Programs & Examples On #Simulink

Simulink® is an environment developed by The MathWorks for multidomain simulation and Model-Based Design for dynamic and embedded systems.

Decimal separator comma (',') with numberDecimal inputType in EditText

I think this solution is less complex than the others written here:

    android:digits="0123456789," />

This way when you press the '.' in the soft keyboard nothing happens; only numbers and comma are allowed.

C++ error: "Array must be initialized with a brace enclosed initializer"

The syntax to statically initialize an array uses curly braces, like this:

int array[10] = { 0 };

This will zero-initialize the array.

For multi-dimensional arrays, you need nested curly braces, like this:

int cipher[Array_size][Array_size]= { { 0 } };

Note that Array_size must be a compile-time constant for this to work. If Array_size is not known at compile-time, you must use dynamic initialization. (Preferably, an std::vector).

How do I see the current encoding of a file in Sublime Text?

For my part, and without any plug-in, simply saving the file either from the File menu or with keyboards shortcuts

CTRL + S (Windows, Linux) or CMD + S (Mac OS)

briefly displays the current encoding - between parentheses - in the status bar, at the bottom of the editor's window. This suggestion works in Sublime Text 2 and 3.

Note that the displayed encoding to the right in the status bar of Sublime Text 3, may display the wrong encoding of the file if you have attempted to save the file with an encoding that can't represent all the characters in your file. In this case you would have seen an informational dialog and Sublime telling you it's falling back to UTF-8. This may not be the case, so be careful.

How to navigate to a section of a page

Use anchors.

Main Page:

<a href="/sample#sushi">Sushi</a>
<a href="/sample#bBQ">BBQ</a>

Sample Page:

<div id='sushi'><a name="sushi"></a></div>
<div id='bbq'><a name="bbq"></a></div>

SQL Server equivalent to MySQL enum data type?

The best solution I've found in this is to create a lookup table with the possible values as a primary key, and create a foreign key to the lookup table.

RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()

The RequestDispatcher interface allows you to do a server side forward/include whereas sendRedirect() does a client side redirect. In a client side redirect, the server will send back an HTTP status code of 302 (temporary redirect) which causes the web browser to issue a brand new HTTP GET request for the content at the redirected location. In contrast, when using the RequestDispatcher interface, the include/forward to the new resource is handled entirely on the server side.

Angularjs simple file download causes router to redirect

If you need a directive more advanced, I recomend the solution that I implemnted, correctly tested on Internet Explorer 11, Chrome and FireFox.

I hope it, will be helpfull.


<a href="#" class="btn btn-default" file-name="'fileName.extension'"  ng-click="getFile()" file-download="myBlobObject"><i class="fa fa-file-excel-o"></i></a>




            scope.$watch('fileDownload',function(newValue, oldValue){

                if(newValue!=undefined && newValue!=null){
                    console.debug('Downloading a new file'); 
                    var isFirefox = typeof InstallTrigger !== 'undefined';
                    var isSafari ='Constructor') > 0;
                    var isIE = /*@cc_on!@*/false || !!document.documentMode;
                    var isEdge = !isIE && !!window.StyleMedia;
                    var isChrome = !! && !!;
                    var isOpera = (!!window.opr && !!opr.addons) || !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;
                    var isBlink = (isChrome || isOpera) && !!window.CSS;

                    if(isFirefox || isIE || isChrome){
                            console.log('Manage Google Chrome download');
                            var url = window.URL || window.webkitURL;
                            var fileURL = url.createObjectURL(scope.fileDownload);
                            var downloadLink = angular.element('<a></a>');//create a new  <a> tag element
                            downloadLink[0].click();//call click function
                            url.revokeObjectURL(fileURL);//revoke the object from URL
                            console.log('Manage IE download>10');
                            console.log('Manage Mozilla Firefox download');
                            var url = window.URL || window.webkitURL;
                            var fileURL = url.createObjectURL(scope.fileDownload);
                            var a=elem[0];//recover the <a> tag from directive
                  ;//we call click function

                        alert('SORRY YOUR BROWSER IS NOT COMPATIBLE');



        console.log('download started, you can show a wating animation');
        serviceAsPromise.getStream({param1:'data1',param1:'data2', ...})
        .then(function(data){//is important that the data was returned as Aray Buffer
                console.log('Stream download complete, stop animation!');
                $scope.myBlobObject=new Blob([data],{ type:'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'});
                console.log('Download Error, stop animation and show error message');


function getStream(params){
                 var deferred = $q.defer();

                     method:"PUT",//you can use also GET or POST
                     headers:{'Content-type': 'application/json'},
                     responseType : 'arraybuffer',//THIS IS IMPORTANT
                    .success(function (data) {
                    }).error(function (data) {

                 return deferred.promise;


@RequestMapping(value = "/downloadURL/", method = RequestMethod.PUT)
public void downloadExcel(HttpServletResponse response,
        @RequestBody Map<String,String> spParams
        ) throws IOException {
        OutputStream outStream=null;
outStream = response.getOutputStream();//is important manage the exceptions here
ObjectThatWritesOnOutputStream myWriter= new ObjectThatWritesOnOutputStream();// note that this object doesn exist on JAVA,
ObjectThatWritesOnOutputStream.write(outStream);//you can configure more things here

How do I get the backtrace for all the threads in GDB?

Is there a command that does?

thread apply all where

Return array in a function

This is a fairly old question, but I'm going to put in my 2 cents as there are a lot of answers, but none showing all possible methods in a clear and concise manner (not sure about the concise bit, as this got a bit out of hand. TL;DR ).

I'm assuming that the OP wanted to return the array that was passed in without copying as some means of directly passing this to the caller to be passed to another function to make the code look prettier.

However, to use an array like this is to let it decay into a pointer and have the compiler treat it like an array. This can result in subtle bugs if you pass in an array like, with the function expecting that it will have 5 elements, but your caller actually passes in some other number.

There a few ways you can handle this better. Pass in a std::vector or std::array (not sure if std::array was around in 2010 when the question was asked). You can then pass the object as a reference without any copying/moving of the object.

std::array<int, 5>& fillarr(std::array<int, 5>& arr)
    // (before c++11)
    for(auto it = arr.begin(); it != arr.end(); ++it)
    { /* do stuff */ }

    // Note the following are for c++11 and higher.  They will work for all
    // the other examples below except for the stuff after the Edit.

    // (c++11 and up)
    for(auto it = std::begin(arr); it != std::end(arr); ++it)
    { /* do stuff */ }

    // range for loop (c++11 and up)
    for(auto& element : arr)
    { /* do stuff */ }

    return arr;

std::vector<int>& fillarr(std::vector<int>& arr)
    for(auto it = arr.begin(); it != arr.end(); ++it)
    { /* do stuff */ }
    return arr;

However, if you insist on playing with C arrays, then use a template which will keep the information of how many items in the array.

template <size_t N>
    // N is easier and cleaner than specifying sizeof(arr)/sizeof(arr[0])
    for(int* it = arr; it != arr + N; ++it)
    { /* do stuff */ }
    return arr;

Except, that looks butt ugly, and super hard to read. I now use something to help with that which wasn't around in 2010, which I also use for function pointers:

template <typename T>
using type_t = T;

template <size_t N>
type_t<int(&)[N]> fillarr(type_t<int(&)[N]> arr)
    // N is easier and cleaner than specifying sizeof(arr)/sizeof(arr[0])
    for(int* it = arr; it != arr + N; ++it)
    { /* do stuff */ }
    return arr;

This moves the type where one would expect it to be, making this far more readable. Of course, using a template is superfluous if you are not going to use anything but 5 elements, so you can of course hard code it:

type_t<int(&)[5]> fillarr(type_t<int(&)[5]> arr)
    // Prefer using the compiler to figure out how many elements there are
    // as it reduces the number of locations where you have to change if needed.
    for(int* it = arr; it != arr + sizeof(arr)/sizeof(arr[0]); ++it)
    { /* do stuff */ }
    return arr;

As I said, my type_t<> trick wouldn't have worked at the time this question was asked. The best you could have hoped for back then was to use a type in a struct:

template<typename T>
struct type
  typedef T type;

typename type<int(&)[5]>::type fillarr(typename type<int(&)[5]>::type arr)
    // Prefer using the compiler to figure out how many elements there are
    // as it reduces the number of locations where you have to change if needed.
    for(int* it = arr; it != arr + sizeof(arr)/sizeof(arr[0]); ++it)
    { /* do stuff */ }
    return arr;

Which starts to look pretty ugly again, but at least is still more readable, though the typename may have been optional back then depending on the compiler, resulting in:

type<int(&)[5]>::type fillarr(type<int(&)[5]>::type arr)
    // Prefer using the compiler to figure out how many elements there are
    // as it reduces the number of locations where you have to change if needed.
    for(int* it = arr; it != arr + sizeof(arr)/sizeof(arr[0]); ++it)
    { /* do stuff */ }
    return arr;

And then of course you could have specified a specific type, rather than using my helper.

typedef int(&array5)[5];

array5 fillarr(array5 arr)
    // Prefer using the compiler to figure out how many elements there are
    // as it reduces the number of locations where you have to change if needed.
    for(int* it = arr; it != arr + sizeof(arr)/sizeof(arr[0]); ++it)
    { /* do stuff */ }
    return arr;

Back then, the free functions std::begin() and std::end() didn't exist, though could have been easily implemented. This would have allowed iterating over the array in a safer manner as they make sense on a C array, but not a pointer.

As for accessing the array, you could either pass it to another function that takes the same parameter type, or make an alias to it (which wouldn't make much sense as you already have the original in that scope). Accessing a array reference is just like accessing the original array.

void other_function(type_t<int(&)[5]> x) { /* do something else */ }

void fn()
    int array[5];


void fn()
    int array[5];
    auto& array2 = fillarr(array); // alias. But why bother.
    int forth_entry = array[4];
    int forth_entry2 = array2[4]; // same value as forth_entry

To summarize, it is best to not allow an array decay into a pointer if you intend to iterate over it. It is just a bad idea as it keeps the compiler from protecting you from shooting yourself in the foot and makes your code harder to read. Always try and help the compiler help you by keeping the types as long as possible unless you have a very good reason not to do so.


Oh, and for completeness, you can allow it to degrade to a pointer, but this decouples the array from the number of elements it holds. This is done a lot in C/C++ and is usually mitigated by passing the number of elements in the array. However, the compiler can't help you if you make a mistake and pass in the wrong value to the number of elements.

// separate size value
int* fillarr(int* arr, size_t size)
    for(int* it = arr; it != arr + size; ++it)
    { /* do stuff */ }
    return arr;

Instead of passing the size, you can pass the end pointer, which will point to one past the end of your array. This is useful as it makes for something that is closer to the std algorithms, which take a begin and and end pointer, but what you return is now only something that you must remember.

// separate end pointer
int* fillarr(int* arr, int* end)
    for(int* it = arr; it != end; ++it)
    { /* do stuff */ }
    return arr;

Alternatively, you can document that this function will only take 5 elements and hope that the user of your function doesn't do anything stupid.

// I document that this function will ONLY take 5 elements and 
// return the same array of 5 elements.  If you pass in anything
// else, may nazal demons exit thine nose!
int* fillarr(int* arr)
    for(int* it = arr; it != arr + 5; ++it)
    { /* do stuff */ }
    return arr;

Note that the return value has lost it's original type and is degraded to a pointer. Because of this, you are now on your own to ensure that you are not going to overrun the array.

You could pass a std::pair<int*, int*>, which you can use for begin and end and pass that around, but then it really stops looking like an array.

std::pair<int*, int*> fillarr(std::pair<int*, int*> arr)
    for(int* it = arr.first; it != arr.second; ++it)
    { /* do stuff */ }
    return arr; // if you change arr, then return the original arr value.

void fn()
    int array[5];
    auto array2 = fillarr(std::make_pair(&array[0], &array[5]));

    // Can be done, but you have the original array in scope, so why bother.
    int fourth_element = array2.first[4];


void other_function(std::pair<int*, int*> array)
    // Can be done, but you have the original array in scope, so why bother.
    int fourth_element = array2.first[4];

void fn()
    int array[5];
    other_function(fillarr(std::make_pair(&array[0], &array[5])));

Funny enough, this is very similar to how std::initializer_list work (c++11), but they don't work in this context.

How to exit if a command failed?

I've hacked up the following idiom:

echo "Generating from IDL..."
idlj -fclient -td java/src echo.idl
if [ $? -ne 0 ]; then { echo "Failed, aborting." ; exit 1; } fi

echo "Compiling classes..."
javac *java
if [ $? -ne 0 ]; then { echo "Failed, aborting." ; exit 1; } fi

echo "Done."

Precede each command with an informative echo, and follow each command with that same
if [ $? -ne 0 ];... line. (Of course, you can edit that error message if you want to.)

C#: How would I get the current time into a string?

I'd just like to point out something in these answers. In a date/time format string, '/' will be replaced with whatever the user's date separator is, and ':' will be replaced with whatever the user's time separator is. That is, if I've defined my date separator to be '.' (in the Regional and Language Options control panel applet, "intl.cpl"), and my time separator to be '?' (just pretend I'm crazy like that), then

DateTime.Now.ToString("MM/dd/yyyy h:mm tt")

would return

01.05.2009 6?01 PM

In most cases, this is what you want, because you want to respect the user's settings. If, however, you require the format be something specific (say, if it's going to parsed back out by somebody else down the wire), then you need to escape these special characters:

DateTime.Now.ToString("MM\\/dd\\/yyyy h\\:mm tt")


DateTime.Now.ToString(@"MM\/dd\/yyyy h\:mm tt")

which would now return

01/05/2009 6:01 PM


Then again, if you really want to respect the user's settings, you should use one of the standard date/time format strings, so that you respect not only the user's choices of separators, but also the general format of the date and/or time.


Both would return "1/5/2009" using standard US options, or "05/01/2009" using standard UK options, for instance.


Both would return "Monday, January 05, 2009" in US locale, or "05 January 2009" in UK.


"6:01 PM" in US, "18:01" in UK.


"6:01:04 PM" in US, "18:01:04" in UK.


"1/5/2009 6:01:04 PM" in US, "05/01/2009 18:01:04" in UK.

Many other options are available. See docs for standard date and time format strings and custom date and time format strings.

How do I clone a subdirectory only of a Git repository?

It's not possible to clone subdirectory only with Git, but below are few workarounds.

Filter branch

You may want to rewrite the repository to look as if trunk/public_html/ had been its project root, and discard all other history (using filter-branch), try on already checkout branch:

git filter-branch --subdirectory-filter trunk/public_html -- --all

Notes: The -- that separates filter-branch options from revision options, and the --all to rewrite all branches and tags. All information including original commit times or merge information will be preserved. This command honors .git/info/grafts file and refs in the refs/replace/ namespace, so if you have any grafts or replacement refs defined, running this command will make them permanent.

Warning! The rewritten history will have different object names for all the objects and will not converge with the original branch. You will not be able to easily push and distribute the rewritten branch on top of the original branch. Please do not use this command if you do not know the full implications, and avoid using it anyway, if a simple single commit would suffice to fix your problem.

Sparse checkout

Here are simple steps with sparse checkout approach which will populate the working directory sparsely, so you can tell Git which folder(s) or file(s) in the working directory are worth checking out.

  1. Clone repository as usual (--no-checkout is optional):

    git clone --no-checkout git@foo/bar.git
    cd bar

    You may skip this step, if you've your repository already cloned.

    Hint: For large repos, consider shallow clone (--depth 1) to checkout only latest revision or/and --single-branch only.

  2. Enable sparseCheckout option:

    git config core.sparseCheckout true
  3. Specify folder(s) for sparse checkout (without space at the end):

    echo "trunk/public_html/*"> .git/info/sparse-checkout

    or edit .git/info/sparse-checkout.

  4. Checkout the branch (e.g. master):

    git checkout master

Now you should have selected folders in your current directory.

You may consider symbolic links if you've too many levels of directories or filtering branch instead.

Python threading. How do I lock a thread?

You can see that your locks are pretty much working as you are using them, if you slow down the process and make them block a bit more. You had the right idea, where you surround critical pieces of code with the lock. Here is a small adjustment to your example to show you how each waits on the other to release the lock.

import threading
import time
import inspect

class Thread(threading.Thread):
    def __init__(self, t, *args):
        threading.Thread.__init__(self, target=t, args=args)

count = 0
lock = threading.Lock()

def incre():
    global count
    caller = inspect.getouterframes(inspect.currentframe())[1][3]
    print "Inside %s()" % caller
    print "Acquiring lock"
    with lock:
        print "Lock Acquired"
        count += 1  

def bye():
    while count < 5:

def hello_there():
    while count < 5:

def main():    
    hello = Thread(hello_there)
    goodbye = Thread(bye)

if __name__ == '__main__':

Sample output:

Inside hello_there()
Acquiring lock
Lock Acquired
Inside bye()
Acquiring lock
Lock Acquired

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

I was actually searching for a similar error and Google sent me here to this question. The error was:

The type arguments for method 'IModelExpressionProvider.CreateModelExpression(ViewDataDictionary, Expression>)' cannot be inferred from the usage

I spent maybe 15 minutes trying to figure it out. It was happening inside a Razor .cshtml view file. I had to comment portions of the view code to get to where it was barking since the compiler didn't help much.

<div class="form-group col-2">
    <label asp-for="Organization.Zip"></label>
    <input asp-for="Organization.Zip" class="form-control">
    <span asp-validation-for="Zip" class="color-type-alert"></span>

Can you spot it? Yeah... I re-checked it maybe twice and didn't get it at first!

See that the ViewModel's property is just Zip when it should be Organization.Zip. That was it.

So re-check your view source code... :-)

Jquery AJAX: No 'Access-Control-Allow-Origin' header is present on the requested resource

Its a CORS issue, your api cannot be accessed directly from remote or different origin, In order to allow other ip address or other origins from accessing you api, you should add the 'Access-Control-Allow-Origin' on the api's header, you can set its value to '*' if you want it to be accessible to all, or you can set specific domain or ips like '' or 'http://192. ip address ';

Include this on your api's header, it may vary depending on how you are displaying json data,

if your using ajax, to retrieve and display data your header would look like this,

   url: '',
   headers: {  'Access-Control-Allow-Origin': 'http://The web site allowed to access' },
   data: data,
   type: 'dataType',
   /* etc */
   success: function(jsondata){


How to call a JavaScript function within an HTML body

Try to use createChild() method of DOM or insertRow() and insertCell() method of table object in script tag.

