places
  registered S3 method for t from namespace stats
with value

function (x) 
    cl <- oldClass(x)
    other <- !(cl %in% c("ts", "mts"))
    class(x) <- if (any(other)) 
    attr(x, "tsp") <- NULL
<bytecode: 0x294e410>
<environment: namespace:stats>

The S4 method dispatch system

The S4 system is a newer method dispatch system and is an alternative to the S3 system. Here is an example of an S4 function:

> library(Matrix)
Loading required package: lattice
> chol2inv
standardGeneric for "chol2inv" defined from package "base"

function (x, ...) 
<bytecode: 0x000000000eafd790>
<environment: 0x000000000eb06f10>
Methods may be defined for arguments: x
Use  showMethods("chol2inv")  for currently available ones.

The output already offers a lot of information. standardGeneric is an indicator of an S4 function. The method to see defined S4 methods is offered helpfully:

> showMethods(chol2inv)
Function: chol2inv (package base)

getMethod can be used to see the source code of one of the methods:

> getMethod("chol2inv", "diagonalMatrix")
Method Definition:

function (x, ...) 
<bytecode: 0x000000000ea2cc70>
<environment: namespace:Matrix>

target  "diagonalMatrix"
defined "diagonalMatrix"

There are also methods with more complex signatures for each method, for example

Function: extract (package raster)
x="Raster", y="data.frame"
x="Raster", y="Extent"
x="Raster", y="matrix"
x="Raster", y="SpatialLines"
x="Raster", y="SpatialPoints"
x="Raster", y="SpatialPolygons"
x="Raster", y="vector"

To see the source code for one of these methods the entire signature must be supplied, e.g.

getMethod("extract" , signature = c( x = "Raster" , y = "SpatialPolygons") )

It will not suffice to supply the partial signature

#Error in getMethod("extract", signature = "SpatialPolygons") : 
#  No method found for function "extract" and signature SpatialPolygons

Functions that call unexported functions

In the case of ts.union, .cbindts and .makeNamesTs are unexported functions from the stats namespace. You can view the source code of unexported functions by using the ::: operator or getAnywhere.

> stats:::.makeNamesTs
function (...) 
    l <- as.list(substitute(list(...)))[-1L]
    nm <- names(l)
    fixup <- if (is.null(nm)) 
    else nm == ""
    dep <- sapply(l[fixup], function(x) deparse(x)[1L])
    if (is.null(nm)) 
    if (any(fixup)) 
        nm[fixup] <- dep
<bytecode: 0x38140d0>
<environment: namespace:stats>

Functions that call compiled code

Note that "compiled" does not refer to byte-compiled R code as created by the compiler package. The <bytecode: 0x294e410> line in the above output indicates that the function is byte-compiled, and you can still view the source from the R command line.

Functions that call .C, .Call, .Fortran, .External, .Internal, or .Primitive are calling entry points in compiled code, so you will have to look at sources of the compiled code if you want to fully understand the function. This GitHub mirror of the R source code is a decent place to start. The function pryr::show_c_source can be a useful tool as it will take you directly to a GitHub page for .Internal and .Primitive calls. Packages may use .C, .Call, .Fortran, and .External; but not .Internal or .Primitive, because these are used to call functions built into the R interpreter.

Calls to some of the above functions may use an object instead of a character string to reference the compiled function. In those cases, the object is of class "NativeSymbolInfo", "RegisteredNativeSymbol", or "NativeSymbol"; and printing the object yields useful information. For example, optim calls .External2(C_optimhess, res$par, fn1, gr1, con) (note that's C_optimhess, not "C_optimhess"). optim is in the stats package, so you can type stats:::C_optimhess to see information about the compiled function being called.

Compiled code in a package

If you want to view compiled code in a package, you will need to download/unpack the package source. The installed binaries are not sufficient. A package's source code is available from the same CRAN (or CRAN compatible) repository that the package was originally installed from. The download.packages() function can get the package source for you.

download.packages(pkgs = "Matrix", 
                  destdir = ".",
                  type = "source")

This will download the source version of the Matrix package and save the corresponding .tar.gz file in the current directory. Source code for compiled functions can be found in the src directory of the uncompressed and untared file. The uncompressing and untaring step can be done outside of R, or from within R using the untar() function. It is possible to combine the download and expansion step into a single call (note that only one package at a time can be downloaded and unpacked in this way):

untar(download.packages(pkgs = "Matrix",
                        destdir = ".",
                        type = "source")[,2])

Alternatively, if the package development is hosted publicly (e.g. via GitHub, R-Forge, or, you can probably browse the source code online.

