Programs & Examples On #Erlang

Erlang is a general-purpose, garbage-collected programming language and runtime environment, with built-in support for concurrency, distribution and fault tolerance.

Speed comparison with Project Euler: C vs Python vs Erlang vs Haskell

Question 1: Do Erlang, Python and Haskell lose speed due to using arbitrary length integers or don't they as long as the values are less than MAXINT?

Question one can be answered in the negative for Erlang. The last question is answered by using Erlang appropriately, as in:

Since it's faster than your initial C example, I would guess there are numerous problems as others have already covered in detail.

This Erlang module executes on a cheap netbook in about 5 seconds ... It uses the network threads model in erlang and, as such demonstrates how to take advantage of the event model. It could be distributed over many nodes. And it's fast. Not my code.

-author("Jannich Brendle, [email protected],").  

server() ->  

server(Number) ->  
  receive {getwork, Worker_PID} -> Worker_PID ! {work,Number,Number+100},  
  {result,T} -> io:format("The result is: \~w.\~n", [T]);  
  _ -> server(Number)  

worker(Server_PID) ->  
  Server_PID ! {getwork, self()},  
  receive {work,Start,End} -> solve(Start,End,Server_PID)  

start() ->  
  Server_PID = spawn(p12dist, server, []),  
  spawn(p12dist, worker, [Server_PID]),  
  spawn(p12dist, worker, [Server_PID]),  
  spawn(p12dist, worker, [Server_PID]),  
  spawn(p12dist, worker, [Server_PID]).

solve(N,End,_) when N =:= End -> no_solution;

solve(N,End,Server_PID) ->  
  case (divisor(T,round(math:sqrt(T))) > 500) of  
    true ->  
      Server_PID ! {result,T};  
    false ->  

divisors(N) ->  

divisor(_,0) -> 1;  
divisor(N,I) ->  
  case (N rem I) =:= 0 of  
  true ->  
  false ->  

The test below took place on an: Intel(R) Atom(TM) CPU N270 @ 1.60GHz

~$ time erl -noshell -s p12dist start

The result is: 76576500.


BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
       (v)ersion (k)ill (D)b-tables (d)istribution

real    0m5.510s
user    0m5.836s
sys 0m0.152s

OSX -bash: composer: command not found

Tested on Mac OSX after installing via instructions on composer website:

sudo mv composer.phar /usr/local/bin/composer

Passing structs to functions

It is possible to construct a struct inside the function arguments:

function({ .variable = PUT_DATA_HERE });

How to add percent sign to NSString

iOS 9.2.1, Xcode 7.2.1, ARC enabled

You can always append the '%' by itself without any other format specifiers in the string you are appending, like so...

int test = 10;

NSString *stringTest = [NSString stringWithFormat:@"%d", test];
stringTest = [stringTest stringByAppendingString:@"%"];
NSLog(@"%@", stringTest);

For iOS7.0+

To expand the answer to other characters that might cause you conflict you may choose to use:

- (NSString *)stringByAddingPercentEncodingWithAllowedCharacters:(NSCharacterSet *)allowedCharacters

Written out step by step it looks like this:

int test = 10;

NSString *stringTest = [NSString stringWithFormat:@"%d", test];
stringTest = [[stringTest stringByAppendingString:@"%"] 
             [NSCharacterSet alphanumericCharacterSet]];
stringTest = [stringTest stringByRemovingPercentEncoding];

NSLog(@"percent value of test: %@", stringTest);

Or short hand:

NSLog(@"percent value of test: %@", [[[[NSString stringWithFormat:@"%d", test] 
stringByAppendingString:@"%"] stringByAddingPercentEncodingWithAllowedCharacters:
[NSCharacterSet alphanumericCharacterSet]] stringByRemovingPercentEncoding]);

Thanks to all the original contributors. Hope this helps. Cheers!

SQL update from one Table to another based on a ID match

update from one table to another table on id matched

     TABLE1 t1, 
     TABLE2 t2
     t1.column_name = t2.column_name 

Matplotlib - Move X-Axis label downwards, but not X-Axis Ticks

If the variable ax.xaxis._autolabelpos = True, matplotlib sets the label position in function _update_label_position in according to (some excerpts):

    bboxes, bboxes2 = self._get_tick_bboxes(ticks_to_draw, renderer)
    bbox = mtransforms.Bbox.union(bboxes)
    bottom = bbox.y0
    x, y = self.label.get_position()
    self.label.set_position((x, bottom - self.labelpad * self.figure.dpi / 72.0))

You can set the label position independently of the ticks by using:

    ax.xaxis.set_label_coords(x0, y0)

that sets _autolabelpos to False or as mentioned above by changing the labelpad parameter.

How do I unload (reload) a Python module?

For those like me who want to unload all modules (when running in the Python interpreter under Emacs):

   for mod in sys.modules.values():

More information is in Reloading Python modules.

Rails 4 LIKE query - ActiveRecord adds quotes


 def, page = 1 )
    paginate :per_page => 5, :page => page,
      :conditions => ["name LIKE  ? OR postal_code like ?", "%#{search}%","%#{search}%"],   order => 'name'

See the docs on AREL conditions for more info.

ISO C90 forbids mixed declarations and code in C

I think you should move the variable declaration to top of block. I.e.

    int i = 0;


    int i = 0;

Dynamically load JS inside JS

You can use jQuery's $.getScript() method to do it but if you want a more full feature one, yepnope.js is your choice. It supports conditional loading of scripts and stylesheets and it's easy to use.

Checking if a variable is defined?

Please note the distinction between "defined" and "assigned".

$ ruby -e 'def f; if 1>2; x=99; end;p x, defined? x; end;f'

x is defined even though it is never assigned!

Windows Explorer "Command Prompt Here"

For Windows vista and Windows 7 ,to open the command prompt 1) go to folder you want to work

2)In address bar type- cmd

press enter

it will open the command prompt for that location

Add event handler for body.onload by javascript within <body> part

You should really use the following instead (works in all newer browsers):

window.addEventListener('DOMContentLoaded', init, false);

creating an array of structs in c++

It works perfectly. I have gcc compiler C++11 ready. Try this and you'll see:

#include <iostream>

using namespace std;

int main()
    int pause;

    struct Customer
           int uid;
           string name;

    Customer customerRecords[2];
    customerRecords[0] = {25, "Bob Jones"};
    customerRecords[1] = {26, "Jim Smith"};
    cout << customerRecords[0].uid << " " << customerRecords[0].name << endl;
    cout << customerRecords[1].uid << " " << customerRecords[1].name << endl;
    cin >> pause;
return 0;

T-SQL Cast versus Convert

CAST uses ANSI standard. In case of portability, this will work on other platforms. CONVERT is specific to sql server. But is very strong function. You can specify different styles for dates

string in namespace std does not name a type

You need to add:

#include <string>

In your header file.

How to declare empty list and then add string in scala?

Scala lists are immutable by default. You cannot "add" an element, but you can form a new list by appending the new element in front. Since it is a new list, you need to reassign the reference (so you can't use a val).

var dm  = List[String]()
var dk = List[Map[String,AnyRef]]()


dm = "text" :: dm
dk = Map(1 -> "ok") :: dk

The operator :: creates the new list. You can also use the shorter syntax:

dm ::= "text" 
dk ::= Map(1 -> "ok")

NB: In scala don't use the type Object but Any, AnyRef or AnyVal.

How to remove package using Angular CLI?

You can use npm uninstall <package-name> will remove it from your package.json file and from node_modules.

If you do ng help command, you will see that there is no ng remove/delete supported command. So, basically you cannot revert the ng add behavior yet.

How to disable compiler optimizations in gcc?

To test without copy elision and see you copy/move constructors/operators in action add "-fno-elide-constructors".

Even with no optimizations (-O0 ), GCC and Clang will still do copy elision, which has the effect of skipping copy/move constructors in some cases. See this question for the details about copy elision.

However, in Clang 3.4 it does trigger a bug (an invalid temporary object without calling constructor), which is fixed in 3.5.

Find files with size in Unix

find . -size +10000k -exec ls -sd {} +

If your version of find won't accept the + notation (which acts rather like xargs does), then you might use (GNU find and xargs, so find probably supports + anyway):

find . -size +10000k -print0 | xargs -0 ls -sd

or you might replace the + with \; (and live with the relative inefficiency of this), or you might live with problems caused by spaces in names and use the portable:

find . -size +10000k -print | xargs ls -sd

The -d on the ls commands ensures that if a directory is ever found (unlikely, but...), then the directory information will be printed, not the files in the directory. And, if you're looking for files more than 1 MB (as a now-deleted comment suggested), you need to adjust the +10000k to 1000k or maybe +1024k, or +2048 (for 512-byte blocks, the default unit for -size). This will list the size and then the file name. You could avoid the need for -d by adding -type f to the find command, of course.

Choosing the best concurrency list in Java

Any Java collection can be made to be Thread-safe like so:

List newList = Collections.synchronizedList(oldList);

Or to create a brand new thread-safe list:

List newList = Collections.synchronizedList(new ArrayList());

What does Statement.setFetchSize(nSize) method really do in SQL Server JDBC driver?

In JDBC, the setFetchSize(int) method is very important to performance and memory-management within the JVM as it controls the number of network calls from the JVM to the database and correspondingly the amount of RAM used for ResultSet processing.

Inherently if setFetchSize(10) is being called and the driver is ignoring it, there are probably only two options:

  1. Try a different JDBC driver that will honor the fetch-size hint.
  2. Look at driver-specific properties on the Connection (URL and/or property map when creating the Connection instance).

The RESULT-SET is the number of rows marshalled on the DB in response to the query. The ROW-SET is the chunk of rows that are fetched out of the RESULT-SET per call from the JVM to the DB. The number of these calls and resulting RAM required for processing is dependent on the fetch-size setting.

So if the RESULT-SET has 100 rows and the fetch-size is 10, there will be 10 network calls to retrieve all of the data, using roughly 10*{row-content-size} RAM at any given time.

The default fetch-size is 10, which is rather small. In the case posted, it would appear the driver is ignoring the fetch-size setting, retrieving all data in one call (large RAM requirement, optimum minimal network calls).

What happens underneath is that it doesn't actually fetch one row at a time from the RESULT-SET. It fetches that from the (local) ROW-SET and fetches the next ROW-SET (invisibly) from the server as it becomes exhausted on the local client.

All of this depends on the driver as the setting is just a 'hint' but in practice I have found this is how it works for many drivers and databases (verified in many versions of Oracle, DB2 and MySQL).

500 Error on AppHarbor but downloaded build works on my machine

Just a wild guess: (not much to go on) but I have had similar problems when, for example, I was using the IIS rewrite module on my local machine (and it worked fine), but when I uploaded to a host that did not have that add-on module installed, I would get a 500 error with very little to go on - sounds similar. It drove me crazy trying to find it.

So make sure whatever options/addons that you might have and be using locally in IIS are also installed on the host.

Similarly, make sure you understand everything that is being referenced/used in your web.config - that is likely the problem area.

How to commit and rollback transaction in sql server?

As per

@@ERROR: Returns the error number for the last Transact-SQL statement executed.

You will have to check after each statement in order to perform the rollback and return.

Commit can be at the end.


How to check if mod_rewrite is enabled in php?

I like Christian Roy's solution:

###  .htaccess

<IfModule mod_rewrite.c>

    # Tell PHP that the mod_rewrite module is ENABLED.

    RewriteEngine on
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    # The rest of your rewrite rules here


Then, you can check in your PHP code for

    array_key_exists('HTTP_MOD_REWRITE', $_SERVER);

No idea if this works also with IIS (I have no way to check) but the odds are good.

Long vs Integer, long vs int, what to use and when?

  • By default use an int, when holding numbers.
  • If the range of int is too small, use a long
  • If the range of long is too small, use BigInteger
  • If you need to handle your numbers as object (for example when putting them into a Collection, handling null, ...) use Integer/Long instead

How to make a custom LinkedIn share button

You can customize the standard Linkedin button like this, after the page load:

$(".IN-widget span:first-of-type").css({
                'border': '2px solid #DCDCDC',
                '-webkit-border-radius': '3px',
                '-moz-border-radius': '3px',
                'border-radius': '3px'

Purpose of ESI & EDI registers?

There are a few operations you can only do with DI/SI (or their extended counterparts, if you didn't learn ASM in 1985). Among these are


Which are, respectively, operations for repeated (= mass) storing, loading and scanning. What you do is you set up SI and/or DI to point at one or both operands, perhaps put a count in CX and then let 'er rip. These are operations that work on a bunch of bytes at a time, and they kind of put the CPU in automatic. Because you're not explicitly coding loops, they do their thing more efficiently (usually) than a hand-coded loop.

Just in case you're wondering: Depending on how you set the operation up, repeated storing can be something simple like punching the value 0 into a large contiguous block of memory; MOVSB is used, I think, to copy data from one buffer (well, any bunch of bytes) to another; and SCASB is used to look for a byte that matches some search criterion (I'm not sure if it's only searching on equality, or what – you can look it up :) )

That's most of what those regs are for.