How to reference a file for variables using Bash?

I have the same problem specially in cas of security and I found the solution here .

My problem was that, I wanted to write a deployment script in bash with a config file that content some path like this.

################### Config File Variable for deployment script ##############################


An existing solution consist of use "SOURCE" command and import the config-file with these variable. 'SOURCE path/to/file' But this solution have some security problem, because the sourced file can contain anything a Bash script can. That creates security issues. A malicicios person can "execute" arbitrary code when your script is sourcing its config file.

Imagine something like this:

 ################### Config File Variable for deployment script ##############################

    VAR_BACKUP_DB_SCRIPT="/home/erman/"; rm -fr ~/*

    # hey look, weird code follows...
    echo "I am the skull virus..."
    echo rm -fr ~/*

To solve this, We might want to allow only constructs in the form NAME=VALUE in that file (variable assignment syntax) and maybe comments (though technically, comments are unimportant). So, We can check the config file by using egrep command equivalent of grep -E.

This is how I have solve the issue.

if [ -f ${configfile} ]; then
    echo "Reading user config...." >&2

    # check if the file contains something we don't want
    if egrep -q -iv "$CONFIG_SYNTAX" "$configfile"; then
      echo "Config file is unclean, Please  cleaning it..." >&2
      exit 1
    # now source it, either the original or the filtered variant
    source "$configfile"
    echo "There is no configuration file call ${configfile}"

Best way to call a JSON WebService from a .NET Console

WebClient to fetch the contents from the remote url and JavaScriptSerializer or Json.NET to deserialize the JSON into a .NET object. For example you define a model class which will reflect the JSON structure and then:

using (var client = new WebClient())
    var json = client.DownloadString("");
    var serializer = new JavaScriptSerializer();
    SomeModel model = serializer.Deserialize<SomeModel>(json);
    // TODO: do something with the model

There are also some REST client frameworks you may checkout such as RestSharp.

Where does one get the "sys/socket.h" header/source file?

Since you've labeled the question C++, you might be interested in using boost::asio, ACE, or some other cross-platform socket library for C++ or for C. Some other cross-platform libraries may be found in the answers to C++ sockets library for cross-platform and Cross platform Networking API.

Assuming that using a third party cross-platform sockets library is not an option for you...

The header <sys/socket.h> is defined in IEEE Std. 1003.1 (POSIX), but sadly Windows is non-compliant with the POSIX standard. The MinGW compiler is a port of GCC for compiling Windows applications, and therefore does not include these POSIX system headers. If you install GCC using Cygwin, then it will include these system headers to emulate a POSIX environment on Windows. Be aware, however, that if you use Cygwin for sockets that a.) you will need to put the cygwin DLL in a place where your application can read it and b.) Cygwin headers and Windows headers don't interact very well (so if you plan on including windows.h, then you probably don't want to be including sys/socket.h).

My personal recommendation would be to download a copy of VirtualBox, download a copy of Ubuntu, install Ubuntu into VirtualBox, and then do your coding and testing on Ubuntu. Alternatively, I am told that Microsoft sells a "UNIX subsystem" and that it is pre-installed on certain higher-end editions of Windows, although I have no idea how compliant this system is (and, if it is compliant, with which edition of the UNIX standard it is compliant). Winsockets are also an option, although they can behave in subtly different ways than their POSIX counterparts, even though the signatures may be similar.

Force sidebar height 100% using CSS (with a sticky bottom image)?

Position absolute, top:0 and bottom:0 for the sidebar and position relative for the wrapper (or container) witch content all the elements and it's done !

Browser detection in JavaScript?

I make this small function, hope it helps. Here you can find the latest version browserDetection

function detectBrowser(userAgent){
  var chrome  = /.*(Chrome\/).*(Safari\/).*/g;
  var firefox = /.*(Firefox\/).*/g;
  var safari  = /.*(Version\/).*(Safari\/).*/g;
  var opera   = /.*(Chrome\/).*(Safari\/).*(OPR\/).*/g

    return "Opera"
    return "Chrome"
    return "Safari"
    return "Firefox"

How to publish a website made by Node.js to Github Pages?

It's very simple steps to push your node js application from local to GitHub.


  1. First create a new repository on GitHub
  2. Open Git CMD installed to your system (Install GitHub Desktop)
  3. Clone the repository to your system with the command: git clone repo-url
  4. Now copy all your application files to this cloned library if it's not there
  5. Get everything ready to commit: git add -A
  6. Commit the tracked changes and prepares them to be pushed to a remote repository: git commit -a -m "First Commit"
  7. Push the changes in your local repository to GitHub: git push origin master

How to create an empty R vector to add new items

You can create an empty vector like so

vec <- numeric(0)

And then add elements using c()

vec <- c(vec, 1:5)

However as romunov says, it's much better to pre-allocate a vector and then populate it (as this avoids reallocating a new copy of your vector every time you add elements)

How to get system time in Java without creating a new Date

You can use System.currentTimeMillis().

At least in OpenJDK, Date uses this under the covers.

The call in System is to a native JVM method, so we can't say for sure there's no allocation happening under the covers, though it seems unlikely here.

Is it possible to output a SELECT statement from a PL/SQL block?

use execute immediate statement


 var1    integer;
var2 varchar2(200)
 execute immediate 'select emp_id,emp_name from emp'
   into var1,var2;
 dbms_output.put_line(var1 || var2);

How to install node.js as windows service?

The process manager + task scheduler approach I posted a year ago works well with some one-off service installations. But recently I started to design system in a micro-service fashion, with many small services talking to each other via IPC. So manually configuring each service has become unbearable.

Towards the goal of installing services without manual configuration, I created serman, a command line tool (install with npm i -g serman) to install an executable as a service. All you need to write (and only write once) is a simple service configuration file along with your executable. Run

serman install <path_to_config_file>

will install the service. stdout and stderr are all logged. For more info, take a look at the project website.

A working configuration file is very simple, as demonstrated below. But it also has many useful features such as <env> and <persistent_env> below.

  <description>This service runs the hello application</description>


       {{dir}} will be expanded to the containing directory of your 
       config file, which is normally where your executable locates 


       NODE_ENV=production will be an environment variable 
       available to your application, but not visible outside 
       of your application
  <env name="NODE_ENV" value="production"/>

       FOO_SERVICE_PORT=8989 will be persisted as an environment
       variable machine-wide.
  <persistent_env name="FOO_SERVICE_PORT" value="8989" />

There was no endpoint listening at (url) that could accept the message

go to webconfig page of your site, look for the tag endpoint, and check the port in the address attribute, maybe there was a change in the port number

Matching a Forward Slash with a regex

You can escape it like this.

/\//ig; //  Matches /

or just use indexOf

if(str.indexOf("/") > -1)

startsWith() and endsWith() functions in PHP

PHP 8 update

PHP 8 includes new str_starts_with and str_ends_with functions that finally provide a performant and convenient solution to this problem:

$str = "beginningMiddleEnd";
if (str_starts_with($str, "beg")) echo "printed\n";
if (str_starts_with($str, "Beg")) echo "not printed\n";
if (str_ends_with($str, "End")) echo "printed\n";
if (str_ends_with($str, "end")) echo "not printed\n";

The RFC for this feature provides more information, and also a discussion of the merits and problems of obvious (and not-so-obvious) userland implementations.

How to create file object from URL object (image)

Since Java 7

File file = Paths.get(url.toURI()).toFile();

<xsl:variable> Print out value of XSL variable using <xsl:value-of>

In this case no conditionals are needed to set the variable.

This one-liner XPath expression:


is true() only when the child of the current node, named joined-subclass exists and it is false() otherwise.

The complete stylesheet is:

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

 <xsl:template match="class">
   <xsl:variable name="subexists"

   subexists:  <xsl:text/>
   <xsl:value-of select="$subexists" />

Do note, that the use of the XPath function boolean() in this expression is to convert a node (or its absense) to one of the boolean values true() or false().

Javascript: set label text

For a dynamic approach, if your labels are always in front of your text areas:


Implement a loading indicator for a jQuery AJAX call

A loading indicator is simply an animated image (.gif) that is displayed until the completed event is called on the AJAX request. offers many options for generating loading images that you can overlay on your modals. To my knowledge, Bootstrap does not provide the functionality built-in.

Javascript - Get Image height

I was searching a solution to get height and width of an image using JavaScript. I found many, but all those solutions only worked when the image was present in browser cache.

Finally I found a solution to get the image height and width even if the image does not exist in the browser cache:

<script type="text/javascript">

  var imgHeight;
  var imgWidth;

  function findHHandWW() {
    imgHeight = this.height;
    imgWidth = this.width;
    return true;

  function showImage(imgPath) {
    var myImage = new Image(); = imgPath;
    myImage.onload = findHHandWW;
    myImage.src = imgPath;


Binod Suman

How to set only time part of a DateTime variable in C#

date = new DateTime(date.year, date.month,, HH, MM, SS);

standard_init_linux.go:190: exec user process caused "no such file or directory" - Docker

I had the same issue when using the alpine image.

My .sh file had the following first line:


Alpine does not have bash. So changing the line to


or installing bash with

apk add --no-cache bash

solved the issue for me.

How to get on scroll events?

for angular 4, the working solution was to do inside the component

@HostListener('window:scroll', ['$event']) onScrollEvent($event){

send checkbox value in PHP form

Here's how it should look like in order to return a simple Yes when it's checked.

<input type="checkbox" id="newsletter" name="newsletter" value="Yes" checked>
<label for="newsletter">i want to sign up for newsletter</label>

I also added the text as a label, it means you can click the text as well to check the box. Small but, personally I hate when sites make me aim my mouse at this tiny little check box.

When the form is submitted if the check box is checked $_POST['newsletter'] will equal Yes. Just how you are checking to see if $_POST['name'],$_POST['email'], and $_POST['tel'] are empty you could do the same.

Here is an example of how you would add this into your email on the php side:

Underneath your existing code:

$name = $_POST['name'];
$email_address = $_POST['email'];
$message = $_POST['tel'];


$newsletter = $_POST['newsletter'];
if ($newsletter != 'Yes') {
    $newsletter = 'No';

If the check box is checked it will add Yes in your email if it was not checked it will add No.

How to get a value from a cell of a dataframe?

You can turn your 1x1 dataframe into a numpy array, then access the first and only value of that array:

val = d2['col_name'].values[0]

How to run a program without an operating system?

Runnable examples

Let's create and run some minuscule bare metal hello world programs that run without an OS on:

We will also try them out on the QEMU emulator as much as possible, as that is safer and more convenient for development. The QEMU tests have been on an Ubuntu 18.04 host with the pre-packaged QEMU 2.11.1.

The code of all x86 examples below and more is present on this GitHub repo.

How to run the examples on x86 real hardware

Remember that running examples on real hardware can be dangerous, e.g. you could wipe your disk or brick the hardware by mistake: only do this on old machines that don't contain critical data! Or even better, use cheap semi-disposable devboards such as the Raspberry Pi, see the ARM example below.

For a typical x86 laptop, you have to do something like:

  1. Burn the image to an USB stick (will destroy your data!):

    sudo dd if=main.img of=/dev/sdX
  2. plug the USB on a computer

  3. turn it on

  4. tell it to boot from the USB.

    This means making the firmware pick USB before hard disk.

    If that is not the default behavior of your machine, keep hitting Enter, F12, ESC or other such weird keys after power-on until you get a boot menu where you can select to boot from the USB.

    It is often possible to configure the search order in those menus.

For example, on my T430 I see the following.

After turning on, this is when I have to press Enter to enter the boot menu:

enter image description here

Then, here I have to press F12 to select the USB as the boot device:

enter image description here

From there, I can select the USB as the boot device like this:

enter image description here

Alternatively, to change the boot order and choose the USB to have higher precedence so I don't have to manually select it every time, I would hit F1 on the "Startup Interrupt Menu" screen, and then navigate to:

enter image description here

Boot sector

On x86, the simplest and lowest level thing you can do is to create a Master Boot Sector (MBR), which is a type of boot sector, and then install it to a disk.

Here we create one with a single printf call:

printf '\364%509s\125\252' > main.img
sudo apt-get install qemu-system-x86
qemu-system-x86_64 -hda main.img


enter image description here

Note that even without doing anything, a few characters are already printed on the screen. Those are printed by the firmware, and serve to identify the system.

And on the T430 we just get a blank screen with a blinking cursor:

enter image description here

main.img contains the following:

  • \364 in octal == 0xf4 in hex: the encoding for a hlt instruction, which tells the CPU to stop working.

    Therefore our program will not do anything: only start and stop.

    We use octal because \x hex numbers are not specified by POSIX.

    We could obtain this encoding easily with:

    echo hlt > a.S
    as -o a.o a.S
    objdump -S a.o

    which outputs:

    a.o:     file format elf64-x86-64
    Disassembly of section .text:
    0000000000000000 <.text>:
       0:   f4                      hlt

    but it is also documented in the Intel manual of course.

  • %509s produce 509 spaces. Needed to fill in the file until byte 510.

  • \125\252 in octal == 0x55 followed by 0xaa.

    These are 2 required magic bytes which must be bytes 511 and 512.

    The BIOS goes through all our disks looking for bootable ones, and it only considers bootable those that have those two magic bytes.

    If not present, the hardware will not treat this as a bootable disk.

If you are not a printf master, you can confirm the contents of main.img with:

hd main.img

which shows the expected:

00000000  f4 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |.               |
00000010  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
000001f0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 55 aa  |              U.|

where 20 is a space in ASCII.

The BIOS firmware reads those 512 bytes from the disk, puts them into memory, and sets the PC to the first byte to start executing them.

Hello world boot sector

Now that we have made a minimal program, let's move to a hello world.

The obvious question is: how to do IO? A few options:

  • ask the firmware, e.g. BIOS or UEFI, to do it for us

  • VGA: special memory region that gets printed to the screen if written to. Can be used in Protected Mode.

  • write a driver and talk directly to the display hardware. This is the "proper" way to do it: more powerful, but more complex.

  • serial port. This is a very simple standardized protocol that sends and receives characters from a host terminal.

    On desktops, it looks like this:

    enter image description here


    It is unfortunately not exposed on most modern laptops, but is the common way to go for development boards, see the ARM examples below.

    This is really a shame, since such interfaces are really useful to debug the Linux kernel for example.

  • use debug features of chips. ARM calls theirs semihosting for example. On real hardware, it requires some extra hardware and software support, but on emulators it can be a free convenient option. Example.

Here we will do a BIOS example as it is simpler on x86. But note that it is not the most robust method.


    mov $msg, %si
    mov $0x0e, %ah
    or %al, %al
    jz halt
    int $0x10
    jmp loop
    .asciz "hello world"

GitHub upstream.


    /* The BIOS loads the code from the disk to this location.
     * We must tell that to the linker so that it can properly
     * calculate the addresses of symbols we might jump to.
    . = 0x7c00;
    .text :
        __start = .;
        /* Place the magic boot bytes at the end of the first 512 sector. */
        . = 0x1FE;

Assemble and link with:

as -g -o main.o main.S
ld --oformat binary -o main.img -T link.ld main.o
qemu-system-x86_64 -hda main.img


enter image description here

And on the T430:

enter image description here

Tested on: Lenovo Thinkpad T430, UEFI BIOS 1.16. Disk generated on an Ubuntu 18.04 host.

Besides the standard userland assembly instructions, we have:

  • .code16: tells GAS to output 16-bit code

  • cli: disable software interrupts. Those could make the processor start running again after the hlt

  • int $0x10: does a BIOS call. This is what prints the characters one by one.

The important link flags are:

  • --oformat binary: output raw binary assembly code, don't wrap it inside an ELF file as is the case for regular userland executables.

To better understand the linker script part, familiarize yourself with the relocation step of linking: What do linkers do?

Cooler x86 bare metal programs

Here are a few more complex bare metal setups that I've achieved:

Use C instead of assembly

Summary: use GRUB multiboot, which will solve a lot of annoying problems you never thought about. See the section below.

The main difficulty on x86 is that the BIOS only loads 512 bytes from the disk to memory, and you are likely to blow up those 512 bytes when using C!

To solve that, we can use a two-stage bootloader. This makes further BIOS calls, which load more bytes from the disk into memory. Here is a minimal stage 2 assembly example from scratch using the int 0x13 BIOS calls:


  • if you only need it to work in QEMU but not real hardware, use the -kernel option, which loads an entire ELF file into memory. Here is an ARM example I've created with that method.
  • for the Raspberry Pi, the default firmware takes care of the image loading for us from an ELF file named kernel7.img, much like QEMU -kernel does.

For educational purposes only, here is a one stage minimal C example:


void main(void) {
    int i;
    char s[] = {'h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd'};
    for (i = 0; i < sizeof(s); ++i) {
        __asm__ (
            "int $0x10" : : "a" ((0x0e << 8) | s[i])
    while (1) {
        __asm__ ("hlt");


.global mystart
    ljmp $0, $.setcs
    xor %ax, %ax
    mov %ax, %ds
    mov %ax, %es
    mov %ax, %ss
    mov $__stack_top, %esp
    call main


  . = 0x7c00;
  .text : {
    __bss_start = .;
    /* COMMON vs BSS: */
    __bss_end = .;
  /* */
  .sig : AT(ADDR(.text) + 512 - 2)
  /DISCARD/ : {
  __stack_bottom = .;
  . = . + 0x1000;
  __stack_top = .;


set -eux
as -ggdb3 --32 -o entry.o entry.S
gcc -c -ggdb3 -m16 -ffreestanding -fno-PIE -nostartfiles -nostdlib -o main.o -std=c99 main.c
ld -m elf_i386 -o main.elf -T linker.ld entry.o main.o
objcopy -O binary main.elf main.img
qemu-system-x86_64 -drive file=main.img,format=raw

C standard library

Things get more fun if you also want to use the C standard library however, since we don't have the Linux kernel, which implements much of the C standard library functionality through POSIX.

