Programs & Examples On #Opennetcf.ioc

CSS: transition opacity on mouse-out?

You're applying transitions only to the :hover pseudo-class, and not to the element itself.

.item {   
  height:200px;
  width:200px;
  background:red; 
  -webkit-transition: opacity 1s ease-in-out;
  -moz-transition: opacity 1s ease-in-out;
  -ms-transition: opacity 1s ease-in-out;
  -o-transition: opacity 1s ease-in-out;
  transition: opacity 1s ease-in-out;
}

.item:hover {
  zoom: 1;
  filter: alpha(opacity=50);
  opacity: 0.5;
}

Demo: http://jsfiddle.net/7uR8z/6/

If you don't want the transition to affect the mouse-over event, but only mouse-out, you can turn transitions off for the :hover state :

.item:hover {
  -webkit-transition: none;
  -moz-transition: none;
  -ms-transition: none;
  -o-transition: none;
  transition: none;
  zoom: 1;
  filter: alpha(opacity=50);
  opacity: 0.5;
}

Demo: http://jsfiddle.net/7uR8z/3/

Creating an R dataframe row-by-row

I've found this way to create dataframe by raw without matrix.

With automatic column name

df<-data.frame(
        t(data.frame(c(1,"a",100),c(2,"b",200),c(3,"c",300)))
        ,row.names = NULL,stringsAsFactors = FALSE
    )

With column name

df<-setNames(
        data.frame(
            t(data.frame(c(1,"a",100),c(2,"b",200),c(3,"c",300)))
            ,row.names = NULL,stringsAsFactors = FALSE
        ), 
        c("col1","col2","col3")
    )

How to calculate UILabel height dynamically?

The current solution has been deprecated as of iOS 7.

Here is an updated solution:

+ (CGFloat)heightOfCellWithIngredientLine:(NSString *)ingredientLine
                       withSuperviewWidth:(CGFloat)superviewWidth
{
    CGFloat labelWidth                  = superviewWidth - 30.0f;
    //    use the known label width with a maximum height of 100 points
    CGSize labelContraints              = CGSizeMake(labelWidth, 100.0f);

    NSStringDrawingContext *context     = [[NSStringDrawingContext alloc] init];

    CGRect labelRect                    = [ingredientLine boundingRectWithSize:labelContraints
                                                        options:NSStringDrawingUsesLineFragmentOrigin
                                                     attributes:nil
                                                        context:context];

    //    return the calculated required height of the cell considering the label
    return labelRect.size.height;
}

The reason that my solution is set up like this is because I am using a UITableViewCell and resizing the cell dynamically relative to how much room the label will take up.

How to disable XDebug

(This is for CentOS)

Rename the config file and restart apache.

sudo mv /etc/php.d/xdebug.ini /etc/php.d/xdebug.ini.old
sudo service httpd restart

Do the reverse to re-enable.

select certain columns of a data table

DataView dv = new DataView(Your DataTable);

DataTable dt = dv.ToTable(true, "Your Specific Column Name");

The dt contains only selected column values.

Error handling in AngularJS http get then construct

I could not really work with the above. So this might help someone.

$http.get(url)
  .then(
    function(response) {
        console.log('get',response)
    }
  ).catch(
    function(response) {
    console.log('return code: ' + response.status);
    }
  )

See also the $http response parameter.

PostgreSQL: Show tables in PostgreSQL

You can list the tables in the current database with \dt.

Fwiw, \d tablename will show details about the given table, something like show columns from tablename in MySQL, but with a little more information.

Display only 10 characters of a long string?

@jolly.exe

Nice example Jolly. I updated your version which limits the character length as opposed to the number of words. I also added setting the title to the real original innerHTML , so users can hover and see what is truncated.

HTML

<div id="stuff">a reallly really really long titleasdfasdfasdfasdfasdfasdfasdfadsf</div> 

JS

 function cutString(id){    
     var text = document.getElementById(id).innerHTML;         
     var charsToCutTo = 30;
        if(text.length>charsToCutTo){
            var strShort = "";
            for(i = 0; i < charsToCutTo; i++){
                strShort += text[i];
            }
            document.getElementById(id).title = "text";
            document.getElementById(id).innerHTML = strShort + "...";
        }            
     };

cutString('stuff'); 

PHP expects T_PAAMAYIM_NEKUDOTAYIM?

This is also coming when you apply a constant in PHP to the empty() function:

if (!empty(SOME_CONSTANT)) {

}

That was my case. I solved it by using this:

$string = SOME_CONSTANT;
if (!empty($string)) {

}

JDBC ResultSet: I need a getDateTime, but there is only getDate and getTimeStamp

The answer by Leos Literak is correct but now outdated, using one of the troublesome old date-time classes, java.sql.Timestamp.

tl;dr

it is really a DATETIME in the DB

Nope, it is not. No such data type as DATETIME in Oracle database.

I was looking for a getDateTime method.

Use java.time classes in JDBC 4.2 and later rather than troublesome legacy classes seen in your Question. In particular, rather than java.sql.TIMESTAMP, use Instant class for a moment such as the SQL-standard type TIMESTAMP WITH TIME ZONE.

Contrived code snippet:

if( 
    JDBCType.valueOf( 
        myResultSetMetaData.getColumnType( … )
    )
    .equals( JDBCType.TIMESTAMP_WITH_TIMEZONE ) 
) {
    Instant instant = myResultSet.getObject( … , Instant.class ) ;
}

Oddly enough, the JDBC 4.2 specification does not require support for the two most commonly used java.time classes, Instant and ZonedDateTime. So if your JDBC does not support the code seen above, use OffsetDateTime instead.

OffsetDateTime offsetDateTime = myResultSet.getObject( … , OffsetDateTime.class ) ;

Details

I would like to get the DATETIME column from an Oracle DB Table with JDBC.

According to this doc, there is no column data type DATETIME in the Oracle database. That terminology seems to be Oracle’s word to refer to all their date-time types as a group.

I do not see the point of your code that detects the type and branches on which data-type. Generally, I think you should be crafting your code explicitly in the context of your particular table and particular business problem. Perhaps this would be useful in some kind of generic framework. If you insist, read on to learn about various types, and to learn about the extremely useful new java.time classes built into Java 8 and later that supplant the classes used in your Question.

Smart objects, not dumb strings

valueToInsert = aDate.toString();

You appear to trying to exchange date-time values with your database as text, as String objects. Don’t.

To exchange date-time values with your database, use date-time objects. Now in Java 8 and later, that means java.time objects, as discussed below.

Various type systems

You may be confusing three sets of date-time related data types:

  • Standard SQL types
  • Proprietary types
  • JDBC types

SQL standard types

The SQL standard defines five types:

  • DATE
  • TIME WITHOUT TIME ZONE
  • TIME WITH TIME ZONE
  • TIMESTAMP WITHOUT TIME ZONE
  • TIMESTAMP WITH TIME ZONE

Date-only

  • DATE
    Date only, no time, no time zone.

Time-Of-Day-only

  • TIME or TIME WITHOUT TIME ZONE
    Time only, no date. Silently ignores any time zone specified as part of input.
  • TIME WITH TIME ZONE (or TIMETZ)
    Time only, no date. Applies time zone and Daylight Saving Time rules if sufficient data is included with input. Of questionable usefulness given the other data types, as discussed in Postgres doc.

Date And Time-Of-Day

  • TIMESTAMP or TIMESTAMP WITHOUT TIME ZONE
    Date and time, but ignores time zone. Any time zone information passed to the database is ignores with no adjustment to UTC. So this does not represent a specific moment on the timeline, but rather a range of possible moments over about 26-27 hours. Use this if the time zone or offset are (a) unknown or (b) irrelevant such as "All our factories around the world close at noon for lunch". If you have any doubts, not likely the right type.
  • TIMESTAMP WITH TIME ZONE (or TIMESTAMPTZ)
    Date and time with respect for time zone. Note that this name is something of a misnomer depending on the implementation. Some systems may store the given time zone info. In other systems such as Postgres the time zone information is not stored, instead the time zone information passed to the database is used to adjust the date-time to UTC.

Proprietary

Many database offer their own date-time related types. The proprietary types vary widely. Some are old, legacy types that should be avoided. Some are believed by the vendor to offer certain benefits; you decide whether to stick with the standard types only or not. Beware: Some proprietary types have a name conflicting with a standard type; I’m looking at you Oracle DATE.

JDBC

The Java platform's handles the internal details of date-time differently than does the SQL standard or specific databases. The job of a JDBC driver is to mediate between these differences, to act as a bridge, translating the types and their actual implemented data values as needed. The java.sql.* package is that bridge.

JDBC legacy classes

Prior to Java 8, the JDBC spec defined 3 types for date-time work. The first two are hacks as before Version 8, Java lacked any classes to represent a date-only or time-only value.

  • java.sql.Date
    Simulates a date-only, pretends to have no time, no time zone. Can be confusing as this class is a wrapper around java.util.Date which tracks both date and time. Internally, the time portion is set to zero (midnight UTC).
  • java.sql.Time
    Time only, pretends to have no date, and no time zone. Can also be confusing as this class too is a thin wrapper around java.util.Date which tracks both date and time. Internally, the date is set to zero (January 1, 1970).
  • java.sql.TimeStamp
    Date and time, but no time zone. This too is a thin wrapper around java.util.Date.

So that answers your question regarding no "getDateTime" method in the ResultSet interface. That interface offers getter methods for the three bridging data types defined in JDBC:

Note that the first lack any concept of time zone or offset-from-UTC. The last one, java.sql.Timestamp is always in UTC despite what its toString method tells you.

JDBC modern classes

You should avoid those poorly-designed JDBC classes listed above. They are supplanted by the java.time types.

  • Instead of java.sql.Date, use LocalDate. Suits SQL-standard DATE type.
  • Instead of java.sql.Time, use LocalTime. Suits SQL-standard TIME WITHOUT TIME ZONE type.
  • Instead of java.sql.Timestamp, use Instant. Suits SQL-standard TIMESTAMP WITH TIME ZONE type.

As of JDBC 4.2 and later, you can directly exchange java.time objects with your database. Use setObject/getObject methods.

Insert/update.

myPreparedStatement.setObject( … , instant ) ;

Retrieval.

Instant instant = myResultSet.getObject( … , Instant.class ) ;

The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).

Adjusting time zone

If you want to see the moment of an Instant as viewed through the wall-clock time used by the people of a particular region (a time zone) rather than as UTC, adjust by applying a ZoneId to get a ZonedDateTime object.

ZoneId zAuckland = ZoneId.of( "Pacific/Auckland" ) ;
ZonedDateTime zdtAuckland = instant.atZone( zAuckland ) ;

The resulting ZonedDateTime object is the same moment, the same simultaneous point on the timeline. A new day dawns earlier to the east, so the date and time-of-day will differ. For example, a few minutes after midnight in New Zealand is still “yesterday” in UTC.

You can apply yet another time zone to either the Instant or ZonedDateTime to see the same simultaneous moment through yet another wall-clock time used by people in some other region.

ZoneId zMontréal = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdtMontréal = zdtAuckland.withZoneSameInstant( zMontréal ) ;  // Or, for the same effect: instant.atZone( zMontréal ) 

So now we have three objects (instant, zdtAuckland, zMontréal) all representing the same moment, same point on the timeline.

Detecting type

To get back to the code in Question about detecting the data-type of the databases: (a) not my field of expertise, (b) I would avoid this as mentioned up top, and (c) if you insist on this, beware that as of Java 8 and later, the java.sql.Types class is outmoded. That class is now replaced by a proper Java Enum of JDBCType that implements the new interface SQLType. See this Answer to a related Question.

This change is listed in JDBC Maintenance Release 4.2, sections 3 & 4. To quote:

Addition of the java.sql.JDBCType Enum

An Enum used to identify generic SQL Types, called JDBC Types. The intent is to use JDBCType in place of the constants defined in Types.java.

The enum has the same values as the old class, but now provides type-safety.

A note about syntax: In modern Java, you can use a switch on an Enum object. So no need to use cascading if-then statements as seen in your Question. The one catch is that the enum object’s name must be used unqualified when switching for some obscure technical reason, so you must do your switch on TIMESTAMP_WITH_TIMEZONE rather than the qualified JDBCType.TIMESTAMP_WITH_TIMEZONE. Use a static import statement.

So, all that is to say that I guess (I’ve not tried yet) you can do something like the following code example.

final int columnType = myResultSetMetaData.getColumnType( … ) ;
final JDBCType jdbcType = JDBCType.valueOf( columnType ) ;

switch( jdbcType ) {  

    case DATE :  // FYI: Qualified type name `JDBCType.DATE` not allowed in a switch, because of an obscure technical issue. Use a `static import` statement.
        …
        break ;

    case TIMESTAMP_WITH_TIMEZONE :
        …
        break ;

    default :
        … 
        break ;

}

enter image description here


About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.


UPDATE: The Joda-Time project, now in maintenance mode, advises migration to the java.time classes. This section left intact as history.

Joda-Time

Prior to Java 8 (java.time.* package), the date-time classes bundled with java (java.util.Date & Calendar, java.text.SimpleDateFormat) are notoriously troublesome, confusing, and flawed.

A better practice is to take what your JDBC driver gives you and from that create Joda-Time objects, or in Java 8, java.time.* package. Eventually, you should see new JDBC drivers that automatically use the new java.time.* classes. Until then some methods have been added to classes such as java.sql.Timestamp to interject with java.time such as toInstant and fromInstant.