C++ float array initialization

You only initialize the first N positions to the values in braces and all others are initialized to 0. In this case, N is the number of arguments you passed to the initialization list, i.e.,

float arr1[10] = { };       // all elements are 0
float arr2[10] = { 0 };     // all elements are 0
float arr3[10] = { 1 };     // first element is 1, all others are 0
float arr4[10] = { 1, 2 };  // first element is 1, second is 2, all others are 0

Usage of \b and \r in C

The characters will get send just like that to the underlying output device (in your case probably a terminal emulator).

It is up to the terminal's implementation then how those characters get actually displayed. For example, a bell (\a) could trigger a beep sound on some terminals, a flash of the screen on others, or it will be completely ignored. It all depends on how the terminal is configured.

Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null

Another way this issue can pop up on your screen is when you give a condition and insert the return inside of it. If the condition is not satisfied, then there is nothing to return. Hence the error.

export default function Component({ yourCondition }) {

    if(yourCondition === "something") {
            This will throw this error if this condition is false.

All that I did was to insert an outer return with null and it worked fine again.

How to read a Parquet file into Pandas DataFrame?

Update: since the time I answered this there has been a lot of work on this look at Apache Arrow for a better read and write of parquet. Also:

There is a python parquet reader that works relatively well:

It will create python objects and then you will have to move them to a Pandas DataFrame so the process will be slower than pd.read_csv for example.

How to fix the error; 'Error: Bootstrap tooltips require Tether ('

Works for generator-aspnetcore-spa and bootstrap 4.

// ===== file: webpack.config.vendor.js =====    
module.exports = (env) => {
    plugins: [
        new webpack.ProvidePlugin({ $: 'jquery', 
                                    jQuery: 'jquery',
                                    'window.jQuery': 'jquery',
                                    'window.Tether': 'tether',
                                    tether: 'tether', 
                                    Tether: 'tether' }), 
// Maps these identifiers to the jQuery package 
// (because Bootstrap expects it to be a global variable)

Regex to check whether a string contains only numbers

var reg = /^\d+$/;

should do it. The original matches anything that consists of exactly one digit.

What is a Question Mark "?" and Colon ":" Operator Used for?

This is the ternary conditional operator, which can be used anywhere, not just the print statement. It's sometimes just called "the ternary operator", but it's not the only ternary operator, just the most common one.

Here's a good example from Wikipedia demonstrating how it works:

A traditional if-else construct in C, Java and JavaScript is written:

if (a > b) {
    result = x;
} else {
    result = y;

This can be rewritten as the following statement:

result = a > b ? x : y;

Basically it takes the form:

boolean statement ? true result : false result;

So if the boolean statement is true, you get the first part, and if it's false you get the second one.

Try these if that still doesn't make sense:

System.out.println(true ? "true!" : "false.");
System.out.println(false ? "true!" : "false.");

How to create an AVD for Android 4.0

This site Android Create AVD shows you how to install the latest version of the Android SDK and AVD version 4 in Eclipse with video and screenshots if you're still stuck?

Xcode 10: A valid provisioning profile for this executable was not found

I've tried all the other answers, but (surprisingly) none of them have worked for me. In the end, I figured my development account has to be "Trusted" by the device for it to run.

This can be configured in your iOS device, under Settings > General > Device Management > Developer App. You should ensure your account is marked as trusted.

WARNING: Can't verify CSRF token authenticity rails

Use jquery.csrf (

  • Rails 5.1 or later

    $ yarn add jquery.csrf
    //= require jquery.csrf
  • Rails 5.0 or before

    source '' do
      gem 'rails-assets-jquery.csrf'
    //= require jquery.csrf
  • Source code

    (function($) {
      $(document).ajaxSend(function(e, xhr, options) {
        var token = $('meta[name="csrf-token"]').attr('content');
        if (token) xhr.setRequestHeader('X-CSRF-Token', token);

How to change button color with tkinter

When you do self.button = Button(...).grid(...), what gets assigned to self.button is the result of the grid() command, not a reference to the Button object created.

You need to assign your self.button variable before packing/griding it. It should look something like this:

self.button = Button(self,text="Click Me",command=self.color_change,bg="blue")
self.button.grid(row = 2, column = 2, sticky = W)

How to trigger the onclick event of a marker on a Google Maps V3?

For future Googlers, If you get an error similar below after you trigger click for a polygon

"Uncaught TypeError: Cannot read property 'vertex' of undefined"

then try the code below

google.maps.event.trigger(polygon, "click", {});

Use tnsnames.ora in Oracle SQL Developer

I had the same problem, tnsnames.ora worked fine for all other tools but SQL Developer would not use it. I tried all the suggestions on the web I could find, including the solutions on the link provided here.
Nothing worked.

It turns out that the database was caching backup copies of tnsnames.ora like tnsnames.ora.bk2, tnsnames09042811AM4501.bak, tnsnames.ora.bk etc. These files were not readable by the average user.

I suspect sqldeveloper is pattern matching for the name and it was trying to read one of these backup copies and couldn't. So it just fails gracefully and shows nothing in drop down list.

The solution is to make all the files readable or delete or move the backup copies out of the Admin directory.

Remove the last character from a string

You can use substr:

echo substr('a,b,c,d,e,', 0, -1);
# => 'a,b,c,d,e'

Unable to launch the IIS Express Web server

Before you try anything else, make sure you 1. restart visual studio (mostly for refreshing memory resident options from files) and 2. restart your system (mostly for invalid file locking). If your problem is such temporary or self-fixed those will do without changing anything. It worked for me with PC restart. Also if you work on a multi-user project make sure you have the latest workable version - someone else may had check in something invalid by mistake at e.g. the project file and you mess with your system for no reason. If those won't work, then you probably need to alter some setting(s) that are stuck, missing or need modification - there are plenty propositions on other answers.

How to convert Nonetype to int or string?

A common "Pythonic" way to handle this kind of situation is known as EAFP for "It's easier to ask forgiveness than permission". Which usually means writing code that assumes everything is fine, but then wrapping it with a try...except block to handle things—just in case—it's not.

Here's that coding style applied to your problem:

    my_value = int(my_value)
except TypeError:
    my_value = 0  # or whatever you want to do

answer = my_value / divisor

Or perhaps the even simpler and slightly faster:

    answer = int(my_value) / divisor
except TypeError:
    answer = 0

The inverse and more traditional approach is known as LBYL which stands for "Look before you leap" is what @Soviut and some of the others have suggested. For additional coverage of this topic see my answer and associated comments to the question Determine whether a key is present in a dictionary elsewhere on this site.

One potential problem with EAFP is that it can hide the fact that something is wrong with some other part of your code or third-party module you're using, especially when the exceptions frequently occur (and therefore aren't really "exceptional" cases at all).

data.table vs dplyr: can one do something well the other can't or does poorly?

Reading Hadley and Arun's answers one gets the impression that those who prefer dplyr's syntax would have in some cases to switch over to data.table or compromise for long running times.

But as some have already mentioned, dplyr can use data.table as a backend. This is accomplished using the dtplyr package which recently had it's version 1.0.0 release. Learning dtplyr incurs practically zero additional effort.

When using dtplyr one uses the function lazy_dt() to declare a lazy data.table, after which standard dplyr syntax is used to specify operations on it. This would look something like the following:

new_table <- mtcars2 %>% 
  lazy_dt() %>%
  filter(wt < 5) %>% 
  mutate(l100k = 235.21 / mpg) %>% # liters / 100 km
  group_by(cyl) %>% 
  summarise(l100k = mean(l100k))


#> Source: local data table [?? x 2]
#> Call:   `_DT1`[wt < 5][, `:=`(l100k = 235.21/mpg)][, .(l100k = mean(l100k)), 
#>     keyby = .(cyl)]
#>     cyl l100k
#>   <dbl> <dbl>
#> 1     4  9.05
#> 2     6 12.0 
#> 3     8 14.9 
#> # Use to access results

The new_table object is not evaluated until calling on it at which point the underlying data.table operation is executed.

I've recreated a benchmark analysis done by data.table author Matt Dowle back at December 2018 which covers the case of operations over large numbers of groups. I've found that dtplyr indeed enables for the most part those who prefer the dplyr syntax to keep using it while enjoying the speed offered by data.table.

How do I measure time elapsed in Java?

If the purpose is to simply print coarse timing information to your program logs, then the easy solution for Java projects is not to write your own stopwatch or timer classes, but just use the org.apache.commons.lang.time.StopWatch class that is part of Apache Commons Lang.

final StopWatch stopwatch = new StopWatch();
LOGGER.debug("Starting long calculations: {}", stopwatch);
LOGGER.debug("Time after key part of calcuation: {}", stopwatch);
LOGGER.debug("Finished calculating {}", stopwatch);

How to set python variables to true or false?

Python boolean keywords are True and False, notice the capital letters. So like this:

a = True;
b = True;
match_var = True if a == b else False
print match_var;

When compiled and run, this prints:


Why is my element value not getting changed? Am I using the wrong function?

How to address your textbox depends on the HTML-code:

<!-- 1 --><input type="textbox" id="Tue" />
<!-- 2 --><input type="textbox" name="Tue" />

If you use the 'id' attribute:

var textbox = document.getElementById('Tue');

for 'name':

var textbox = document.getElementsByName('Tue')[0]

(Note that getElementsByName() returns all elements with the name as array, therefore we use [0] to access the first one)

Then, use the 'value' attribute:

textbox.value = 'Foobar';

How to get first and last day of previous month (with timestamp) in SQL Server

SELECT DATEADD(m,DATEDIFF(m,0,GETDATE())-1,0) AS PreviousMonthStart

SELECT DATEADD(ms,-2,DATEADD(month, DATEDIFF(month, 0, GETDATE()), 0)) AS PreviousMonthEnd

Display SQL query results in php

You need to fetch the data from each row of the resultset obtained from the query. You can use mysql_fetch_array() for this.

// Process all rows
while($row = mysql_fetch_array($result)) {
    echo $row['column_name']; // Print a single column data
    echo print_r($row);       // Print the entire row data

Change your code to this :

$sql="SELECT * FROM  modul1open WHERE idM1O>=(SELECT FLOOR( MAX( idM1O ) * RAND( ) )  FROM  modul1open) 

$result = mysql_query($sql);
while($row = mysql_fetch_array($result)) {
    echo $row['fieldname']; 

Read a plain text file with php

W3Schools is your friend:

And here: has more info on fopen including what the modes are.

What W3Schools says:

$file = fopen("test.txt","r");

while(! feof($file))
  echo fgets($file). "<br />";


fopen opens the file (in this case test.txt with mode 'r' which means read-only and places the pointer at the beginning of the file)

The while loop tests to check if it's at the end of file (feof) and while it isn't it calls fgets which gets the current line where the pointer is.

Continues doing this until it is the end of file, and then closes the file.

Facebook OAuth "The domain of this URL isn't included in the app's domain"

Facebook Login -> Settings -> Valid OAuth redirect URIs -> insert the domains of your redirect url, remember you should add 'https' or http. eg: if your redirect url is, you only need to enter, it's ok for me.

How do I revert a Git repository to a previous commit?

Assuming you're talking about master and on that respective branch (that said, this could be any working branch you're concerned with):

# Reset local master branch to November 3rd commit ID
git reset --hard 0d1d7fc32e5a947fbd92ee598033d85bfc445a50

# Reset remote master branch to November 3rd commit ID
git push -f origin 0d1d7fc32e5a947fbd92ee598033d85bfc445a50:master

I found the answer from in a blog post (now no longer exists)

Note that this is Resetting and Forcing the change to the remote, so that if others on your team have already git pulled, you will cause problems for them. You are destroying the change history, which is an important reason why people use git in the first place.

Better to use revert (see other answers) than reset. If you're a one man team then it probably doesn't matter.

Vibrate and Sound defaults on notification

Notification Vibrate

mBuilder.setVibrate(new long[] { 1000, 1000});



for more sound option

Node.js Generate html

You can use jade + express:

app.get('/', function (req, res) { res.render('index', { title : 'Home' } ) });

above you see 'index' and an object {title : 'Home'}, 'index' is your html and the object is your data that will be rendered in your html.

Why does CSV file contain a blank line in between each data line when outputting with Dictwriter in Python

I just tested your snippet, and their is no double spacing line here. The end-of-line are \r\n, so what i would check in your case is:

  1. your editor is reading correctly DOS file
  2. no \n exist in values of your rows dict.

(Note that even by putting a value with \n, DictWriter automaticly quote the value.)

When should I write the keyword 'inline' for a function/method?

C++ inline is totally different to C inline.