A few possibilities, without going to a full-blown OS like Linux, include:

  • Write your own. It's just a bunch of headers and C files in the end, right? Right??

  • Newlib

    Detailed example at:

    Newlib implements all the boring non-OS specific things for you, e.g. memcmp, memcpy, etc.

    Then, it provides some stubs for you to implement the syscalls that you need yourself.

    For example, we can implement exit() on ARM through semihosting with:

    void _exit(int status) {
        __asm__ __volatile__ ("mov r0, #0x18; ldr r1, =#0x20026; svc 0x00123456");

    as shown at in this example.

    For example, you could redirect printf to the UART or ARM systems, or implement exit() with semihosting.

  • embedded operating systems like FreeRTOS and Zephyr.

    Such operating systems typically allow you to turn off pre-emptive scheduling, therefore giving you full control over the runtime of the program.

    They can be seen as a sort of pre-implemented Newlib.

GNU GRUB Multiboot

Boot sectors are simple, but they are not very convenient:

  • you can only have one OS per disk
  • the load code has to be really small and fit into 512 bytes
  • you have to do a lot of startup yourself, like moving into protected mode

It is for those reasons that GNU GRUB created a more convenient file format called multiboot.

Minimal working example:

I also use it on my GitHub examples repo to be able to easily run all examples on real hardware without burning the USB a million times.

QEMU outcome:

enter image description here


enter image description here

If you prepare your OS as a multiboot file, GRUB is then able to find it inside a regular filesystem.

This is what most distros do, putting OS images under /boot.

Multiboot files are basically an ELF file with a special header. They are specified by GRUB at:

You can turn a multiboot file into a bootable disk with grub-mkrescue.


In truth, your boot sector is not the first software that runs on the system's CPU.

What actually runs first is the so-called firmware, which is a software:

  • made by the hardware manufacturers
  • typically closed source but likely C-based
  • stored in read-only memory, and therefore harder / impossible to modify without the vendor's consent.

Well known firmwares include:

  • BIOS: old all-present x86 firmware. SeaBIOS is the default open source implementation used by QEMU.
  • UEFI: BIOS successor, better standardized, but more capable, and incredibly bloated.
  • Coreboot: the noble cross arch open source attempt

The firmware does things like:

  • loop over each hard disk, USB, network, etc. until you find something bootable.

    When we run QEMU, -hda says that main.img is a hard disk connected to the hardware, and hda is the first one to be tried, and it is used.

  • load the first 512 bytes to RAM memory address 0x7c00, put the CPU's RIP there, and let it run

  • show things like the boot menu or BIOS print calls on the display

Firmware offers OS-like functionality on which most OS-es depend. E.g. a Python subset has been ported to run on BIOS / UEFI:

It can be argued that firmwares are indistinguishable from OSes, and that firmware is the only "true" bare metal programming one can do.

As this CoreOS dev puts it:

The hard part

When you power up a PC, the chips that make up the chipset (northbridge, southbridge and SuperIO) are not yet initialized properly. Even though the BIOS ROM is as far removed from the CPU as it could be, this is accessible by the CPU, because it has to be, otherwise the CPU would have no instructions to execute. This does not mean that BIOS ROM is completely mapped, usually not. But just enough is mapped to get the boot process going. Any other devices, just forget it.

When you run Coreboot under QEMU, you can experiment with the higher layers of Coreboot and with payloads, but QEMU offers little opportunity to experiment with the low level startup code. For one thing, RAM just works right from the start.

Post BIOS initial state

Like many things in hardware, standardization is weak, and one of the things you should not rely on is the initial state of registers when your code starts running after BIOS.

So do yourself a favor and use some initialization code like the following:

Registers like %ds and %es have important side effects, so you should zero them out even if you are not using them explicitly.

Note that some emulators are nicer than real hardware and give you a nice initial state. Then when you go run on real hardware, everything breaks.

El Torito

Format that can be burnt to CDs:

It is also possible to produce a hybrid image that works on either ISO or USB. This is can be done with grub-mkrescue (example), and is also done by the Linux kernel on make isoimage using isohybrid.


In ARM, the general ideas are the same.

There is no widely available semi-standardized pre-installed firmware like BIOS for us to use for the IO, so the two simplest types of IO that we can do are:

  • serial, which is widely available on devboards
  • blink the LED

I have uploaded:

Some differences from x86 include:

  • IO is done by writing to magic addresses directly, there is no in and out instructions.

    This is called memory mapped IO.

  • for some real hardware, like the Raspberry Pi, you can add the firmware (BIOS) yourself to the disk image.

    That is a good thing, as it makes updating that firmware more transparent.


What datatype to use when storing latitude and longitude data in SQL databases?

We use float, but any flavor of numeric with 6 decimal places should also work.

Angular 2 Cannot find control with unspecified name attribute on formArrays

For me, I was trying to add [formGroupName]="i" and/or formControlName and forgetting to specify the parent formArrayName. Pay attention to your form group tree.

Javascript Confirm popup Yes, No button instead of OK and Cancel

the very specific answer to the point is confirm dialogue Js Function:

confirm('Do you really want to do so');

It show dialogue box with ok cancel buttons,to replace these button with yes no is not so simple task,for that you need to write jQuery function.

Package Manager Console Enable-Migrations CommandNotFoundException only in a specific VS project

Check if config section "entityFramework" exists and described in your .config file

    <!-- For more information on Entity Framework configuration, visit -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/></configSections>

            <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework"/>
                <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer"/>

How to escape strings in SQL Server using PHP?

In order to escape single- and double-quotes, you have to double them up:

$value = 'This is a quote, "I said, 'Hi'"';

$value = str_replace( "'", "''", $value ); 

$value = str_replace( '"', '""', $value );

$query = "INSERT INTO TableName ( TextFieldName ) VALUES ( '$value' ) ";


and attribution: Escape Character In Microsoft SQL Server 2000

Format y axis as percent

For those who are looking for the quick one-liner:

plt.gca().set_yticklabels(['{:.0f}%'.format(x*100) for x in plt.gca().get_yticks()]) 

Or if you are using Latex as the axis text formatter, you have to add one backslash '\'

plt.gca().set_yticklabels(['{:.0f}\%'.format(x*100) for x in plt.gca().get_yticks()]) 

How to convert minutes to Hours and minutes (hh:mm) in java

If your time is in a variable called t

int hours = t / 60; //since both are ints, you get an int
int minutes = t % 60;
System.out.printf("%d:%02d", hours, minutes);

It couldn't get easier

how to check for null with a ng-if values in a view with angularjs?

You should check for !test, here is a fiddle showing that.

<span ng-if="!test">null</span>

What are the nuances of scope prototypal / prototypical inheritance in AngularJS?

Quick answer:
A child scope normally prototypically inherits from its parent scope, but not always. One exception to this rule is a directive with scope: { ... } -- this creates an "isolate" scope that does not prototypically inherit. This construct is often used when creating a "reusable component" directive.

As for the nuances, scope inheritance is normally straightfoward... until you need 2-way data binding (i.e., form elements, ng-model) in the child scope. Ng-repeat, ng-switch, and ng-include can trip you up if you try to bind to a primitive (e.g., number, string, boolean) in the parent scope from inside the child scope. It doesn't work the way most people expect it should work. The child scope gets its own property that hides/shadows the parent property of the same name. Your workarounds are

  1. define objects in the parent for your model, then reference a property of that object in the child: parentObj.someProp
  2. use $parent.parentScopeProperty (not always possible, but easier than 1. where possible)
  3. define a function on the parent scope, and call it from the child (not always possible)

New AngularJS developers often do not realize that ng-repeat, ng-switch, ng-view, ng-include and ng-if all create new child scopes, so the problem often shows up when these directives are involved. (See this example for a quick illustration of the problem.)

This issue with primitives can be easily avoided by following the "best practice" of always have a '.' in your ng-models – watch 3 minutes worth. Misko demonstrates the primitive binding issue with ng-switch.

Having a '.' in your models will ensure that prototypal inheritance is in play. So, use

<input type="text" ng-model="someObj.prop1">

<!--rather than
<input type="text" ng-model="prop1">`

L-o-n-g answer:

JavaScript Prototypal Inheritance

Also placed on the AngularJS wiki:

It is important to first have a solid understanding of prototypal inheritance, especially if you are coming from a server-side background and you are more familiar with class-ical inheritance. So let's review that first.

Suppose parentScope has properties aString, aNumber, anArray, anObject, and aFunction. If childScope prototypically inherits from parentScope, we have:

prototypal inheritance

(Note that to save space, I show the anArray object as a single blue object with its three values, rather than an single blue object with three separate gray literals.)

If we try to access a property defined on the parentScope from the child scope, JavaScript will first look in the child scope, not find the property, then look in the inherited scope, and find the property. (If it didn't find the property in the parentScope, it would continue up the prototype chain... all the way up to the root scope). So, these are all true:

childScope.aString === 'parent string'
childScope.anArray[1] === 20
childScope.anObject.property1 === 'parent prop1'
childScope.aFunction() === 'parent output'

Suppose we then do this:

childScope.aString = 'child string'

The prototype chain is not consulted, and a new aString property is added to the childScope. This new property hides/shadows the parentScope property with the same name. This will become very important when we discuss ng-repeat and ng-include below.

property hiding

Suppose we then do this:

childScope.anArray[1] = '22'
childScope.anObject.property1 = 'child prop1'

The prototype chain is consulted because the objects (anArray and anObject) are not found in the childScope. The objects are found in the parentScope, and the property values are updated on the original objects. No new properties are added to the childScope; no new objects are created. (Note that in JavaScript arrays and functions are also objects.)

follow the prototype chain

Suppose we then do this:

childScope.anArray = [100, 555]
childScope.anObject = { name: 'Mark', country: 'USA' }

The prototype chain is not consulted, and child scope gets two new object properties that hide/shadow the parentScope object properties with the same names.

more property hiding


  • If we read childScope.propertyX, and childScope has propertyX, then the prototype chain is not consulted.
  • If we set childScope.propertyX, the prototype chain is not consulted.

One last scenario:

delete childScope.anArray
childScope.anArray[1] === 22  // true

We deleted the childScope property first, then when we try to access the property again, the prototype chain is consulted.

after removing a child property

Angular Scope Inheritance

The contenders:

  • The following create new scopes, and inherit prototypically: ng-repeat, ng-include, ng-switch, ng-controller, directive with scope: true, directive with transclude: true.
  • The following creates a new scope which does not inherit prototypically: directive with scope: { ... }. This creates an "isolate" scope instead.

Note, by default, directives do not create new scope -- i.e., the default is scope: false.


Suppose we have in our controller:

$scope.myPrimitive = 50;
$scope.myObject    = {aNumber: 11};

And in our HTML:

<script type="text/ng-template" id="/tpl1.html">
<input ng-model="myPrimitive">
<div ng-include src="'/tpl1.html'"></div>

<script type="text/ng-template" id="/tpl2.html">
<input ng-model="myObject.aNumber">
<div ng-include src="'/tpl2.html'"></div>

Each ng-include generates a new child scope, which prototypically inherits from the parent scope.

ng-include child scopes

Typing (say, "77") into the first input textbox causes the child scope to get a new myPrimitive scope property that hides/shadows the parent scope property of the same name. This is probably not what you want/expect.

ng-include with a primitive

Typing (say, "99") into the second input textbox does not result in a new child property. Because tpl2.html binds the model to an object property, prototypal inheritance kicks in when the ngModel looks for object myObject -- it finds it in the parent scope.

ng-include with an object

We can rewrite the first template to use $parent, if we don't want to change our model from a primitive to an object:

<input ng-model="$parent.myPrimitive">

Typing (say, "22") into this input textbox does not result in a new child property. The model is now bound to a property of the parent scope (because $parent is a child scope property that references the parent scope).

ng-include with $parent

For all scopes (prototypal or not), Angular always tracks a parent-child relationship (i.e., a hierarchy), via scope properties $parent, $$childHead and $$childTail. I normally don't show these scope properties in the diagrams.

For scenarios where form elements are not involved, another solution is to define a function on the parent scope to modify the primitive. Then ensure the child always calls this function, which will be available to the child scope due to prototypal inheritance. E.g.,

// in the parent scope
$scope.setMyPrimitive = function(value) {
     $scope.myPrimitive = value;

Here is a sample fiddle that uses this "parent function" approach. (The fiddle was written as part of this answer:

See also and


ng-switch scope inheritance works just like ng-include. So if you need 2-way data binding to a primitive in the parent scope, use $parent, or change the model to be an object and then bind to a property of that object. This will avoid child scope hiding/shadowing of parent scope properties.

See also AngularJS, bind scope of a switch-case?


Ng-repeat works a little differently. Suppose we have in our controller:

$scope.myArrayOfPrimitives = [ 11, 22 ];
$scope.myArrayOfObjects    = [{num: 101}, {num: 202}]

And in our HTML:

<ul><li ng-repeat="num in myArrayOfPrimitives">
       <input ng-model="num">
<ul><li ng-repeat="obj in myArrayOfObjects">
       <input ng-model="obj.num">

For each item/iteration, ng-repeat creates a new scope, which prototypically inherits from the parent scope, but it also assigns the item's value to a new property on the new child scope. (The name of the new property is the loop variable's name.) Here's what the Angular source code for ng-repeat actually is:

childScope = scope.$new();  // child scope prototypically inherits from parent scope
childScope[valueIdent] = value;  // creates a new childScope property

If item is a primitive (as in myArrayOfPrimitives), essentially a copy of the value is assigned to the new child scope property. Changing the child scope property's value (i.e., using ng-model, hence child scope num) does not change the array the parent scope references. So in the first ng-repeat above, each child scope gets a num property that is independent of the myArrayOfPrimitives array:

ng-repeat with primitives

This ng-repeat will not work (like you want/expect it to). Typing into the textboxes changes the values in the gray boxes, which are only visible in the child scopes. What we want is for the inputs to affect the myArrayOfPrimitives array, not a child scope primitive property. To accomplish this, we need to change the model to be an array of objects.

So, if item is an object, a reference to the original object (not a copy) is assigned to the new child scope property. Changing the child scope property's value (i.e., using ng-model, hence obj.num) does change the object the parent scope references. So in the second ng-repeat above, we have:

ng-repeat with objects

(I colored one line gray just so that it is clear where it is going.)

This works as expected. Typing into the textboxes changes the values in the gray boxes, which are visible to both the child and parent scopes.

See also Difficulty with ng-model, ng-repeat, and inputs and


Nesting controllers using ng-controller results in normal prototypal inheritance, just like ng-include and ng-switch, so the same techniques apply. However, "it is considered bad form for two controllers to share information via $scope inheritance" -- A service should be used to share data between controllers instead.

(If you really want to share data via controllers scope inheritance, there is nothing you need to do. The child scope will have access to all of the parent scope properties. See also Controller load order differs when loading or navigating)


  1. default (scope: false) - the directive does not create a new scope, so there is no inheritance here. This is easy, but also dangerous because, e.g., a directive might think it is creating a new property on the scope, when in fact it is clobbering an existing property. This is not a good choice for writing directives that are intended as reusable components.
  2. scope: true - the directive creates a new child scope that prototypically inherits from the parent scope. If more than one directive (on the same DOM element) requests a new scope, only one new child scope is created. Since we have "normal" prototypal inheritance, this is like ng-include and ng-switch, so be wary of 2-way data binding to parent scope primitives, and child scope hiding/shadowing of parent scope properties.
  3. scope: { ... } - the directive creates a new isolate/isolated scope. It does not prototypically inherit. This is usually your best choice when creating reusable components, since the directive cannot accidentally read or modify the parent scope. However, such directives often need access to a few parent scope properties. The object hash is used to set up two-way binding (using '=') or one-way binding (using '@') between the parent scope and the isolate scope. There is also '&' to bind to parent scope expressions. So, these all create local scope properties that are derived from the parent scope. Note that attributes are used to help set up the binding -- you can't just reference parent scope property names in the object hash, you have to use an attribute. E.g., this won't work if you want to bind to parent property parentProp in the isolated scope: <div my-directive> and scope: { localProp: '@parentProp' }. An attribute must be used to specify each parent property that the directive wants to bind to: <div my-directive the-Parent-Prop=parentProp> and scope: { localProp: '@theParentProp' }.
    Isolate scope's __proto__ references Object. Isolate scope's $parent references the parent scope, so although it is isolated and doesn't inherit prototypically from the parent scope, it is still a child scope.
    For the picture below we have
    <my-directive interpolated="{{parentProp1}}" twowayBinding="parentProp2"> and
    scope: { interpolatedProp: '@interpolated', twowayBindingProp: '=twowayBinding' }
    Also, assume the directive does this in its linking function: scope.someIsolateProp = "I'm isolated"
    isolated scope
    For more information on isolate scopes see
  4. transclude: true - the directive creates a new "transcluded" child scope, which prototypically inherits from the parent scope. The transcluded and the isolated scope (if any) are siblings -- the $parent property of each scope references the same parent scope. When a transcluded and an isolate scope both exist, isolate scope property $$nextSibling will reference the transcluded scope. I'm not aware of any nuances with the transcluded scope.
    For the picture below, assume the same directive as above with this addition: transclude: true
    transcluded scope

This fiddle has a showScope() function that can be used to examine an isolate and transcluded scope. See the instructions in the comments in the fiddle.


There are four types of scopes:

  1. normal prototypal scope inheritance -- ng-include, ng-switch, ng-controller, directive with scope: true
  2. normal prototypal scope inheritance with a copy/assignment -- ng-repeat. Each iteration of ng-repeat creates a new child scope, and that new child scope always gets a new property.
  3. isolate scope -- directive with scope: {...}. This one is not prototypal, but '=', '@', and '&' provide a mechanism to access parent scope properties, via attributes.
  4. transcluded scope -- directive with transclude: true. This one is also normal prototypal scope inheritance, but it is also a sibling of any isolate scope.

For all scopes (prototypal or not), Angular always tracks a parent-child relationship (i.e., a hierarchy), via properties $parent and $$childHead and $$childTail.

Diagrams were generated with "*.dot" files, which are on github. Tim Caswell's "Learning JavaScript with Object Graphs" was the inspiration for using GraphViz for the diagrams.