String

As for the latter part of the question, rendering a String… A formatter object should be used to generate a string value.

The old-fashioned way is with java.text.SimpleDateFormat. Not recommended.

Joda-Time provide various built-in formatters, and you may also define your own. But for writing logs or reports as you mentioned, the best choice may be ISO 8601 format. That format happens to be the default used by Joda-Time and java.time.

Example Code

//java.sql.Timestamp timestamp = resultSet.getTimestamp(i);
// Or, fake it 
// long m = DateTime.now().getMillis();
// java.sql.Timestamp timestamp = new java.sql.Timestamp( m );

//DateTime dateTimeUtc = new DateTime( timestamp.getTime(), DateTimeZone.UTC );
DateTime dateTimeUtc = new DateTime( DateTimeZone.UTC ); // Defaults to now, this moment.

// Convert as needed for presentation to user in local time zone.
DateTimeZone timeZone = DateTimeZone.forID("Europe/Paris");
DateTime dateTimeZoned = dateTimeUtc.toDateTime( timeZone );

Dump to console…

System.out.println( "dateTimeUtc: " + dateTimeUtc );
System.out.println( "dateTimeZoned: " + dateTimeZoned );

When run…

dateTimeUtc: 2014-01-16T22:48:46.840Z
dateTimeZoned: 2014-01-16T23:48:46.840+01:00

Regex for allowing alphanumeric,-,_ and space

For me I wanted a regex which supports a strings as preceding. Basically, the motive is to support some foreign countries postal format as it should be an alphanumeric with spaces allowed.

  1. ABC123
  2. ABC 123
  3. ABC123(space)
  4. ABC 123 (space)

So I ended up by writing custom regex as below.

/^([a-z]+[\s]*[0-9]+[\s]*)+$/i

enter image description here

Here, I gave * in [\s]* as it is not mandatory to have a space. A postal code may or may not contains space in my case.

python global name 'self' is not defined

In Python self is the conventional name given to the first argument of instance methods of classes, which is always the instance the method was called on:

class A(object):
  def f(self):
    print self

a = A()
a.f()

Will give you something like

<__main__.A object at 0x02A9ACF0>

What should I do if the current ASP.NET session is null?

Yes, the Session object might be null, but only in certain circumstances, which you will only rarely run into:

If you only have code in pages, you won't run into this. Most of my ASP .NET code uses Session without checking for null repeatedly. It is, however, something to think about if you are developing an IHttpModule or otherwise is down in the grittier details of ASP .NET.

Edit

In answer to the comment: Whether or not session state is available depends on whether the AcquireRequestState event has run for the request. This is where the session state module does it's work by reading the session cookie and finding the appropiate set of session variables for you.

AcquireRequestState runs before control is handed to your Page. So if you are calling other functionality, including static classes, from your page, you should be fine.

If you have some classes doing initialization logic during startup, for example on the Application_Start event or by using a static constructor, Session state might not be available. It all boils down to whether there is a current request and AcquireRequestState has been run.

Also, should the client have disabled cookies, the Session object will still be available - but on the next request, the user will return with a new empty Session. This is because the client is given a Session statebag if he does not have one already. If the client does not transport the session cookie, we have no way of identifying the client as the same, so he will be handed a new session again and again.

How can I limit possible inputs in a HTML5 "number" element?

Max length will not work with <input type="number" the best way i know is to use oninput event to limit the maxlength. Please see the below code for simple implementation.

<input name="somename"
    oninput="javascript: if (this.value.length > this.maxLength) this.value = this.value.slice(0, this.maxLength);"
    type = "number"
    maxlength = "6"
 />

How do you create an asynchronous method in C#?

If you didn't want to use async/await inside your method, but still "decorate" it so as to be able to use the await keyword from outside, TaskCompletionSource.cs:

public static Task<T> RunAsync<T>(Func<T> function)
{ 
    if (function == null) throw new ArgumentNullException(“function”); 
    var tcs = new TaskCompletionSource<T>(); 
    ThreadPool.QueueUserWorkItem(_ =>          
    { 
        try 
        {  
           T result = function(); 
           tcs.SetResult(result);  
        } 
        catch(Exception exc) { tcs.SetException(exc); } 
   }); 
   return tcs.Task; 
}

From here and here

To support such a paradigm with Tasks, we need a way to retain the Task façade and the ability to refer to an arbitrary asynchronous operation as a Task, but to control the lifetime of that Task according to the rules of the underlying infrastructure that’s providing the asynchrony, and to do so in a manner that doesn’t cost significantly. This is the purpose of TaskCompletionSource.

I saw it's also used in the .NET source, e.g. WebClient.cs:

    [HostProtection(ExternalThreading = true)]
    [ComVisible(false)]
    public Task<string> UploadStringTaskAsync(Uri address, string method, string data)
    {
        // Create the task to be returned
        var tcs = new TaskCompletionSource<string>(address);

        // Setup the callback event handler
        UploadStringCompletedEventHandler handler = null;
        handler = (sender, e) => HandleCompletion(tcs, e, (args) => args.Result, handler, (webClient, completion) => webClient.UploadStringCompleted -= completion);
        this.UploadStringCompleted += handler;

        // Start the async operation.
        try { this.UploadStringAsync(address, method, data, tcs); }
        catch
        {
            this.UploadStringCompleted -= handler;
            throw;
        }

        // Return the task that represents the async operation
        return tcs.Task;
    }

Finally, I also found the following useful:

I get asked this question all the time. The implication is that there must be some thread somewhere that’s blocking on the I/O call to the external resource. So, asynchronous code frees up the request thread, but only at the expense of another thread elsewhere in the system, right? No, not at all.

To understand why asynchronous requests scale, I’ll trace a (simplified) example of an asynchronous I/O call. Let’s say a request needs to write to a file. The request thread calls the asynchronous write method. WriteAsync is implemented by the Base Class Library (BCL), and uses completion ports for its asynchronous I/O. So, the WriteAsync call is passed down to the OS as an asynchronous file write. The OS then communicates with the driver stack, passing along the data to write in an I/O request packet (IRP).

This is where things get interesting: If a device driver can’t handle an IRP immediately, it must handle it asynchronously. So, the driver tells the disk to start writing and returns a “pending” response to the OS. The OS passes that “pending” response to the BCL, and the BCL returns an incomplete task to the request-handling code. The request-handling code awaits the task, which returns an incomplete task from that method and so on. Finally, the request-handling code ends up returning an incomplete task to ASP.NET, and the request thread is freed to return to the thread pool.

Introduction to Async/Await on ASP.NET

If the target is to improve scalability (rather than responsiveness), it all relies on the existence of an external I/O that provides the opportunity to do that.

Image Processing: Algorithm Improvement for 'Coca-Cola Can' Recognition

Fun problem: when I glanced at your bottle image I thought it was a can too. But, as a human, what I did to tell the difference is that I then noticed it was also a bottle...

So, to tell cans and bottles apart, how about simply scanning for bottles first? If you find one, mask out the label before looking for cans.

Not too hard to implement if you're already doing cans. The real downside is it doubles your processing time. (But thinking ahead to real-world applications, you're going to end up wanting to do bottles anyway ;-)

Remove item from list based on condition

Here is a solution for those, who want to remove it from the database with Entity Framework:

prods.RemoveWhere(s => s.ID == 1);

And the extension method itself:

using System;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore;

namespace LivaNova.NGPDM.Client.Services.Data.Extensions
{
    public static class DbSetExtensions
    {
        public static void RemoveWhere<TEntity>(this DbSet<TEntity> entities, Expression<Func<TEntity, bool>> predicate) where TEntity : class
        {
            var records = entities
                .Where(predicate)
                .ToList();
            if (records.Count > 0)
                entities.RemoveRange(records);
        }
    }
}

P.S. This simulates the method RemoveAll() that's not available for DB sets of the entity framework.

remove url parameters with javascript or jquery

What am I missing?

Why not:

url.split('?')[0] 

DataGridView changing cell background color

dataGridView1[row, col].Style.BackColor = System.Drawing.Color.Red;

Why doesn't list have safe "get" method like dictionary?

Instead of using .get, using like this should be ok for lists. Just a usage difference.

>>> l = [1]
>>> l[10] if 10 < len(l) else 'fail'
'fail'

In Tensorflow, get the names of all the Tensors in a graph

The following solution works for me in TensorFlow 2.3 -

def load_pb(path_to_pb):
    with tf.io.gfile.GFile(path_to_pb, 'rb') as f:
        graph_def = tf.compat.v1.GraphDef()
        graph_def.ParseFromString(f.read())
    with tf.Graph().as_default() as graph:
        tf.import_graph_def(graph_def, name='')
        return graph
tf_graph = load_pb(MODEL_FILE)
sess = tf.compat.v1.Session(graph=tf_graph)

# Show tensor names in graph
for op in tf_graph.get_operations():
    print(op.values())

where MODEL_FILE is the path to your frozen graph.

Taken from here.

Debugging Stored Procedure in SQL Server 2008

Well the answer was sitting right in front of me the whole time.

In SQL Server Management Studio 2008 there is a Debug button in the toolbar. Set a break point in a query window to step through.

I dismissed this functionality at the beginning because I didn't think of stepping INTO the stored procedure, which you can do with ease.

SSMS basically does what FinnNK mentioned with the MSDN walkthrough but automatically.

So easy! Thanks for your help FinnNK.

Edit: I should add a step in there to find the stored procedure call with parameters I used SQL Profiler on my database.

WordPress: get author info from post id

If you want it outside of loop then use the below code.

<?php
$author_id = get_post_field ('post_author', $cause_id);
$display_name = get_the_author_meta( 'display_name' , $author_id ); 
echo $display_name;
?>

How can I get the URL of the current tab from a Google Chrome extension?

For those using the context menu api, the docs are not immediately clear on how to obtain tab information.

  chrome.contextMenus.onClicked.addListener(function(info, tab) {
    console.log(info);
    return console.log(tab);
  });

https://developer.chrome.com/extensions/contextMenus

How to undo the last commit in git

Try simply to reset last commit using --soft flag

git reset --soft HEAD~1

Note :

For Windows, wrap the HEAD parts in quotes like git reset --soft "HEAD~1"

What is the easiest way to clear a database from the CLI with manage.py in Django?

You can use the Django-Truncate library to delete all data of a table without destroying the table structure.

Example:

  1. First, install django-turncate using your terminal/command line:
pip install django-truncate
  1. Add "django_truncate" to your INSTALLED_APPS in the settings.py file:
INSTALLED_APPS = [
    ...
    'django_truncate',
]
  1. Use this command in your terminal to delete all data of the table from the app.
python manage.py truncate --apps app_name --models table_name

Differences between socket.io and websockets

https://socket.io/docs/#What-Socket-IO-is-not (with my emphasis)

What Socket.IO is not

Socket.IO is NOT a WebSocket implementation. Although Socket.IO indeed uses WebSocket as a transport when possible, it adds some metadata to each packet: the packet type, the namespace and the packet id when a message acknowledgement is needed. That is why a WebSocket client will not be able to successfully connect to a Socket.IO server, and a Socket.IO client will not be able to connect to a WebSocket server either. Please see the protocol specification here.

// WARNING: the client will NOT be able to connect!
const client = io('ws://echo.websocket.org');

Angular2 @Input to a property with get/set

Updated accepted answer to angular 7.0.1 on stackblitz here: https://stackblitz.com/edit/angular-inputsetter?embed=1&file=src/app/app.component.ts

directives are no more in Component decorator options. So I have provided sub directive to app module.

thank you @thierry-templier!

CSS: Center block, but align contents to the left

For those of us still working with older browsers, here's some extended backwards compatibility:

_x000D_
_x000D_
<div style="text-align: center;">
    <div style="display:-moz-inline-stack; display:inline-block; zoom:1; *display:inline; text-align: left;">
        Line 1: Testing<br>
        Line 2: More testing<br>
        Line 3: Even more testing<br>
    </div>
</div>
_x000D_
_x000D_
_x000D_

Partially inspired by this post: https://stackoverflow.com/a/12567422/14999964.

C - reading command line parameters

When you write your main function, you typically see one of two definitions:

  • int main(void)
  • int main(int argc, char **argv)

The second form will allow you to access the command line arguments passed to the program, and the number of arguments specified (arguments are separated by spaces).

The arguments to main are:

  • int argc - the number of arguments passed into your program when it was run. It is at least 1.
  • char **argv - this is a pointer-to-char *. It can alternatively be this: char *argv[], which means 'array of char *'. This is an array of C-style-string pointers.

Basic Example

For example, you could do this to print out the arguments passed to your C program:

#include <stdio.h>

int main(int argc, char **argv)
{
    for (int i = 0; i < argc; ++i)
    {
        printf("argv[%d]: %s\n", i, argv[i]);
    }
}

I'm using GCC 4.5 to compile a file I called args.c. It'll compile and build a default a.out executable.

[birryree@lilun c_code]$ gcc -std=c99 args.c

Now run it...

[birryree@lilun c_code]$ ./a.out hello there
argv[0]: ./a.out
argv[1]: hello
argv[2]: there

So you can see that in argv, argv[0] is the name of the program you ran (this is not standards-defined behavior, but is common. Your arguments start at argv[1] and beyond.

So basically, if you wanted a single parameter, you could say...

./myprogram integral


A Simple Case for You

And you could check if argv[1] was integral, maybe like strcmp("integral", argv[1]) == 0.