#include <iostream>
extern inline int i[];
int i [5];
struct c {
  int function (){return 1;} //implicitly inline
  static inline int j = 3; //explicitly inline
int main() {
  c j;
  std::cout << i;

inline on its own affects the compiler, assembler and the linker. It is a directive to the compiler saying only emit a symbol for this function/data if it's used in the translation unit, and if it is, then like class methods, tell the assembler to store them in the section .section .text.c::function(),"axG",@progbits,c::function(),comdat or .section .bss.i,"awG",@nobits,i,comdat for data. Template instantiations also go in their own comdat groups.

This follows .section name, "flags"MG, @type, entsize, GroupName[, linkage]. For instance, the section name is .text.c::function(). axG means the section is allocatable, executable and in a group i.e. a group name will be specified (and there is no M flag so no entsize will be specified); @progbits means the section contains data and isn't blank; c::function() is the group name and the group has comdat linkage meaning that in all object files, all sections encountered with this group name tagged with comdat will be removed from the final executable except for 1 i.e. the compiler makes sure that there is only one definition in the translation unit and then tells the assembler to put it in its own group in the object file (1 section in 1 group) and then the linker will make sure that if any object files have a group with the same name, then only include one in the final .exe. The difference between inline and not using inline is now visible to the assembler and as a result the linker, because it's not stored in the regular .data or .text etc by the assembler due to their directives.

static inline in a class means this it a type definition and not declaration (allows static member to be defined in the class) and make it inline; it now behaves as above.

static inline at file scope only affects the compiler. It means to the compiler: only emit a symbol for this function/data if it's used in the translation unit and do so as a regular static symbol (store in.text /.data without .globl directive). To the assembler there is now no difference between static and static inline

extern inline is a declaration that means you must define this symbol in the translation unit or throw compiler error; if it's defined then treat it as a regular inline and to the assembler and linker there will be no difference between extern inline and inline, so this is a compiler guard only.

extern inline int i[];
extern int i[]; //allowed repetition of declaration with incomplete type, inherits inline property
extern int i[5]; //declaration now has complete type
extern int i[5]; //allowed redeclaration if it is the same complete type or has not yet been completed
extern int i[6]; //error, redeclaration with different complete type
int i[5]; //definition, must have complete type and same complete type as the declaration if there is a declaration with a complete type

The whole of the above without the error line collapses to inline int i[5]. Obviously if you did extern inline int i[] = {5}; then extern would be ignored due to the explicit definition through assignment.

inline on a namespace, see this and this

Forward X11 failed: Network error: Connection refused

Do not log in as a root user, try another one with sudo permissions.

How do I get the list of keys in a Dictionary?

You should be able to just look at .Keys:

    Dictionary<string, int> data = new Dictionary<string, int>();
    data.Add("abc", 123);
    data.Add("def", 456);
    foreach (string key in data.Keys)

Create a root password for PHPMyAdmin

  • Go tohttp://localhost/security/index.php
  • Select language, it redirects to http://localhost/security/xamppsecurity.php
  • You will find an option to change the password here

Most Useful Attributes

I'd suggest [TestFixture] and [Test] - from the nUnit library.

Unit tests in your code provide safety in refactoring and codified documentation.

What's "this" in JavaScript onclick?

this referes to the object the onclick method belongs to. So inside func this would be the DOM node of the a element and this.innerText would be here.

How can I test an AngularJS service from the console?

TLDR: In one line the command you are looking for:


Deep dive

AngularJS uses Dependency Injection (DI) to inject services/factories into your components,directives and other services. So what you need to do to get a service is to get the injector of AngularJS first (the injector is responsible for wiring up all the dependencies and providing them to components).

To get the injector of your app you need to grab it from an element that angular is handling. For example if your app is registered on the body element you call injector = angular.element(document.body).injector()

From the retrieved injector you can then get whatever service you like with injector.get('ServiceName')

More information on that in this answer: Can't retrieve the injector from angular
And even more here: Call AngularJS from legacy code

Another useful trick to get the $scope of a particular element. Select the element with the DOM inspection tool of your developer tools and then run the following line ($0 is always the selected element):

How to add data into ManyToMany field?

In case someone else ends up here struggling to customize admin form Many2Many saving behaviour, you can't call self.instance.my_m2m.add(obj) in your override, as later populates your m2m from self.cleaned_data['my_m2m'] which overwrites your changes. Instead call:

my_m2ms = list(self.cleaned_data['my_m2ms'])
self.cleaned_data['my_m2ms'] = my_m2ms

(It is fine to convert the incoming QuerySet to a list - the ManyToManyField does that anyway.)

How to send email from localhost WAMP Server to send email Gmail Hotmail or so forth?

Here are the steps for send email from localhost by wamp server with Sendmail.

  1. First, you need to download Sendmail zip file link
  2. Extract the zip file and put it on C:\wamp
  3. Now, you need to edit Sendmail.ini on C:\wamp\sendmail\sendmail.ini 
[email protected]
  1. Access your email account. Click the Gear Tool > Settings > Forwarding and POP/IMAP > IMAP access. Click "Enable IMAP", then save your changes
  2. Run your WAMP Server. Enable ssl_module under Apache Module.
  3. Next, enable php_openssl and php_sockets under PHP.
  4. ** Now the important part open php.ini file on "C:\wamp\bin\php\php5.5.12\php.ini" and "C:\wamp\bin\apache\apache2.4.9\bin\php.ini" set sendmail_path **

sendmail_path = "C:\wamp\sendmail\sendmail.exe -t"

  1. Restart Wamp Server.

It will surely be worked.

SSRS Conditional Formatting Switch or IIF

To dynamically change the color of a text box goto properties, goto font/Color and set the following expression

=SWITCH(Fields!CurrentRiskLevel.Value = "Low", "Green",
Fields!CurrentRiskLevel.Value = "Moderate", "Blue",
Fields!CurrentRiskLevel.Value = "Medium", "Yellow",
Fields!CurrentRiskLevel.Value = "High", "Orange",
Fields!CurrentRiskLevel.Value = "Very High", "Red"

Same way for tolerance

=SWITCH(Fields!Tolerance.Value = "Low", "Red",
Fields!Tolerance.Value = "Moderate", "Orange",
Fields!Tolerance.Value = "Medium", "Yellow",
Fields!Tolerance.Value = "High", "Blue",
Fields!Tolerance.Value = "Very High", "Green")

Importing modules from parent folder

In a Jupyter Notebook

As long as you're working in a Jupyter Notebook, this short solution might be useful:

%cd ..
import nib

It works even without an file.

I tested it with Anaconda3 on Linux and Windows 7.

When is a C++ destructor called?

  1. Pointers -- Regular pointers don't support RAII. Without an explicit delete, there will be garbage. Fortunately C++ has auto pointers that handle this for you!

  2. Scope -- Think of when a variable becomes invisible to your program. Usually this is at the end of {block}, as you point out.

  3. Manual destruction -- Never attempt this. Just let scope and RAII do the magic for you.

window.onbeforeunload and window.onunload is not working in Firefox, Safari, Opera?

I was able to get it to work in IE and FF with jQuery's:

$(window).bind('beforeunload', function(){


instead of: unload, onunload, or onbeforeunload

Why would one use nested classes in C++?

Nested classes are cool for hiding implementation details.


class List
        List(): head(nullptr), tail(nullptr) {}
        class Node
                  int   data;
                  Node* next;
                  Node* prev;
        Node*     head;
        Node*     tail;

Here I don't want to expose Node as other people may decide to use the class and that would hinder me from updating my class as anything exposed is part of the public API and must be maintained forever. By making the class private, I not only hide the implementation I am also saying this is mine and I may change it at any time so you can not use it.

Look at std::list or std::map they all contain hidden classes (or do they?). The point is they may or may not, but because the implementation is private and hidden the builders of the STL were able to update the code without affecting how you used the code, or leaving a lot of old baggage laying around the STL because they need to maintain backwards compatibility with some fool who decided they wanted to use the Node class that was hidden inside list.

How to get column by number in Pandas?

One is a column (aka Series), while the other is a DataFrame:

In [1]: df = pd.DataFrame([[1,2], [3,4]], columns=['a', 'b'])

In [2]: df
   a  b
0  1  2
1  3  4

The column 'b' (aka Series):

In [3]: df['b']
0    2
1    4
Name: b, dtype: int64

The subdataframe with columns (position) in [1]:

In [4]: df[[1]]
0  2
1  4

Note: it's preferable (and less ambiguous) to specify whether you're talking about the column name e.g. ['b'] or the integer location, since sometimes you can have columns named as integers:

In [5]: df.iloc[:, [1]]
0  2
1  4

In [6]: df.loc[:, ['b']]
0  2
1  4

In [7]: df.loc[:, 'b']
0    2
1    4
Name: b, dtype: int64

Find the most frequent number in a NumPy array

If you're willing to use SciPy:

>>> from scipy.stats import mode
>>> mode([1,2,3,1,2,1,1,1,3,2,2,1])
(array([ 1.]), array([ 6.]))
>>> most_frequent = mode([1,2,3,1,2,1,1,1,3,2,2,1])[0][0]
>>> most_frequent

Is it possible to use the SELECT INTO clause with UNION [ALL]?

This works in SQL Server:

SELECT * INTO tmpFerdeen FROM (
  SELECT top 100 * 
  FROM Customers
  SELECT top 100 * 
  FROM CustomerEurope
  SELECT top 100 * 
  FROM CustomerAsia
  SELECT top 100 * 
  FROM CustomerAmericas
) as tmp

Why am I seeing net::ERR_CLEARTEXT_NOT_PERMITTED errors after upgrading to Cordova Android 8?

Cleartext here represents unencrypted information. Since Android 9, it is recommended that apps should call HTTPS APIs to make sure there is no eves dropping.

However, if we still need to call HTTP APIs, we can do following:

Platform: Ionic 4

Create a file named: network_security_config.xml under project-root/resources/android/xml

Add following lines:

<?xml version="1.0" encoding="utf-8"?>
   <domain-config cleartextTrafficPermitted="true">

Now in project-root/config.xml, update following lines:

<platform name="android">
    <edit-config file="app/src/main/AndroidManifest.xml" mode="merge" target="/manifest/application" xmlns:android="">
        <application android:usesCleartextTraffic="true" />
        <application android:networkSecurityConfig="@xml/network_security_config" />
    ... other statements...

It should work now.

How to center an image horizontally and align it to the bottom of the container?

This also works (taken a hint from this question)

.image_block {
  height: 175px;
.image_block a img{
 margin:auto; /* Required */
 position:absolute; /* Required */
 bottom:0; /* Aligns at the bottom */
 left:0;right:0; /* Aligns horizontal center */
 max-height:100%; /* images bigger than 175 px  */
 max-width:100%;  /* will be shrinked to size */ 

ActionBarActivity: cannot be resolved to a type

I was also following the instructions on

and even though I did everything in the tutorial, as soon as "extends Action" is changed to "extends ActionBarActivity" all sorts of errors appear in Eclipse, including the "ActionBarActivitycannot be resolved to a type"

None of the above solutions worked for me, but what did work is adding this line to the top:


.rar, .zip files MIME Type

The answers from freedompeace, Kiyarash and Sam Vloeberghs:

.rar    application/x-rar-compressed, application/octet-stream
.zip    application/zip, application/octet-stream, application/x-zip-compressed, multipart/x-zip

I would do a check on the file name too. Here is how you could check if the file is a RAR or ZIP file. I tested it by creating a quick command line application.


if (isRarOrZip($argv[1])) {
    echo 'It is probably a RAR or ZIP file.';
} else {
    echo 'It is probably not a RAR or ZIP file.';

function isRarOrZip($file) {
    // get the first 7 bytes
    $bytes = file_get_contents($file, FALSE, NULL, 0, 7);
    $ext = strtolower(substr($file, - 4));

    // RAR magic number: Rar!\x1A\x07\x00
    if ($ext == '.rar' and bin2hex($bytes) == '526172211a0700') {
        return TRUE;

    // ZIP magic number: none, though PK\003\004, PK\005\006 (empty archive), 
    // or PK\007\008 (spanned archive) are common.
    if ($ext == '.zip' and substr($bytes, 0, 2) == 'PK') {
        return TRUE;

    return FALSE;

Notice that it still won't be 100% certain, but it is probably good enough.

$ rar.exe l is not RAR archive

But even WinRAR detects non RAR files as SFX archives:

$ rar.exe l somefile.srr
SFX Volume somefile.srr

Get decimal portion of a number with JavaScript

Use 1, not 2.

js> 2.3 % 1

Duplicate headers received from server

Double quotes around the filename in the header is the standard per MDN web docs. Omitting the quotes creates multiple opportunities for problems arising from characters in the filename. not found, what is it exactly?

As eaon21 and monkey said, source map files basically turn minified code into its unminified version for debugging.

You can find the .map files here. Just add them into the same directory as the minified js files and it'll stop complaining. The reason they get fetched is the


at the end of angular.min.js. If you don't want to add the .map files you can remove those lines and it'll stop the fetch attempt, but if you plan on debugging it's always good to keep the source maps linked.

Overflow:hidden dots at the end

You can use text-overflow: ellipsis; which according to caniuse is supported by all the major browsers.