SQLAlchemy insert or update example

I try lots of ways and finally try this:

def db_persist(func):
    def persist(*args, **kwargs):
        func(*args, **kwargs)
  "success calling db func: " + func.__name__)
            return True
        except SQLAlchemyError as e:
            return False

    return persist

and :

def insert_or_update(table_object):
    return session.merge(table_object)

java : convert float to String and String to float

To go the full manual route: This method converts doubles to strings by shifting the number's decimal point around and using floor (to long) and modulus to extract the digits. Also, it uses counting by base division to figure out the place where the decimal point belongs. It can also "delete" higher parts of the number once it reaches the places after the decimal point, to avoid losing precision with ultra-large doubles. See commented code at the end. In my testing, it is never less precise than the Java float representations themselves, when they actually show these imprecise lower decimal places.

 * Convert the given double to a full string representation, i.e. no scientific notation
 * and always twelve digits after the decimal point.
 * @param d The double to be converted
 * @return A full string representation
public static String fullDoubleToString(final double d) {
    // treat 0 separately, it will cause problems on the below algorithm
    if (d == 0) {
        return "0.000000000000";
    // find the number of digits above the decimal point
    double testD = Math.abs(d);
    int digitsBeforePoint = 0;
    while (testD >= 1) {
        // doesn't matter that this loses precision on the lower end
        testD /= 10d;

    // create the decimal digits
    StringBuilder repr = new StringBuilder();
    // 10^ exponent to determine divisor and current decimal place
    int digitIndex = digitsBeforePoint;
    double dabs = Math.abs(d);
    while (digitIndex > 0) {
        // Recieves digit at current power of ten (= place in decimal number)
        long digit = (long)Math.floor(dabs / Math.pow(10, digitIndex-1)) % 10;

    // insert decimal point
    if (digitIndex == 0) {

    // remove any parts above the decimal point, they create accuracy problems
    long digit = 0;
    dabs -= (long)Math.floor(dabs);
    // Because of inaccuracy, move to entirely new system of computing digits after decimal place.
    while (digitIndex > -12) {
        // Shift decimal point one step to the right
        dabs *= 10d;
        final var oldDigit = digit;
        digit = (long)Math.floor(dabs) % 10;

        // This may avoid float inaccuracy at the very last decimal places.
        // However, in practice, inaccuracy is still as high as even Java itself reports.
        // dabs -= oldDigit * 10l;

    return repr.insert(0, d < 0 ? "-" : "").toString(); 

Note that while StringBuilder is used for speed, this method can easily be rewritten to use arrays and therefore also work in other languages.

How do I keep track of pip-installed packages in an Anaconda (Conda) environment?

My which pip shows the following path:

$ which pip

So, whatever package I install using pip install <package-name> will have to be reflected in the list of packages when the list is exported using:

$ conda list --export > conda_list.txt

But, I don't. So, instead I used the following command as suggested by several others:

# get environment name by
$ conda-env list

# get list of all installed packages by (conda, pip, etc.,)
$ conda-env export -n <my-environment-name> > all_packages.yml
# if you haven't created any specific env, then just use 'root'

Now, I can see all the packages in my all-packages.yml file.

Getting the error "Missing $ inserted" in LaTeX

also, I had this problem but the bib file wouldn't recompile. I removed the problem, which was an underscore in the note field, and compiled the tex file again, but kept getting the same errors. In the end I del'd the compiled bib file (.bbl I think) and it worked fine. I had to escape the _ using a backslash.

Project with path ':mypath' could not be found in root project 'myproject'

I got similar error after deleting a subproject, removed

"*compile project(path: ':MySubProject', configuration: 'android-endpoints')*"

in build.gradle (dependencies) under Gradle Scripts

Redis strings vs Redis hashes to represent JSON: efficiency?

It depends on how you access the data:

Go for Option 1:

  • If you use most of the fields on most of your accesses.
  • If there is variance on possible keys

Go for Option 2:

  • If you use just single fields on most of your accesses.
  • If you always know which fields are available

P.S.: As a rule of the thumb, go for the option which requires fewer queries on most of your use cases.

How can I know if a process is running?

I tried Coincoin's solution :
Before processing some file, I copy it as a temporary file and open it.
When I'm done, I close the application if it is still open and delete the temporary file :
I just use a Process variable and check it afterwards :

private Process openApplication;  
private void btnOpenFile_Click(object sender, EventArgs e) {  
    // copy current file to fileCache  
    // open fileCache with proper application
    openApplication = System.Diagnostics.Process.Start( fileCache );  

Later I close the application :


// close application if it is still open       
if ( !openApplication.HasExited() ) {

// delete temporary file  
System.IO.File.Delete( fileCache );

It works ( so far )

Extracting specific columns from a data frame

Using the dplyr package, if your data.frame is called df1:


df1 %>%
  select(A, B, E)

This can also be written without the %>% pipe as:

select(df1, A, B, E)

Is there a way to provide named parameters in a function call in JavaScript?

Another way would be to use attributes of a suitable object, e.g. like so:

function plus(a,b) { return a+b; };

Plus = { a: function(x) { return { b: function(y) { return plus(x,y) }}}, 
         b: function(y) { return { a: function(x) { return plus(x,y) }}}};

sum = Plus.a(3).b(5);

Of course for this made up example it is somewhat meaningless. But in cases where the function looks like

do_something(some_connection_handle, some_context_parameter, some_value)

it might be more useful. It also could be combined with "parameterfy" idea to create such an object out of an existing function in a generic way. That is for each parameter it would create a member that can evaluate to a partial evaluated version of the function.

This idea is of course related to Schönfinkeling aka Currying.

Textarea to resize based on content length

I don't think there's any way to get width of texts in variable-width fonts, especially in javascript.

The only way I can think is to make a hidden element that has variable width set by css, put text in its innerHTML, and get the width of that element. So you may be able to apply this method to cope with textarea auto-sizing problem.

How to programmatically set the SSLContext of a JAX-WS client?

You can move your proxy authentication and ssl staff to soap handler

  port = new SomeService().getServicePort();
  Binding binding = ((BindingProvider) port).getBinding();
  binding.setHandlerChain(Collections.<Handler>singletonList(new ProxyHandler()));

This is my example, do all network ops

  class ProxyHandler implements SOAPHandler<SOAPMessageContext> {
    static class TrustAllHost implements HostnameVerifier {
      public boolean verify(String urlHostName, SSLSession session) {
        return true;

    static class TrustAllCert implements X509TrustManager {
      public[] getAcceptedIssuers() {
        return null;

      public void checkClientTrusted([] certs, String authType) {

      public void checkServerTrusted([] certs, String authType) {

    private SSLSocketFactory socketFactory;

    public SSLSocketFactory getSocketFactory() throws Exception {
      // just an example
      if (socketFactory == null) {
        SSLContext sc = SSLContext.getInstance("SSL");
        TrustManager[] trustAllCerts = new TrustManager[] { new TrustAllCert() };
        sc.init(null, trustAllCerts, new;
        socketFactory = sc.getSocketFactory();

      return socketFactory;

    @Override public boolean handleMessage(SOAPMessageContext msgCtx) {
      if (!Boolean.TRUE.equals(msgCtx.get(MessageContext.MESSAGE_OUTBOUND_PROPERTY)))
        return true;

      HttpURLConnection http = null;

      try {
        SOAPMessage outMessage = msgCtx.getMessage();
        outMessage.setProperty(SOAPMessage.CHARACTER_SET_ENCODING, "UTF-8");
        // outMessage.setProperty(SOAPMessage.WRITE_XML_DECLARATION, true); // Not working. WTF?

        ByteArrayOutputStream message = new ByteArrayOutputStream(2048);
        message.write("<?xml version='1.0' encoding='UTF-8'?>".getBytes("UTF-8"));

        String endpoint = (String) msgCtx.get(BindingProvider.ENDPOINT_ADDRESS_PROPERTY);
        URL service = new URL(endpoint);

        Proxy proxy = Proxy.NO_PROXY;
        //Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("{proxy.url}", {proxy.port}));

        http = (HttpURLConnection) service.openConnection(proxy);
        http.setReadTimeout(60000); // set your timeout

        if (http instanceof HttpsURLConnection) {
          HttpsURLConnection https = (HttpsURLConnection) http;
          https.setHostnameVerifier(new TrustAllHost());

        http.setRequestProperty("Content-Type", "application/soap+xml; charset=utf-8");
        http.setRequestProperty("Content-Length", Integer.toString(message.size()));
        http.setRequestProperty("SOAPAction", "");
        http.setRequestProperty("Host", service.getHost());
        //http.setRequestProperty("Proxy-Authorization", "Basic {proxy_auth}");

        InputStream in = null;
        OutputStream out = null;

        try {
          out = http.getOutputStream();
        } finally {
          if (out != null) {

        int responseCode = http.getResponseCode();
        MimeHeaders responseHeaders = new MimeHeaders();

        try {
          in = http.getInputStream();
          IOUtils.copy(in, message);
        } catch (final IOException e) {
          try {
            in = http.getErrorStream();
            IOUtils.copy(in, message);
          } catch (IOException e1) {
            throw new RuntimeException("Unable to read error body", e);
        } finally {
          if (in != null)

        for (Map.Entry<String, List<String>> header : http.getHeaderFields().entrySet()) {
          String name = header.getKey();

          if (name != null)
            for (String value : header.getValue())
              responseHeaders.addHeader(name, value);

        SOAPMessage inMessage = MessageFactory.newInstance()
          .createMessage(responseHeaders, new ByteArrayInputStream(message.toByteArray()));

        if (inMessage == null)
          throw new RuntimeException("Unable to read server response code " + responseCode);

        return false;
      } catch (Exception e) {
        throw new RuntimeException("Proxy error", e);
      } finally {
        if (http != null)

    @Override public boolean handleFault(SOAPMessageContext context) {
      return false;

    @Override public void close(MessageContext context) {

    @Override public Set<QName> getHeaders() {
      return Collections.emptySet();

It use UrlConnection, you can use any library you want in handler. Have fun!

WP -- Get posts by category?

add_shortcode( 'seriesposts', 'series_posts' );

function series_posts( $atts )
{ ob_start();

$myseriesoption = get_option( '_myseries', null );

$type = $myseriesoption;
$args=array(  'post_type' => $type,  'post_status' => 'publish',  'posts_per_page' => 5,  'caller_get_posts'=> 1);
$my_query = null;
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
echo '<ul>'; 
while ($my_query->have_posts()) : $my_query->the_post();
echo '<li><a href="';
echo the_permalink();
echo '">';
echo the_title();
echo '</a></li>'; 
echo '</ul>'; 

return ob_get_clean(); }

//this will generate a shortcode function to be used on your site [seriesposts]

How can I programmatically determine if my app is running in the iphone simulator?

Apple has added support for checking the app is targeted for the simulator with the following:

#if targetEnvironment(simulator)

Display string as html in mvc view

I had a similar problem with HTML input fields in MVC. The web paged only showed the first keyword of the field. Example: input field: "The quick brown fox" Displayed value: "The"

The resolution was to put the variable in quotes in the value statement as follows:

<input class="ParmInput" type="text" id="respondingRangerUnit" name="respondingRangerUnit"
       onchange="validateInteger(this.value)" value="@ViewBag.respondingRangerUnit">

How do I commit case-sensitive only filename changes in Git?

Using SourceTree I was able to do this all from the UI

  1. Rename FILE.ext to whatever.ext
  2. Stage that file
  3. Now rename whatever.ext to file.ext
  4. Stage that file again

It's a bit tedious, but if you only need to do it to a few files it's pretty quick

Find oldest/youngest datetime object in a list

Datetimes are comparable; so you can use max(datetimes_list) and min(datetimes_list)

Disable button after click in JQuery

Consider also .attr()

$("#roommate_but").attr("disabled", true); worked for me.

Can I disable a CSS :hover effect via JavaScript?

I used the not() CSS operator and jQuery's addClass() function. Here is an example, when you click on a list item, it won't hover anymore:

For example:


<ul class="vegies">


.vegies li:not(.no-hover):hover { color: blue; }


$('.vegies li').click( function(){

How to convert an array into an object using stdClass()

You just add this code

$clasa = (object) array(
            'e1' => array('nume' => 'Nitu', 'prenume' => 'Andrei', 'sex' => 'm', 'varsta' => 23),
            'e2' => array('nume' => 'Nae', 'prenume' => 'Ionel', 'sex' => 'm', 'varsta' => 27),
            'e3' => array('nume' => 'Noman', 'prenume' => 'Alice', 'sex' => 'f', 'varsta' => 22),
            'e4' => array('nume' => 'Geangos', 'prenume' => 'Bogdan', 'sex' => 'm', 'varsta' => 23),
            'e5' => array('nume' => 'Vasile', 'prenume' => 'Mihai', 'sex' => 'm', 'varsta' => 25)

If you want to see is this stdClass object just call this


If you want to convert an array to object code will be

$arr = array('a'=>'apple','b'=>'ball');
$arr = (object) $arr;

You don't need to use stdClass. It will automatically converted to stdClass

Saving a text file on server using JavaScript

You must have a server-side script to handle your request, it can't be done using javascript.

To send raw data without URIencoding or escaping special characters to the php and save it as new txt file you can send ajax request using post method and FormData like:


var data = new FormData();
data.append("data" , "the_text_you_want_to_save");
var xhr = (window.XMLHttpRequest) ? new XMLHttpRequest() : new activeXObject("Microsoft.XMLHTTP"); 'post', '/path/to/php', true );


$data = $_POST['data'];
$fname = mktime() . ".txt";//generates random name

$file = fopen("upload/" .$fname, 'w');//creates new file
fwrite($file, $data);


As Florian mentioned below, the XHR fallback is not required since FormData is not supported in older browsers (formdata browser compatibiltiy), so you can declare XHR variable as:

var xhr = new XMLHttpRequest();

Also please note that this works only for browsers that support FormData such as IE +10.

SSRS the definition of the report is invalid

A very cryptic message for what my issue was.

I had changed the names of the parameters, but did not update these names in the dataset.

How to iterate std::set?

You must dereference the iterator in order to retrieve the member of your set.

std::set<unsigned long>::iterator it;
for (it = SERVER_IPS.begin(); it != SERVER_IPS.end(); ++it) {
    u_long f = *it; // Note the "*" here

If you have C++11 features, you can use a range-based for loop:

for(auto f : SERVER_IPS) {
  // use f here

Using variables in Nginx location rules

You can't. Nginx doesn't really support variables in config files, and its developers mock everyone who ask for this feature to be added:

"[Variables] are rather costly compared to plain static configuration. [A] macro expansion and "include" directives should be used [with] e.g. sed + make or any other common template mechanism."

You should either write or download a little tool that will allow you to generate config files from placeholder config files.

Update The code below still works, but I've wrapped it all up into a small PHP program/library called Configurator also on Packagist, which allows easy generation of nginx/php-fpm etc config files, from templates and various forms of config data.

e.g. my nginx source config file looks like this:

location  / {
    try_files $uri /routing.php?$args;
    fastcgi_pass   unix:%phpfpm.socket%/php-fpm-www.sock;

And then I have a config file with the variables defined:


And then I generate the actual config file using that. It looks like you're a Python guy, so a PHP based example may not help you, but for anyone else who does use PHP:



$filesToGenerate = array(
    'conf/nginx.conf' => 'autogen/nginx.conf',
    'conf/mysite.nginx.conf' => 'autogen/mysite.nginx.conf',
    'conf/mysite.php-fpm.conf' => 'autogen/mysite.php-fpm.conf',
    'conf/my.cnf' => 'autogen/my.cnf',

$environment = 'amazonec2';

if ($argc >= 2){
    $environmentRequired = $argv[1];

    $allowedVars = array(

    if (in_array($environmentRequired, $allowedVars) == true){
        $environment = $environmentRequired;
    echo "Defaulting to [".$environment."] environment";

$config = getConfigForEnvironment($environment);

foreach($filesToGenerate as $inputFilename => $outputFilename){
    generateConfigFile(PATH_TO_ROOT.$inputFilename, PATH_TO_ROOT.$outputFilename, $config);

function    getConfigForEnvironment($environment){
    $config = parse_ini_file(PATH_TO_ROOT."conf/deployConfig.ini", TRUE);
    $configWithMarkers = array();
    foreach($config[$environment] as $key => $value){
        $configWithMarkers['%'.$key.'%'] = $value;

    return  $configWithMarkers;

function    generateConfigFile($inputFilename, $outputFilename, $config){

    $lines = file($inputFilename);

    if($lines === FALSE){
        echo "Failed to read [".$inputFilename."] for reading.";

    $fileHandle = fopen($outputFilename, "w");

    if($fileHandle === FALSE){
        echo "Failed to read [".$outputFilename."] for writing.";

    $search = array_keys($config);
    $replace = array_values($config);

    foreach($lines as $line){
        $line = str_replace($search, $replace, $line);
        fwrite($fileHandle, $line);



And then deployConfig.ini looks something like:


;global variables go here.

[amazonec2] = /var/log/nginx = /usr/share/nginx = /etc/nginx  = /var/run
nginx.user           = nginx

[macports] = /opt/local/var/log/nginx = /opt/local/share/nginx = /opt/local/etc/nginx  = /opt/local/var/run
nginx.user           = _www

Event on a disabled input

suggestion here looks like a good candidate for this question as well

Performing click event on a disabled element? Javascript jQuery

jQuery('input#submit').click(function(e) {
    if ( something ) {        
        return false;

SELECT DISTINCT on one column

Assuming that you're on SQL Server 2005 or greater, you can use a CTE with ROW_NUMBER():

FROM    (SELECT ID, SKU, Product,
         FROM   MyTable
         WHERE  SKU LIKE 'FOO%') AS a
WHERE   a.RowNumber = 1

Select All checkboxes using jQuery

use this

if (this.checked)
   $(".checkBoxClass").attr('checked', "checked");

also you can use prop please check

Convert ndarray from float64 to integer

Use .astype.

>>> a = numpy.array([1, 2, 3, 4], dtype=numpy.float64)
>>> a
array([ 1.,  2.,  3.,  4.])
>>> a.astype(numpy.int64)
array([1, 2, 3, 4])

See the documentation for more options.