So in your code...

#include <stdio.h>
#include <string.h>

int main(int argc, char **argv)
{
    if (argc < 2) // no arguments were passed
    {
        // do something
    }

    if (strcmp("integral", argv[1]) == 0)
    {
        runIntegral(...); //or something
    }
    else
    {
        // do something else.
    }
}

Better command line parsing

Of course, this was all very rudimentary, and as your program gets more complex, you'll likely want more advanced command line handling. For that, you could use a library like GNU getopt.

Can't access 127.0.0.1

If it's a DNS problem, you could try:

  • ipconfig /flushdns
  • ipconfig /registerdns

If this doesn't fix it, you could try editing the hosts file located here:

C:\Windows\System32\drivers\etc\hosts

And ensure that this line (and no other line referencing localhost) is in there:

127.0.0.1 localhost

How to order events bound with jQuery

If order is important you can create your own events and bind callbacks to fire when those events are triggered by other callbacks.

$('#mydiv').click(function(e) {
    // maniplate #mydiv ...
    $('#mydiv').trigger('mydiv-manipulated');
});

$('#mydiv').bind('mydiv-manipulated', function(e) {
    // do more stuff now that #mydiv has been manipulated
    return;
});

Something like that at least.

Unsupported method: BaseConfig.getApplicationIdSuffix()

Alright I figured out how to fix this issue.

  • Open build.gradle and change the gradle version to the recommended version:
    classpath 'com.android.tools.build:gradle:1.3.0' to
    classpath 'com.android.tools.build:gradle:2.3.2'
  • Hit 'Try Again'
  • In the messages box it'll say 'Fix Gradle Wrapper and re-import project' Click that, since the minimum gradle version is 3.3
  • A new error will popup and say The SDK Build Tools revision (23.0.1) is too low for project ':app'. Minimum required is 25.0.0 - Hit Update Build Tools version and sync project
  • A window may popup that says Android Gradle Plugin Update recommended, just update from there.

Now the project should be runnable now on any of your android virtual devices.

Alter table to modify default value of column

Following Justin's example, the command below works in Postgres:

alter table foo alter column col2 set default 'bar';

How do I edit an incorrect commit message in git ( that I've pushed )?

At our shop, I introduced the convention of adding recognizably named annotated tags to commits with incorrect messages, and using the annotation as the replacement.

Even though this doesn't help folks who run casual "git log" commands, it does provide us with a way to fix incorrect bug tracker references in the comments, and all my build and release tools understand the convention.

This is obviously not a generic answer, but it might be something folks can adopt within specific communities. I'm sure if this is used on a larger scale, some sort of porcelain support for it may crop up, eventually...

Creating a simple XML file using python

I just finished writing an xml generator, using bigh_29's method of Templates ... it's a nice way of controlling what you output without too many Objects getting 'in the way'.

As for the tag and value, I used two arrays, one which gave the tag name and position in the output xml and another which referenced a parameter file having the same list of tags. The parameter file, however, also has the position number in the corresponding input (csv) file where the data will be taken from. This way, if there's any changes to the position of the data coming in from the input file, the program doesn't change; it dynamically works out the data field position from the appropriate tag in the parameter file.

How can I get all sequences in an Oracle database?

select sequence_owner, sequence_name from dba_sequences;


DBA_SEQUENCES -- all sequences that exist 
ALL_SEQUENCES  -- all sequences that you have permission to see 
USER_SEQUENCES  -- all sequences that you own

Note that since you are, by definition, the owner of all the sequences returned from USER_SEQUENCES, there is no SEQUENCE_OWNER column in USER_SEQUENCES.

Error 5 : Access Denied when starting windows service

Computer -> Manage -> Service -> [your service] properties. Then the the tab with the account information. Play with those settings, like run the service with administrator account or so.

That did it for me.

EDIT: What also can be the problem is that, most services are run as LOCAL SERVICE or LOCAL SYSTEM accounts. Now when you run C:/my-admin-dir/service.exe with those accounts but they are not allowed to execute anything in that directory, you will get error 5. So locate the executable of the service, RMB the directory -> Properties -> Security and make sure that the account the service is run with, is in the list of users that are alloewd to have full control over the directory.

Converting int to string in C

Use snprintf - it is standard an available in every compilator. Query it for the size needed by calling it with NULL, 0 parameters. Allocate one character more for null at the end.

int length = snprintf( NULL, 0, "%d", x );
char* str = malloc( length + 1 );
snprintf( str, length + 1, "%d", x );
...
free(str);

How can I filter a date of a DateTimeField in Django?

See the article Django Documentation

ur_data_model.objects.filter(ur_date_field__gte=datetime(2009, 8, 22), ur_date_field__lt=datetime(2009, 8, 23))

Date Conversion from String to sql Date in Java giving different output?

mm stands for "minutes". Use MM instead:

SimpleDateFormat sdf1 = new SimpleDateFormat("dd-MM-yyyy");

100% width Twitter Bootstrap 3 template

In BOOTSTRAP 4 you can use

<div class="row m-0">
my fullwidth div
</div>

... if you just use a .row without the .m-0 as a top level div, you will have unwanted margin, which makes the page wider than the browser window and cause a horizontal scrollbar.

Concatenating variables in Bash

Try doing this, there's no special character to concatenate in bash :

mystring="${arg1}12${arg2}endoffile"

explanations

If you don't put brackets, you will ask to concatenate $arg112 + $argendoffile (I guess that's not what you asked) like in the following example :

mystring="$arg112$arg2endoffile"

The brackets are delimiters for the variables when needed. When not needed, you can use it or not.

another solution

(less portable : require bash > 3.1)

$ arg1=foo
$ arg2=bar
$ mystring="$arg1"
$ mystring+="12"
$ mystring+="$arg2"
$ mystring+="endoffile"
$ echo "$mystring"
foo12barendoffile

See http://mywiki.wooledge.org/BashFAQ/013

SQL - IF EXISTS UPDATE ELSE INSERT Syntax Error

INSERT INTO component_psar (tbl_id, row_nr, col_1, col_2, col_3, col_4, col_5, col_6, unit, add_info, fsar_lock)
VALUES('2', '1', '1', '1', '1', '1', '1', '1', '1', '1', 'N')
ON DUPLICATE KEY UPDATE col_1 = VALUES(col_1), col_2 = VALUES(col_2), col_3 = VALUES(col_3), col_4 = VALUES(col_4), col_5 = VALUES(col_5), col_6 = VALUES(col_6), unit = VALUES(unit), add_info = VALUES(add_info), fsar_lock = VALUES(fsar_lock)

Would work with tbl_id and row_nr having UNIQUE key.

This is the method DocJonas linked to with an example.

Turn off textarea resizing

this will do your job

  textarea{
        resize:none;
    }

enter image description here

What is middleware exactly?

There are (at least) three different definitions I'm aware of

  • in business computing, middleware is messaging and integration software between applications and services

  • in gaming, middleware is pretty well anything that is provided by a third-party

  • in (some) embedded software systems, middleware provides services that applications use, which are composed out of the functions provided by the hardware abstraction layer - it sits between the application layer and the hardware abstraction layer.

Shortcuts in Objective-C to concatenate NSStrings

An option:

[NSString stringWithFormat:@"%@/%@/%@", one, two, three];

Another option:

I'm guessing you're not happy with multiple appends (a+b+c+d), in which case you could do:

NSLog(@"%@", [Util append:one, @" ", two, nil]); // "one two"
NSLog(@"%@", [Util append:three, @"/", two, @"/", one, nil]); // three/two/one

using something like

+ (NSString *) append:(id) first, ...
{
    NSString * result = @"";
    id eachArg;
    va_list alist;
    if(first)
    {
        result = [result stringByAppendingString:first];
        va_start(alist, first);
        while (eachArg = va_arg(alist, id)) 
        result = [result stringByAppendingString:eachArg];
        va_end(alist);
    }
    return result;
}

What does FETCH_HEAD in Git mean?

The FETCH_HEAD is a reference to the tip of the last fetch, whether that fetch was initiated directly using the fetch command or as part of a pull. The current value of FETCH_HEAD is stored in the .git folder in a file named, you guessed it, FETCH_HEAD.

So if I issue:

git fetch https://github.com/ryanmaxwell/Fragaria

FETCH_HEAD may contain

3cfda7cfdcf9fb78b44d991f8470df56723658d3        https://github.com/ryanmaxwell/Fragaria

If I have the remote repo configured as a remote tracking branch then I can follow my fetch with a merge of the tracking branch. If I don't I can merge the tip of the last fetch directly using FETCH_HEAD.

git merge FETCH_HEAD

Can .NET load and parse a properties file equivalent to Java Properties class?

C# generally uses xml-based config files rather than the *.ini-style file like you said, so there's nothing built-in to handle this. However, google returns a number of promising results.

How to disable Excel's automatic cell reference change after copy/paste?

From http://spreadsheetpage.com/index.php/tip/making_an_exact_copy_of_a_range_of_formulas_take_2:

  1. Put Excel in formula view mode. The easiest way to do this is to press Ctrl+` (that character is a "backwards apostrophe," and is usually on the same key that has the ~ (tilde).
  2. Select the range to copy.
  3. Press Ctrl+C
  4. Start Windows Notepad
  5. Press Ctrl+V to past the copied data into Notepad
  6. In Notepad, press Ctrl+A followed by Ctrl+C to copy the text
  7. Activate Excel and activate the upper left cell where you want to paste the formulas. And, make sure that the sheet you are copying to is in formula view mode.
  8. Press Ctrl+V to paste.
  9. Press Ctrl+` to toggle out of formula view mode.

Note: If the paste operation back to Excel doesn't work correctly, chances are that you've used Excel's Text-to-Columns feature recently, and Excel is trying to be helpful by remembering how you last parsed your data. You need to fire up the Convert Text to Columns Wizard. Choose the Delimited option and click Next. Clear all of the Delimiter option checkmarks except Tab.

Or, from http://spreadsheetpage.com/index.php/tip/making_an_exact_copy_of_a_range_of_formulas/:

If you're a VBA programmer, you can simply execute the following code: 
With Sheets("Sheet1")
 .Range("A11:D20").Formula = .Range("A1:D10").Formula
End With

getting the reason why websockets closed with close code 1006

It looks like this is the case when Chrome is not compliant with WebSocket standard. When the server initiates close and sends close frame to a client, Chrome considers this to be an error and reports it to JS side with code 1006 and no reason message. In my tests, Chrome never responds to server-initiated close frames (close code 1000) suggesting that code 1006 probably means that Chrome is reporting its own internal error.

P.S. Firefox v57.00 handles this case properly and successfully delivers server's reason message to JS side.

Set height of chart in Chart.js

He's right. If you want to stay with jQuery you could do this

var ctx = $('#myChart')[0];
ctx.height = 500;

or

var ctx = $('#myChart');
ctx.attr('height',500);

How to set value to variable using 'execute' in t-sql?

You can use output parameters with sp_executesql.

DECLARE @dbName nvarchar(128) = 'myDb'
DECLARE @siteId int 
DECLARE @SQL nvarchar(max) = N'SELECT TOP 1 @siteId = Id FROM ' + quotename(@dbName) + N'..myTbl'
exec sp_executesql @SQL, N'@siteId int out', @siteId out
select @siteId

Remove a prefix from a string

regex solution (The best way is the solution by @Elazar this is just for fun)

import re
def remove_prefix(text, prefix):
    return re.sub(r'^{0}'.format(re.escape(prefix)), '', text)

>>> print remove_prefix('template.extensions', 'template.')
extensions

Check that a input to UITextField is numeric only

#pragma mark - UItextfield Delegate

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if ([string isEqualToString:@"("]||[string isEqualToString:@")"]) {
        return TRUE;
    }

    NSLog(@"Range ==%d  ,%d",range.length,range.location);
    //NSRange *CURRANGE = [NSString  rangeOfString:string];

    if (range.location == 0 && range.length == 0) {
        if ([string isEqualToString:@"+"]) {
            return TRUE;
        }
    }
    return [self isNumeric:string];
}

-(BOOL)isNumeric:(NSString*)inputString{
    BOOL isValid = NO;
    NSCharacterSet *alphaNumbersSet = [NSCharacterSet decimalDigitCharacterSet];
    NSCharacterSet *stringSet = [NSCharacterSet characterSetWithCharactersInString:inputString];
    isValid = [alphaNumbersSet isSupersetOfSet:stringSet];
    return isValid;
}

Adding Multiple Values in ArrayList at a single index

Use two dimensional array instead. For instance, int values[][] = new int[2][5]; Arrays are faster, when you are not manipulating much.

Add a link to an image in a css style sheet

You can not do that...

via css the URL you put on the background-image is just for the image.

Via HTML you have to add the href for your hyperlink in this way:

<a href="http://home.com" id="logo">Your logo</a>

With text-indent and some other css you can adjust your a element to show just the image and clicking on it you will go to your link.


EDIT:

I'm here again to show you and explain why my solution is much better:

<a href="http://home.com" id="logo">Your logo name</a>

This block of HTML is SEO friendly because you have some text inside your link!

How to style it with css:

#logo {
  background-image: url(images/logo.png);
  display: block;
  margin: 0 auto;
  text-indent: -9999px;
  width: 981px;
  height: 180px;
}

Then if you don't care about SEO good to choose the other answer.

How to normalize a 2-dimensional numpy array in python less verbose?