Here's a demo on jsbin.

.cut-text { 
  text-overflow: ellipsis;
  overflow: hidden; 
  width: 160px; 
  height: 1.2em; 
  white-space: nowrap;
<div class="cut-text">
I like big butts and I can not lie.

How to update parent's state in React?

For child-parent communication you should pass a function setting the state from parent to child, like this

class Parent extends React.Component {_x000D_
  constructor(props) {_x000D_
    this.handler = this.handler.bind(this)_x000D_
  handler() {_x000D_
      someVar: 'some value'_x000D_
  render() {_x000D_
    return <Child handler = {this.handler} />_x000D_
class Child extends React.Component {_x000D_
  render() {_x000D_
    return <Button onClick = {this.props.handler}/ >_x000D_

This way the child can update the parent's state with the call of a function passed with props.

But you will have to rethink your components' structure, because as I understand components 5 and 3 are not related.

One possible solution is to wrap them in a higher level component which will contain the state of both component 1 and 3. This component will set the lower level state through props.

How do you run a js file using npm scripts?

You should use npm run-script build or npm build <project_folder>. More info here:

Your password does not satisfy the current policy requirements

The problem is that your password wont match the password validation rules. You can simple follow below steps to solve your problem.

You can simply see password validation configuration matrix by typing below code.

mysql-> SHOW VARIABLES LIKE 'validate_password%';

Then in your matrix you can find below variables with corresponding values and in there you have to check validate_password_length , validate_password_number_count and validate_password_policy.

Check the values used for those variables. Make sure your validate_password_length should not be greater than 6. You can set that to 6 by using below code.

SET GLOBAL validate_password_length = 6;

And after that you need to set validate_password_number_count to 0. Do it by using below code.

SET GLOBAL validate_password_number_count = 0;

Finally you have to set you validate_password_policy to low. Having that as Medium or High wont allow your less secure passwords. Set that to low by below code.

SET GLOBAL validate_password_policy=LOW;

Multiple left-hand assignment with JavaScript

Assignment in javascript works from right to left. var var1 = var2 = var3 = 1;.

If the value of any of these variables is 1 after this statement, then logically it must have started from the right, otherwise the value or var1 and var2 would be undefined.

You can think of it as equivalent to var var1 = (var2 = (var3 = 1)); where the inner-most set of parenthesis is evaluated first.

Pass user defined environment variable to tomcat

My recipe to fix it:

  1. DID NOT WORK >> Set as system environment variable: I had set the environment variable in my mac bash_profile, however, Tomcat did not see that variable.

  2. DID NOT WORK >> Apache's recommendation was to have user-defined environment variables in file and I did that.

  3. THIS WORKED!! >> After a little research into Tomcat startup scripts, I found that environment variables set using are lost during the startup. So I had to edit my against the recommendation of Apache and that did the trick.

Add your -DUSER_DEFINED variable in the run command in

  -classpath "\"$CLASSPATH\"" \ \"\"$CATALINA_BASE/conf/catalina.policy\"" \
  -Dcatalina.base="\"$CATALINA_BASE\"" \
  -Dcatalina.home="\"$CATALINA_HOME\"" \"\"$CATALINA_TMPDIR\"" \
  org.apache.catalina.startup.Bootstrap "$@" start

P.S: This problem could have been local to my computer. Others would have different problems. Adding my answer to this post just in case anyone is still facing issues with Tomcat not seeing the environment vars after trying out all recommended approaches.

How to initialize all members of an array to the same value?

Nobody has mentioned the index order to access the elements of the initialized array. My example code will give an illustrative example to it.

#include <iostream>

void PrintArray(int a[3][3])
    std::cout << "a11 = " << a[0][0] << "\t\t" << "a12 = " << a[0][1] << "\t\t" << "a13 = " << a[0][2] << std::endl;
    std::cout << "a21 = " << a[1][0] << "\t\t" << "a22 = " << a[1][1] << "\t\t" << "a23 = " << a[1][2] << std::endl;
    std::cout << "a31 = " << a[2][0] << "\t\t" << "a32 = " << a[2][1] << "\t\t" << "a33 = " << a[2][2] << std::endl;
    std::cout << std::endl;

int wmain(int argc, wchar_t * argv[])
    int a1[3][3] =  {   11,     12,     13,     // The most
                        21,     22,     23,     // basic
                        31,     32,     33  };  // format.

    int a2[][3] =   {   11,     12,     13,     // The first (outer) dimension
                        21,     22,     23,     // may be omitted. The compiler
                        31,     32,     33  };  // will automatically deduce it.

    int a3[3][3] =  {   {11,    12,     13},    // The elements of each
                        {21,    22,     23},    // second (inner) dimension
                        {31,    32,     33} };  // can be grouped together.

    int a4[][3] =   {   {11,    12,     13},    // Again, the first dimension
                        {21,    22,     23},    // can be omitted when the 
                        {31,    32,     33} };  // inner elements are grouped.


    // This part shows in which order the elements are stored in the memory.
    int * b = (int *) a1;   // The output is the same for the all four arrays.
    for (int i=0; i<9; i++)
        std::cout << b[i] << '\t';

    return 0;

The output is:

a11 = 11                a12 = 12                a13 = 13
a21 = 21                a22 = 22                a23 = 23
a31 = 31                a32 = 32                a33 = 33

a11 = 11                a12 = 12                a13 = 13
a21 = 21                a22 = 22                a23 = 23
a31 = 31                a32 = 32                a33 = 33

a11 = 11                a12 = 12                a13 = 13
a21 = 21                a22 = 22                a23 = 23
a31 = 31                a32 = 32                a33 = 33

a11 = 11                a12 = 12                a13 = 13
a21 = 21                a22 = 22                a23 = 23
a31 = 31                a32 = 32                a33 = 33

11      12      13      21      22      23      31      32      33

What is the best way to delete a value from an array in Perl?

I think your solution is the simplest and most maintainable.

The rest of the post documents the difficulty of turning tests on elements into splice offsets. Thus, making it a more complete answer.

Look at the gyrations you have to go through to have an efficient (i.e. one-pass) algorithm to turn tests on list items into indexes. And it's not that intuitive at all.

sub array_remove ( \@& ) { 
    my ( $arr_ref, $test_block ) = @_;
    my $sp_start  = 0;
    my $sp_len    = 0;
    for ( my $inx = 0; $inx <= $#$arr_ref; $inx++ ) {
        local $_ = $arr_ref->[$inx];
        next unless $test_block->( $_ );
        if ( $sp_len > 0 && $inx > $sp_start + $sp_len ) {
            splice( @$arr_ref, $sp_start, $sp_len );
            $inx    = $inx - $sp_len;
            $sp_len = 0;
        $sp_start = $inx if ++$sp_len == 1;
    splice( @$arr_ref, $sp_start, $sp_len ) if $sp_len > 0;

Concatenating two std::vectors

If your goal is simply to iterate over the range of values for read-only purposes, an alternative is to wrap both vectors around a proxy (O(1)) instead of copying them (O(n)), so they are promptly seen as a single, contiguous one.

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

VecProxy<int> AB(A, B);  // ----> O(1)!

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

Refer to for more details, including the 'VecProxy' implementation as well as pros & cons.

How to globally replace a forward slash in a JavaScript string?

Without using regex (though I would only do this if the search string is user input):

var str = 'Hello/ world/ this has two slashes!';
alert(str.split('/').join(',')); // alerts 'Hello, world, this has two slashes!' 

Format Instant to String

Time Zone

To format an Instant a time-zone is required. Without a time-zone, the formatter does not know how to convert the instant to human date-time fields, and therefore throws an exception.

The time-zone can be added directly to the formatter using withZone().

DateTimeFormatter formatter =
    DateTimeFormatter.ofLocalizedDateTime( FormatStyle.SHORT )
                     .withLocale( Locale.UK )
                     .withZone( ZoneId.systemDefault() );

If you specifically want an ISO-8601 format with no explicit time-zone (as the OP asked), with the time-zone implicitly UTC, you need


Generating String

Now use that formatter to generate the String representation of your Instant.

Instant instant =;
String output = formatter.format( instant );

Dump to console.

System.out.println("formatter: " + formatter + " with zone: " + formatter.getZone() + " and Locale: " + formatter.getLocale() );
System.out.println("instant: " + instant );
System.out.println("output: " + output );

When run.

formatter: Localized(SHORT,SHORT) with zone: US/Pacific and Locale: en_GB
instant: 2015-06-02T21:34:33.616Z
output: 02/06/15 14:34

Getting request payload from POST request in Java servlet

You can use Buffer Reader from request to read

    // Read from request
    StringBuilder buffer = new StringBuilder();
    BufferedReader reader = request.getReader();
    String line;
    while ((line = reader.readLine()) != null) {
    String data = buffer.toString()

Issue with background color in JavaFX 8

Try this one in your css document,

-fx-background-color : #ffaadd;


-fx-base : #ffaadd; 

Also, you can set background color on your object with this code directly.

yourPane.setBackground(new Background(new BackgroundFill(Color.DARKGREEN, CornerRadii.EMPTY, Insets.EMPTY)));

Should you use .htm or .html file extension? What is the difference, and which file is correct?

I have a site that is all .htm and was told by a computer "know it all" to change to .html because it would help google rank.. saved time and $

How to convert map to url query string?

Using EntrySet and Streams:

  .map(e -> e.getKey() + "=" + e.getValue())

File to byte[] in Java

RandomAccessFile f = new RandomAccessFile(fileName, "r");
byte[] b = new byte[(int)f.length()];

Documentation for Java 8:

CSS scale down image to fit in containing div, without specifing original size

if you want both width and the height you can try

 background-size: cover !important;

but this wont distort the image but fill the div.

What is the syntax to insert one list into another list in python?

If we just do x.append(y), y gets referenced into x such that any changes made to y will affect appended x as well. So if we need to insert only elements, we should do following:

x = [1,2,3] y = [4,5,6] x.append(y[:])

Observable Finally on Subscribe

The current "pipable" variant of this operator is called finalize() (since RxJS 6). The older and now deprecated "patch" operator was called finally() (until RxJS 5.5).

I think finalize() operator is actually correct. You say:

do that logic only when I subscribe, and after the stream has ended

which is not a problem I think. You can have a single source and use finalize() before subscribing to it if you want. This way you're not required to always use finalize():

let source = new Observable(observer => {;
  observer.error('error message');;

  finalize(() => console.log('Finally callback')),
  value => console.log('#1 Next:', value),
  error => console.log('#1 Error:', error),
  () => console.log('#1 Complete')

  value => console.log('#2 Next:', value),
  error => console.log('#2 Error:', error),
  () => console.log('#2 Complete')


This prints to console:

#1 Next: 1
#2 Next: 1
#1 Error: error message
Finally callback
#2 Error: error message

Jan 2019: Updated for RxJS 6

How to send POST in angularjs with multiple params?

If you're using ASP.NET MVC and Web API chances are you have the Newtonsoft.Json NuGet package installed.This library has a class called JObject which allows you to pass through multiple parameters:

Api Controller:

public class ProductController : ApiController
    public void Post(Newtonsoft.Json.Linq.JObject data)

        Product product = data["product"].ToObject<Product>();
        Product product2 = data["product2"].ToObject<Product>();

        int someRandomNumber = data["randomNumber"].ToObject<int>();
        string productName = product.ProductName;
        string product2Name = product2.ProductName;

public class Product
    public int ProductID { get; set; }
    public string ProductName { get; set; }


<script src="~/Scripts/angular.js"></script>
<script type="text/javascript">
    var myApp = angular.module("app", []);
    myApp.controller('controller', function ($scope, $http) {

        $scope.AddProducts = function () {
            var product = {
                ProductID: 0,
                ProductName: "Orange",

            var product2 = {
                ProductID: 1,
                ProductName: "Mango",

            var data = {
                product: product,
                product2: product2,

            $"/api/Product", data).
            success(function (data, status, headers, config) {
            error(function (data, status, headers, config) {
                alert("An error occurred during the AJAX request");
<div ng-app="app" ng-controller="controller">
    <input type="button" ng-click="AddProducts()" value="Get Full Name" />

Access-Control-Allow-Origin Multiple Origin Domains?

Here's an expanded option for apache that includes some of the latest and planned font definitions:

<FilesMatch "\.(ttf|otf|eot|woff|woff2|sfnt|svg)$">
    <IfModule mod_headers.c>
        SetEnvIf Origin "^http(s)?://(.+\.)?(domainname1|domainname2|domainname3)\.(?:com|net|org)$" AccessControlAllowOrigin=$0$1$2
        Header add Access-Control-Allow-Origin %{AccessControlAllowOrigin}e env=AccessControlAllowOrigin
        Header set Access-Control-Allow-Credentials true

Reverse ip, find domain names on ip address

windows user can just using the simple nslookup command

G:\wwwRoot\JavaScript Testing>nslookup


G:\wwwRoot\JavaScript Testing>

if you want get more info, please check the following answer!