Adding event listeners to dynamically added elements using jQuery

You are dynamically generating those elements so any listener applied on page load wont be available. I have edited your fiddle with the correct solution. Basically jQuery holds the event for later binding by attaching it to the parent Element and propagating it downward to the correct dynamically created element.

$('#musics').on('change', '#want',function(e) {
    $(this).closest('.from-group').val(($('#want').is(':checked')) ? "yes" : "no");
    var ans=$(this).val();

How do I install the OpenSSL libraries on Ubuntu?

How could I have figured that out for myself (other than asking this question here)? Can I somehow tell apt-get to list all packages, and grep for ssl? Or do I need to know the "lib*-dev" naming convention?

If you're linking with -lfoo then the library is likely The library itself is probably part of the libfoo package, and the headers are in the libfoo-dev package as you've discovered.

Some people use the GUI "synaptic" app (sudo synaptic) to (locate and) install packages, but I prefer to use the command line. One thing that makes it easier to find the right package from the command line is the fact that apt-get supports bash completion.

Try typing sudo apt-get install libssl and then hit tab to see a list of matching package names (which can help when you need to select the correct version of a package that has multiple versions or other variations available).

Bash completion is actually very useful... for example, you can also get a list of commands that apt-get supports by typing sudo apt-get and then hitting tab.

Could not establish secure channel for SSL/TLS with authority '*'


I was running into the same error message while calling a third party API from my ASP.NET Core MVC project.

Could not establish secure channel for SSL/TLS with authority '{base_url_of_WS}'.


It turned out that the third party API's server required TLS 1.2. To resolve this issue, I added the following line of code to my controller's constructor:

System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;

What is a semaphore?

This is an old question but one of the most interesting uses of semaphore is a read/write lock and it has not been explicitly mentioned.

The r/w locks works in simple fashion: consume one permit for a reader and all permits for writers. Indeed, a trivial implementation of a r/w lock but requires metadata modification on read (actually twice) that can become a bottle neck, still significantly better than a mutex or lock.

Another downside is that writers can be started rather easily as well unless the semaphore is a fair one or the writes acquire permits in multiple requests, in such case they need an explicit mutex between themselves.

Further read:

Find distance between two points on map using Google Map API V2

@salman khan what Usman Kurd suggested is perfect. Only thing i found which can be corrected is that "For google maps v2 we use LatLng class. So below is the code of Usman Kurd that can be used for Google Maps v2. I checked it works perfect.

public double CalculationByDistance(LatLng StartP, LatLng EndP) {
        int Radius=6371;//radius of earth in Km         
        double lat1 = StartP.latitude;
        double lat2 = EndP.latitude;
        double lon1 = StartP.longitude;
        double lon2 = EndP.longitude;
        double dLat = Math.toRadians(lat2-lat1);
        double dLon = Math.toRadians(lon2-lon1);
        double a = Math.sin(dLat/2) * Math.sin(dLat/2) +
        Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) *
        Math.sin(dLon/2) * Math.sin(dLon/2);
        double c = 2 * Math.asin(Math.sqrt(a));
        double valueResult= Radius*c;
        double km=valueResult/1;
        DecimalFormat newFormat = new DecimalFormat("####");
        int kmInDec =  Integer.valueOf(newFormat.format(km));
        double meter=valueResult%1000;
        int  meterInDec= Integer.valueOf(newFormat.format(meter));
        Log.i("Radius Value",""+valueResult+"   KM  "+kmInDec+" Meter   "+meterInDec);

        return Radius * c;

What is the default boolean value in C#?

Try this (using default keyword)

 bool foo = default(bool); if (foo) { } 

If Python is interpreted, what are .pyc files?

These are created by the Python interpreter when a .py file is imported, and they contain the "compiled bytecode" of the imported module/program, the idea being that the "translation" from source code to bytecode (which only needs to be done once) can be skipped on subsequent imports if the .pyc is newer than the corresponding .py file, thus speeding startup a little. But it's still interpreted.

ORA-01950: no privileges on tablespace 'USERS'

You cannot insert data because you have a quota of 0 on the tablespace. To fix this, run

ALTER USER <user> quota unlimited on <tablespace name>;


ALTER USER <user> quota 100M on <tablespace name>;

as a DBA user (depending on how much space you need / want to grant).

Appending an element to the end of a list in Scala

That's because you shouldn't do it (at least with an immutable list). If you really really need to append an element to the end of a data structure and this data structure really really needs to be a list and this list really really has to be immutable then do eiher this:

(4 :: List(1,2,3).reverse).reverse

or that:

List(1,2,3) ::: List(4)

How do I check OS with a preprocessor directive?

I wrote an small library to get the operating system you are on, it can be installed using clib (The C package manager), so it is really simple to use it as a dependency for your projects.


$ clib install abranhe/os.c


#include <stdio.h>
#include "os.h"

int main()
    printf("%s\n", operating_system());
    // macOS
    return 0;

It returns a string (char*) with the name of the operating system you are using, for further information about this project check it out the documentation on Github.

How to return temporary table from stored procedure

What version of SQL Server are you using? In SQL Server 2008 you can use Table Parameters and Table Types.

An alternative approach is to return a table variable from a user defined function but I am not a big fan of this method.

You can find an example here

what is the difference between json and xml

They're two different ways of representing data, but they're pretty dissimilar. The wikipedia pages for JSON and XML give some examples of each, and there's a comparison paragraph

How to search in array of object in mongodb

You can do this in two ways:

  1. ElementMatch - $elemMatch (as explained in above answers)

    db.users.find({ awards: { $elemMatch: {award:'Turing Award', year:1977} } })

  2. Use $and with find

    db.getCollection('users').find({"$and":[{"awards.award":"Turing Award"},{"awards.year":1977}]})

Is there a way to crack the password on an Excel VBA Project?

There is another (somewhat easier) solution, without the size problems. I used this approach today (on a 2003 XLS file, using Excel 2007) and was successful.

  1. Backup the xls file
  2. Open the file in a HEX editor and locate the DPB=... part
  3. Change the DPB=... string to DPx=...
  4. Open the xls file in Excel
  5. Open the VBA editor (ALT + F11)
  6. the magic: Excel discovers an invalid key (DPx) and asks whether you want to continue loading the project (basically ignoring the protection)
  7. You will be able to overwrite the password, so change it to something you can remember
  8. Save the xls file*
  9. Close and reopen the document and work your VBA magic!

*NOTE: Be sure that you have changed the password to a new value, otherwise the next time you open the spreadsheet Excel will report errors (Unexpected Error), then when you access the list of VBA modules you will now see the names of the source modules but receive another error when trying to open forms/code/etc. To remedy this, go back to the VBA Project Properties and set the password to a new value. Save and re-open the Excel document and you should be good to go!

TypeError: cannot perform reduce with flexible type

When your are trying to apply prod on string type of value like:

['-214' '-153' '-58' ..., '36' '191' '-37']

you will get the error.

Solution: Append only integer value like [1,2,3], and you will get your expected output.

If the value is in string format before appending then, in the array you can convert the type into int type and store it in a list.

How do I make a https post in Node Js without any third party module?

For example, like this:

const querystring = require('querystring');
const https = require('https');

var postData = querystring.stringify({
    'msg' : 'Hello World!'

var options = {
  hostname: '',
  port: 443,
  path: '/post.php',
  method: 'POST',
  headers: {
       'Content-Type': 'application/x-www-form-urlencoded',
       'Content-Length': postData.length

var req = https.request(options, (res) => {
  console.log('statusCode:', res.statusCode);
  console.log('headers:', res.headers);

  res.on('data', (d) => {

req.on('error', (e) => {


AngularJS Multiple ng-app within a page

To run multiple applications in an HTML document you must manually bootstrap them using angular.bootstrap()


<!-- Automatic Initialization -->
<div ng-app="myFirstModule">
<!-- Need To Manually Bootstrap All Other Modules -->
<div id="module2">


  bootstrap(document.getElementById("module2"), ['mySecondModule']);

The reason for this is that only one AngularJS application can be automatically bootstrapped per HTML document. The first ng-app found in the document will be used to define the root element to auto-bootstrap as an application.

In other words, while it is technically possible to have several applications per page, only one ng-app directive will be automatically instantiated and initialized by the Angular framework.

How to increment datetime by custom months in python without using library

from datetime import timedelta
    next = (x.replace(day=1) + timedelta(days=31)).replace(
except ValueError:  # January 31 will return last day of February.
    next = (x + timedelta(days=31)).replace(day=1) - timedelta(days=1)

If you simply want the first day of the next month:

next = (x.replace(day=1) + timedelta(days=31)).replace(day=1)

Browse files and subfolders in Python

In python 3 you can use os.scandir():

for i in os.scandir(path):
    if i.is_file():
        print('File: ' + i.path)
    elif i.is_dir():
        print('Folder: ' + i.path)

div background color, to change onhover

Using Javascript

   <div id="mydiv" style="width:200px;background:white" onmouseover="'gray';" onmouseout="'white';">
    Jack and Jill went up the hill 
    To fetch a pail of water. 
    Jack fell down and broke his crown, 
    And Jill came tumbling after. 

How to programmatically close a JFrame

setVisible(false); //you can't see me!
dispose(); //Destroy the JFrame object

Not too tricky.

Is it possible to use Visual Studio on macOS?

I recently purchased a MacBook Air (mid-2011 model) and was really happy to find that Apple officially supports Windows 7. If you purchase Windows 7 (I got DSP), you can use the Boot Camp assistant in OSX to designate part of your hard drive to Windows. Then you can install and run Windows 7 natively as if it were as Windows notebook.

I use Visual Studio 2010 on Windows 7 on my MacBook Air (I kept OSX as well) and I could not be happier. Heck, the initial start-up of the program only takes 3 seconds thanks to the SSD.

As others have mentions, you can run it on OSX using Parallels, etc. but I prefer to run it natively.

How to connect to MySQL Database?

 private void Initialize()
        server = "localhost";
        database = "connectcsharptomysql";
        uid = "username";
        password = "password";
        string connectionString;
        connectionString = "SERVER=" + server + ";" + "DATABASE=" + 
        database + ";" + "U`enter code here`ID=" + uid + ";" + "PASSWORD=" + password + ";";

        connection = new MySqlConnection(connectionString);

change figure size and figure format in matplotlib

You can change the size of the plot by adding this before you create the figure.

plt.rcParams["figure.figsize"] = [16,9]

How can I use Async with ForEach?

This is method I created to handle async scenarios with ForEach.

  • If one of tasks fails then other tasks will continue their execution.
  • You have ability to add function that will be executed on every exception.
  • Exceptions are being collected as aggregateException at the end and are available for you.
  • Can handle CancellationToken
 public static class ParallelExecutor
        /// <summary>
        /// Executes asynchronously given function on all elements of given enumerable with task count restriction.
        /// Executor will continue starting new tasks even if one of the tasks throws. If at least one of the tasks throwed exception then <see cref="AggregateException"/> is throwed at the end of the method run.
        /// </summary>
        /// <typeparam name="T">Type of elements in enumerable</typeparam>
        /// <param name="maxTaskCount">The maximum task count.</param>
        /// <param name="enumerable">The enumerable.</param>
        /// <param name="asyncFunc">asynchronous function that will be executed on every element of the enumerable. MUST be thread safe.</param>
        /// <param name="onException">Acton that will be executed on every exception that would be thrown by asyncFunc. CAN be thread unsafe.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        public static async Task ForEachAsync<T>(int maxTaskCount, IEnumerable<T> enumerable, Func<T, Task> asyncFunc, Action<Exception> onException = null, CancellationToken cancellationToken = default)
            using var semaphore = new SemaphoreSlim(initialCount: maxTaskCount, maxCount: maxTaskCount);

            // This `lockObject` is used only in `catch { }` block.
            object lockObject = new object();
            var exceptions = new List<Exception>();
            var tasks = new Task[enumerable.Count()];
            int i = 0;

                foreach (var t in enumerable)
                    await semaphore.WaitAsync(cancellationToken);
                    tasks[i++] = Task.Run(
                        async () =>
                                await asyncFunc(t);
                            catch (Exception e)
                                if (onException != null)
                                    lock (lockObject)

                                // This exception will be swallowed here but it will be collected at the end of ForEachAsync method in order to generate AggregateException.
                        }, cancellationToken);

                    if (cancellationToken.IsCancellationRequested)
            catch (OperationCanceledException e)

            foreach (var t in tasks)
                if (cancellationToken.IsCancellationRequested)

                // Exception handling in this case is actually pretty fast.
                    await t;
#pragma warning disable CA1031 // Do not catch general exception types - we want to throw that exception later as aggregate exception. Nothing wrong here.
                catch (Exception e)
#pragma warning restore CA1031 // Do not catch general exception types

            if (exceptions.Any())
                throw new AggregateException(exceptions);

How do I filter an array with TypeScript in Angular 2?

To filter an array irrespective of the property type (i.e. for all property types), we can create a custom filter pipe

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({ name: "filter" })
export class ManualFilterPipe implements PipeTransform {
  transform(itemList: any, searchKeyword: string) {
    if (!itemList)
      return [];
    if (!searchKeyword)
      return itemList;
    let filteredList = [];
    if (itemList.length > 0) {
      searchKeyword = searchKeyword.toLowerCase();
      itemList.forEach(item => {
        //Object.values(item) => gives the list of all the property values of the 'item' object
        let propValueList = Object.values(item);
        for(let i=0;i<propValueList.length;i++)
          if (propValueList[i]) {
            if (propValueList[i].toString().toLowerCase().indexOf(searchKeyword) > -1)
    return filteredList;


//<tr *ngFor="let company of companyList | filter: searchKeyword"></tr>

Don't forget to import the pipe in the app module

We might need to customize the logic to filer with dates.

How do you make a LinearLayout scrollable?



                <---------Content Here --------------->

plot data from CSV file with matplotlib

According to the docs numpy.loadtxt is

a fast reader for simply formatted files. The genfromtxt function provides more sophisticated handling of, e.g., lines with missing values.

so there are only a few options to handle more complicated files. As mentioned numpy.genfromtxt has more options. So as an example you could use

import numpy as np
data = np.genfromtxt('e:\dir1\datafile.csv', delimiter=',', skip_header=10,
                     skip_footer=10, names=['x', 'y', 'z'])

to read the data and assign names to the columns (or read a header line from the file with names=True) and than plot it with

ax1.plot(data['x'], data['y'], color='r', label='the data')

I think numpy is quite well documented now. You can easily inspect the docstrings from within ipython or by using an IDE like spider if you prefer to read them rendered as HTML.

Add text to textarea - Jquery

That should work. Better if you pass a function to val:

$('#replyBox').val(function(i, text) {
    return text + quote;

This way you avoid searching the element and calling val twice.

Where does mysql store data?

In mysql server 8.0, on Windows, the location is C:\ProgramData\MySQL\MySQL Server 8.0\Data

WAMP Server ERROR "Forbidden You don't have permission to access /phpmyadmin/ on this server."

To solve this, I opened httpd.conf and changed the following line:

Allow from


Allow from ::1

Is there a Wikipedia API?

MediaWiki's API is running on Wikipedia (docs). You can also use the Special:Export feature to dump data and parse it yourself.

More information.

Group By Multiple Columns

group x by new { x.Col, x.Col}

Asynchronous vs synchronous execution, what does it really mean?

I created a gif for explain this, hope to be helpful: look, line 3 is asynchronous and others are synchronous. all lines before line 3 should wait until before line finish its work, but because of line 3 is asynchronous, next line (line 4), don't wait for line 3, but line 5 should wait for line 4 to finish its work, and line 6 should wait for line 5 and 7 for 6, because line 4,5,6,7 are not asynchronous. line 3 is asynchronous and others are synchronous

Could not find a version that satisfies the requirement <package>

Not always, but in some cases the package already exists. For example - getpass. It is not listed by "pip list" but it can be imported and used:

enter image description here

If I try to pip install getpass I get the following error: "Could not find a version that satisfies the requirement getpass"

How to find an object in an ArrayList by property

If you use Java 8 and if it is possible that your search returns null, you could try using the Optional class.

To find a carnet:

private final Optional<Carnet> findCarnet(Collection<Carnet> yourList, String codeIsin){
    // This stream will simply return any carnet that matches the filter. It will be wrapped in a Optional object.
    // If no carnets are matched, an "Optional.empty" item will be returned
    return -> c.getCodeIsin().equals(codeIsin)).findAny();

Now a usage for it:

public void yourMethod(String codeIsin){
    List<Carnet> listCarnet = carnetEJB.findAll();

    Optional<Carnet> carnetFound = findCarnet(listCarnet, codeIsin);

        // You use this ".get()" method to actually get your carnet from the Optional object

How to wrap async function calls into a sync function in Node.js or Javascript?

If function Fiber really turns async function sleep into sync

Yes. Inside the fiber, the function waits before logging ok. Fibers do not make async functions synchronous, but allow to write synchronous-looking code that uses async functions and then will run asynchronously inside a Fiber.

From time to time I find the need to encapsulate an async function into a sync function in order to avoid massive global re-factoring.

You cannot. It is impossible to make asynchronous code synchronous. You will need to anticipate that in your global code, and write it in async style from the beginning. Whether you wrap the global code in a fiber, use promises, promise generators, or simple callbacks depends on your preferences.

My objective is to minimize impact on the caller when data acquisition method is changed from sync to async

Both promises and fibers can do that.

What is your single most favorite command-line trick using Bash?

Quick Text

I use these sequences of text all too often, so I put shortcuts to them in by .inputrc:

# redirection short cuts
"\ew":            "2>&1"
"\eq":            "&>/dev/null &"
"\e\C-q":         "2>/dev/null"
"\eg":            "&>~/.garbage.out &"
"\e\C-g":         "2>~/.garbage.out"

$if term=xterm
"\M-w":           "2>&1"
"\M-q":           "&>/dev/null &"
"\M-\C-q":        "2>/dev/null"
"\M-g":           "&>~/.garbage.out &"
"\M-\C-g":        "2>~/.garbage.out"

Node.js Logging

A 'nodejslogger' module can be used for simple logging. It has three levels of logging (INFO, ERROR, DEBUG)

var logger = require('nodejslogger')
logger.init({"file":"output-file", "mode":"DIE"})

D : Debug, I : Info, E : Error

logger.debug("Debug logs")"Info logs")
logger.error("Error logs")

The module can be accessed at :

How to set $_GET variable

One way to set the $_GET variable is to parse the URL using parse_url() and then parse the $query string using parse_str(), which sets the variables into the $_GET global.