Broadcasting is really good for this:

row_sums = a.sum(axis=1)
new_matrix = a / row_sums[:, numpy.newaxis]

row_sums[:, numpy.newaxis] reshapes row_sums from being (3,) to being (3, 1). When you do a / b, a and b are broadcast against each other.

You can learn more about broadcasting here or even better here.

How to check whether the user uploaded a file in PHP?

You should use $_FILES[$form_name]['error']. It returns UPLOAD_ERR_NO_FILE if no file was uploaded. Full list: PHP: Error Messages Explained

function isUploadOkay($form_name, &$error_message) {
    if (!isset($_FILES[$form_name])) {
        $error_message = "No file upload with name '$form_name' in form.";
        return false;
    }
    $error = $_FILES[$form_name]['error'];

    // List at: http://php.net/manual/en/features.file-upload.errors.php
    if ($error != UPLOAD_ERR_OK) {
        switch ($error) {
            case UPLOAD_ERR_INI_SIZE:
                $error_message = 'The uploaded file exceeds the upload_max_filesize directive in php.ini.';
                break;

            case UPLOAD_ERR_FORM_SIZE:
                $error_message = 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.';
                break;

            case UPLOAD_ERR_PARTIAL:
                $error_message = 'The uploaded file was only partially uploaded.';
                break;

            case UPLOAD_ERR_NO_FILE:
                $error_message = 'No file was uploaded.';
                break;

            case UPLOAD_ERR_NO_TMP_DIR:
                $error_message = 'Missing a temporary folder.';
                break;

            case UPLOAD_ERR_CANT_WRITE:
                $error_message = 'Failed to write file to disk.';
                break;

            case UPLOAD_ERR_EXTENSION:
                $error_message = 'A PHP extension interrupted the upload.';
                break;

            default:
                $error_message = 'Unknown error';
            break;
        }
        return false;
    }

    $error_message = null;
    return true;
}

The #include<iostream> exists, but I get an error: identifier "cout" is undefined. Why?

cout is in std namespace, you shall use std::cout in your code. And you shall not add using namespace std; in your header file, it's bad to mix your code with std namespace, especially don't add it in header file.

Angular 4 HttpClient Query Parameters

I ended up finding it through the IntelliSense on the get() function. So, I'll post it here for anyone who is looking for similar information.

Anyways, the syntax is nearly identical, but slightly different. Instead of using URLSearchParams() the parameters need to be initialized as HttpParams() and the property within the get() function is now called params instead of search.

import { HttpClient, HttpParams } from '@angular/common/http';
getLogs(logNamespace): Observable<any> {

    // Setup log namespace query parameter
    let params = new HttpParams().set('logNamespace', logNamespace);

    return this._HttpClient.get(`${API_URL}/api/v1/data/logs`, { params: params })
}

I actually prefer this syntax as its a little more parameter agnostic. I also refactored the code to make it slightly more abbreviated.

getLogs(logNamespace): Observable<any> {

    return this._HttpClient.get(`${API_URL}/api/v1/data/logs`, {
        params: new HttpParams().set('logNamespace', logNamespace)
    })
}

Multiple Parameters

The best way I have found thus far is to define a Params object with all of the parameters I want to define defined within. As @estus pointed out in the comment below, there are a lot of great answers in This Question as to how to assign multiple parameters.

getLogs(parameters) {

    // Initialize Params Object
    let params = new HttpParams();

    // Begin assigning parameters
    params = params.append('firstParameter', parameters.valueOne);
    params = params.append('secondParameter', parameters.valueTwo);

    // Make the API call using the new parameters.
    return this._HttpClient.get(`${API_URL}/api/v1/data/logs`, { params: params })

Multiple Parameters with Conditional Logic

Another thing I often do with multiple parameters is allow the use of multiple parameters without requiring their presence in every call. Using Lodash, it's pretty simple to conditionally add/remove parameters from calls to the API. The exact functions used in Lodash or Underscores, or vanilla JS may vary depending on your application, but I have found that checking for property definition works pretty well. The function below will only pass parameters that have corresponding properties within the parameters variable passed into the function.

getLogs(parameters) {

    // Initialize Params Object
    let params = new HttpParams();

    // Begin assigning parameters
    if (!_.isUndefined(parameters)) {
        params = _.isUndefined(parameters.valueOne) ? params : params.append('firstParameter', parameters.valueOne);
        params = _.isUndefined(parameters.valueTwo) ? params : params.append('secondParameter', parameters.valueTwo);
    }

    // Make the API call using the new parameters.
    return this._HttpClient.get(`${API_URL}/api/v1/data/logs`, { params: params })

How do I pass an object to HttpClient.PostAsync and serialize as a JSON body?

@arad good point. In fact I just found this extension method (.NET 5.0):

PostAsJsonAsync<TValue>(HttpClient, String, TValue, CancellationToken)

from https://docs.microsoft.com/en-us/dotnet/api/system.net.http.json.httpclientjsonextensions.postasjsonasync?view=net-5.0

So one can now:

var data = new { foo = "Hello"; bar = 42; };
var response = await _Client.PostAsJsonAsync(_Uri, data, cancellationToken);

Fastest way to count number of occurrences in a Python list

You can use pandas, by transforming the list to a pd.Series then simply use .value_counts()

import pandas as pd
a = ['1', '1', '1', '1', '1', '1', '2', '2', '2', '2', '7', '7', '7', '10', '10']
a_cnts = pd.Series(a).value_counts().to_dict()

Input  >> a_cnts["1"], a_cnts["10"]
Output >> (6, 2)

Validate email with a regex in jQuery

function mailValidation(val) {
    var expr = /^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;

    if (!expr.test(val)) {
        $('#errEmail').text('Please enter valid email.');
    }
    else {
        $('#errEmail').hide();
    }
}

Get Absolute URL from Relative path (refactored method)

When you want to generate URL from your Business Logic layer, you do not have the flexibility of using ASP.NET Web Form's Page class/ Control's ResolveUrl(..) etc. Moreover, you may need to generate URL from ASP.NET MVC controller too where you not only miss the Web Form's ResolveUrl(..) method, but also you cannot get the Url.Action(..) even though Url.Action takes only Controller name and Action name, not the relative url.

I tried using

var uri = new Uri(absoluteUrl, relativeUrl)

approach, but there is a problem too. If the web application is hosted in IIS virtual directory, where the url of the app is like this : http://localhost/MyWebApplication1/, and the relative url is "/myPage" then the relative url is resolved as "http://localhost/MyPage" which is another problem.

Therefore, in order to overcome such problems, I have written a UrlUtils class which can work from a class library. So, it wont depend on Page class but it depends on ASP.NET MVC. So, if you dont mind adding reference to MVC dll to your class library project then my class will work smoothly. I have tested in IIS virtual directory scenario where the web application url is like this : http://localhost/MyWebApplication/MyPage. I realized that, sometimes we need to make sure that the Absolute url is SSL url or non SSL url. So, I wrote my class library supporting this option. I have restricted this class library so that the relative url can be absolute url or a relative url that starts with '~/'.

Using this library, I can call

string absoluteUrl = UrlUtils.MapUrl("~/Contact");

Returns : http://localhost/Contact when the page url is : http://localhost/Home/About

Returns : http://localhost/MyWebApplication/Contact when the page url is : http://localhost/MyWebApplication/Home/About

  string absoluteUrl = UrlUtils.MapUrl("~/Contact", UrlUtils.UrlMapOptions.AlwaysSSL);

Returns : **https**://localhost/MyWebApplication/Contact when the page url is : http://localhost/MyWebApplication/Home/About

Here is my class Library :

 public class UrlUtils
    {
        public enum UrlMapOptions
        {
            AlwaysNonSSL,
            AlwaysSSL,
            BasedOnCurrentScheme
        }

        public static string MapUrl(string relativeUrl, UrlMapOptions option = UrlMapOptions.BasedOnCurrentScheme)
        {
            if (relativeUrl.StartsWith("http://", StringComparison.OrdinalIgnoreCase) ||
                relativeUrl.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
                return relativeUrl;

            if (!relativeUrl.StartsWith("~/"))
                throw new Exception("The relative url must start with ~/");

            UrlHelper theHelper = new UrlHelper(HttpContext.Current.Request.RequestContext);

            string theAbsoluteUrl = HttpContext.Current.Request.Url.GetLeftPart(UriPartial.Authority) +
                                           theHelper.Content(relativeUrl);

            switch (option)
            {
                case UrlMapOptions.AlwaysNonSSL:
                    {
                        return theAbsoluteUrl.StartsWith("https://", StringComparison.OrdinalIgnoreCase)
                            ? string.Format("http://{0}", theAbsoluteUrl.Remove(0, 8))
                            : theAbsoluteUrl;
                    }
                case UrlMapOptions.AlwaysSSL:
                    {
                        return theAbsoluteUrl.StartsWith("https://", StringComparison.OrdinalIgnoreCase)
                            ? theAbsoluteUrl
                            : string.Format("https://{0}", theAbsoluteUrl.Remove(0, 7));
                    }
            }

            return theAbsoluteUrl;
        }
    }   

Cannot find module '@angular/compiler'

This command is working fine for me ubuntu 16.04 LTS:

npm install --save-dev @angular/cli@latest

How to install "make" in ubuntu?

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

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

sudo apt-get install build-essential

Why doesn't wireshark detect my interface?

This is usually caused by incorrectly setting up permissions related to running Wireshark correctly. While you can avoid this issue by running Wireshark with elevated privileges (e.g. with sudo), it should generally be avoided (see here, specifically here). This sometimes results from an incomplete or partially successful installation of Wireshark. Since you are running Ubuntu, this can be resolved by following the instructions given in this answer on the Wireshark Q&A site. In summary, after installing Wireshark, execute the following commands:

sudo dpkg-reconfigure wireshark-common 
sudo usermod -a -G wireshark $USER

Then log out and log back in (or reboot), and Wireshark should work correctly without needing additional privileges. Finally, if the problem is still not resolved, it may be that dumpcap was not correctly configured, or there is something else preventing it from operating correctly. In this case, you can set the setuid bit for dumpcap so that it always runs as root.

sudo chmod 4711 `which dumpcap`

One some distros you might get the following error when you execute the command above:

chmod: missing operand after ‘4711’

Try 'chmod --help' for more information.

In this case try running

sudo chmod 4711 `sudo which dumpcap`

Why am I getting Unknown error in line 1 of pom.xml?

Got this error on eclipse IDE version 4.10, Spring boot 2.2.0.M4, changed the Spring boot version to 2.2.0.M2 (after many other solutions recommended and it solved the error). Maybe something missing or broken in the latest version of Spring boot starter project module maven POM.

Android - Adding at least one Activity with an ACTION-VIEW intent-filter after Updating SDK version 23

You can remove the warning by adding the below code in <intent-filter> inside <activity>

<action android:name="android.intent.action.VIEW" />

javascript create empty array of a given size

1) To create new array which, you cannot iterate over, you can use array constructor:

Array(100) or new Array(100)


2) You can create new array, which can be iterated over like below:

a) All JavaScript versions

  • Array.apply: Array.apply(null, Array(100))

b) From ES6 JavaScript version

  • Destructuring operator: [...Array(100)]
  • Array.prototype.fill Array(100).fill(undefined)
  • Array.from Array.from({ length: 100 })

You can map over these arrays like below.

  • Array(4).fill(null).map((u, i) => i) [0, 1, 2, 3]

  • [...Array(4)].map((u, i) => i) [0, 1, 2, 3]

  • Array.apply(null, Array(4)).map((u, i) => i) [0, 1, 2, 3]

  • Array.from({ length: 4 }).map((u, i) => i) [0, 1, 2, 3]

How do I resolve a HTTP 414 "Request URI too long" error?

I have a simple workaround.

Suppose your URI has a string stringdata that is too long. You can simply break it into a number of parts depending on the limits of your server. Then submit the first one, in my case to write a file. Then submit the next ones to append to previously added data.

Add custom icons to font awesome

In Font Awesome 5, you can create custom icons with your own SVG data. Here's a demo GitHub repo that you can play with. And here's a CodePen that shows how something similar might be done in <script> blocks.

In either case, it simply involves using library.add() to add an object like this:

export const faSomeObjectName = {
  // Use a prefix like 'fac' that doesn't conflict with a prefix in the standard Font Awesome styles
  // (So avoid fab, fal, fas, far, fa)
  prefix: string,
  iconName: string, // Any name you like
  icon: [
    number, // width
    number, // height
    string[], // ligatures
    string, // unicode (if relevant)
    string // svg path data
  ]
}

Note that the element labelled by the comment "svg path data" in the code sample is what will be assigned as the value of the d attribute on a <path> element that is a child of the <svg>. Like this (leaving out some details for clarity):

<svg>
  <path d=SVG_PATH_DATA></path>
</svg>

(Adapted from my similar answer here: https://stackoverflow.com/a/50338775/4642871)

Get response from PHP file using AJAX

var data="your data";//ex data="id="+id;
      $.ajax({
       method : "POST",
       url : "file name",  //url: "demo.php"
       data : "data",
       success : function(result){
               //set result to div or target 
              //ex $("#divid).html(result)
        }
   });

How to add "class" to host element?

You can simply add @HostBinding('class') class = 'someClass'; inside your @Component class.