When to use MongoDB or other document oriented database systems?

After two years using MongoDb for a social app, I have witnessed what it really means to live without a SQL RDBMS.

  1. You end up writing jobs to do things like joining data from different tables/collections, something that an RDBMS would do for you automatically.
  2. Your query capabilities with NoSQL are drastically crippled. MongoDb may be the closest thing to SQL but it is still extremely far behind. Trust me. SQL queries are super intuitive, flexible and powerful. MongoDb queries are not.
  3. MongoDb queries can retrieve data from only one collection and take advantage of only one index. And MongoDb is probably one of the most flexible NoSQL databases. In many scenarios, this means more round-trips to the server to find related records. And then you start de-normalizing data - which means background jobs.
  4. The fact that it is not a relational database means that you won't have (thought by some to be bad performing) foreign key constrains to ensure that your data is consistent. I assure you this is eventually going to create data inconsistencies in your database. Be prepared. Most likely you will start writing processes or checks to keep your database consistent, which will probably not perform better than letting the RDBMS do it for you.
  5. Forget about mature frameworks like hibernate.

I believe that 98% of all projects probably are way better with a typical SQL RDBMS than with NoSQL.

IntelliJ - show where errors are

In my case, IntelliJ was simply in power safe mode

Drawing a simple line graph in Java

Just complementing Hovercraft Full Of Eels's solution:

I reworked his code, tweaked it a bit, adding a grid, axis labels and now the Y-axis goes from the minimum value present up to the maximum value. I planned on adding a couple of getters/setters but I didn't need them, you can add them if you want.

Here is the Gist link, I'll also paste the code below: GraphPanel on Gist

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class GraphPanel extends JPanel {

    private int width = 800;
    private int heigth = 400;
    private int padding = 25;
    private int labelPadding = 25;
    private Color lineColor = new Color(44, 102, 230, 180);
    private Color pointColor = new Color(100, 100, 100, 180);
    private Color gridColor = new Color(200, 200, 200, 200);
    private static final Stroke GRAPH_STROKE = new BasicStroke(2f);
    private int pointWidth = 4;
    private int numberYDivisions = 10;
    private List<Double> scores;

    public GraphPanel(List<Double> scores) {
        this.scores = scores;

    protected void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        double xScale = ((double) getWidth() - (2 * padding) - labelPadding) / (scores.size() - 1);
        double yScale = ((double) getHeight() - 2 * padding - labelPadding) / (getMaxScore() - getMinScore());

        List<Point> graphPoints = new ArrayList<>();
        for (int i = 0; i < scores.size(); i++) {
            int x1 = (int) (i * xScale + padding + labelPadding);
            int y1 = (int) ((getMaxScore() - scores.get(i)) * yScale + padding);
            graphPoints.add(new Point(x1, y1));

        // draw white background
        g2.fillRect(padding + labelPadding, padding, getWidth() - (2 * padding) - labelPadding, getHeight() - 2 * padding - labelPadding);

        // create hatch marks and grid lines for y axis.
        for (int i = 0; i < numberYDivisions + 1; i++) {
            int x0 = padding + labelPadding;
            int x1 = pointWidth + padding + labelPadding;
            int y0 = getHeight() - ((i * (getHeight() - padding * 2 - labelPadding)) / numberYDivisions + padding + labelPadding);
            int y1 = y0;
            if (scores.size() > 0) {
                g2.drawLine(padding + labelPadding + 1 + pointWidth, y0, getWidth() - padding, y1);
                String yLabel = ((int) ((getMinScore() + (getMaxScore() - getMinScore()) * ((i * 1.0) / numberYDivisions)) * 100)) / 100.0 + "";
                FontMetrics metrics = g2.getFontMetrics();
                int labelWidth = metrics.stringWidth(yLabel);
                g2.drawString(yLabel, x0 - labelWidth - 5, y0 + (metrics.getHeight() / 2) - 3);
            g2.drawLine(x0, y0, x1, y1);

        // and for x axis
        for (int i = 0; i < scores.size(); i++) {
            if (scores.size() > 1) {
                int x0 = i * (getWidth() - padding * 2 - labelPadding) / (scores.size() - 1) + padding + labelPadding;
                int x1 = x0;
                int y0 = getHeight() - padding - labelPadding;
                int y1 = y0 - pointWidth;
                if ((i % ((int) ((scores.size() / 20.0)) + 1)) == 0) {
                    g2.drawLine(x0, getHeight() - padding - labelPadding - 1 - pointWidth, x1, padding);
                    String xLabel = i + "";
                    FontMetrics metrics = g2.getFontMetrics();
                    int labelWidth = metrics.stringWidth(xLabel);
                    g2.drawString(xLabel, x0 - labelWidth / 2, y0 + metrics.getHeight() + 3);
                g2.drawLine(x0, y0, x1, y1);

        // create x and y axes 
        g2.drawLine(padding + labelPadding, getHeight() - padding - labelPadding, padding + labelPadding, padding);
        g2.drawLine(padding + labelPadding, getHeight() - padding - labelPadding, getWidth() - padding, getHeight() - padding - labelPadding);

        Stroke oldStroke = g2.getStroke();
        for (int i = 0; i < graphPoints.size() - 1; i++) {
            int x1 = graphPoints.get(i).x;
            int y1 = graphPoints.get(i).y;
            int x2 = graphPoints.get(i + 1).x;
            int y2 = graphPoints.get(i + 1).y;
            g2.drawLine(x1, y1, x2, y2);

        for (int i = 0; i < graphPoints.size(); i++) {
            int x = graphPoints.get(i).x - pointWidth / 2;
            int y = graphPoints.get(i).y - pointWidth / 2;
            int ovalW = pointWidth;
            int ovalH = pointWidth;
            g2.fillOval(x, y, ovalW, ovalH);

//    @Override
//    public Dimension getPreferredSize() {
//        return new Dimension(width, heigth);
//    }
    private double getMinScore() {
        double minScore = Double.MAX_VALUE;
        for (Double score : scores) {
            minScore = Math.min(minScore, score);
        return minScore;

    private double getMaxScore() {
        double maxScore = Double.MIN_VALUE;
        for (Double score : scores) {
            maxScore = Math.max(maxScore, score);
        return maxScore;

    public void setScores(List<Double> scores) {
        this.scores = scores;

    public List<Double> getScores() {
        return scores;

    private static void createAndShowGui() {
        List<Double> scores = new ArrayList<>();
        Random random = new Random();
        int maxDataPoints = 40;
        int maxScore = 10;
        for (int i = 0; i < maxDataPoints; i++) {
            scores.add((double) random.nextDouble() * maxScore);
//            scores.add((double) i);
        GraphPanel mainPanel = new GraphPanel(scores);
        mainPanel.setPreferredSize(new Dimension(800, 600));
        JFrame frame = new JFrame("DrawGraph");

    public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {

It looks like this: Example pic

Class method decorator with self arguments?

Another option would be to abandon the syntactic sugar and decorate in the __init__ of the class.

def countdown(number):
    def countdown_decorator(func):
        def func_wrapper():
            for index in reversed(range(1, number+1)):
        return func_wrapper
    return countdown_decorator

class MySuperClass():
    def __init__(self, number):
        self.number = number
        self.do_thing = countdown(number)(self.do_thing)
    def do_thing(self):
        print('im doing stuff!')

myclass = MySuperClass(3)


which would print

im doing stuff!

How to add line breaks to an HTML textarea?

You need to use \n for linebreaks inside textarea

SQL left join vs multiple tables on FROM line?

When you need an outer join the second syntax is not always required:


  FROM a, b
 WHERE a.x = b.x(+)

MSSQLServer (although it's been deprecated in 2000 version)/Sybase:

  FROM a, b
 WHERE a.x *= b.x

But returning to your question. I don't know the answer, but it is probably related to the fact that a join is more natural (syntactically, at least) than adding an expression to a where clause when you are doing exactly that: joining.

Certificate has either expired or has been revoked

In case it helps anyone: Xcode 11.x I revoked also (deleted) a certificate in App Developer account. Then I thought I had deleted the certificate too in Keychain access but kept getting error messages, when trying to upload an app update to the AppStore.

I then found out that there are two separate places in keychain access, where in one the certificate is kept (funny enough under keys, once login is selected in keychains) and in the other one the private key (of course under the item certificates in keychains). I made sure that both are deleted and now all is good.

Moving Git repository content to another repository preserving history

Perfectly described here

First, we have to fetch all of the remote branches and tags from the existing repository to our local index:

git fetch origin

We can check for any missing branches that we need to create a local copy of:

git branch -a

Let’s use the SSH-cloned URL of our new repository to create a new remote in our existing local repository:

git remote add new-origin [email protected]:manakor/manascope.git

Now we are ready to push all local branches and tags to the new remote named new-origin:

git push --all new-origin 
git push --tags new-origin

Let’s make new-origin the default remote:

git remote rm origin

Rename new-origin to just origin, so that it becomes the default remote:

git remote rename new-origin origin

Parsing HTTP Response in Python

You can also use python's requests library instead.

import requests

url = ''    
response = requests.get(url)    
dict = response.json()

Now you can manipulate the "dict" like a python dictionary.

How to change the Text color of Menu item in Android?

to change menu item text color use below code

<style name="AppToolbar" parent="Theme.AppCompat.Light.NoActionBar">
<item name="android:itemTextAppearance">@style/menu_item_color</item>


<style name="menu_item_color">
<item name="android:textColor">@color/app_font_color</item>

Get RETURN value from stored procedure in SQL

Assign after the EXEC token:

DECLARE @returnValue INT

EXEC @returnValue = SP_One

How to search in an array with preg_match?

Use preg_grep

$array = preg_grep(
    array( 'file' , 'my string  => name', 'this')

In DB2 Display a table's definition

I just came across this query to describe a table in winsql

select NAME,TBNAME,COLTYPE,LENGTH,REMARKS,SCALE from sysibm.syscolumns
where tbcreator = 'Schema_name' and tbname='Table_name' ;

Reliable and fast FFT in Java

FFTW is the 'fastest fourier transform in the west', and has some Java wrappers:

Hope that helps!

Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set()

If you are running your application just on localhost and it is not yet live, I believe it is very difficult to send mail using this.

Once you put your application online, I believe that this problem should be automatically solved. By the way,ini_set() helps you to change the values in php.ini during run time.

This is the same question as Failed to connect to mailserver at "localhost" port 25

also check this php mail function not working

JavaScript Array Push key value

You may use:

To create array of objects:

var source = ['left', 'top'];
const result = => ({[arrValue]: 0}));


var source = ['left', 'top'];_x000D_
const result = => ({[value]: 0}));_x000D_

Or if you wants to create a single object from values of arrays:

var source = ['left', 'top'];
const result = source.reduce((obj, arrValue) => (obj[arrValue] = 0, obj), {});


var source = ['left', 'top'];_x000D_
const result = source.reduce((obj, arrValue) => (obj[arrValue] = 0, obj), {});_x000D_

Page unload event in

There is an event Page.Unload. At that moment page is already rendered in HTML and HTML can't be modified. Still, all page objects are available.

What is the meaning of ToString("X2")?

It formats the string as two uppercase hexadecimal characters.

In more depth, the argument "X2" is a "format string" that tells the ToString() method how it should format the string. In this case, "X2" indicates the string should be formatted in Hexadecimal.

byte.ToString() without any arguments returns the number in its natural decimal representation, with no padding.

Microsoft documents the standard numeric format strings which generally work with all primitive numeric types' ToString() methods. This same pattern is used for other types as well: for example, standard date/time format strings can be used with DateTime.ToString().

How to use null in switch

Just consider how the SWITCH might work,

  • in case of primitives we know it can fail with NPE for auto-boxing
  • but for String or enum, it might be invoking equals method, which obviously needs a LHS value on which equals is being invoked. So, given no method can be invoked on a null, switch cant handle null.

What is the C++ function to raise a number to a power?

Note that the use of pow(x,y) is less efficient than x*x*x y times as shown and answered here

So if you're going for efficiency use x*x*x.

Python: Random numbers into a list

Here I use the sample method to generate 10 random numbers between 0 and 100.