Compiled code in a base package

Certain packages are considered "base" packages. These packages ship with R and their version is locked to the version of R. Examples include base, compiler, stats, and utils. As such, they are not available as separate downloadable packages on CRAN as described above. Rather, they are part of the R source tree in individual package directories under /src/library/. How to access the R source is described in the next section.

Compiled code built into the R interpreter

If you want to view the code built-in to the R interpreter, you will need to download/unpack the R sources; or you can view the sources online via the R Subversion repository or Winston Chang's github mirror.

Uwe Ligges's R news article (PDF) (p. 43) is a good general reference of how to view the source code for .Internal and .Primitive functions. The basic steps are to first look for the function name in src/main/names.c and then search for the "C-entry" name in the files in src/main/*.

MySQL: Insert datetime into other datetime field


    UPDATE products SET former_date=20111218131717 WHERE id=1

Alternatively, you might want to look at using the STR_TO_DATE (see STR_TO_DATE(str,format)) function.

Numpy: Divide each row by a vector element

Here you go. You just need to use None (or alternatively np.newaxis) combined with broadcasting:

In [6]: data - vector[:,None]
array([[0, 0, 0],
       [0, 0, 0],
       [0, 0, 0]])

In [7]: data / vector[:,None]
array([[1, 1, 1],
       [1, 1, 1],
       [1, 1, 1]])

Align items in a stack panel?

For those who stumble upon this question, here's how to achieve this layout with a Grid:

    <TextBlock Text="Server:"/>
    <TextBlock Text="" HorizontalAlignment="Right"/>



Replace transparency in PNG images with white background

This works for me:

convert -flatten img1.png img1-white.png

Documentation references:

Sticky and NON-Sticky sessions

When your website is served by only one web server, for each client-server pair, a session object is created and remains in the memory of the web server. All the requests from the client go to this web server and update this session object. If some data needs to be stored in the session object over the period of interaction, it is stored in this session object and stays there as long as the session exists.

However, if your website is served by multiple web servers which sit behind a load balancer, the load balancer decides which actual (physical) web-server should each request go to. For example, if there are 3 web servers A, B and C behind the load balancer, it is possible that is served from server A, is served from server B and are served from server C.

Now, if the requests are being served from (physically) 3 different servers, each server has created a session object for you and because these session objects sit on three independent boxes, there's no direct way of one knowing what is there in the session object of the other. In order to synchronize between these server sessions, you may have to write/read the session data into a layer which is common to all - like a DB. Now writing and reading data to/from a db for this use-case may not be a good idea. Now, here comes the role of sticky-session.

If the load balancer is instructed to use sticky sessions, all of your interactions will happen with the same physical server, even though other servers are present. Thus, your session object will be the same throughout your entire interaction with this website.

To summarize, In case of Sticky Sessions, all your requests will be directed to the same physical web server while in case of a non-sticky loadbalancer may choose any webserver to serve your requests.

As an example, you may read about Amazon's Elastic Load Balancer and sticky sessions here :

HTML Mobile -forcing the soft keyboard to hide

For further readers/searchers:

As Rene Pot points out on this topic,

By adding the attribute readonly (or readonly="readonly") to the input field you should prevent anyone typing anything in it, but still be able to launch a click event on it.

With this method, you can avoid popping up the "soft" Keyboard and still launch click events / fill the input by any on-screen keyboard.

This solution also works fine with date-time-pickers which generally already implement controls.

Check, using jQuery, if an element is 'display:none' or block on click

You can use :visible for visible elements and :hidden to find out hidden elements. This hidden elements have display attribute set to none.

hiddenElements = $(':hidden');
visibleElements = $(':visible');

To check particular element.

if($('#yourID:visible').length == 0)


Elements are considered visible if they consume space in the document. Visible elements have a width or height that is greater than zero, Reference

You can also use is() with :visible



If you want to check value of display then you can use css()

if($('#yourID').css('display') == 'none')


If you are using display the following values display can have.

display: none

display: inline

display: block

display: list-item

display: inline-block

Check complete list of possible display values here.