Example:

@Component({
   selector: 'body',
   template: 'app-element'       
})
export class App implements OnInit {

  @HostBinding('class') class = 'someClass';

  constructor() {}      

  ngOnInit() {}
}

Compare two objects in Java with possible null values

This is what Java internal code uses (on other compare methods):

public static boolean compare(String str1, String str2) {
    return (str1 == null ? str2 == null : str1.equals(str2));
}

Boolean Field in Oracle

A working example to implement the accepted answer by adding a "Boolean" column to an existing table in an oracle database (using number type):

ALTER TABLE my_table_name ADD (
my_new_boolean_column number(1) DEFAULT 0 NOT NULL
CONSTRAINT my_new_boolean_column CHECK (my_new_boolean_column in (1,0))
);

This creates a new column in my_table_name called my_new_boolean_column with default values of 0. The column will not accept NULL values and restricts the accepted values to either 0 or 1.

Java JDBC - How to connect to Oracle using Service Name instead of SID

Try this: jdbc:oracle:thin:@oracle.hostserver2.mydomain.ca:1522/ABCD

Edit: per comment below this is actualy correct: jdbc:oracle:thin:@//oracle.hostserver2.mydomain.ca:1522/ABCD (note the //)

Here is a link to a helpful article

IP to Location using Javascript

It's quite easy with an API that maps IP address to location. Run the snippet to get city & country for the IP in the input box.

_x000D_
_x000D_
$('.send').on('click', function(){_x000D_
_x000D_
  $.getJSON('https://ipapi.co/'+$('.ip').val()+'/json', function(data){_x000D_
      $('.city').text(data.city);_x000D_
      $('.country').text(data.country);_x000D_
  });_x000D_
});
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
_x000D_
<input class="ip" value="8.8.8.8">_x000D_
<button class="send">Go</button>_x000D_
<br><br>_x000D_
<span class="city"></span>, _x000D_
<span class="country"></span>
_x000D_
_x000D_
_x000D_

Disable mouse scroll wheel zoom on embedded Google Maps

I tried the first answer in this discussion and it wasn't working for me no matter what I did so I came up with my own solution:

Wrap the iframe with a class (.maps in this example) and ideally embedresponsively code: http://embedresponsively.com/ — Change the CSS of the iframe to pointer-events: none and then using jQuery's click function to the parent element you can change the iframes css to pointer-events:auto

HTML

<div class='embed-container maps'>
    <iframe width='600' height='450' frameborder='0' src='http://foo.com'></iframe>
</div>

CSS

.maps iframe{
    pointer-events: none;
}

jQuery

$('.maps').click(function () {
    $('.maps iframe').css("pointer-events", "auto");
});

$( ".maps" ).mouseleave(function() {
  $('.maps iframe').css("pointer-events", "none"); 
});

I'm sure there's a JavaScript only way of doing this, if someone wants to add to this feel free.

The JavaScript way to reactivate the pointer-events is pretty simple. Just give an Id to the iFrame (i.e. "iframe"), then apply an onclick event to the cointainer div:

onclick="document.getElementById('iframe').style.pointerEvents= 'auto'"

<div class="maps" onclick="document.getElementById('iframe').style.pointerEvents= 'auto'">
   <iframe id="iframe" src="" width="100%" height="450" frameborder="0" style="border:0" allowfullscreen></iframe>
</div>

How to split a data frame?

subset() is also useful:

subset(DATAFRAME, COLUMNNAME == "")

For a survey package, maybe the survey package is pertinent?

http://faculty.washington.edu/tlumley/survey/

What is the fastest way to compare two sets in Java?

There's an O(N) solution for very specific cases where:

  • the sets are both sorted
  • both sorted in the same order

The following code assumes that both sets are based on the records comparable. A similar method could be based on on a Comparator.

    public class SortedSetComparitor <Foo extends Comparable<Foo>> 
            implements Comparator<SortedSet<Foo>> {

        @Override
        public int compare( SortedSet<Foo> arg0, SortedSet<Foo> arg1 ) {
            Iterator<Foo> otherRecords = arg1.iterator();
            for (Foo thisRecord : arg0) {
                // Shorter sets sort first.
                if (!otherRecords.hasNext()) return 1;
                int comparison = thisRecord.compareTo(otherRecords.next());
                if (comparison != 0) return comparison;
            }
            // Shorter sets sort first
            if (otherRecords.hasNext()) return -1;
            else return 0;
        }
    }

How can I change the user on Git Bash?

If you want to change the user at git Bash .You just need to configure particular user and email(globally) at the git bash.

$ git config --global user.name "abhi"
$ git config --global user.email "[email protected]"

Note: No need to delete the user from Keychain .

How do you specifically order ggplot2 x axis instead of alphabetical order?

It is a little difficult to answer your specific question without a full, reproducible example. However something like this should work:

#Turn your 'treatment' column into a character vector
data$Treatment <- as.character(data$Treatment)
#Then turn it back into a factor with the levels in the correct order
data$Treatment <- factor(data$Treatment, levels=unique(data$Treatment))

In this example, the order of the factor will be the same as in the data.csv file.

If you prefer a different order, you can order them by hand:

data$Treatment <- factor(data$Treatment, levels=c("Y", "X", "Z"))

However this is dangerous if you have a lot of levels: if you get any of them wrong, that will cause problems.

Identifier not found error on function call

You have to define void swapCase before the main definition.

How Should I Set Default Python Version In Windows?

This work for me.

If you want to use the python 3.6 you must move the python3.6 on the top of the list.

The same applies to the python2.7 If you want to have the 2.7 as default then make sure you move the python2.7 on the very top on the list.

step 1

enter image description here

step 2

enter image description here

step 3

enter image description here

then close any cmd command prompt and opened again, it should work as expected.

python --version

>>> Python 3.6

javascript return true or return false when and how to use it?

I think a lot of times when you see this code, it's from people who are in the habit of event handlers for forms, buttons, inputs, and things of that sort.

Basically, when you have something like:

<form onsubmit="return callSomeFunction();"></form>

or

<a href="#" onclick="return callSomeFunction();"></a>`

and callSomeFunction() returns true, then the form or a will submit, otherwise it won't.

Other more obvious general purposes for returning true or false as a result of a function are because they are expected to return a boolean.

How to get element's width/height within directives and component?

For a bit more flexibility than with micronyks answer, you can do it like that:

1. In your template, add #myIdentifier to the element you want to obtain the width from. Example:

<p #myIdentifier>
  my-component works!
</p>

2. In your controller, you can use this with @ViewChild('myIdentifier') to get the width:

import {AfterViewInit, Component, ElementRef, OnInit, ViewChild} from '@angular/core';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.scss']
})
export class MyComponentComponent implements AfterViewInit {

  constructor() { }

  ngAfterViewInit() {
    console.log(this.myIdentifier.nativeElement.offsetWidth);
  }

  @ViewChild('myIdentifier')
  myIdentifier: ElementRef;

}

Security

About the security risk with ElementRef, like this, there is none. There would be a risk, if you would modify the DOM using an ElementRef. But here you are only getting DOM Elements so there is no risk. A risky example of using ElementRef would be: this.myIdentifier.nativeElement.onclick = someFunctionDefinedBySomeUser;. Like this Angular doesn't get a chance to use its sanitisation mechanisms since someFunctionDefinedBySomeUser is inserted directly into the DOM, skipping the Angular sanitisation.

Converting list to *args when calling function

yes, using *arg passing args to a function will make python unpack the values in arg and pass it to the function.

so:

>>> def printer(*args):
 print args


>>> printer(2,3,4)
(2, 3, 4)
>>> printer(*range(2, 5))
(2, 3, 4)
>>> printer(range(2, 5))
([2, 3, 4],)
>>> 

How to change max_allowed_packet size

The max_allowed_packet variable can be set globally by running a query.

However, if you do not change it in the my.ini file (as dragon112 suggested), the value will reset when the server restarts, even if you set it globally.

To change the max allowed packet for everyone to 1GB until the server restarts:

SET GLOBAL max_allowed_packet=1073741824;

Does the join order matter in SQL?

For INNER joins, no, the order doesn't matter. The queries will return same results, as long as you change your selects from SELECT * to SELECT a.*, b.*, c.*.


For (LEFT, RIGHT or FULL) OUTER joins, yes, the order matters - and (updated) things are much more complicated.

First, outer joins are not commutative, so a LEFT JOIN b is not the same as b LEFT JOIN a

Outer joins are not associative either, so in your examples which involve both (commutativity and associativity) properties:

a LEFT JOIN b 
    ON b.ab_id = a.ab_id
  LEFT JOIN c
    ON c.ac_id = a.ac_id

is equivalent to:

a LEFT JOIN c 
    ON c.ac_id = a.ac_id
  LEFT JOIN b
    ON b.ab_id = a.ab_id

but:

a LEFT JOIN b 
    ON  b.ab_id = a.ab_id
  LEFT JOIN c
    ON  c.ac_id = a.ac_id
    AND c.bc_id = b.bc_id

is not equivalent to:

a LEFT JOIN c 
    ON  c.ac_id = a.ac_id
  LEFT JOIN b
    ON  b.ab_id = a.ab_id
    AND b.bc_id = c.bc_id

Another (hopefully simpler) associativity example. Think of this as (a LEFT JOIN b) LEFT JOIN c:

a LEFT JOIN b 
    ON b.ab_id = a.ab_id          -- AB condition
 LEFT JOIN c
    ON c.bc_id = b.bc_id          -- BC condition

This is equivalent to a LEFT JOIN (b LEFT JOIN c):

a LEFT JOIN  
    b LEFT JOIN c
        ON c.bc_id = b.bc_id          -- BC condition
    ON b.ab_id = a.ab_id          -- AB condition

only because we have "nice" ON conditions. Both ON b.ab_id = a.ab_id and c.bc_id = b.bc_id are equality checks and do not involve NULL comparisons.

You can even have conditions with other operators or more complex ones like: ON a.x <= b.x or ON a.x = 7 or ON a.x LIKE b.x or ON (a.x, a.y) = (b.x, b.y) and the two queries would still be equivalent.

If however, any of these involved IS NULL or a function that is related to nulls like COALESCE(), for example if the condition was b.ab_id IS NULL, then the two queries would not be equivalent.

How do I change the android actionbar title and icon

For set Title :

getActionBar().setTitle("Title");

For set Icon :

getActionBar().setIcon(R.drawable.YOUR_ICON_NAME);

Open text file and program shortcut in a Windows batch file

In some cases, when opening a LNK file it is expecting the end of the application run.

In such cases it is better to use the following syntax (so you do not have to wait the end of the application):

START /B /I "MyTitleApp" "myshortcut.lnk"

To open a TXT file can be in the way already indicated (because notepad.exxe not interrupt the execution of the start command)

START notepad "myfile.txt"

Creating folders inside a GitHub repository without using Git

Another thing you can do is just drag a folder from your computer into the GitHub repository page. This folder does have to have at least 1 item in it, though.

How to extract hours and minutes from a datetime.datetime object?

Don't know how you want to format it, but you can do:

print("Created at %s:%s" % (t1.hour, t1.minute))

for example.

Add disabled attribute to input element using Javascript

$("input").attr("disabled", true); as of... I don't know any more.

It's December 2013 and I really have no idea what to tell you.

First it was always .attr(), then it was always .prop(), so I came back here updated the answer and made it more accurate.

Then a year later jQuery changed their minds again and I don't even want to keep track of this.

Long story short, as of right now, this is the best answer: "you can use both... but it depends."

You should read this answer instead: https://stackoverflow.com/a/5876747/257493

And their release notes for that change are included here:

Neither .attr() nor .prop() should be used for getting/setting value. Use the .val() method instead (although using .attr("value", "somevalue") will continue to work, as it did before 1.6).

Summary of Preferred Usage

The .prop() method should be used for boolean attributes/properties and for properties which do not exist in html (such as window.location). All other attributes (ones you can see in the html) can and should continue to be manipulated with the .attr() method.

Or in other words:

".prop = non-document stuff"

".attr" = document stuff

... ...

May we all learn a lesson here about API stability...

what is the difference between OLE DB and ODBC data sources?

To know why M$ invents OLEDB, you can't compare OLEDB with ODBC. Instead, you should compare OLEDB with DAO,RDO, or ADO. The latter largely relies on SQL. However, OLEDB relies on COM. But ODBC is already there many years, so there's a OLEDB-ODBC bridges to remedy this. I think there's a big picture when M$ invents OLEDB.

Regular expression for a string that does not start with a sequence

You could use a negative look-ahead assertion:

^(?!tbd_).+

Or a negative look-behind assertion:

(^.{1,3}$|^.{4}(?<!tbd_).*)

Or just plain old character sets and alternations:

^([^t]|t($|[^b]|b($|[^d]|d($|[^_])))).*

Dynamically replace img src attribute with jQuery

This is what you wanna do:

var oldSrc = 'http://example.com/smith.gif';
var newSrc = 'http://example.com/johnson.gif';
$('img[src="' + oldSrc + '"]').attr('src', newSrc);

Move the most recent commit(s) to a new branch with Git

How can I go from this

A - B - C - D - E 
                |
                master

to this?

A - B - C - D - E 
    |           |
    master      newbranch

With two commands

  • git branch -m master newbranch

giving

A - B - C - D - E 
                |
                newbranch

and

  • git branch master B

giving

A - B - C - D - E
    |           |
    master      newbranch

Importing CommonCrypto in a Swift framework

It happened the same to me after updating Xcode. I tried everything I can do such as reinstalling cocoapods and cleaning the project, but it didn't work. Now it's been solved after restart the system.