Note: I'm using Python 3's range function (not xrange).

import random

print(random.sample(range(0, 100), 10))

The output is placed into a list:

[11, 72, 64, 65, 16, 94, 29, 79, 76, 27]

While variable is not defined - wait

async, await implementation, improvement over @Toprak's answer

(async() => {
    console.log("waiting for variable");
    while(!window.hasOwnProperty("myVar")) // define the condition as you like
        await new Promise(resolve => setTimeout(resolve, 1000));
    console.log("variable is defined");
console.log("above code doesn't block main function stack");

After revisiting the OP's question. There is actually a better way to implement what was intended: "variable set callback". Although the below code only works if the desired variable is encapsulated by an object (or window) instead of declared by let or var (I left the first answer because I was just doing improvement over existing answers without actually reading the original question):

let obj = encapsulatedObject || window;
Object.defineProperty(obj, "myVar", {
    configurable: true,
        Object.defineProperty(obj, "myVar", {
            configurable: true, enumerable: true, writable: true, value: v });
        console.log("window.myVar is defined");

see Object.defineProperty or use es6 proxy (which is probably overkill)

If you are looking for more:

 * combining the two as suggested by @Emmanuel Mahuni,
 * and showing an alternative to handle defineProperty setter and getter

let obj = {} || window;
(async() => {
  let _foo = await new Promise(res => {
    Object.defineProperty(obj, "foo", { set: res });
  console.log(" is defined with value:", _foo);
IMPORTANT: note that is still undefined
the reason is out of scope of this question/answer
take a research of Object.defineProperty to see more


console.log("test start");
setTimeout(async () => {
  console.log("about to assign"); = "Hello World!";
  // try uncomment the following line and compare the output
  // await new Promise(res => setTimeout(res));
  console.log("finished assigning");
  console.log("value of",; // undefined
  // console: is defined with value: Hello World!
}, 2000);

Selectors in Objective-C?

NSString's method is lowercaseString (0 arguments), not lowercaseString: (1 argument).

open cv error: (-215) scn == 3 || scn == 4 in function cvtColor

Give the full path of image with forward slash. It solved the error for me.


import numpy as np
import cv2

img = cv2.imread('C:/Python34/images/2015-05-27-191152.jpg')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

Also, if you give 0 in second parameter while loading image using cv2.imread than no need to convert image using cvtColor, it is already loaded as grayscale image eg.

import numpy as np
import cv2

gray = cv2.imread('C:/Python34/images/2015-05-27-191152.jpg',0)

How many bytes does one Unicode character take?

You won't see a simple answer because there isn't one.

First, Unicode doesn't contain "every character from every language", although it sure does try.

Unicode itself is a mapping, it defines codepoints and a codepoint is a number, associated with usually a character. I say usually because there are concepts like combining characters. You may be familiar with things like accents, or umlauts. Those can be used with another character, such as an a or a u to create a new logical character. A character therefore can consist of 1 or more codepoints.

To be useful in computing systems we need to choose a representation for this information. Those are the various unicode encodings, such as utf-8, utf-16le, utf-32 etc. They are distinguished largely by the size of of their codeunits. UTF-32 is the simplest encoding, it has a codeunit that is 32bits, which means an individual codepoint fits comfortably into a codeunit. The other encodings will have situations where a codepoint will need multiple codeunits, or that particular codepoint can't be represented in the encoding at all (this is a problem for instance with UCS-2).

Because of the flexibility of combining characters, even within a given encoding the number of bytes per character can vary depending on the character and the normalization form. This is a protocol for dealing with characters which have more than one representation (you can say "an 'a' with an accent" which is 2 codepoints, one of which is a combining char or "accented 'a'" which is one codepoint).

AngularJS not detecting Access-Control-Allow-Origin header?

There's a workaround for those who want to use Chrome. This extension allows you to request any site with AJAX from any source, since it adds 'Access-Control-Allow-Origin: *' header to the response.

As an alternative, you can add this argument to your Chrome launcher: --disable-web-security. Note that I'd only use this for development purposes, not for normal "web surfing". For reference see Run Chromium with Flags.

As a final note, by installing the extension mentioned on the first paragraph, you can easily enable/disable CORS.

Detect when an HTML5 video finishes

You can simply add onended="myFunction()" to your video tag.

<video onended="myFunction()">
  Your browser does not support the video tag.

<script type='text/javascript'>
  function myFunction(){
    console.log("The End.")

What does the @ symbol before a variable name mean in C#?

The @ symbol allows you to use reserved word. For example:

int @class = 15;

The above works, when the below wouldn't:

int class = 15;

python: How do I know what type of exception occurred?

Just refrain from catching the exception and the traceback that Python prints will tell you what exception occurred.

Git removing upstream from local repository

Using git version there is no "remove" command for remote. Use "rm" instead.

$ git remote rm upstream
$ git remote add upstream

or, as noted in the previous answer, set-url works.

I don't know when the command changed, but Ubuntu 12.04 shipped with

Multiple argument IF statement - T-SQL

Your code is valid (with one exception). It is required to have code between BEGIN and END.


--do some work


print ''

I think maybe you saw "END and not "AND"

adding text to an existing text element in javascript via DOM

The reason that appendChild is not a function is because you're executing it on the textContent of your p element.

You instead just need to select the paragraph itself, and then append your new text node to that:

var paragraph = document.getElementById("p");_x000D_
var text = document.createTextNode("This just got added");_x000D_
<p id="p">This is some text</p>

However instead, if you like, you can just modify the text itself (rather than adding a new node):

var paragraph = document.getElementById("p");_x000D_
paragraph.textContent += "This just got added";
<p id="p">This is some text</p>

How do I calculate square root in Python?

If you want to do it the way the calculator actually does it, use the Babylonian technique. It is explained here and here.

Suppose you want to calculate the square root of 2:


a1 = (a/2)+1
b1 = a/a1
aminus1 = a1
bminus1 = b1

while (aminus1-bminus1 > 0):
    an = 0.5 * (aminus1 + bminus1)
    bn = a / an
    aminus1 = an
    bminus1 = bn

SQL query for getting data for last 3 months


Mureinik's suggested method will return the same results, but doing it this way your query can benefit from any indexes on Date_Column.

or you can check against last 90 days.

WHERE Date_Column >= DATEADD(DAY, -90, GETDATE()) 

How to parse JSON in Scala using standard Scala classes?

You can do like this! Very easy to parse JSON code :P

package org.sqkb.service.common.bean

import java.text.SimpleDateFormat

import org.json4s
import org.json4s.JValue
import org.json4s.jackson.JsonMethods._
//import org.sqkb.service.common.kit.{IsvCode}

import scala.util.Try

case class Order(log: String) {

  implicit lazy val formats = org.json4s.DefaultFormats

  lazy val json: json4s.JValue = parse(log)

  lazy val create_time: String = (json \ "create_time").extractOrElse("1970-01-01 00:00:00")
  lazy val site_id: String = (json \ "site_id").extractOrElse("")
  lazy val alipay_total_price: Double = (json \ "alipay_total_price").extractOpt[String].filter(_.nonEmpty).getOrElse("0").toDouble
  lazy val gmv: Double = alipay_total_price
  lazy val pub_share_pre_fee: Double = (json \ "pub_share_pre_fee").extractOpt[String].filter(_.nonEmpty).getOrElse("0").toDouble
  lazy val profit: Double = pub_share_pre_fee

  lazy val trade_id: String = (json \ "trade_id").extractOrElse("")
  lazy val unid: Long = Try((json \ "unid").extractOpt[String].filter(_.nonEmpty).get.toLong).getOrElse(0L)
  lazy val cate_id1: Int = (json \ "cate_id").extractOrElse(0)
  lazy val cate_id2: Int = (json \ "subcate_id").extractOrElse(0)
  lazy val cate_id3: Int = (json \ "cate_id3").extractOrElse(0)
  lazy val cate_id4: Int = (json \ "cate_id4").extractOrElse(0)
  lazy val coupon_id: Long = (json \ "coupon_id").extractOrElse(0)

  lazy val platform: Option[String] = Order.siteMap.get(site_id)

  def time_fmt(fmt: String = "yyyy-MM-dd HH:mm:ss"): String = {
    val dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
    val date = dateFormat.parse(this.create_time)
    new SimpleDateFormat(fmt).format(date)


Creating Scheduled Tasks

You can use Task Scheduler Managed Wrapper:

using System;
using Microsoft.Win32.TaskScheduler;

class Program
   static void Main(string[] args)
      // Get the service on the local machine
      using (TaskService ts = new TaskService())
         // Create a new task definition and assign properties
         TaskDefinition td = ts.NewTask();
         td.RegistrationInfo.Description = "Does something";

         // Create a trigger that will fire the task at this time every other day
         td.Triggers.Add(new DailyTrigger { DaysInterval = 2 });

         // Create an action that will launch Notepad whenever the trigger fires
         td.Actions.Add(new ExecAction("notepad.exe", "c:\\test.log", null));

         // Register the task in the root folder
         ts.RootFolder.RegisterTaskDefinition(@"Test", td);

         // Remove the task we just created

Alternatively you can use native API or go for Quartz.NET. See this for details.

Qt 5.1.1: Application failed to start because platform plugin "windows" is missing

Lets say, you wanted to have some CGAL-Demos portable. So you'd have a folder "CGAL", and in it, 1 subfolder called "lib": all (common) support-dlls for any programs in the CGAL-folder go here. In our example, this would be the Dll-Download: simply unzip into the "lib" directory. The further you scroll down on the demos-page, the more impressive the content. In my case, the polyhedron-demo seemed about right. If this runs on my 10+ yo notebook, I'm impressed. So I created a folder "demo" in the "CGAL"-directory, alongside "lib". Now create a .cmd-file in that folder. I named mine "Polyhedron.cmd". So we have a directory structure like this:

 CGAL - the bag for all the goodies
  lib - all libraries for all CGAL-packages
 demo - all the demos I'm interested in
[...] - certainly some other collections, several apps per folder...
Polyhedron.cmd - and a little script for every Qt-exe to make it truly portable.

In this little example, "Polyhedron.cmd" contains the following text:

@echo off
set "me=%~dp0"
set PATH=%me%lib
set "QT_PLUGIN_PATH=%me%lib\plugins"
start /b "CGAL Polyhedron Demo" "%me%demo\polyhedron\polyhedron_3.exe"

All scripts can be the same apart from the last line, obviously. The only caveat is: the "DOS-Window" stays open for as long as you use the actual program. Close the shell-window, and you kill the *.exe as well. Whereever you copy the "CGAL"-folder, as the weird "%~dp0"-wriggle represents the full path to the *.cmd-file that we started, with trailing "\". So "%me%lib" is always the full path to the actual library ("CGAL\lib" in my case). The next 2 lines tell Qt where its "runtime" files are. This will be at least the file "qwindows.dll" for Windows-Qt programs plus any number of *.dlls. If I remember rightly, the Dll-library (at least when I downloaded it) had a little "bug" since it contains the "platforms"-directory with qwindows.dll in it. So when you open the lib directory, you need to create a folder "plugins" next to "platforms", and then move into "plugins". If a Qt-app, any Qt-app, doesn't find "qwindows.dll", it cannot find "windows". And it expects it in a directory named "platforms" in the "plugins" directory, which it has to get told by the OS its running on...and if the "QT_PLUGIN_PATH" is not exactly pointing to all the helper-dlls you need, some Qt-programs will still run with no probs. And some complain about missing *.dlls you've never heard off...

How to auto-scroll to end of div when data is added?

var objDiv = document.getElementById("divExample");
objDiv.scrollTop = objDiv.scrollHeight;

update columns values with column of another table based on condition

This will surely work:

UPDATE table1
SET table1.price=(SELECT table2.price
  FROM table2
  WHERE AND table2.item=table1.item);

Call ASP.NET function from JavaScript?

You can do it asynchronously using .NET Ajax PageMethods. See here or here.

Make HTML5 video poster be same size as video itself

I came up with this idea and it works perfectly. Okay so basically we want to get rid of the videos first frame from the display and then resize the poster to the videos actual size. If we then set the dimensions we have completed one of these tasks. Then only one remains. So now, the only way I know to get rid of the first frame is to actually define a poster. However we are going to give the video a faked one, one that doesn't exist. This will result in a blank display with the background transparent. I.e. our parent div's background will be visible.

Simple to use, however it might not work with all web browsers if you want to resize the dimension of the background of the div to the dimension of the video since my code is using "background-size".


<div class="video_poster">
    <video poster="dasdsadsakaslmklda.jpg" controls>
        <source src="videos/myvideo.mp4" type="video/mp4">
        Your browser does not support the video tag.


    background-size:694px 390px;

Which is better: <script type="text/javascript">...</script> or <script>...</script>

You need to use <script type="text/javascript"> </script> unless you're using html5. In that case you are encouraged to prefer <script> ... </script> (because type attribute is specified by default to that value)

How do I limit the number of returned items?

models.Post.find({published: true}, {sort: {'date': -1}, limit: 20}, function(err, posts) {
 // `posts` with sorted length of 20

MIME types missing in IIS 7 for ASP.NET - 404.17


I chose the "ISAPI & CGI Restrictions" after clicking the server name (not the site name) in IIS Manager, and right clicked the "ASP.NET v4.0.30319" lines and chose "Allow".

After turning on ASP.NET from "Programs and Features > Turn Windows features on or off", you must install ASP.NET from the Windows command prompt. The MIME types don't ever show up, but after doing this command, I noticed these extensions showed up under the IIS web site "Handler Mappings" section of IIS Manager.