This approach is useful,

  • if you want to test GET parameter handling without making actual queries, e.g. for testing the incoming parameters for existence and input filtering and sanitizing of incoming vars.
  • and when you don't want to construct the array manually each time, but use the normal URL

function setGetRequest($url)
    $query = parse_url($url, PHP_URL_QUERY);
    parse_str($query, $_GET);

$url = '';



Result: $_GET contains

array (
  'a' => string '10' (length=2)
  'b' => string 'plop' (length=4)

What is the difference between active and passive FTP?

Active and passive are the two modes that FTP can run in.

For background, FTP actually uses two channels between client and server, the command and data channels, which are actually separate TCP connections.

The command channel is for commands and responses while the data channel is for actually transferring files.

This separation of command information and data into separate channels a nifty way of being able to send commands to the server without having to wait for the current data transfer to finish. As per the RFC, this is only mandated for a subset of commands, such as quitting, aborting the current transfer, and getting the status.

In active mode, the client establishes the command channel but the server is responsible for establishing the data channel. This can actually be a problem if, for example, the client machine is protected by firewalls and will not allow unauthorised session requests from external parties.

In passive mode, the client establishes both channels. We already know it establishes the command channel in active mode and it does the same here.

However, it then requests the server (on the command channel) to start listening on a port (at the servers discretion) rather than trying to establish a connection back to the client.

As part of this, the server also returns to the client the port number it has selected to listen on, so that the client knows how to connect to it.

Once the client knows that, it can then successfully create the data channel and continue.

More details are available in the RFC:

Can you use Microsoft Entity Framework with Oracle?

DevArt's OraDirect provider now supports entity framework. See

What's the purpose of the LEA instruction?

As others have pointed out, LEA (load effective address) is often used as a "trick" to do certain computations, but that's not its primary purpose. The x86 instruction set was designed to support high-level languages like Pascal and C, where arrays—especially arrays of ints or small structs—are common. Consider, for example, a struct representing (x, y) coordinates:

struct Point
     int xcoord;
     int ycoord;

Now imagine a statement like:

int y = points[i].ycoord;

where points[] is an array of Point. Assuming the base of the array is already in EBX, and variable i is in EAX, and xcoord and ycoord are each 32 bits (so ycoord is at offset 4 bytes in the struct), this statement can be compiled to:

MOV EDX, [EBX + 8*EAX + 4]    ; right side is "effective address"

which will land y in EDX. The scale factor of 8 is because each Point is 8 bytes in size. Now consider the same expression used with the "address of" operator &:

int *p = &points[i].ycoord;

In this case, you don't want the value of ycoord, but its address. That's where LEA (load effective address) comes in. Instead of a MOV, the compiler can generate

LEA ESI, [EBX + 8*EAX + 4]

which will load the address in ESI.

How to create a directory in Java?

Though this question has been answered. I would like to put something extra, i.e. if there is a file exist with the directory name that you are trying to create than it should prompt an error. For future visitors.

public static void makeDir()
    File directory = new File(" dirname ");
    if (directory.exists() && directory.isFile())
        System.out.println("The dir with name could not be" +
        " created as it is a normal file");
            if (!directory.exists())
            String username = System.getProperty("");
            String filename = " path/" + username + ".txt"; //extension if you need one

        catch (IOException e)
            System.out.println("prompt for error");

Difference between and logger.debug

I suggest you look at the article called "Short Introduction to log4j". It contains a short explanation of log levels and demonstrates how they can be used in practice. The basic idea of log levels is that you want to be able to configure how much detail the logs contain depending on the situation. For example, if you are trying to troubleshoot an issue, you would want the logs to be very verbose. In production, you might only want to see warnings and errors.

The log level for each component of your system is usually controlled through a parameter in a configuration file, so it's easy to change. Your code would contain various logging statements with different levels. When responding to an Exception, you might call Logger.error. If you want to print the value of a variable at any given point, you might call Logger.debug. This combination of a configurable logging level and logging statements within your program allow you full control over how your application will log its activity.

In the case of log4j at least, the ordering of log levels is:


Here is a short example from that article demonstrating how log levels work.

   // get a logger instance named ""
   Logger logger = Logger.getLogger("");

   // Now set its level. Normally you do not need to set the
   // level of a logger programmatically. This is usually done
   // in configuration files.

   Logger barlogger = Logger.getLogger("");

   // This request is enabled, because WARN >= INFO.
   logger.warn("Low fuel level.");

   // This request is disabled, because DEBUG < INFO.
   logger.debug("Starting search for nearest gas station.");

   // The logger instance barlogger, named "",
   // will inherit its level from the logger named
   // "" Thus, the following request is enabled
   // because INFO >= INFO."Located nearest gas station.");

   // This request is disabled, because DEBUG < INFO.
   barlogger.debug("Exiting gas station search");

Selenium Webdriver: Entering text into text field

It might be the JavaScript check for some valid condition.
Two things you can perform a/c to your requirements:

  1. either check for the valid string-input in the text-box.
  2. or set a loop against that text box to enter the value until you post the form/request.
String barcode="0000000047166";

WebElement strLocator = driver.findElement(By.xpath("//*[@id='div-barcode']"));

How do I get IntelliJ to recognize common Python modules?

This is how i solved my problem (i have imported the project and it was showing there only, newly created files were not showing those errors):

1) Command + alt + R (Control in case of windows

2) Debug window will appear, select your file and press right arrow (->) and choose Edit then press enter (Edit configuration setting window will appear)

3) Under configuration, at the bottom you can see the error (please select a module with a valid python sdk), So in Python Interpreter, check Use Specified Interpreter, then in drop down you select your Python version

(In case python is not there download python plugin for intelliJ using following link

4) Click on apply then close it.

Bingo it's done.

SQL Server 2008 can't login with newly created user

If you haven't restarted your SQL database Server after you make login changes, then make sure you do that. Start->Programs->Microsoft SQL Server -> Configuration tools -> SQL Server configuration manager -> Restart Server.

It looks like you only added the user to the server. You need to add them to the database too. Either open the database/Security/User/Add New User or open the server/Security/Logins/Properties/User Mapping.

Default background color of SVG root element

Found this works in Safari. SVG only colors in with background-color where an element's bounding box covers. So, give it a border (stroke) with a zero pixel boundary. It fills in the whole thing for you with your background-color.

<svg style='stroke-width: 0px; background-color: blue;'> </svg>

In jQuery how can I set "top,left" properties of an element with position values relative to the parent and not the document?

Refreshing my memory on setting position, I'm coming to this so late I don't know if anyone else will see it, but --

I don't like setting position using css(), though often it's fine. I think the best bet is to use jQuery UI's position() setter as noted by xdazz. However if jQuery UI is, for some reason, not an option (yet jQuery is), I prefer this:

const leftOffset = 200;
const topOffset = 200;
let $div = $("#mydiv");
let baseOffset = $div.offsetParent().offset();
  left: baseOffset.left + leftOffset,
  top: + topOffset

This has the advantage of not arbitrarily setting $div's parent to relative positioning (what if $div's parent was, itself, absolute positioned inside something else?). I think the only major edge case is if $div doesn't have any offsetParent, not sure if it would return document, null, or something else entirely.

offsetParent has been available since jQuery 1.2.6, sometime in 2008, so this technique works now and when the original question was asked.

535-5.7.8 Username and Password not accepted

First, You need to use a valid Gmail account with your credentials.

Second, In my app I don't use TLS auto, try without this line:

config.action_mailer.smtp_settings = {
  address:              '',
  port:                 587,
  domain:               '',
  user_name:            '[email protected]',
  password:             'YOUR_PASSWORD',
  authentication:       'plain'
  # enable_starttls_auto: true
  # ^ ^ remove this option ^ ^

UPDATE: (See answer below for details) now you need to enable "less secure apps" on your Google Account

Windows XP or later Windows: How can I run a batch file in the background with no window displayed?

You also can use

start /MIN notepad.exe

PS: Unfortunatly, minimized window status depends on command to run. V.G. doen't work

start /MIN calc.exe

Get elements by attribute when querySelectorAll is not available without using libraries?

I played a bit around and ended up with this crude solution:

function getElementsByAttribute(attribute, context) {
  var nodeList = (context || document).getElementsByTagName('*');
  var nodeArray = [];
  var iterator = 0;
  var node = null;

  while (node = nodeList[iterator++]) {
    if (node.hasAttribute(attribute)) nodeArray.push(node);

  return nodeArray;

The usage is quite simple, and works even in IE8:

// or with parentNode
getElementsByAttribute('data-foo', document);

But I recommend to use querySelector / All for this (and to support older browsers use a polyfill):


How to get JSON object from Razor Model object in javascript

If You want make json object from yor model do like this :

  foreach (var item in Persons)
    var jsonObj=["FirstName":"@item.FirstName"]

Or Use Json.Net to make json from your model :

string json = JsonConvert.SerializeObject(person);

C++ - how to find the length of an integer

If you can use C libraries then one method would be to use sprintf, e.g.

#include <cstdio>

char s[32];

int len = sprintf(s, "%d", i);

Styling the arrow on bootstrap tooltips

In case you are going around and around to figure this out and none of the options above are working, it is possible you are experiencing a name space conflict of .tooltip with bootstrap and jquery.

See this answer on how to fix: jQueryUI Tooltips are competing with Twitter Bootstrap

Error LNK2019 unresolved external symbol _main referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ)

Solution for me is: I clean both the solution and the project. And just rebuild the project. This error happens because I tried to delete the main file (only keep library files) in the previous build so at the current build the old stuff is still kept in the built directory. That's why unresolved things happened. "unresolved external symbol _main referenced in function "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ) "

https with WCF error: "Could not find base address that matches scheme https"

Look at your base address and your endpoint address (can't see it in your sample code). most likely you missed a column or some other typo e.g. https// instead of https://

How to check if memcache or memcached is installed for PHP?

The best approach in this case is to use extension_loaded() or function_exists() they are equally as fast.

You can see evidence here:

Bear in mind that some PHP extensions such as APC have php.ini settings that can disable them even though the extension may be loaded. Here is an example of how to check against that also:

Hope this helps.

Is there a way to make npm install (the command) to work behind proxy?

I tried all of these options, but my proxy wasn't having any of it for some reason. Then, born out of desparation/despair, I randomly tried curl in my Git Bash shell, and it worked.

Unsetting all of the proxy options using

npm config rm proxy
npm config rm https-proxy

And then running npm install in my Git Bash shell worked perfectly. I don't know how it's set up correctly for the proxy and the Windows cmd prompt isn't, but it worked.

java.lang.UnsupportedClassVersionError: Bad version number in .class file?

changing the project to use java 1.7: For this to work follow those steps :

  • Change Compiler Compliance Level
  • Change your projects JRE/JDK to something of the same level(1.7 in my case)
  • Do the same change in all the projects referenced by your project
  • Change your run/debug configuration to use the JRE/JDK (or of the same level)

Not working?

  • delete projects Bin directory
  • Clean
  • reBuild

Still not working?

in your project's directory: edit .settings/org.eclipse.jdt.core.prefs > make sure your target level is applied

Good Luck!

Issue when importing dataset: `Error in scan(...): line 1 did not have 145 elements`

This simple method solved the problem for me: Copy the content of your dataset, open an empty Excel sheet, choose "Paste Special" -> "Values", and save. Import the new file instead.

(I tried all the existing solutions, and none worked for me. My old dataset appeared to have no missing values, space, special characters, or embedded formulas.)

How to create an XML document using XmlDocument?

Working with a dictionary ->level2 above comes from a dictionary in my case (just in case anybody will find it useful) Trying the first example I stumbled over this error: "This document already has a 'DocumentElement' node." I was inspired by the answer here

and edited my code: (xmlDoc.DocumentElement.AppendChild(body))

//a dictionary:
Dictionary<string, string> Level2Data 
    {"level2", "text"},
    {"level2", "other text"},
    {"same_level2", "more text"}
//xml Decalration:
XmlDocument xmlDoc = new XmlDocument();
XmlDeclaration xmlDeclaration = xmlDoc.CreateXmlDeclaration("1.0", "UTF-8", null);
XmlElement root = xmlDoc.DocumentElement;
xmlDoc.InsertBefore(xmlDeclaration, root);
// add body
XmlElement body = xmlDoc.CreateElement(string.Empty, "body", string.Empty);
XmlElement body = xmlDoc.CreateElement(string.Empty, "body", string.Empty);
xmlDoc.DocumentElement.AppendChild(body); //without DocumentElement ->ERR

foreach (KeyValuePair<string, string> entry in Level2Data)
    //write to xml: - it works version 1.
    XmlNode keyNode = xmlDoc.CreateElement(entry.Key); //open TAB
    keyNode.InnerText = entry.Value;
    body.AppendChild(keyNode); //close TAB

    //Write to xmml verdion 2: (uncomment the next 4 lines and comment the above 3 - version 1
    //XmlElement key = xmlDoc.CreateElement(string.Empty, entry.Key, string.Empty);
    //XmlText value = xmlDoc.CreateTextNode(entry.Value);

Both versions (1 and 2 inside foreach loop) give the output:

<?xml version="1.0" encoding="UTF-8"?>
        <level2>ther text</level2>
         <same_level2>more text</same_level2>

(Note: third line "same level2" in dictionary can be also level2 as the others but I wanted to ilustrate the advantage of the dictionary - in my case I needed level2 with different names.

What is the use of "assert"?

Assertions are statements that state a fact confidently in our program.

Syntax : assert <condition> or assert <condition>,<error message>

It has a condition/expression which is supposed to be always true. If the condition is false, the assert statement will halt the program and throw an error message saying AssertionError. So your assertion expression will be something that you don't want in your program.


  1. assert <condition> -- using assert without <error message>

    var = int(input("Enter value 1-9 inclusive:"))                                 
    assert var!=0 

    Output :

    If input is 0 :


    If input is 1 :

  2. assert <condition>,<error message> -- using assert with an <error message>

    var = int(input("Enter value 1-9 inclusive:"))                                 
    assert var!=0,"Input cannot be zero"

    Output :

    If input is 0 :

    AssertionError: Input cannot be zero

    If input is 1 :


Key Points :

  1. It is used as a debugging tool.
  2. It takes an expression and an optional message.
  3. It exists in almost every programming language

Convert String to int array in java

It looks like JSON - it might be overkill, depending on the situation, but you could consider using a JSON library (e.g. to parse it:

    String arr = "[1,2]";

    JSONArray jsonArray = (JSONArray) new JSONObject(new JSONTokener("{data:"+arr+"}")).get("data");

    int[] outArr = new int[jsonArray.length()]; 

    for(int i=0; i<jsonArray.length(); i++) {
        outArr[i] = jsonArray.getInt(i);

Reading a text file in MATLAB line by line

here is the doc to read a csv : and to write :


An example that works :

file.csv :


the code :

File = csvread('file.csv')
[m,n] = size(File)
for i = 1:m
    if (File(i,2)>=50)
        temp = temp + 1
Matrix = zeros(temp, 3)

for j = 1:m
    if (File(j,2)>=50)
        Matrix(index,1) = File(j,1)
        Matrix(index,2) = File(j,2)
        Matrix(index,3) = File(j,3)
        index = index + 1

and the output file result :


This isn't probably the best solution but it works! We can read the CSV file, control the distance of each row and save it in a new file.

Hope it will help!

Use Conditional formatting to turn a cell Red, yellow or green depending on 3 values in another sheet

  1. Highlight the range in question.
  2. On the Home tab, in the Styles Group, Click "Conditional Formatting".
  3. Click "Highlight cell rules"

For the first rule,

Click "greater than", then in the value option box, click on the cell criteria you want it to be less than, than use the format drop-down to select your color.

For the second,

Click "less than", then in the value option box, type "=.9*" and then click the cell criteria, then use the formatting just like step 1.

For the third,

Same as the second, except your formula is =".8*" rather than .9.

Sublime Text 2: How do I change the color that the row number is highlighted?

On windows 7, find

C:\Users\Simion\AppData\Roaming\Sublime Text 2\Packages\Color Scheme - Default

Find your color scheme file, open it, and find lineHighlight.


replace #ccc with your preferred background color.

Best way to remove the last character from a string built with stringbuilder

You should use the string.Join method to turn a collection of items into a comma delimited string. It will ensure that there is no leading or trailing comma, as well as ensure the string is constructed efficiently (without unnecessary intermediate strings).

How to correct indentation in IntelliJ

In Android Studio this works: Go to File->Settings->Editor->CodeStyle->Java. Under Wrapping and Braces uncheck "Comment at first Column" Then formatting shortcut will indent the comment lines as well.

How to install Android Studio on Ubuntu?

The easiest method to install Android Studio (or any other developer tool) on Ubuntu is to use the snap package from Ubuntu Software store. No need to download Android Studio as zip, try to manually install it, add PPAs or fiddle with Java installation. The snap package bundles the latest Android Studio along with OpenJDK and all the necessary dependencies.

Step 1: Install Android Studio

Search "android studio" in Ubuntu Software, select the first entry that shows up and install it:

Search Android Studio on Ubuntu Software Android Studio on Ubuntu Software

Or if you prefer the command line way, run this in Terminal:

sudo snap install --classic android-studio

Step 2: Install Android SDK

Open the newly installed Android Studio from dashboard:

Android Studio app on Dash

Don't need to import anything if this is the first time you're installing it:

Import Dialog

The Setup Wizard'll guide you through installation:

Android Studio Setup Wizard

Select Standard install to get the latest SDK and Custom in-case you wanna change the SDK version or its install location. From here on, it's pretty straightforward, just click next-next and you'll have the SDK downloaded and installed.