Int or Number DataType for DataAnnotation validation attribute

I was able to bypass all the framework messages by making the property a string in my view model.

[Range(0, 15, ErrorMessage = "Can only be between 0 .. 15")]
[StringLength(2, ErrorMessage = "Max 2 digits")]
[Remote("PredictionOK", "Predict", ErrorMessage = "Prediction can only be a number in range 0 .. 15")]
public string HomeTeamPrediction { get; set; }

Then I need to do some conversion in my get method:

viewModel.HomeTeamPrediction = databaseModel.HomeTeamPrediction.ToString();

and post method:

databaseModel.HomeTeamPrediction = int.Parse(viewModel.HomeTeamPrediction);

This works best when using the range attribute, otherwise some additional validation would be needed to make sure the value is a number.

You can also specify the type of number by changing the numbers in the range to the correct type:

[Range(0, 10000000F, ErrorMessageResourceType = typeof(GauErrorMessages), ErrorMessageResourceName = nameof(GauErrorMessages.MoneyRange))]

How do I rename a Git repository?

Rename PRJ0.git to PROJ1.git, then edit the URL variable located in the .git/config file of your project.

How to use LogonUser properly to impersonate domain user from workgroup client

I have been successfull at impersonating users in another domain, but only with a trust set up between the 2 domains.

var token = IntPtr.Zero;
var result = LogonUser(userID, domain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref token);
if (result)
{
    return WindowsIdentity.Impersonate(token);
}

Static variables in C++

Excuse me when I answer your questions out-of-order, it makes it easier to understand this way.

When static variable is declared in a header file is its scope limited to .h file or across all units.

There is no such thing as a "header file scope". The header file gets included into source files. The translation unit is the source file including the text from the header files. Whatever you write in a header file gets copied into each including source file.

As such, a static variable declared in a header file is like a static variable in each individual source file.

Since declaring a variable static this way means internal linkage, every translation unit #includeing your header file gets its own, individual variable (which is not visible outside your translation unit). This is usually not what you want.

I would like to know what is the difference between static variables in a header file vs declared in a class.

In a class declaration, static means that all instances of the class share this member variable; i.e., you might have hundreds of objects of this type, but whenever one of these objects refers to the static (or "class") variable, it's the same value for all objects. You could think of it as a "class global".

Also generally static variable is initialized in .cpp file when declared in a class right ?

Yes, one (and only one) translation unit must initialize the class variable.

So that does mean static variable scope is limited to 2 compilation units ?

As I said:

  • A header is not a compilation unit,
  • static means completely different things depending on context.

Global static limits scope to the translation unit. Class static means global to all instances.

I hope this helps.

PS: Check the last paragraph of Chubsdad's answer, about how you shouldn't use static in C++ for indicating internal linkage, but anonymous namespaces. (Because he's right. ;-) )

How can I find which tables reference a given table in Oracle SQL Developer?

To add to the above answer for sql developer plugin, using the below xml will help in getting the column associated with the foreign key.

    <items>
        <item type="editor" node="TableNode" vertical="true">
        <title><![CDATA[FK References]]></title>
        <query>
            <sql>
                <![CDATA[select a.owner,
                                a.constraint_name,
                                a.table_name,
                                b.column_name,
                                a.status
                         from   all_constraints a
                         join   all_cons_columns b ON b.constraint_name = a.constraint_name
                         where  a.constraint_type = 'R'
                                and exists(
                                   select 1
                                   from   all_constraints
                                   where  constraint_name=a.r_constraint_name
                                          and constraint_type in ('P', 'U')
                                          and table_name = :OBJECT_NAME
                                          and owner = :OBJECT_OWNER)
                                   order by table_name, constraint_name]]>
            </sql>
        </query>
        </item>
    </items>

Android changing Floating Action Button color

if you try to change color of FAB by using app, there some problem. frame of button have different color, so what you must to do:

app:backgroundTint="@android:color/transparent"

and in code set the color:

actionButton.setBackgroundTintList(ColorStateList.valueOf(getResources().getColor(R.color.white)));

Checking if a date is valid in javascript

Try this:

var date = new Date();
console.log(date instanceof Date && !isNaN(date.valueOf()));

This should return true.

UPDATED: Added isNaN check to handle the case commented by Julian H. Lam

How to submit form on change of dropdown list?

Very easy to use select option submit

<select name="sortby" onchange="this.form.submit()">
       <option value="">Featured</option>
       <option value="asc" >Price: Low to High</option>
        <option value="desc">Price: High to Low</option>                                   
</select>

This code use and enjoy now:

Read More: Go Link

How to import a bak file into SQL Server Express

I had the same error. What worked for me is when you go for the SMSS GUI option, look at General, Files in Options settings. After I did that (replace DB, set location) all went well.

Non-static method requires a target

I've found this issue to be prevalent in Entity Framework when we instantiate an Entity manually rather than through DBContext which will resolve all the Navigation Properties. If there are Foreign Key references (Navigation Properties) between tables and you use those references in your lambda (e.g. ProductDetail.Products.ID) then that "Products" context remains null if you manually created the Entity.

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)

Loading and parsing a JSON file with multiple JSON objects

That is ill-formatted. You have one JSON object per line, but they are not contained in a larger data structure (ie an array). You'll either need to reformat it so that it begins with [ and ends with ] with a comma at the end of each line, or parse it line by line as separate dictionaries.

How to use setInterval and clearInterval?

I used angular with electron,

In my case, setInterval returns a Nodejs Timer object. which when I called clearInterval(timerobject) it did not work.

I had to get the id first and call to clearInterval

clearInterval(timerobject._id)

I have struggled many hours with this. hope this helps.

Count the number of occurrences of each letter in string

//This is JavaScript Code.

function countWordOccurences()
{
    // You can use array of words or a sentence split with space.
    var sentence = "The quick brown fox jumped over the lazy dog.";
    //var sentenceArray = ['asdf', 'asdf', 'sfd', 'qwr', 'qwr'];
    var sentenceArray = sentence.split(' ', 1000); 
    var output;
    var temp;
    for(var i = 0; i < sentenceArray.length; i++) {
        var k = 1;
        for(var j = i + 1; j < sentenceArray.length; j++) {
            if(sentenceArray[i] == sentenceArray[j])
                    k = k + 1;
        }
        if(k > 1) {
            i = i + 1;
            output = output + ',' + k + ',' + k;
        }
        else
            output = output + ',' + k;
    }
    alert(sentenceArray + '\n' + output.slice(10).split(',', 500));
}

You can see it live --> http://jsfiddle.net/rammipr/ahq8nxpf/

How to change a particular element of a C++ STL vector

Even though @JamesMcNellis answer is a valid one I would like to explain something about error handling and also the fact that there is another way of doing what you want.

You have four ways of accessing a specific item in a vector:

  • Using the [] operator
  • Using the member function at(...)
  • Using an iterator in combination with a given offset
  • Using std::for_each from the algorithm header of the standard C++ library. This is another way which I can recommend (it uses internally an iterator). You can read more about it for example here.

In the following examples I will be using the following vector as a lab rat and explaining the first three methods:

static const int arr[] = {1, 2, 3, 4};
std::vector<int> v(arr, arr+sizeof(arr)/sizeof(arr[0]));

This creates a vector as seen below:

1 2 3 4

First let's look at the [] way of doing things. It works in pretty much the same way as you expect when working with a normal array. You give an index and possibly you access the item you want. I say possibly because the [] operator doesn't check whether the vector actually has that many items. This leads to a silent invalid memory access. Example:

v[10] = 9;

This may or may not lead to an instant crash. Worst case is of course is if it doesn't and you actually get what seems to be a valid value. Similar to arrays this may lead to wasted time in trying to find the reason why for example 1000 lines of code later you get a value of 100 instead of 234, which is somewhat connected to that very location where you retrieve an item from you vector.

A much better way is to use at(...). This will automatically check for out of bounds behaviour and break throwing an std::out_of_range. So in the case when we have

v.at(10) = 9;

We will get:

terminate called after throwing an instance of 'std::out_of_range'
what(): vector::_M_range_check: __n (which is 10) >= this->size() (which is 4)

The third way is similar to the [] operator in the sense you can screw things up. A vector just like an array is a sequence of continuous memory blocks containing data of the same type. This means that you can use your starting address by assigning it to an iterator and then just add an offset to this iterator. The offset simply stands for how many items after the first item you want to traverse:

std::vector<int>::iterator it = v.begin(); // First element of your vector
*(it+0) = 9;  // offest = 0 basically means accessing v.begin()
// Now we have 9 2 3 4 instead of 1 2 3 4
*(it+1) = -1; // offset = 1 means first item of v plus an additional one
// Now we have 9 -1 3 4 instead of 9 2 3 4
// ...

As you can see we can also do

*(it+10) = 9;

which is again an invalid memory access. This is basically the same as using at(0 + offset) but without the out of bounds error checking.

I would advice using at(...) whenever possible not only because it's more readable compared to the iterator access but because of the error checking for invalid index that I have mentioned above for both the iterator with offset combination and the [] operator.

Force GUI update from UI Thread

Think I have the answer, distilled from the above and a little experimentation.

progressBar.Value = progressBar.Maximum - 1;
progressBar.Maximum = progressBar.Value;

I tried decrementing the value and the screen updated even in debug mode, but that would not work for setting progressBar.Value to progressBar.Maximum, because you cannot set the progress bar value above the maximum, so I first set the progressBar.Value to progressBar.Maximum -1, then set progressBar.Maxiumum to equal progressBar.Value. They say there is more than one way of killing a cat. Sometimes I'd like to kill Bill Gates or whoever it is now :o).

With this result, I did not even appear to need to Invalidate(), Refresh(), Update(), or do anything to the progress bar or its Panel container or the parent Form.

What is the difference between a function expression vs declaration in JavaScript?

Regarding 3rd definition:

var foo = function foo() { return 5; }

Heres an example which shows how to use possibility of recursive call:

a = function b(i) { 
  if (i>10) {
    return i;
  }
  else {
    return b(++i);
  }
}

console.log(a(5));  // outputs 11
console.log(a(10)); // outputs 11
console.log(a(11)); // outputs 11
console.log(a(15)); // outputs 15

Edit: more interesting example with closures:

a = function(c) {
 return function b(i){
  if (i>c) {
   return i;
  }
  return b(++i);
 }
}
d = a(5);
console.log(d(3)); // outputs 6
console.log(d(8)); // outputs 8

How can I select multiple columns from a subquery (in SQL Server) that should have one record (select top 1) for each record in the main query?

i think that is what you want.

SELECT 
      A.SalesOrderID, 
      A.OrderDate, 
      FooFromB.*

FROM A,
     (SELECT TOP 1 B.Foo
      FROM B
      WHERE A.SalesOrderID = B.SalesOrderID
      ) AS FooFromB

WHERE A.Date BETWEEN '2000-1-4' AND '2010-1-4'

CSS getting text in one line rather than two

Add white-space: nowrap;:

.garage-title {
    clear: both;
    display: inline-block;
    overflow: hidden;
    white-space: nowrap;
}

jsFiddle

Convert varchar to float IF ISNUMERIC

I found this very annoying bug while converting EmployeeID values with ISNUMERIC:

SELECT DISTINCT [EmployeeID],
ISNUMERIC(ISNULL([EmployeeID], '')) AS [IsNumericResult],

CASE WHEN COALESCE(NULLIF(tmpImport.[EmployeeID], ''), 'Z')
    LIKE '%[^0-9]%' THEN 'NonNumeric' ELSE 'Numeric'
END AS [IsDigitsResult]
FROM [MyTable]

This returns:

EmployeeID IsNumericResult MyCustomResult
---------- --------------- --------------
           0               NonNumeric
00000000c  0               NonNumeric
00D026858  1               NonNumeric

(3 row(s) affected)

Hope this helps!

Javascript: Setting location.href versus location

A couple of years ago, location did not work for me in IE and location.href did (and both worked in other browsers). Since then I have always just used location.href and never had trouble again. I can't remember which version of IE that was.

How to upload a project to Github

Follow these steps to upload your project to Github

1) git init

2) git add .

3) git commit -m "Add all my files"

4) git remote add origin https://github.com/yourusername/your-repo-name.git

Upload of project from scratch require git pull origin master.

5) git pull origin master

6) git push origin master

If any problem occurs in pushing use git push --force origin master

CodeIgniter PHP Model Access "Unable to locate the model you have specified"

Change your model file name, start with upper case letter like this: Logon_model.php

This happens when we migrate our project from windows server to LINUX server because linux is case sensitive while windows is not.

So, on windows even if don't write file name with upper case then also it will work fine but not on linux.

Where is the list of predefined Maven properties

I think the best place to look is the Super POM.

As an example, at the time of writing, the linked reference shows some of the properties between lines 32 - 48.

The interpretation of this is to follow the XPath as a . delimited property.