C:\>cd C:\Windows\Microsoft.NET\Framework64\v4.0.30319

C:\Windows\Microsoft.NET\Framework64\v4.0.30319>dir aspnet_reg*
 Volume in drive C is Windows
 Volume Serial Number is 8EE6-5DD0

 Directory of C:\Windows\Microsoft.NET\Framework64\v4.0.30319

03/18/2010  08:23 PM            19,296 aspnet_regbrowsers.exe
03/18/2010  08:23 PM            36,696 aspnet_regiis.exe
03/18/2010  08:23 PM           102,232 aspnet_regsql.exe
               3 File(s)        158,224 bytes
               0 Dir(s)  34,836,508,672 bytes free

C:\Windows\Microsoft.NET\Framework64\v4.0.30319>aspnet_regiis.exe -i
Start installing ASP.NET (4.0.30319).
Finished installing ASP.NET (4.0.30319).


However, I still got this error. But if you do what I mentioned for the "Fix", this will go away.

HTTP Error 404.2 - Not Found
The page you are requesting cannot be served because of the ISAPI and CGI Restriction list settings on the Web server.

php exec command (or similar) to not wait for result

This uses wget to notify a URL of something without waiting.

$command = 'wget -qO-';
exec('nohup ' . $command . ' >> /dev/null 2>&1 & echo $!', $pid);

This uses ls to update a log without waiting.

$command = 'ls -la > content.log';
exec('nohup ' . $command . ' >> /dev/null 2>&1 & echo $!', $pid);

Replace Multiple String Elements in C#

If you are simply after a pretty solution and don't need to save a few nanoseconds, how about some LINQ sugar?

var input = "test1test2test3";
var replacements = new Dictionary<string, string> { { "1", "*" }, { "2", "_" }, { "3", "&" } };

var output = replacements.Aggregate(input, (current, replacement) => current.Replace(replacement.Key, replacement.Value));

Perl: Use s/ (replace) and return new string

If you have Perl 5.14 or greater, you can use the /r option with the substitution operator to perform non-destructive substitution:

print "bla: ", $myvar =~ s/a/b/r, "\n";

In earlier versions you can achieve the same using a do() block with a temporary lexical variable, e.g.:

print "bla: ", do { (my $tmp = $myvar) =~ s/a/b/; $tmp }, "\n";

Paging UICollectionView by cells, not screen

Partly based on StevenOjo's answer. I've tested this using a horizontal scrolling and no Bounce UICollectionView. cellSize is CollectionViewCell size. You can tweak factor to modify scrolling sensitivity.

override func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    targetContentOffset.pointee = scrollView.contentOffset
    var factor: CGFloat = 0.5
    if velocity.x < 0 {
        factor = -factor
    let indexPath = IndexPath(row: (scrollView.contentOffset.x/cellSize.width + factor).int, section: 0)
    collectionView?.scrollToItem(at: indexPath, at: .left, animated: true)

Convert php array to Javascript

Is very simple I use this way:


var arrayJavascript = <?php echo json_encode($arrayPhp) ?>;

Convert PHP array to Javascript


What is the correct format to use for Date/Time in an XML file

If you are manually assembling the XML string use var.ToUniversalTime().ToString("yyyy-MM-dd'T'HH:mm:ss.fffffffZ")); That will output the official XML Date Time format. But you don't have to worry about format if you use the built-in serialization methods.

Two values from one input in python?

a,b=[int(x) for x in input().split()]


10 8

10 8

How can I convert uppercase letters to lowercase in Notepad++

First select the text
To convert lowercase to uppercase, press Ctrl+Shift+U
To convert uppercase to lowercase, press Ctrl+U

Delete all lines beginning with a # from a file

I'm a little surprised nobody has suggested the most obvious solution:

grep -v '^#' filename

This solves the problem as stated.

But note that a common convention is for everything from a # to the end of a line to be treated as a comment:

sed 's/#.*$//' filename

though that treats, for example, a # character within a string literal as the beginning of a comment (which may or may not be relevant for your case) (and it leaves empty lines).

A line starting with arbitrary whitespace followed by # might also be treated as a comment:

grep -v '^ *#' filename

if whitespace is only spaces, or

grep -v '^[  ]#' filename

where the two spaces are actually a space followed by a literal tab character (type "control-v tab").

For all these commands, omit the filename argument to read from standard input (e.g., as part of a pipe).

How can I format a String number to have commas and round?

You might want to look at the DecimalFormat class; it supports different locales (eg: in some countries that would get formatted as 1.000.500.000,57 instead).

You also need to convert that string into a number, this can be done with:

double amount = Double.parseDouble(number);

Code sample:

String number = "1000500000.574";
double amount = Double.parseDouble(number);
DecimalFormat formatter = new DecimalFormat("#,###.00");


Looking to understand the iOS UIViewController lifecycle

As of iOS 6 and onward. The new diagram is as follows:

enter image description here

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Taking up @ZF007's answer, this is not answering your question as a whole, but can be the solution for the same error. I post it here since I have not found a direct solution as an answer to this error message elsewhere on Stack Overflow.

The error appears when you check whether an array was empty or not.

  • if np.array([1,2]): print(1) --> ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all().

  • if np.array([1,2])[0]: print(1) --> no ValueError, but: if np.array([])[0]: print(1) --> IndexError: index 0 is out of bounds for axis 0 with size 0.

  • if np.array([1]): print(1) --> no ValueError, but again will not help at an array with many elements.

  • if np.array([]): print(1) --> DeprecationWarning: The truth value of an empty array is ambiguous. Returning False, but in future this will result in an error. Use 'array.size > 0' to check that an array is not empty.

Doing so:

  • if np.array([]).size: print(1) solved the error.

E: Unable to locate package mongodb-org

All steps are correct just change the Step 4 as below

  • Step 4: Install the last stable MongoDB version and all the necessary packages on our system

Command: sudo apt-get install mongodb

It has worked for me.

How to set up a squid Proxy with basic username and password authentication?

Here's what I had to do to setup basic auth on Ubuntu 14.04 (didn't find a guide anywhere else)

Basic squid conf

/etc/squid3/squid.conf instead of the super bloated default config file

auth_param basic program /usr/lib/squid3/basic_ncsa_auth /etc/squid3/passwords
auth_param basic realm proxy
acl authenticated proxy_auth REQUIRED
http_access allow authenticated

# Choose the port you want. Below we set it to default 3128.
http_port 3128

Please note the basic_ncsa_auth program instead of the old ncsa_auth

squid 2.x

For squid 2.x you need to edit /etc/squid/squid.conf file and place:

auth_param basic program /usr/lib/squid/digest_pw_auth /etc/squid/passwords
auth_param basic realm proxy
acl authenticated proxy_auth REQUIRED
http_access allow authenticated

Setting up a user

sudo htpasswd -c /etc/squid3/passwords username_you_like

and enter a password twice for the chosen username then

sudo service squid3 restart

squid 2.x

sudo htpasswd -c /etc/squid/passwords username_you_like

and enter a password twice for the chosen username then

sudo service squid restart

htdigest vs htpasswd

For the many people that asked me: the 2 tools produce different file formats:

  • htdigest stores the password in plain text.
  • htpasswd stores the password hashed (various hashing algos are available)

Despite this difference in format basic_ncsa_auth will still be able to parse a password file generated with htdigest. Hence you can alternatively use:

sudo htdigest -c /etc/squid3/passwords realm_you_like username_you_like

Beware that this approach is empirical, undocumented and may not be supported by future versions of Squid.

On Ubuntu 14.04 htdigest and htpasswd are both available in the [apache2-utils][1] package.


Similar as above applies, but file paths are different.

Install squid

brew install squid

Start squid service

brew services start squid

Squid config file is stored at /usr/local/etc/squid.conf.

Comment or remove following line:

http_access allow localnet

Then similar to linux config (but with updated paths) add this:

auth_param basic program /usr/local/Cellar/squid/4.8/libexec/basic_ncsa_auth /usr/local/etc/squid_passwords
auth_param basic realm proxy
acl authenticated proxy_auth REQUIRED
http_access allow authenticated

Note that path to basic_ncsa_auth may be different since it depends on installed version when using brew, you can verify this with ls /usr/local/Cellar/squid/. Also note that you should add the above just bellow the following section:


Now generate yourself a user:password basic auth credential (note: htpasswd and htdigest are also both available on MacOS)

htpasswd -c /usr/local/etc/squid_passwords username_you_like

Restart the squid service

brew services restart squid

ImportError: No module named six

on Ubuntu Bionic (18.04), six is already install for python2 and python3 but I have the error launching Wammu. @3ygun solution worked for me to solve

ImportError: No module named six

when launching Wammu

If it's occurred for python3 program, six come with

pip3 install six

and if you don't have pip3:

apt install python3-pip

with sudo under Ubuntu!

Display JSON Data in HTML Table

Try this:




<table id="table" class="hidden">


$('#search').click(function() {
        type: 'POST',
        url: 'cityResults.htm',
        data: $('#cityDetails').serialize(),
        dataType:"json", //to parse string into JSON object,
        success: function(data){ 
                var len = data.length;
                var txt = "";
                if(len > 0){
                    for(var i=0;i<len;i++){
                        if(data[i].city && data[i].cStatus){
                            txt += "<tr><td>"+data[i].city+"</td><td>"+data[i].cStatus+"</td></tr>";
                    if(txt != ""){
        error: function(jqXHR, textStatus, errorThrown){
            alert('error: ' + textStatus + ': ' + errorThrown);
    return false;//suppress natural form submission

How do I remove blank pages coming between two chapters in Appendix?

I tried Noah's suggestion which leads to the best solution up to now.

Just insert \let\cleardoublepage\clearpage before all the parts with the blank pages Especially when you use \documentclass[12pt,a4paper]{book}

frederic snyers's advice \documentclass[oneside]{book} is also very good and solves the problem, but if we just want to use the book.cls or article.cls, the one would make a big difference presenting your particles.

Hence, Big support to \let\cleardoublepage\clearpage for the people who will ask the same question in the future.

Rails 4 Authenticity Token

If you're using jQuery with rails, be wary of allowing entry to methods without verifying the authenticity token.

jquery-ujs can manage the tokens for you

You should have it already as part of the jquery-rails gem, but you might need to include it in application.js with

//= require jquery_ujs

That's all you need - your ajax call should now work

For more information, see:

How to trim white spaces of array values in php

array_walk() can be used with trim() to trim array

function trim_value(&$value) 
    $value = trim($value); 

$fruit = array('apple','banana ', ' cranberry ');

array_walk($fruit, 'trim_value');


See 2nd example at

SQL Server function to return minimum date (January 1, 1753)

This is what I use to get the minimum date in SQL Server. Please note that it is globalisation friendly:

CREATE FUNCTION [dbo].[DateTimeMinValue]()
RETURNS datetime
    CAST('17530101' AS datetime))

Call using:

SELECT [dbo].[DateTimeMinValue]()

Create a custom View by inflating a layout?

Here is a simple demo to create customview (compoundview) by inflating from xml



    <declare-styleable name="CustomView">
        <attr format="string" name="text"/>
        <attr format="reference" name="image"/>


class CustomView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) :
        ConstraintLayout(context, attrs, defStyleAttr) {

    init {

    private fun init(attrs: AttributeSet?) {
        View.inflate(context, R.layout.custom_layout, this)

        val ta = context.obtainStyledAttributes(attrs, R.styleable.CustomView)
        try {
            val text = ta.getString(R.styleable.CustomView_text)
            val drawableId = ta.getResourceId(R.styleable.CustomView_image, 0)
            if (drawableId != 0) {
                val drawable = AppCompatResources.getDrawable(context, drawableId)
            text_title.text = text
        } finally {


We should use merge here instead of ConstraintLayout because

If we use ConstraintLayout here, layout hierarchy will be ConstraintLayout->ConstraintLayout -> ImageView + TextView => we have 1 redundant ConstraintLayout => not very good for performance

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

        tools:src="@mipmap/ic_launcher" />

        tools:text="Text" />


Using activity_main.xml

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

        app:text="Android" />

        app:text="ADB" />



enter image description here

Github demo

Get the selected option id with jQuery

Th easiest way to this is var id = $(this).val(); from inside an event like on change.

Property 'map' does not exist on type 'Observable<Response>'

Thanks to




import { map } from 'rxjs/operators';

courseRef: AngularFireList<any>;
courses$: Observable<any[]>;

this.courseRef = db.list('/tags');$ = this.courseRef.snapshotChanges()
  .pipe(map(changes => {
      return => ({ key: c.payload.key, ...c.payload.val() 

.gitignore all the .DS_Store files in every folder and subfolder

I think the problem you're having is that in some earlier commit, you've accidentally added .DS_Store files to the repository. Of course, once a file is tracked in your repository, it will continue to be tracked even if it matches an entry in an applicable .gitignore file.

You have to manually remove the .DS_Store files that were added to your repository. You can use

git rm --cached .DS_Store

Once removed, git should ignore it. You should only need the following line in your root .gitignore file: .DS_Store. Don't forget the period!

git rm --cached .DS_Store

removes only .DS_Store from the current directory. You can use

find . -name .DS_Store -print0 | xargs -0 git rm --ignore-unmatch

to remove all .DS_Stores from the repository.