To check the display property with JavaScript

var isVisible = document.getElementById("yourID").style.display == "block";
var isHidden = document.getElementById("yourID").style.display == "none"; 

Insert Unicode character into JavaScript

Although @ruakh gave a good answer, I will add some alternatives for completeness:

You could in fact use even var Omega = '&#937;' in JavaScript, but only if your JavaScript code is:

  • inside an event attribute, as in onclick="var Omega = '&#937'; alert(Omega)" or
  • in a script element inside an XHTML (or XHTML + XML) document served with an XML content type.

In these cases, the code will be first (before getting passed to the JavaScript interpreter) be parsed by an HTML parser so that character references like &#937; are recognized. The restrictions make this an impractical approach in most cases.

You can also enter the O character as such, as in var Omega = 'O', but then the character encoding must allow that, the encoding must be properly declared, and you need software that let you enter such characters. This is a clean solution and quite feasible if you use UTF-8 encoding for everything and are prepared to deal with the issues created by it. Source code will be readable, and reading it, you immediately see the character itself, instead of code notations. On the other hand, it may cause surprises if other people start working with your code.

Using the \u notation, as in var Omega = '\u03A9', works independently of character encoding, and it is in practice almost universal. It can however be as such used only up to U+FFFF, i.e. up to \uffff, but most characters that most people ever heard of fall into that area. (If you need “higher” characters, you need to use either surrogate pairs or one of the two approaches above.)

You can also construct a character using the String.fromCharCode() method, passing as a parameter the Unicode number, in decimal as in var Omega = String.fromCharCode(937) or in hexadecimal as in var Omega = String.fromCharCode(0x3A9). This works up to U+FFFF. This approach can be used even when you have the Unicode number in a variable.

Converting float to char*

char array[10];
sprintf(array, "%f", 3.123);

sprintf: (from MSDN)

Android ADB stop application command like "force-stop" for non rooted device

If you have a rooted device you can use kill command

Connect to your device with adb:

adb shell

Once the session is established, you have to escalade privileges:




will list running processes. Note down the PID of the process you want to terminate. Then get rid of it

kill PID

How can I add a volume to an existing Docker container?

The best way is to copy all the files and folders inside a directory on your local file system by: docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH

SRC_PATH is on container DEST_PATH is on localhost

Then do docker-compose down attach a volume to the same DEST_PATH and run Docker containers by using docker-compose up -d

Add volume by following in docker-compose.yml


How to append a date in batch files

I've used the environment variables technique covered here:

Here's the code from that site:

::~~Author~~.          Brett Middleton
::~~Email_Address~~. [email protected]
::~~Script_Type~~.   nt command line batch
::~~Sub_Type~~. Misc
::~~Keywords~~. environment variables

::Sets or clears a group of environment variables containing components of the current date extracted from the string returned by the DATE /T command.  These variables can be used to name files, control the flow of execution, etc.


@echo off

::  SetEnvDate1.CMD                                                     6/30/98
::  Description  :  Sets or clears a group of environment variables containing
::               :  components of the current date extracted from the string
::               :  returned by the DATE /T command.  These variables can be
::               :  used to name files, control the flow of execution, etc.
::               :
::  Requires     :  Windows NT with command extensions enabled
::               :
::  Tested       :  Yes, as demonstration
::               :
::  Contact      :  Brett Middleton <[email protected]>
::               :  Animal and Dairy Science Department
::               :  University of Georgia, Athens
::  SetEnvDate1 can be used as a model for coding date/time routines in
::  other scripts, or can be used by itself as a utility that is called
::  from other scripts.
::  Run or call SetEnvDate1 without arguments to set the date variables.
::  Variables are set for the day abbreviation (DT_DAY), month number (DT_MM),
::  day number (DT_DD) and four-digit year (DT_YYYY).
::  When the variables are no longer needed, clean up the environment by
::  calling the script again with the CLEAR argument.  E.g.,
::       call SetEnvDate1 clear
::  A time variable could be added by parsing the string returned by the
::  built-in TIME /T command.  This is left as an exercise for the reader. B-)
::  This script illustrates the following NT command extensions:
::  1.  Use of the extended IF command to do case-insensitive comparisons.
::  2.  Use of the extended DATE command.
::  3.  Use of the extended FOR command to parse a string returned by a
::      command or program.
::  4.  Use of the "()" conditional processing symbols to group commands
::      for conditional execution.  All commands between the parens will
::      be executed if the preceeding IF or FOR statement is TRUE.