So, for example:

${project.build.testOutputDirectory} == ${project.build.directory}/test-classes

And:

${project.build.directory} == ${project.basedir}/target

Thus combining them, we find:

${project.build.testOutputDirectory} == ${project.basedir}/target/test-classes

(To reference the resources directory(s), see this stackoverflow question)


<project>
    <modelVersion>4.0.0</modelVersion>
    .
    .
    .
    <build>
        <directory>${project.basedir}/target</directory>
        <outputDirectory>${project.build.directory}/classes</outputDirectory>
        <finalName>${project.artifactId}-${project.version}</finalName>
        <testOutputDirectory>${project.build.directory}/test-classes</testOutputDirectory>
        <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>
        <scriptSourceDirectory>src/main/scripts</scriptSourceDirectory>
        <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory>
        <resources>
            <resource>
                <directory>${project.basedir}/src/main/resources</directory>
            </resource>
        </resources>
        <testResources>
            <testResource>
                <directory>${project.basedir}/src/test/resources</directory>
            </testResource>
        </testResources>
        .
        .
        .
    </build>
    .
    .
    .
</project>

Working around MySQL error "Deadlock found when trying to get lock; try restarting transaction"

If you are using InnoDB or any row-level transactional RDBMS, then it is possible that any write transaction can cause a deadlock, even in perfectly normal situations. Larger tables, larger writes, and long transaction blocks will often increase the likelihood of deadlocks occurring. In your situation, it's probably a combination of these.

The only way to truly handle deadlocks is to write your code to expect them. This generally isn't very difficult if your database code is well written. Often you can just put a try/catch around the query execution logic and look for a deadlock when errors occur. If you catch one, the normal thing to do is just attempt to execute the failed query again.

I highly recommend you read this page in the MySQL manual. It has a list of things to do to help cope with deadlocks and reduce their frequency.

MySQL search and replace some text in a field

 UPDATE table SET field = replace(field, text_needs_to_be_replaced, text_required);

Like for example, if I want to replace all occurrences of John by Mark I will use below,

UPDATE student SET student_name = replace(student_name, 'John', 'Mark');

How does Git handle symbolic links?

"Editor's" note: This post may contain outdated information. Please see comments and this question regarding changes in Git since 1.6.1.

Symlinked directories:

It's important to note what happens when there is a directory which is a soft link. Any Git pull with an update removes the link and makes it a normal directory. This is what I learnt hard way. Some insights here and here.

Example

Before

 ls -l
 lrwxrwxrwx 1 admin adm   29 Sep 30 15:28 src/somedir -> /mnt/somedir

git add/commit/push

It remains the same

After git pull AND some updates found

 drwxrwsr-x 2 admin adm 4096 Oct  2 05:54 src/somedir

How do I SET the GOPATH environment variable on Ubuntu? What file must I edit?

GOPATH is an environment variable to your work-space location. GOROOT is an environment variable to your installation directory. Although GOROOT and GOPATH is automatically set (if there would not be a bug) during the installation time, to specify it manually you can follow below process. Moreover, for more information you can refer to GO's wiki page.

It is better to set GOPATH to a directory inside your home directory, e.g., $HOME/go, %USERPROFILE%\go (Windows).

  1. This is a solution mac, which is tested on macOS Sierra, ver. 10.12, and also in Gogland-EAP, which has been introduced as an IDE for Go programming by JetBrains.

On your Terminal type

vim ~/.profile

in opened document on the Terminal press i and add the following path

GOPATH=/path/to/a/directory/inside/home/directory
GOROOT=/path/to/you/go/library
PATH=$PATH:$GOPATH:$GOROOT:$GOROOT/bin

press ESC and type :x. Lastly, you should restart (close and open) your terminal or Logout and Login again.

  1. For Windows and Linux configuration, please refer to Go wiki page at Githab on Setting GOPATH-Golang.

CAUTION Do not set both GOROOT and GOPATH to the same directory, otherwise you will get a warning.

JavaScript equivalent of PHP's in_array()

var a = [1,2,3,4,5,6,7,8,9];

var isSixInArray = a.filter(function(item){return item==6}).length ? true : false;

var isSixInArray = a.indexOf(6)>=0;

How can I find out the current route in Rails?

You can do request.env['REQUEST_URI'] to see the full requested URI.. it will output something like below

http://localhost:3000/client/1/users/1?name=test

Customize the Authorization HTTP header

I would recommend not to use HTTP authentication with custom scheme names. If you feel that you have something of generic use, you can define a new scheme, though. See http://greenbytes.de/tech/webdav/draft-ietf-httpbis-p7-auth-latest.html#rfc.section.2.3 for details.

C Macro definition to determine big endian or little endian machine?

You can in fact access the memory of a temporary object by using a compound literal (C99):

#define IS_LITTLE_ENDIAN (1 == *(unsigned char *)&(const int){1})

Which GCC will evaluate at compile time.

Using regular expression in css?

As complement of this answer you can use $ to get the end matches and * to get matches anywhere in the value name.

Matches anywhere: .col-md, .left-col, .col, .tricolor, etc.

[class*="col"]

Matches at the beginning: .col-md, .col-sm-6, etc.

[class^="col-"]

Matches at the ending: .left-col, .right-col, etc.

[class$="-col"]

How can I loop through a C++ map of maps?

You can use an iterator.

typedef std::map<std::string, std::map<std::string, std::string>>::iterator it_type;
for(it_type iterator = m.begin(); iterator != m.end(); iterator++) {
    // iterator->first = key
    // iterator->second = value
    // Repeat if you also want to iterate through the second map.
}

Any implementation of Ordered Set in Java?

Try using java.util.TreeSet that implements SortedSet.

To quote the doc:

"The elements are ordered using their natural ordering, or by a Comparator provided at set creation time, depending on which constructor is used"

Note that add, remove and contains has a time cost log(n).

If you want to access the content of the set as an Array, you can convert it doing:

YourType[] array = someSet.toArray(new YourType[yourSet.size()]); 

This array will be sorted with the same criteria as the TreeSet (natural or by a comparator), and in many cases this will have a advantage instead of doing a Arrays.sort()

How to select all and copy in vim?

ggVG 

will select from beginning to end

What online brokers offer APIs?

There are a few. I was looking into MBTrading for a friend. I didn't get too far, as my friend lost interest. Seemed relatively straigt forward with a C# and VB.Net SDK. They had some docs and everything. This was ~6 months ago, so it may be better (or worse) by now.

IIRC, you can create a demo account for free. I don't remember all the details, but it let you connect to their test server and pull quotes and make fake trades and such to get your software fine tuned.

Don't know much about cost for an actual account or anything.

Get next element in foreach loop

A unique approach would be to reverse the array and then loop. This will work for non-numerically indexed arrays as well:

$items = array(
    'one'   => 'two',
    'two'   => 'two',
    'three' => 'three'
);
$backwards = array_reverse($items);
$last_item = NULL;

foreach ($backwards as $current_item) {
    if ($last_item === $current_item) {
        // they match
    }
    $last_item = $current_item;
}

If you are still interested in using the current and next functions, you could do this:

$items = array('two', 'two', 'three');
$length = count($items);
for($i = 0; $i < $length - 1; ++$i) {
    if (current($items) === next($items)) {
        // they match
    }
}

#2 is probably the best solution. Note, $i < $length - 1; will stop the loop after comparing the last two items in the array. I put this in the loop to be explicit with the example. You should probably just calculate $length = count($items) - 1;

How to install the Raspberry Pi cross compiler on my Linux host machine?

You may use clang as well. It used to be faster than GCC, and now it is quite a stable thing. It is much easier to build clang from sources (you can really drink cup of coffee during build process).

In short:

  1. Get clang binaries (sudo apt-get install clang).. or download and build (read instructions here)
  2. Mount your raspberry rootfs (it may be the real rootfs mounted via sshfs, or an image).
  3. Compile your code:

    path/to/clang --target=arm-linux-gnueabihf --sysroot=/some/path/arm-linux-gnueabihf/sysroot my-happy-program.c -fuse-ld=lld
    

Optionally you may use legacy arm-linux-gnueabihf binutils. Then you may remove "-fuse-ld=lld" flag at the end.

Below is my cmake toolchain file.

toolchain.cmake

set(CMAKE_SYSTEM_VERSION 1)
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR arm)

# Custom toolchain-specific definitions for your project
set(PLATFORM_ARM "1")
set(PLATFORM_COMPILE_DEFS "COMPILE_GLES")

# There we go!
# Below, we specify toolchain itself!

set(TARGET_TRIPLE arm-linux-gnueabihf)

# Specify your target rootfs mount point on your compiler host machine
set(TARGET_ROOTFS /Volumes/rootfs-${TARGET_TRIPLE})

# Specify clang paths
set(LLVM_DIR /Users/stepan/projects/shared/toolchains/llvm-7.0.darwin-release-x86_64/install)
set(CLANG ${LLVM_DIR}/bin/clang)
set(CLANGXX ${LLVM_DIR}/bin/clang++)

# Specify compiler (which is clang)
set(CMAKE_C_COMPILER   ${CLANG})
set(CMAKE_CXX_COMPILER ${CLANGXX})

# Specify binutils

set (CMAKE_AR      "${LLVM_DIR}/bin/llvm-ar" CACHE FILEPATH "Archiver")
set (CMAKE_LINKER  "${LLVM_DIR}/bin/llvm-ld" CACHE FILEPATH "Linker")
set (CMAKE_NM      "${LLVM_DIR}/bin/llvm-nm" CACHE FILEPATH "NM")
set (CMAKE_OBJDUMP "${LLVM_DIR}/bin/llvm-objdump" CACHE FILEPATH "Objdump")
set (CMAKE_RANLIB  "${LLVM_DIR}/bin/llvm-ranlib" CACHE FILEPATH "ranlib")

# You may use legacy binutils though.
#set(BINUTILS /usr/local/Cellar/arm-linux-gnueabihf-binutils/2.31.1)
#set (CMAKE_AR      "${BINUTILS}/bin/${TARGET_TRIPLE}-ar" CACHE FILEPATH "Archiver")
#set (CMAKE_LINKER  "${BINUTILS}/bin/${TARGET_TRIPLE}-ld" CACHE FILEPATH "Linker")
#set (CMAKE_NM      "${BINUTILS}/bin/${TARGET_TRIPLE}-nm" CACHE FILEPATH "NM")
#set (CMAKE_OBJDUMP "${BINUTILS}/bin/${TARGET_TRIPLE}-objdump" CACHE FILEPATH "Objdump")
#set (CMAKE_RANLIB  "${BINUTILS}/bin/${TARGET_TRIPLE}-ranlib" CACHE FILEPATH "ranlib")

# Specify sysroot (almost same as rootfs)
set(CMAKE_SYSROOT ${TARGET_ROOTFS})
set(CMAKE_FIND_ROOT_PATH ${TARGET_ROOTFS})

# Specify lookup methods for cmake
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

# Sometimes you also need this:
# set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)

# Specify raspberry triple
set(CROSS_FLAGS "--target=${TARGET_TRIPLE}")

# Specify other raspberry related flags
set(RASP_FLAGS "-D__STDC_CONSTANT_MACROS -D__STDC_LIMIT_MACROS")

# Gather and distribute flags specified at prev steps.
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${CROSS_FLAGS} ${RASP_FLAGS}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CROSS_FLAGS} ${RASP_FLAGS}")

# Use clang linker. Why?
# Well, you may install custom arm-linux-gnueabihf binutils,
# but then, you also need to recompile clang, with customized triple;
# otherwise clang will try to use host 'ld' for linking,
# so... use clang linker.
set(CMAKE_EXE_LINKER_FLAGS ${CMAKE_EXE_LINKER_FLAGS} -fuse-ld=lld)

Java: Date from unix timestamp

This is the right way:

Date date = new Date ();
date.setTime((long)unix_time*1000);

Why is php not running?

You need to add the semicolon to the end of all php things like echo, functions, etc.

change <?php phpinfo() ?> to <?php phpinfo(); ?>

If that does not work, use php's function ini_set to show errors: ini_set('display_errors', 1);

Saving and loading objects and using pickle

You didn't open the file in binary mode.

open("Fruits.obj",'rb')

Should work.

For your second error, the file is most likely empty, which mean you inadvertently emptied it or used the wrong filename or something.

(This is assuming you really did close your session. If not, then it's because you didn't close the file between the write and the read).

I tested your code, and it works.

How to use local docker images with Minikube?

There is one essay and effective way to push your local Docker image directly to minikube, which will save time from building the images in minikube again.

minikube cache add <Image name>

More details here

All possible method to push images to minikube are mention here: https://minikube.sigs.k8s.io/docs/handbook/pushing/

How to set $_GET variable

I know this is an old thread, but I wanted to post my 2 cents...

Using Javascript you can achieve this without using $_POST, and thus avoid reloading the page..

<script>
function ButtonPressed()
{
window.location='index.php?view=next'; //this will set $_GET['view']='next'
}
</script>

<button type='button' onClick='ButtonPressed()'>Click me!</button>

<?PHP
 if(isset($_GET['next']))
    {
          echo "This will display after pressing the 'Click Me' button!";
    }
 ?>

After updating Entity Framework model, Visual Studio does not see changes

You should have a <XXX>Model.tt file somewhere which is the T4 template that generates your model classes.

If it is in a different project, it will not update when you save the edmx file.

Anyway, try right-clicking on it in Solution Explorer and choosing Run Custom Tool

When should iteritems() be used instead of items()?

As the dictionary documentation for python 2 and python 3 would tell you, in python 2 items returns a list, while iteritems returns a iterator.

In python 3, items returns a view, which is pretty much the same as an iterator.

If you are using python 2, you may want to user iteritems if you are dealing with large dictionaries and all you want to do is iterate over the items (not necessarily copy them to a list)

Closing Excel Application using VBA

I think your problem is that it's closing the document that calls the macro before sending the command to quit the application.