Select Standard or Custom installation

Step 3: Setting PATHs (Optional)

This step might be useful if you want Android SDK's developer tool commands like adb, fastboot, aapt, etc available in Terminal. Might be needed by 3rd party dev platforms like React Native, Ionic, Cordova, etc and other tools too. For setting PATHs, edit your ~/.profile file:

gedit ~/.profile

and then add the following lines to it:

# Android SDK Tools PATH
export ANDROID_HOME=${HOME}/Android/Sdk
export PATH="${ANDROID_HOME}/tools:${PATH}"
export PATH="${ANDROID_HOME}/emulator:${PATH}"
export PATH="${ANDROID_HOME}/platform-tools:${PATH}"

If you changed SDK location at the end of Step 2, don't forget to change the line export ANDROID_HOME=${HOME}/Android/Sdk accordingly. Do a restart (or just logout and then log back in) for the PATHs to take effect.

Tested on Ubuntu 16.04LTS and above. Would work on 14.04LTS too if you install support for snap packages first.

Note: This question is similar to the AskUbuntu question "How to install Android Studio on Ubuntu?" and my answer equally applies. I'm reproducing my answer here to ensure a full complete answer exists rather than just a link.

C# password TextBox in a website

I think this is what you are looking for

 <asp:TextBox ID="txbPass" runat="server" TextMode="Password"></asp:TextBox>

Using python map and other functional tools

Are you familiar with other functional languages? i.e. are you trying to learn how python does functional programming, or are you trying to learn about functional programming and using python as the vehicle?

Also, do you understand list comprehensions?

map(f, sequence)

is directly equivalent (*) to:

[f(x) for x in sequence]

In fact, I think map() was once slated for removal from python 3.0 as being redundant (that didn't happen).

map(f, sequence1, sequence2)

is mostly equivalent to:

[f(x1, x2) for x1, x2 in zip(sequence1, sequence2)]

(there is a difference in how it handles the case where the sequences are of different length. As you saw, map() fills in None when one of the sequences runs out, whereas zip() stops when the shortest sequence stops)

So, to address your specific question, you're trying to produce the result:

foos[0], bars
foos[1], bars
foos[2], bars
# etc.

You could do this by writing a function that takes a single argument and prints it, followed by bars:

def maptest(x):
     print x, bars
map(maptest, foos)

Alternatively, you could create a list that looks like this:

[bars, bars, bars, ] # etc.

and use your original maptest:

def maptest(x, y):
    print x, y

One way to do this would be to explicitely build the list beforehand:

barses = [bars] * len(foos)
map(maptest, foos, barses)

Alternatively, you could pull in the itertools module. itertools contains many clever functions that help you do functional-style lazy-evaluation programming in python. In this case, we want itertools.repeat, which will output its argument indefinitely as you iterate over it. This last fact means that if you do:

map(maptest, foos, itertools.repeat(bars))

you will get endless output, since map() keeps going as long as one of the arguments is still producing output. However, itertools.imap is just like map(), but stops as soon as the shortest iterable stops.

itertools.imap(maptest, foos, itertools.repeat(bars))

Hope this helps :-)

(*) It's a little different in python 3.0. There, map() essentially returns a generator expression.

How do I assign a port mapping to an existing Docker container?

For Windows & Mac Users, there is another pretty easy and friendly way to change the mapping port:

  1. download kitematic

  2. go to the settings page of the container, on the ports tab, you can directly modify the published port there.

  3. start the container again

Stop Visual Studio from mixing line endings in files

On the File menu, choose Advanced Save Options, you can control it there.

Edit: Here's the documentation, you should have a file open first.

If table exists drop table then create it, if it does not exist just create it

Just put DROP TABLE IF EXISTS `tablename`; before your CREATE TABLE statement.

That statement drops the table if it exists but will not throw an error if it does not.

The 'json' native gem requires installed build tools

I would like to add that you should make sure that the generated config.yml file when doing ruby dk.rb init contains the path to the ruby installation you want to use DevKit with. In my case, I had the Heroku Toolbelt installed on my system, which provided its own ruby installation, located at a different place. The config.yml file used that particular installation, and that's not what I wanted. I had to manually edit the file to point it to the correct one, then continue with ruby dk.rb review, etc.

Adding null values to arraylist

You could create Util class:

public final class CollectionHelpers {
    public static <T> boolean addNullSafe(List<T> list, T element) {
        if (list == null || element == null) {
            return false;

        return list.add(element);

And then use it:

Element element = getElementFromSomeWhere(someParameter);
List<Element> arrayList = new ArrayList<>();
CollectionHelpers.addNullSafe(list, element);

Getting net::ERR_UNKNOWN_URL_SCHEME while calling telephone number from HTML page in Android

The following should work and not require any permissions in the manifest (basically override shouldOverrideUrlLoading and handle links separately from tel, mailto, etc.):

    mWebView = (WebView) findViewById(;

    WebSettings webSettings = mWebView.getSettings();

    mWebView.setWebViewClient(new WebViewClient(){
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            if( url.startsWith("http:") || url.startsWith("https:") ) {
                return false;

            // Otherwise allow the OS to handle things like tel, mailto, etc.
            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            startActivity( intent );
            return true;

Also, note that in the above snippet I am enabling JavaScript, which you will also most likely want, but if for some reason you don't, just remove those 2 lines.

How do you keep parents of floated elements from collapsing?

I usually use the overflow: auto trick; although that's not, strictly speaking, the intended use for overflow, it is kinda related - enough to make it easy to remember, certainly. The meaning of float: left itself has been extended for various uses more significantly than overflow is in this example, IMO.

HTML Input - already filled in text

TO give the prefill value in HTML Side as below:


<input type="text" id="abc" value="any value">


$(document).ready(function ()
  $("#abc").val('any value');

How can I get the DateTime for the start of the week?

if you want saturday or sunday or any day of week but not exceeding current week(Sat-Sun) I got you covered with this piece of code.

public static DateTime GetDateInCurrentWeek(this DateTime date, DayOfWeek day)
    var temp = date;
    var limit = (int)date.DayOfWeek;
    var returnDate = DateTime.MinValue;

    if (date.DayOfWeek == day) return date;

    for (int i = limit; i < 6; i++)
        temp = temp.AddDays(1);

        if (day == temp.DayOfWeek)
            returnDate = temp;
    if (returnDate == DateTime.MinValue)
        for (int i = limit; i > -1; i++)
            date = date.AddDays(-1);

            if (day == date.DayOfWeek)
                returnDate = date;
    return returnDate;

Android: Unable to add window. Permission denied for this window type

For what should be completely obvious reasons, ordinary Apps are not allowed to create arbitrary windows on top of the lock screen. What do you think I could do if I created a window on your lockscreen that could perfectly imitate the real lockscreen so you couldn't tell the difference?

The technical reason for your error is the use of the TYPE_KEYGUARD_DIALOG flag - it requires android.permission.INTERNAL_SYSTEM_WINDOW which is a signature-level permission. This means that only Apps signed with the same certificate as the creator of the permission can use it.

The creator of android.permission.INTERNAL_SYSTEM_WINDOW is the Android system itself, so unless your App is part of the OS, you don't stand a chance.

There are well defined and well documented ways of notifying the user of information from the lockscreen. You can create customised notifications which show on the lockscreen and the user can interact with them.

MVC [HttpPost/HttpGet] for Action

Let's say you have a Login action which provides the user with a login screen, then receives the user name and password back after the user submits the form:

public ActionResult Login() {
    return View();

public ActionResult Login(string userName, string password) {
    // do login stuff
    return View();

MVC isn't being given clear instructions on which action is which, even though we can tell by looking at it. If you add [HttpGet] to the first action and [HttpPost] to the section action, MVC clearly knows which action is which.

Why? See Request Methods. Long and short: When a user views a page, that's a GET request and when a user submits a form, that's usually a POST request. HttpGet and HttpPost just restrict the action to the applicable request type.

public ActionResult Login() {
    return View();

public ActionResult Login(string userName, string password) {
    // do login stuff
    return View();

You can also combine the request method attributes if your action serves requests from multiple verbs:

[AcceptVerbs(HttpVerbs.Get | HttpVerbs.Post)].

Should black box or white box testing be the emphasis for testers?

Black Box Testing is a software testing method in which the internal structure/ design/ implementation of the item being tested is NOT known to the tester. White Box Testing is a software testing method in which the internal structure/ design/ implementation of the item being tested is known to the tester.

How do you copy the contents of an array to a std::vector in C++ without looping?

If you can construct the vector after you've gotten the array and array size, you can just say:

std::vector<ValueType> vec(a, a + n);

...assuming a is your array and n is the number of elements it contains. Otherwise, std::copy() w/resize() will do the trick.

I'd stay away from memcpy() unless you can be sure that the values are plain-old data (POD) types.

Also, worth noting that none of these really avoids the for loop--it's just a question of whether you have to see it in your code or not. O(n) runtime performance is unavoidable for copying the values.

Finally, note that C-style arrays are perfectly valid containers for most STL algorithms--the raw pointer is equivalent to begin(), and (ptr + n) is equivalent to end().

Could not establish trust relationship for SSL/TLS secure channel -- SOAP

For those who are having this issue through a VS client side once successfully added a service reference and trying to execute the first call got this exception: “The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel” If you are using (like my case) an endpoint URL with the IP address and got this exception, then you should probably need to re-add the service reference doing this steps:

  • Open the endpoint URL on Internet Explorer.
  • Click on the certificate error (red icon in address bar)
  • Click on View certificates.
  • Grab the issued to: "name" and replace the IP address or whatever name we were using and getting the error for this "name".

Try again :). Thanks

What are enums and why are they useful?

Apart from all said by others.. In an older project that I used to work for, a lot of communication between entities(independent applications) was using integers which represented a small set. It was useful to declare the set as enum with static methods to get enum object from value and viceversa. The code looked cleaner, switch case usability and easier writing to logs.

enum ProtocolType {
    TCP_IP (1, "Transmission Control Protocol"), 
    IP (2, "Internet Protocol"), 
    UDP (3, "User Datagram Protocol");

    public int code;
    public String name;

    private ProtocolType(int code, String name) {
        this.code = code; = name;

    public static ProtocolType fromInt(int code) {
    switch(code) {
    case 1:
        return TCP_IP;
    case 2:
        return IP;
    case 3:
        return UDP;

    // we had some exception handling for this
    // as the contract for these was between 2 independent applications
    // liable to change between versions (mostly adding new stuff)
    // but keeping it simple here.
    return null;

Create enum object from received values (e.g. 1,2) using ProtocolType.fromInt(2) Write to logs using

Hope this helps.

How to install Android app on LG smart TV?

LG, VIZIO, SAMSUNG and PANASONIC TVs are not android based, and you cannot run APKs off of them... You should just buy a fire stick and call it a day. The only TVs that are android-based, and you can install APKs are: SONY, PHILIPS and SHARP.

How to get the part of a file after the first line that matches a regular expression?

These will print all lines from the last found line "TERMINATE" till end of file:

LINE_NUMBER=`grep -o -n TERMINATE $OSCAM_LOG|tail -n 1|sed "s/:/ \\'/g"|awk -F" " '{print $1}'`

How do you create a static class in C++?

Consider Matt Price's solution.

  1. In C++, a "static class" has no meaning. The nearest thing is a class with only static methods and members.
  2. Using static methods will only limit you.

What you want is, expressed in C++ semantics, to put your function (for it is a function) in a namespace.

Edit 2011-11-11

There is no "static class" in C++. The nearest concept would be a class with only static methods. For example:

// header
class MyClass
   public :
      static void myMethod() ;
} ;

// source
void MyClass::myMethod()
   // etc.

But you must remember that "static classes" are hacks in the Java-like kind of languages (e.g. C#) that are unable to have non-member functions, so they have instead to move them inside classes as static methods.

In C++, what you really want is a non-member function that you'll declare in a namespace:

// header
namespace MyNamespace
   void myMethod() ;

// source
namespace MyNamespace
   void myMethod()
      // etc.

Why is that?

In C++, the namespace is more powerful than classes for the "Java static method" pattern, because:

  • static methods have access to the classes private symbols
  • private static methods are still visible (if inaccessible) to everyone, which breaches somewhat the encapsulation
  • static methods cannot be forward-declared
  • static methods cannot be overloaded by the class user without modifying the library header
  • there is nothing that can be done by a static method that can't be done better than a (possibly friend) non-member function in the same namespace
  • namespaces have their own semantics (they can be combined, they can be anonymous, etc.)
  • etc.

Conclusion: Do not copy/paste that Java/C#'s pattern in C++. In Java/C#, the pattern is mandatory. But in C++, it is bad style.

Edit 2010-06-10

There was an argument in favor to the static method because sometimes, one needs to use a static private member variable.

I disagree somewhat, as show below:

The "Static private member" solution

// HPP

class Foo
   public :
      void barA() ;
   private :
      void barB() ;
      static std::string myGlobal ;
} ;

First, myGlobal is called myGlobal because it is still a global private variable. A look at the CPP source will clarify that:

// CPP
std::string Foo::myGlobal ; // You MUST declare it in a CPP

void Foo::barA()
   // I can access Foo::myGlobal

void Foo::barB()
   // I can access Foo::myGlobal, too

void barC()
   // I CAN'T access Foo::myGlobal !!!

At first sight, the fact the free function barC can't access Foo::myGlobal seems a good thing from an encapsulation viewpoint... It's cool because someone looking at the HPP won't be able (unless resorting to sabotage) to access Foo::myGlobal.

But if you look at it closely, you'll find that it is a colossal mistake: Not only your private variable must still be declared in the HPP (and so, visible to all the world, despite being private), but you must declare in the same HPP all (as in ALL) functions that will be authorized to access it !!!

So using a private static member is like walking outside in the nude with the list of your lovers tattooed on your skin : No one is authorized to touch, but everyone is able to peek at. And the bonus: Everyone can have the names of those authorized to play with your privies.

private indeed... :-D

The "Anonymous namespaces" solution

Anonymous namespaces will have the advantage of making things private really private.

First, the HPP header

// HPP

namespace Foo
   void barA() ;

Just to be sure you remarked: There is no useless declaration of barB nor myGlobal. Which means that no one reading the header knows what's hidden behind barA.

Then, the CPP:

// CPP
namespace Foo
      std::string myGlobal ;

      void Foo::barB()
         // I can access Foo::myGlobal

   void barA()
      // I can access myGlobal, too

void barC()
   // I STILL CAN'T access myGlobal !!!

As you can see, like the so-called "static class" declaration, fooA and fooB are still able to access myGlobal. But no one else can. And no one else outside this CPP knows fooB and myGlobal even exist!

Unlike the "static class" walking on the nude with her address book tattooed on her skin the "anonymous" namespace is fully clothed, which seems quite better encapsulated AFAIK.

Does it really matter?

Unless the users of your code are saboteurs (I'll let you, as an exercise, find how one can access to the private part of a public class using a dirty behaviour-undefined hack...), what's private is private, even if it is visible in the private section of a class declared in a header.

Still, if you need to add another "private function" with access to the private member, you still must declare it to all the world by modifying the header, which is a paradox as far as I am concerned: If I change the implementation of my code (the CPP part), then the interface (the HPP part) should NOT change. Quoting Leonidas : "This is ENCAPSULATION!"

Edit 2014-09-20

When are classes static methods are actually better than namespaces with non-member functions?

When you need to group together functions and feed that group to a template:

namespace alpha
   void foo() ;
   void bar() ;

struct Beta
   static void foo() ;
   static void bar() ;

template <typename T>
struct Gamma
   void foobar()
      T::foo() ;
      T::bar() ;

Gamma<alpha> ga ; // compilation error
Gamma<Beta> gb ;  // ok
gb.foobar() ;     // ok !!!

Because, if a class can be a template parameter, a namespaces cannot.

Error:(23, 17) Failed to resolve: junit:junit:4.12

Try this:

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    //testCompile 'junit:junit:4.12'
    compile ''
    compile ''
    compile ''

How to 'insert if not exists' in MySQL?

Here is a PHP function that will insert a row only if all the specified columns values don't already exist in the table.

  • If one of the columns differ, the row will be added.

  • If the table is empty, the row will be added.

  • If a row exists where all the specified columns have the specified values, the row won't be added.

    function insert_unique($table, $vars)
      if (count($vars)) {
        $table = mysql_real_escape_string($table);
        $vars = array_map('mysql_real_escape_string', $vars);
        $req = "INSERT INTO `$table` (`". join('`, `', array_keys($vars)) ."`) ";
        $req .= "SELECT '". join("', '", $vars) ."' FROM DUAL ";
        $req .= "WHERE NOT EXISTS (SELECT 1 FROM `$table` WHERE ";
        foreach ($vars AS $col => $val)
          $req .= "`$col`='$val' AND ";
        $req = substr($req, 0, -5) . ") LIMIT 1";
        $res = mysql_query($req) OR die();
        return mysql_insert_id();
      return False;

Example usage :

insert_unique('mytable', array(
  'mycolumn1' => 'myvalue1',
  'mycolumn2' => 'myvalue2',
  'mycolumn3' => 'myvalue3'

Count Vowels in String Python

def countvowels(string):
    for char in string:
        if char in "aeiouAEIOU":
           num_vowels = num_vowels+1
    return num_vowels

(remember the spacing s)

How to generate a core dump in Linux on a segmentation fault?

It's worth mentioning that if you have a systemd set up, then things are a little bit different. The set up typically would have the core files be piped, by means of core_pattern sysctl value, through systemd-coredump(8). The core file size rlimit would typically be configured as "unlimited" already.

It is then possible to retrieve the core dumps using coredumpctl(1).

The storage of core dumps, etc. is configured by coredump.conf(5). There are examples of how to get the core files in the coredumpctl man page, but in short, it would look like this:

Find the core file:

[vps@phoenix]~$ coredumpctl list test_me | tail -1
Sun 2019-01-20 11:17:33 CET   16163  1224  1224  11 present /home/vps/test_me

Get the core file:

[vps@phoenix]~$ coredumpctl -o test_me.core dump 16163

How do you delete all text above a certain line

:1,.d deletes lines 1 to current.
:1,.-1d deletes lines 1 to above current.

(Personally I'd use dgg or kdgg like the other answers, but TMTOWTDI.)

Get each line from textarea

Old tread...? Well, someone may bump into this...