if not "%1" == "?" goto chkarg
echo Sets or clears date/time variables in the command environment.
echo    SetEnvDate1 [clear]
echo When called without arguments, the variables are created or updated.
echo When called with the CLEAR argument, the variables are deleted.
goto endit

::  Check arguments and select SET or CLEAR routine.  Unrecognized arguments
::  are ignored and SET is assumed.


if /I "%1" == "CLEAR" goto clrvar
goto setvar

::  Set variables for the day abbreviation (DAY), month number (MM), 
::  day number (DD) and 4-digit year (YYYY). 


for /F "tokens=1-4 delims=/ " %%i IN ('date /t') DO (
set DT_DAY=%%i
set DT_MM=%%j
set DT_DD=%%k
set DT_YYYY=%%l)

goto endit

::  Clear all variables from the environment.

for %%v in (DT_DAY DT_MM DT_DD DT_YYYY) do set %%v=
goto endit


Getting error: Peer authentication failed for user "postgres", when trying to get pgsql working with rails

If you have an issue, you need to locate your pg_hba.conf. The command is:

find / -name 'pg_hba.conf' 2>/dev/null

and after that change the configuration file:

Postgresql 9.3

Postgresql 9.3

Postgresql 9.4

Postgresql 9.3

The next step is: Restarting your db instance:

service postgresql-9.3 restart

If you have any problems, you need to set password again:

ALTER USER db_user with password 'db_password';

How to add facebook share button on my website?

For Facebook share with an image without an API and using a # to deep link into a sub page, the trick was to share the image as picture=

The variable mainUrl would be

var d1 = $('.targ .t1').text();
var d2 = $('.targ .t2').text();
var d3 = $('.targ .t3').text();
var d4 = $('.targ .t4').text();
var descript_ = d1 + ' ' + d2 + ' ' + d3 + ' ' + d4;
var descript = encodeURIComponent(descript_);

var imgUrl_ = 'path/to/mypic_'+id+'.jpg';
var imgUrl = mainUrl + encodeURIComponent(imgUrl_);

var shareLink = mainUrl + encodeURIComponent('mypage.html#' + id);

var fbShareLink = shareLink + '&picture=' + imgUrl + '&description=' + descript;
var twShareLink = 'text=' + descript + '&url=' + shareLink;

// facebook
$(".my-btn .facebook").off("tap click").on("tap click",function(){
  var fbpopup ="" + fbShareLink, "pop", "width=600, height=400, scrollbars=no");
  return false;

// twitter
$(".my-btn .twitter").off("tap click").on("tap click",function(){
  var twpopup ="" + twShareLink , "pop", "width=600, height=400, scrollbars=no");
  return false;

Laravel migration: unique key is too long, even if specified

You will not have this problem if you're using MySQL 5.7.7+ or MariaDB 10.2.2+.

To update MariaDB on your Mac using Brew first unlink the current one: brew unlink mariadb and then install a dev one using brew install mariadb --devel

After installation is done stop/start the service running: brew services stop mariadb brew services start mariadb

Current dev version is 10.2.3. After the installation is finished you won't have to worry about this anymore and you can use utf8mb4 (that is now a default in Laravel 5.4) without switching back to utf8 nor editing AppServiceProvider as proposed in the Laravel documentation: (scroll down to: Migration Default String Length)

How to clean old dependencies from maven repositories?

If you are on Unix, you could use the access time of the files in there. Just enable access time for your filesystem, then run a clean build of all your projects you would like to keep dependencies for and then do something like this (UNTESTED!):

find ~/.m2 -amin +5 -iname '*.pom' | while read pom; do parent=`dirname "$pom"`; rm -Rf "$parent"; done

This will find all *.pom files which have last been accessed more than 5 minutes ago (assuming you started your builds max 5 minutes ago) and delete their directories.

Add "echo " before the rm to do a 'dry-run'.