Felt tip: Since you probably never want to include .DS_Store files, make a global rule. First, make a global .gitignore file somewhere, e.g.

echo .DS_Store >> ~/.gitignore_global

Now tell git to use it for all repositories:

git config --global core.excludesfile ~/.gitignore_global

This page helped me answer your question.

implementing merge sort in C++

The problem with merge sort is the merge, if you don't actually need to implement the merge, then it is pretty simple (for a vector of ints):

#include <algorithm>
#include <vector>
using namespace std;

typedef vector<int>::iterator iter;

void mergesort(iter b, iter e) {
    if (e -b > 1) {
        iter m = b + (e -b) / 2;
        mergesort(b, m);
        mergesort(m, e);
        inplace_merge(b, m, e);

Check if Python Package is installed

If you mean a python script, just do something like this:

Python 3.3+ use sys.modules and find_spec:

import importlib.util
import sys

# For illustrative purposes.
name = 'itertools'

if name in sys.modules:
    print(f"{name!r} already in sys.modules")
elif (spec := importlib.util.find_spec(name)) is not None:
    # If you choose to perform the actual import ...
    module = importlib.util.module_from_spec(spec)
    sys.modules[name] = module
    print(f"{name!r} has been imported")
    print(f"can't find the {name!r} module")

Python 3:

    import mymodule
except ImportError as e:
    pass  # module doesn't exist, deal with it.

Python 2:

    import mymodule
except ImportError, e:
    pass  # module doesn't exist, deal with it.

Python return statement error " 'return' outside function"

As per the documentation on the return statement, return may only occur syntactically nested in a function definition. The same is true for yield.

Comparing object properties in c#

If you are only comparing objects of the same type or further down the inheritance chain, why not specify the parameter as your base type, rather than object ?

Also do null checks on the parameter as well.

Furthermore I'd make use of 'var' just to make the code more readable (if its c#3 code)

Also, if the object has reference types as properties then you are just calling ToString() on them which doesn't really compare values. If ToString isn't overwridden then its just going to return the type name as a string which could return false-positives.

How to import a jar in Eclipse

You can add a jar in Eclipse by right-clicking on the Project ? Build Path ? Configure Build Path. Under Libraries tab, click Add Jars or Add External JARs and give the Jar. A quick demo here.

enter image description here

The above solution is obviously a "Quick" one. However, if you are working on a project where you need to commit files to the source control repository, I would recommend adding Jar files to a dedicated library folder within your source control repository and referencing few or all of them as mentioned above.

Hide all elements with class using plain Javascript

function getElementsByClassName(classname, node)  {
    if(!node) node = document.getElementsByTagName("body")[0];
    var a = [];
    var re = new RegExp('\\b' + classname + '\\b');
    var els = node.getElementsByTagName("*");
    for(var i=0,j=els.length; i<j; i++)
    return a;

var elements = new Array();
elements = getElementsByClassName('yourClassName');
for(i in elements ){
     elements[i].style.display = "none";

Finding the type of an object in C++

Your description is a little confusing.

Generally speaking, though some C++ implementations have mechanisms for it, you're not supposed to ask about the type. Instead, you are supposed to do a dynamic_cast on the pointer to A. What this will do is that at runtime, the actual contents of the pointer to A will be checked. If you have a B, you'll get your pointer to B. Otherwise, you'll get an exception or null.

How to access Anaconda command prompt in Windows 10 (64-bit)

Go with the mouse to the Windows Icon (lower left) and start typing "Anaconda". There should show up some matching entries. Select "Anaconda Prompt". A new command window, named "Anaconda Prompt" will open. Now, you can work from there with Python, conda and other tools.

Eclipse not recognizing JVM 1.8

OK, so I don't really know what the problem was, but I simply fixed it by navigating to here and installing 8u74 instead of 8u73 which is what I was prompted to do when I would go to "download latest version" in Java. So changing the versions is what did it in the end. Eclipse launched fine, now. Thanks for everyone's help!

edit: Apr 2018- Now is 8u161 and 8u162 (Just need one, I used 8u162 and it worked.)

Form Submission without page refresh

The problem is the Method 'POST' your form is submitting by using the "post" method, and in the AJAX you are using "GET".

Visual Studio Code Search and Replace with Regular Expressions

Make sure Match Case is selected with Use Regular Expression so this matches. [A-Z]* If match case is not selected, this matches all letters.

What's the best way to do a backwards loop in C/C#/C++?

In C I like to do this:

int i = myArray.Length;
while (i--) {
  myArray[i] = 42;

C# example added by MusiGenesis:

{int i = myArray.Length; while (i-- > 0)
    myArray[i] = 42;

Is there a way to force npm to generate package-lock.json?

If your npm version is lower than version 5 then install the higher version for getting the automatic generation of package-lock.json.

Example: Upgrade your current npm to version 6.14.0

npm i -g [email protected]

You could view the latest npm version list by

npm view npm versions

Unique random string generation

Get Unique Key using GUID Hash code

public static string GetUniqueKey(int length)
    string guidResult = string.Empty;

    while (guidResult.Length < length)
        // Get the GUID.
        guidResult += Guid.NewGuid().ToString().GetHashCode().ToString("x");

    // Make sure length is valid.
    if (length <= 0 || length > guidResult.Length)
        throw new ArgumentException("Length must be between 1 and " + guidResult.Length);

    // Return the first length bytes.
    return guidResult.Substring(0, length);

How to close form

There are different methods to open or close winform. Form.Close() is one method in closing a winform.

When 'Form.Close()' execute , all resources created in that form are destroyed. Resources means control and all its child controls (labels , buttons) , forms etc.

Some other methods to close winform

  1. Form.Hide()
  2. Application.Exit()

Some methods to Open/Start a form

  1. Form.Show()
  2. Form.ShowDialog()
  3. Form.TopMost()

All of them act differently , Explore them !

How to view the current heap size that an application is using?

You can do it by MXBeans

public class Check {
    public static void main(String[] args) {
        MemoryMXBean memBean = ManagementFactory.getMemoryMXBean() ;
        MemoryUsage heapMemoryUsage = memBean.getHeapMemoryUsage();

        System.out.println(heapMemoryUsage.getMax()); // max memory allowed for jvm -Xmx flag (-1 if isn't specified)
        System.out.println(heapMemoryUsage.getCommitted()); // given memory to JVM by OS ( may fail to reach getMax, if there isn't more memory)
        System.out.println(heapMemoryUsage.getUsed()); // used now by your heap
        System.out.println(heapMemoryUsage.getInit()); // -Xms flag

        // |------------------ max ------------------------| allowed to be occupied by you from OS (less than xmX due to empty survival space)
        // |------------------ committed -------|          | now taken from OS
        // |------------------ used --|                    | used by your heap


But remember it is equivalent to Runtime.getRuntime() (took depicted schema from here)

memoryMxBean.getHeapMemoryUsage().getUsed()      <=> runtime.totalMemory() - runtime.freeMemory()
memoryMxBean.getHeapMemoryUsage().getCommitted() <=> runtime.totalMemory()
memoryMxBean.getHeapMemoryUsage().getMax()       <=> runtime.maxMemory()

from javaDoc

init - represents the initial amount of memory (in bytes) that the Java virtual machine requests from the operating system for memory management during startup. The Java virtual machine may request additional memory from the operating system and may also release memory to the system over time. The value of init may be undefined.

used - represents the amount of memory currently used (in bytes).

committed - represents the amount of memory (in bytes) that is guaranteed to be available for use by the Java virtual machine. The amount of committed memory may change over time (increase or decrease). The Java virtual machine may release memory to the system and committed could be less than init. committed will always be greater than or equal to used.

max - represents the maximum amount of memory (in bytes) that can be used for memory management. Its value may be undefined. The maximum amount of memory may change over time if defined. The amount of used and committed memory will always be less than or equal to max if max is defined. A memory allocation may fail if it attempts to increase the used memory such that used > committed even if used <= max would still be true (for example, when the system is low on virtual memory).

    +////////////////           |                  +
    +////////////////           |                  +


As additional note, maxMemory is less than -Xmx because there is necessity at least in one empty survival space, which can't be used for heap allocation.

also it is worth to to take a look at here and especially here

Call Activity method from adapter

For Kotlin:

In your adapter, simply call

(context as Your_Activity_Name).yourMethod()

Disabled UIButton not faded or grey

You can use following code:

sendButton.enabled = YES;
sendButton.alpha = 1.0;


sendButton.enabled = NO;
sendButton.alpha = 0.5;

What to use now Google News API is deprecated?

Looks like you might have until the end of 2013 before they officially close it down.

Also, it sounds like they are building a replacement... but it's going to cost you.

I'd say, go to a different service. I think bing has a news API.

You might enjoy (or not) reading:

MongoDB: How to update multiple documents with a single command?

MongoDB will find only one matching document which matches the query criteria when you are issuing an update command, whichever document matches first happens to be get updated, even if there are more documents which matches the criteria will get ignored.

so to overcome this we can specify "MULTI" option in your update statement, meaning update all those documnets which matches the query criteria. scan for all the documnets in collection finding those which matches the criteria and update :

db.test.update({"foo":"bar"},{"$set":{"test":"success!"}}, {multi:true} )

How to insert new cell into UITableView in Swift

Swift 5.0, 4.0, 3.0 Updated Solution

Insert at Bottom


self.tblView.insertRows(at: [IndexPath.init(row: self.yourArray.count-1, section: 0)], with: .automatic)

Insert at Top of TableView

self.yourArray.insert(msg, at: 0)
self.tblView.insertRows(at: [IndexPath.init(row: 0, section: 0)], with: .automatic)

Regarding C++ Include another class

What is the basic problem in your code?

Your code needs to be separated out in to interfaces(.h) and Implementations(.cpp).
The compiler needs to see the composition of a type when you write something like

ClassTwo obj;

This is because the compiler needs to reserve enough memory for object of type ClassTwo to do so it needs to see the definition of ClassTwo. The most common way to do this in C++ is to split your code in to header files and source files.
The class definitions go in the header file while the implementation of the class goes in to source files. This way one can easily include header files in to other source files which need to see the definition of class who's object they create.

Why can't I simply put all code in cpp files and include them in other files?

You cannot simple put all the code in source file and then include that source file in other files.C++ standard mandates that you can declare a entity as many times as you need but you can define it only once(One Definition Rule(ODR)). Including the source file would violate the ODR because a copy of the entity is created in every translation unit where the file is included.

How to solve this particular problem?

Your code should be organized as follows:


Define ClassOne 


#include <iostream>
#include <string>

class ClassTwo
   string myType;
   void setType(string);
   std::string getType();



Implementation of ClassOne 



void ClassTwo::setType(std::string sType)
    myType = sType;

void ClassTwo::getType(float fVal)
    return myType;


#include <iostream>
#include <string>
#include "file1.h"
#include "file2.h"
using namespace std;

int main()

    ClassOne cone;
    ClassTwo ctwo;

    //some codes

Is there any alternative means rather than including header files?

If your code only needs to create pointers and not actual objects you might as well use Forward Declarations but note that using forward declarations adds some restrictions on how that type can be used because compiler sees that type as an Incomplete type.

How do I remove/delete a virtualenv?

You can follow these steps to remove all the files associated with virtualenv and then reinstall the virtualenv again and using it

cd {python virtualenv folder}

find {broken virtualenv}/ -type l                             ## to list out all the links

deactivate                                           ## deactivate if virtualenv is active

find {broken virtualenv}/ -type l -delete                    ## to delete the broken links

virtualenv {broken virtualenv} --python=python3           ## recreate links to OS's python

workon {broken virtualenv}                       ## activate & workon the fixed virtualenv

pip3 install  ... {other packages required for the project}

apache not accepting incoming connections from outside of localhost

SELinux prevents Apache (and therefore all Apache modules) from making remote connections by default.

# setsebool -P httpd_can_network_connect=1

If "0" then leave the cell blank

=iferror(1/ (1/ H15+G16-F16 ), "")

this way avoids repeating the central calculation (which can often be much longer or more processor hungry than the one you have here...


multiple conditions for JavaScript .includes() method

Another one!

let result_x000D_
const givenStr = 'A, X' //values separated by comma or space._x000D_
const allowed  = ['A', 'B']_x000D_
const given    = givenStr.split(/[\s,]+/).filter(v => v)_x000D_
console.log('given (array):', given)_x000D_
// given contains none or only allowed values:_x000D_
result = given.reduce((acc, val) => {_x000D_
  return acc && allowed.includes(val)_x000D_
}, true)_x000D_
console.log('given contains none or only allowed values:', result)_x000D_
// given contains at least one allowed value:_x000D_
result = given.reduce((acc, val) => {_x000D_
  return acc || allowed.includes(val)_x000D_
}, false)_x000D_
console.log('given contains at least one allowed value:', result)