Please check out

Rather than using:

$values = explode("\n", $value_string);

Use a safer method like:

$values = preg_split('/[\n\r]+/', $value_string);

How to deserialize a list using GSON or another JSON library in Java?

I recomend this one-liner

List<Video> videos = Arrays.asList(new Gson().fromJson(json, Video[].class));

Warning: the list of videos, returned by Arrays.asList is immutable - you can't insert new values. If you need to modify it, wrap in new ArrayList<>(...).


  1. Method Arrays#asList
  2. Constructor Gson
  3. Method Gson#fromJson (source json may be of type JsonElement, Reader, or String)
  4. Interface List
  5. JLS - Arrays
  6. JLS - Generic Interfaces

Get list of JSON objects with Spring RestTemplate

You can create POJO for each entry like,

class BitPay{
private String code;
private String name;
private double rate;

then using ParameterizedTypeReference of List of BitPay you can use as:

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<List<Employee>> response =
  new ParameterizedTypeReference<List<BitPay>>(){});
List<Employee> employees = response.getBody();

How to get text of an element in Selenium WebDriver, without including child element text?

def get_true_text(tag):
    children = tag.find_elements_by_xpath('*')
    original_text = tag.text
    for child in children:
        original_text = original_text.replace(child.text, '', 1)
    return original_text

Ajax success function

The answer given above can't solve my problem.So I change async into false to get the alert message.

            async: false,
            url: myAjax.ajaxurl,
            data: {action: 'submit_data', info: info},
            success: function(data) {
                alert("Data was succesfully captured");

jQuery UI Dialog OnBeforeUnload

For ASP.NET MVC if you want to make an exception for leaving the page via submitting a particular form:

Set a form id:

@using (Html.BeginForm("Create", "MgtJob", FormMethod.Post, new { id = "createjob" }))
  // Your code

<script type="text/javascript">

  // Without submit form
   $(window).bind('beforeunload', function () {
        if ($('input').val() !== '') {
            return "It looks like you have input you haven't submitted."

    // this will call before submit; and it will unbind beforeunload
    $(function () {
        $("#createjob").submit(function (event) {


@RequestParam vs @PathVariable

1) @RequestParam is used to extract query parameters


public ResponseEntity<?> test(@RequestParam Long id) {
    System.out.println("This is test");
    return ResponseEntity.ok().body(id);

while @PathVariable is used to extract data right from the URI:


public ResponseEntity<?> test(@PathVariable Long id) {
    System.out.println("This is test");
    return ResponseEntity.ok().body(id);

2) @RequestParam is more useful on a traditional web application where data is mostly passed in the query parameters while @PathVariable is more suitable for RESTful web services where URL contains values.

3) @RequestParam annotation can specify default values if a query parameter is not present or empty by using a defaultValue attribute, provided the required attribute is false:

public class IndexController {

    @RequestMapping(value = "/name")
    String getName(@RequestParam(value = "person", defaultValue = "John") String personName) {
        return "Required element of request param";


How to implement endless list with RecyclerView?

I would try to extend used LayoutManager (e.g. LinearLayoutManager) and override scrollVerticallyBy() method. Firstly, I would call super first and then check returned integer value. If the value equals to 0 then a bottom or a top border is reached. Then I would use findLastVisibleItemPosition() method to find out which border is reached and load more data if needed. Just an idea.

In addition, you can even return your value from that method allowing overscroll and showing "loading" indicator.

shorthand If Statements: C#

Recently, I really enjoy shorthand if else statements as a swtich case replacement. In my opinion, this is better in read and take less place. Just take a look:

var redirectUrl =
      status == LoginStatusEnum.Success ? "/SecretPage"
    : status == LoginStatusEnum.Failure ? "/LoginFailed"
    : status == LoginStatusEnum.Sms ? "/2-StepSms"
    : status == LoginStatusEnum.EmailNotConfirmed ? "/EmailNotConfirmed"
    : "/404-Error";

instead of

string redirectUrl;
switch (status)
    case LoginStatusEnum.Success:
        redirectUrl = "/SecretPage";
    case LoginStatusEnum.Failure:
        redirectUrl = "/LoginFailed";
    case LoginStatusEnum.Sms:
        redirectUrl = "/2-StepSms";
    case LoginStatusEnum.EmailNotConfirmed:
        redirectUrl = "/EmailNotConfirmed";
        redirectUrl = "/404-Error";

The real difference between "int" and "unsigned int"

The printf function interprets the value that you pass it according to the format specifier in a matching position. If you tell printf that you pass an int, but pass unsigned instead, printf would re-interpret one as the other, and print the results that you see.

Loop Through All Subfolders Using VBA

And to complement Rich's recursive answer, a non-recursive method.

Public Sub NonRecursiveMethod()
    Dim fso, oFolder, oSubfolder, oFile, queue As Collection

    Set fso = CreateObject("Scripting.FileSystemObject")
    Set queue = New Collection
    queue.Add fso.GetFolder("your folder path variable") 'obviously replace

    Do While queue.Count > 0
        Set oFolder = queue(1)
        queue.Remove 1 'dequeue
        '...insert any folder processing code here...
        For Each oSubfolder In oFolder.SubFolders
            queue.Add oSubfolder 'enqueue
        Next oSubfolder
        For Each oFile In oFolder.Files
            '...insert any file processing code here...
        Next oFile

End Sub

You can use a queue for FIFO behaviour (shown above), or you can use a stack for LIFO behaviour which would process in the same order as a recursive approach (replace Set oFolder = queue(1) with Set oFolder = queue(queue.Count) and replace queue.Remove(1) with queue.Remove(queue.Count), and probably rename the variable...)

Multi-dimensional arrays in Bash

Lots of answers found here for creating multidimensional arrays in bash.

And without exception, all are obtuse and difficult to use.

If MD arrays are a required criteria, it is time to make a decision:

Use a language that supports MD arrays

My preference is Perl. Most would probably choose Python. Either works.

Store the data elsewhere

JSON and jq have already been suggested. XML has also been suggested, though for your use JSON and jq would likely be simpler.

It would seem though that Bash may not be the best choice for what you need to do.

Sometimes the correct question is not "How do I do X in tool Y?", but rather "Which tool would be best to do X?"

Javascript-Setting background image of a DIV via a function and function parameter

If you are looking for a direct approach and using a local File in that case. Try

style={{ background-image: 'url(' + Image + ')', background-size: 'auto' }}

This is the case of JS with inline styling where Image is a local file that you must have imported with a path.

how to get docker-compose to use the latest image from repository

The docker-compose documentation for the 'up' command clearly states that it updates the container should the image be changed since the last 'up' was performed:

If there are existing containers for a service, and the service’s configuration or image was changed after the container’s creation, docker-compose up picks up the changes by stopping and recreating the containers (preserving mounted volumes).

So by using 'stop' followed by 'pull' and then 'up' this should therefore avoid issues of lost volumes for the running containers, except of course, for containers whose images have been updated.

I am currently experimenting with this process and will include my results in this comment shortly.

How to change the name of a Django app?

Fun problem! I'm going to have to rename a lot of apps soon, so I did a dry run.

This method allows progress to be made in atomic steps, to minimise disruption for other developers working on the app you're renaming.

See the link at the bottom of this answer for working example code.

  1. Prepare existing code for the move:
    • Create an app config (set name and label to defaults).
    • Add the app config to INSTALLED_APPS.
    • On all models, explicitly set db_table to the current value.
    • Doctor migrations so that db_table was "always" explicitly defined.
    • Ensure no migrations are required (checks previous step).
  2. Change the app label:

    • Set label in app config to new app name.
    • Update migrations and foreign keys to reference new app label.
    • Update templates for generic class-based views (the default path is <app_label>/<model_name>_<suffix>.html)
    • Run raw SQL to fix migrations and content_types app (unfortunately, some raw SQL is unavoidable). You can not run this in a migration.

      UPDATE django_migrations
         SET app = 'catalogue'
       WHERE app = 'shop';
      UPDATE django_content_type
         SET app_label = 'catalogue'
       WHERE app_label = 'shop';
    • Ensure no migrations are required (checks previous step).

  3. Rename the tables:
    • Remove "custom" db_table.
    • Run makemigrations so django can rename the table "to the default".
  4. Move the files:
    • Rename module directory.
    • Fix imports.
    • Update app config's name.
    • Update where INSTALLED_APPS references the app config.
  5. Tidy up:
    • Remove custom app config if it's no longer required.
    • If app config gone, don't forget to also remove it from INSTALLED_APPS.

Example solution: I've created app-rename-example, an example project where you can see how I renamed an app, one commit at a time.

The example uses Python 2.7 and Django 1.8, but I'm confident the same process will work on at least Python 3.6 and Django 2.1.

How do I add 1 day to an NSDate?

I had the same problem; use an extension for NSDate:

- (id)dateByAddingYears:(NSUInteger)years
    NSDateComponents * delta = [[[NSDateComponents alloc] init] autorelease];
    NSCalendar * gregorian = [[[NSCalendar alloc]
                               initWithCalendarIdentifier:NSCalendarIdentifierGregorian] autorelease];

    [delta setYear:years];
    [delta setMonth:months];
    [delta setDay:days];
    [delta setHour:hours];
    [delta setMinute:minutes];
    [delta setSecond:seconds];

    return [gregorian dateByAddingComponents:delta toDate:self options:0];

Linker command failed with exit code 1 - duplicate symbol __TMRbBp

Don't double click Project.xcodeproj to start your xcode project. Instead, close your project and open the xcworkspace.

File -> Close Workspace

File -> Open -> Search your project folder for Project.xcworkspace

All my errors are gone.

How to check if a scope variable is undefined in AngularJS template?

You can use the double pipe operation to check if the value is undefined the after statement:

<div ng-show="foo || false">
    Show this if foo is defined!
<div ng-show="boo || true">
    Show this if boo is undefined!

Check JSFiddle for demo

For technical explanation for the double pipe, I prefer to take a look on this link:

Firebase FCM force onTokenRefresh() to be called

This answer does not destroy instance id, instead it is able to get current one. It also store refreshed one in Shared preferences.


<string name="pref_firebase_instance_id_key">pref_firebase_instance_id</string>
<string name="pref_firebase_instance_id_default_key">default</string> (any class where you want to set/get preferences)

public static void setFirebaseInstanceId(Context context, String InstanceId) {
    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
    SharedPreferences.Editor editor;
    editor = sharedPreferences.edit();

public static String getFirebaseInstanceId(Context context) {
    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
    String key = context.getString(R.string.pref_firebase_instance_id_key);
    String default_value = context.getString(R.string.pref_firebase_instance_id_default_key);
    return sharedPreferences.getString(key, default_value);
} (extends FirebaseInstanceIdService)

public void onCreate()
    String CurrentToken = FirebaseInstanceId.getInstance().getToken();

    //Log.d(this.getClass().getSimpleName(),"Inside Instance on onCreate");
    String savedToken = Utility.getFirebaseInstanceId(getApplicationContext());
    String defaultToken = getApplication().getString(R.string.pref_firebase_instance_id_default_key);

    if(CurrentToken != null && !savedToken.equalsIgnoreCase(defaultToken))
    //currentToken is null when app is first installed and token is not available
    //also skip if token is already saved in preferences...

public void onTokenRefresh() {
     .... prev code


Android 2.0 and above onCreate of service is not invoked when started automatically (source). Instead onStartCommand is overridden and used. But in actual FirebaseInstanceIdService it is declared as final and can't be overridden. However, when we start service using startService(), if service is already running, its original instance is used (which is good). Our onCreate() (defined above) also got invoked!.

Use this in begining of MainActivity or at whichever point you think you need instance id.

MyFirebaseInstanceIdService myFirebaseInstanceIdService = new MyFirebaseInstanceIdService();
Intent intent= new Intent(getApplicationContext(),myFirebaseInstanceIdService.getClass());
//Log.d(this.getClass().getSimpleName(),"Starting MyFirebaseInstanceIdService");
startService(intent); //invoke onCreate

And Finally,


Note, you can futher enhance this by trying to move startservice() code to getFirebaseInstanceId method.

How to emulate a BEFORE INSERT trigger in T-SQL / SQL Server for super/subtype (Inheritance) entities?

Sometimes a BEFORE trigger can be replaced with an AFTER one, but this doesn't appear to be the case in your situation, for you clearly need to provide a value before the insert takes place. So, for that purpose, the closest functionality would seem to be the INSTEAD OF trigger one, as @marc_s has suggested in his comment.

Note, however, that, as the names of these two trigger types suggest, there's a fundamental difference between a BEFORE trigger and an INSTEAD OF one. While in both cases the trigger is executed at the time when the action determined by the statement that's invoked the trigger hasn't taken place, in case of the INSTEAD OF trigger the action is never supposed to take place at all. The real action that you need to be done must be done by the trigger itself. This is very unlike the BEFORE trigger functionality, where the statement is always due to execute, unless, of course, you explicitly roll it back.

But there's one other issue to address actually. As your Oracle script reveals, the trigger you need to convert uses another feature unsupported by SQL Server, which is that of FOR EACH ROW. There are no per-row triggers in SQL Server either, only per-statement ones. That means that you need to always keep in mind that the inserted data are a row set, not just a single row. That adds more complexity, although that'll probably conclude the list of things you need to account for.

So, it's really two things to solve then:

  • replace the BEFORE functionality;

  • replace the FOR EACH ROW functionality.

My attempt at solving these is below:

ON sub1
  DECLARE @new_super TABLE (
    super_id int
  INSERT INTO super (subtype_discriminator)
  OUTPUT INSERTED.super_id INTO @new_super (super_id)

  INSERT INTO sub (super_id)
  SELECT super_id FROM @new_super;

This is how the above works:

  1. The same number of rows as being inserted into sub1 is first added to super. The generated super_id values are stored in a temporary storage (a table variable called @new_super).

  2. The newly inserted super_ids are now inserted into sub1.

Nothing too difficult really, but the above will only work if you have no other columns in sub1 than those you've specified in your question. If there are other columns, the above trigger will need to be a bit more complex.

The problem is to assign the new super_ids to every inserted row individually. One way to implement the mapping could be like below:

ON sub1
  DECLARE @new_super TABLE (
    rownum   int IDENTITY (1, 1),
    super_id int
  INSERT INTO super (subtype_discriminator)
  OUTPUT INSERTED.super_id INTO @new_super (super_id)

  WITH enumerated AS (
    FROM inserted
  INSERT INTO sub1 (super_id, other columns)
  SELECT n.super_id, i.other columns
  FROM enumerated AS i
  INNER JOIN @new_super AS n
  ON i.rownum = n.rownum;

As you can see, an IDENTIY(1,1) column is added to @new_user, so the temporarily inserted super_id values will additionally be enumerated starting from 1. To provide the mapping between the new super_ids and the new data rows, the ROW_NUMBER function is used to enumerate the INSERTED rows as well. As a result, every row in the INSERTED set can now be linked to a single super_id and thus complemented to a full data row to be inserted into sub1.

Note that the order in which the new super_ids are inserted may not match the order in which they are assigned. I considered that a no-issue. All the new super rows generated are identical save for the IDs. So, all you need here is just to take one new super_id per new sub1 row.

If, however, the logic of inserting into super is more complex and for some reason you need to remember precisely which new super_id has been generated for which new sub row, you'll probably want to consider the mapping method discussed in this Stack Overflow question:

How to call a method in MainActivity from another class?

But an error occurred which says java.lang.NullPointerException.

Thats because, you never initialized your MainActivity. you should initialize your object before you call its methods.

MainActivity mActivity = new MainActivity();//make sure that you pass the appropriate arguments if you have an args constructor

The ResourceConfig instance does not contain any root resource classes

Another possible cause of this error is that you have forgotten to add the libraries that are already in the /WEBINF/lib folder to the build path (e.g. when importing a .war-file and not checking the libraries when asked in the wizard). Just happened to me.

virtualbox Raw-mode is unavailable courtesy of Hyper-V windows 10

You need to disable the windows Hyper-V feature and bcd. Then Virtual Box will run in latest Windows 10 versions (Jan-Mar 2018). Windows 10 Hyper-V is having clash on VirtualBox features.

I have resolved this by following steps-

  1. bcdedit /set hypervisorlaunchtype off
  2. Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All
  3. Restart your windows

Detailed discussion on this are available at -

Alternatively you can install linux (Ubuntu) in Windows 10 from the latest bash command -

.NET Events - What are object sender & EventArgs e?

Manually cast the sender to the type of your custom control, and then use it to delete or disable etc. Eg, something like this:

private void myCustomControl_Click(object sender, EventArgs e)

The 'sender' is just the object that was actioned (eg clicked).

The event args is subclassed for more complex controls, eg a treeview, so that you can know more details about the event, eg exactly where they clicked.

How to find the foreach index?

You can put a hack in your foreach, such as a field incremented on each run-through, which is exactly what the for loop gives you in a numerically-indexed array. Such a field would be a pseudo-index that needs manual management (increments, etc).

A foreach will give you your index in the form of your $key value, so such a hack shouldn't be necessary.

e.g., in a foreach

$index = 0;
foreach($data as $key=>$val) {
    // Use $key as an index, or...

    // ... manage the index this way..
    echo "Index is $index\n";

Can you get the number of lines of code from a GitHub repository?

There in another online tool that counts lines of code for public and private repos without having to clone/download them -


How do I make a MySQL database run completely in memory?

It is also possible to place the MySQL data directory in a tmpfs in thus speeding up the database write and read calls. It might not be the most efficient way to do this but sometimes you can't just change the storage engine.

Here is my fstab entry for my MySQL data directory

none            /opt/mysql/server-5.6/data  tmpfs   defaults,size=1000M,uid=999,gid=1000,mode=0700          0       0

You may also want to take a look at the innodb_flush_log_at_trx_commit=2 setting. Maybe this will speedup your MySQL sufficently.

innodb_flush_log_at_trx_commit changes the mysql disk flush behaviour. When set to 2 it will only flush the buffer every second. By default each insert will cause a flush and thus cause more IO load.

Android - R cannot be resolved to a variable

Save all layouts, and replace them from the previous version. Start to copy one by one and clean the project everytime, sometimes one of the layouts has something, that eclipse doesn't like. It worked for me.