Your solution in that case is to not send a command to close the workbook. Instead, you could set the "Saved" state of the workbook to true, which would circumvent any messages about closing an unsaved book. Note: this does not save the workbook; it just makes it look like it's saved.

ThisWorkbook.Saved = True

and then, right after

Application.Quit

Is there a way to use max-width and height for a background image?

As thirtydot said, you can use the CSS3 background-size syntax:

For example:

-o-background-size:35% auto;
-webkit-background-size:35% auto;
-moz-background-size:35% auto;
background-size:35% auto;

However, as also stated by thirtydot, this does not work in IE6, 7 and 8.

See the following links for more information about background-size: http://www.w3.org/TR/css3-background/#the-background-size

Efficient SQL test query or validation query that will work across all (or most) databases

Unfortunately there is no SELECT statement that will always work regardless of database.

Most databases support:

SELECT 1

Some databases don't support this but have a table called DUAL that you can use when you don't need a table:

SELECT 1 FROM DUAL

MySQL also supports this for compatibility reasons, but not all databases do. A workaround for databases that don't support either of the above is to create a table called DUAL that contains a single row, then the above will work.

HSQLDB supports neither of the above, so you can either create the DUAL table or else use:

SELECT 1 FROM any_table_that_you_know_exists_in_your_database

Escape string for use in Javascript regex

Short 'n Sweet

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

Example

escapeRegExp("All of these should be escaped: \ ^ $ * + ? . ( ) | { } [ ]");

>>> "All of these should be escaped: \\ \^ \$ \* \+ \? \. \( \) \| \{ \} \[ \] "

(NOTE: the above is not the original answer; it was edited to show the one from MDN. This means it does not match what you will find in the code in the below npm, and does not match what is shown in the below long answer. The comments are also now confusing. My recommendation: use the above, or get it from MDN, and ignore the rest of this answer. -Darren,Nov 2019)

Install

Available on npm as escape-string-regexp

npm install --save escape-string-regexp

Note

See MDN: Javascript Guide: Regular Expressions

Other symbols (~`!@# ...) MAY be escaped without consequence, but are not required to be.

.

.

.

.

Test Case: A typical url

escapeRegExp("/path/to/resource.html?search=query");

>>> "\/path\/to\/resource\.html\?search=query"

The Long Answer

If you're going to use the function above at least link to this stack overflow post in your code's documentation so that it doesn't look like crazy hard-to-test voodoo.

var escapeRegExp;

(function () {
  // Referring to the table here:
  // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/regexp
  // these characters should be escaped
  // \ ^ $ * + ? . ( ) | { } [ ]
  // These characters only have special meaning inside of brackets
  // they do not need to be escaped, but they MAY be escaped
  // without any adverse effects (to the best of my knowledge and casual testing)
  // : ! , = 
  // my test "~!@#$%^&*(){}[]`/=?+\|-_;:'\",<.>".match(/[\#]/g)

  var specials = [
        // order matters for these
          "-"
        , "["
        , "]"
        // order doesn't matter for any of these
        , "/"
        , "{"
        , "}"
        , "("
        , ")"
        , "*"
        , "+"
        , "?"
        , "."
        , "\\"
        , "^"
        , "$"
        , "|"
      ]

      // I choose to escape every character with '\'
      // even though only some strictly require it when inside of []
    , regex = RegExp('[' + specials.join('\\') + ']', 'g')
    ;

  escapeRegExp = function (str) {
    return str.replace(regex, "\\$&");
  };

  // test escapeRegExp("/path/to/res?search=this.that")
}());

How to give Jenkins more heap space when it´s started as a service under Windows?

I've added to /etc/sysconfig/jenkins (CentOS):

# Options to pass to java when running Jenkins.
#
JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true -Xmx1024m -XX:MaxPermSize=512m"

For ubuntu the same config should be located in /etc/default

How do I validate a date in rails?

Here's a non-chronic answer..

class Pimping < ActiveRecord::Base

validate :valid_date?

def valid_date?
  if scheduled_on.present?
    unless scheduled_on.is_a?(Time)
      errors.add(:scheduled_on, "Is an invalid date.")
    end
  end
end

Assign variable value inside if-statement

Yes, it is possible to assign inside if conditional check. But, your variable should have already been declared to assign something.

How to exclude particular class name in CSS selector?

One way is to use the multiple class selector (no space as that is the descendant selector):

_x000D_
_x000D_
.reMode_hover:not(.reMode_selected):hover _x000D_
{_x000D_
   background-color: #f0ac00;_x000D_
}
_x000D_
<a href="" title="Design" class="reMode_design  reMode_hover">_x000D_
    <span>Design</span>_x000D_
</a>_x000D_
_x000D_
<a href="" title="Design" _x000D_
 class="reMode_design  reMode_hover reMode_selected">_x000D_
    <span>Design</span>_x000D_
</a>
_x000D_
_x000D_
_x000D_

How to copy files across computers using SSH and MAC OS X Terminal

You can do this with the scp command, which uses the ssh protocol to copy files across machines. It extends the syntax of cp to allow references to other systems:

scp username1@hostname1:/path/to/file username2@hostname2:/path/to/other/file

Copy something from this machine to some other machine:

scp /path/to/local/file username@hostname:/path/to/remote/file

Copy something from another machine to this machine:

scp username@hostname:/path/to/remote/file /path/to/local/file

Copy with a port number specified:

scp -P 1234 username@hostname:/path/to/remote/file /path/to/local/file

IntelliJ and Tomcat.. Howto..?

NOTE: Community Edition doesn't support JEE.

First, you will need to install a local Tomcat server. It sounds like you may have already done this.

Next, on the toolbar at the top of IntelliJ, click the down arrow just to the left of the Run and Debug icons. There will be an option to Edit Configurations. In the resulting popup, click the Add icon, then click Tomcat and Local.

From that dialog, you will need to click the Configure... button next to Application Server to tell IntelliJ where Tomcat is installed.

Passing $_POST values with cURL

$query_string = "";

if ($_POST) {
    $kv = array();
    foreach ($_POST as $key => $value) {
        $kv[] = stripslashes($key) . "=" . stripslashes($value);
    }
    $query_string = join("&", $kv);
}

if (!function_exists('curl_init')){
    die('Sorry cURL is not installed!');
}

$url = 'https://www.abcd.com/servlet/';

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, count($kv));
curl_setopt($ch, CURLOPT_POSTFIELDS, $query_string);

curl_setopt($ch, CURLOPT_HEADER, FALSE);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, FALSE);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);

$result = curl_exec($ch);

curl_close($ch);

How to fix missing dependency warning when using useEffect React Hook?

Well if you want to look into this differently, you just need to know what are options does the React has that non exhaustive-deps? One of the reason you should not use a closure function inside the effect is on every render, it will be re-created/destroy again.

So there are multiple React methods in hooks that is considered stable and non-exhausted where you do not have to apply to the useEffect dependencies, and in turn will not break the rules engagement of react-hooks/exhaustive-deps. For example the second return variable of useReducer or useState which is a function.

const [,dispatch] = useReducer(reducer, {});

useEffect(() => {
    dispatch(); // non-exhausted, eslint won't nag about this
}, []);

So in turn you can have all your external dependencies together with your current dependencies coexist together within your reducer function.

const [,dispatch] = useReducer((current, update) => {
    const { foobar } = update;
    // logic

    return { ...current, ...update };
}), {});

const [foobar, setFoobar] = useState(false);

useEffect(() => {
    dispatch({ foobar }); // non-exhausted `dispatch` function
}, [foobar]);

Error:(23, 17) Failed to resolve: junit:junit:4.12

In my case, I just add:

allprojects {
repositories {
    jcenter()
    maven { url 'https://maven.google.com' }
}

}

Checking the form field values before submitting that page

While you have a return value in checkform, it isn't being used anywhere - try using onclick="return checkform()" instead.

You may want to considering replacing this method with onsubmit="return checkform()" in the form tag instead, though both will work for clicking the button.

HTML table with 100% width, with vertical scroll inside tbody

This is the code that works for me to create a sticky thead on a table with a scrollable tbody:

table ,tr td{
    border:1px solid red
}
tbody {
    display:block;
    height:50px;
    overflow:auto;
}
thead, tbody tr {
    display:table;
    width:100%;
    table-layout:fixed;/* even columns width , fix width of table too*/
}
thead {
    width: calc( 100% - 1em )/* scrollbar is average 1em/16px width, remove it from thead width */
}
table {
    width:400px;
}

Algorithm to generate all possible permutations of a list?

As WhirlWind said, you start at the beginning.

You swap cursor with each remaining value, including cursor itself, these are all new instances (I used an int[] and array.clone() in the example).

Then perform permutations on all these different lists, making sure the cursor is one to the right.

When there are no more remaining values (cursor is at the end), print the list. This is the stop condition.

public void permutate(int[] list, int pointer) {
    if (pointer == list.length) {
        //stop-condition: print or process number
        return;
    }
    for (int i = pointer; i < list.length; i++) {
        int[] permutation = (int[])list.clone();.
        permutation[pointer] = list[i];
        permutation[i] = list[pointer];
        permutate(permutation, pointer + 1);
    }
}

How to get a value of an element by name instead of ID

This works fine .. here btnAddCat is button id

$('#btnAddCat').click(function(){
        var eventCategory=$("input[name=txtCategory]").val();
        alert(eventCategory);
    });

How to post query parameters with Axios?

In my case, the API responded with a CORS error. I instead formatted the query parameters into query string. It successfully posted data and also avoided the CORS issue.

        var data = {};

        const params = new URLSearchParams({
          contact: this.ContactPerson,
          phoneNumber: this.PhoneNumber,
          email: this.Email
        }).toString();

        const url =
          "https://test.com/api/UpdateProfile?" +
          params;

        axios
          .post(url, data, {
            headers: {
              aaid: this.ID,
              token: this.Token
            }
          })
          .then(res => {
            this.Info = JSON.parse(res.data);
          })
          .catch(err => {
            console.log(err);
          });

What is the exact location of MySQL database tables in XAMPP folder?

I think the matter is your tables engine. I guess you are using InnoDB for your table. So you can not copy files easily to make a copy.
Take a look at these links:
http://dev.mysql.com/doc/refman/5.0/en/innodb-backup.html
http://dev.mysql.com/doc/refman/5.0/en/innodb-migration.html

Also I recommend you to use something like phpMyAdmin for creating your backup file and then restore the backup file on the next machine using the same IDE.

How can I access iframe elements with Javascript?

If you have the HTML

<form name="formname" .... id="form-first">
    <iframe id="one" src="iframe2.html">
    </iframe>
</form>

and JavaScript

function iframeRef( frameRef ) {
    return frameRef.contentWindow
        ? frameRef.contentWindow.document
        : frameRef.contentDocument
}

var inside = iframeRef( document.getElementById('one') )

inside is now a reference to the document, so you can do getElementsByTagName('textarea') and whatever you like, depending on what's inside the iframe src.

error C2039: 'string' : is not a member of 'std', header file problem

Take care not to include

#include <string.h> 

but only

#include <string>

It took me 1 hour to find this in my code.

Hope this can help

Redirecting to a new page after successful login

Try header("Location:home.php"); instead of showing $msg = 'Login Complete! Thanks'; Hope it'll help you.

How can I check the system version of Android?

Check android.os.Build.VERSION.

  • CODENAME: The current development codename, or the string "REL" if this is a release build.
  • INCREMENTAL: The internal value used by the underlying source control to represent this build.
  • RELEASE: The user-visible version string.

How do I expire a PHP session after 30 minutes?

Just Store the current time and If it exceeds 30 minutes by comparing then destroy the current session.

Write variable to a file in Ansible

Based on Ramon's answer I run into an error. The problem where spaces in the JSON I tried to write I got it fixed by changing the task in the playbook to look like:

- copy:
    content: "{{ your_json_feed }}"
    dest: "/path/to/destination/file"

As of now I am not sure why this was needed. My best guess is that it had something to do with how variables are replaced in Ansible and the resulting file is parsed.

Error when creating a new text file with python?

You can use open(name, 'a')

However, when you enter filename, use inverted commas on both sides, otherwise ".txt"cannot be added to filename

concatenate two strings

You need to use the string concatenation operator +

String both = name + "-" + dest;

How to split data into trainset and testset randomly?

sklearn.cross_validation is deprecated since version 0.18, instead you should use sklearn.model_selection as show below

from sklearn.model_selection import train_test_split
import numpy

with open("datafile.txt", "rb") as f:
   data = f.read().split('\n')
   data = numpy.array(data)  #convert array to numpy type array

   x_train ,x_test = train_test_split(data,test_size=0.5)       #test_size=0.5(whole_data)

Random string generation with upper case letters and digits

this is a take on Anurag Uniyal 's response and something that i was working on myself.

import random
import string

oneFile = open('?Numbers.txt', 'w')
userInput = 0
key_count = 0
value_count = 0
chars = string.ascii_uppercase + string.digits + string.punctuation

for userInput in range(int(input('How many 12 digit keys do you want?'))):
    while key_count <= userInput:
        key_count += 1
        number = random.randint(1, 999)
        key = number

        text = str(key) + ": " + str(''.join(random.sample(chars*6, 12)))
        oneFile.write(text + "\n")
oneFile.close()

How can I create a "Please Wait, Loading..." animation using jQuery?

This would make the buttons disappear, then an animation of "loading" would appear in their place and finally just display a success message.

$(function(){
    $('#submit').click(function(){
        $('#submit').hide();
        $("#form .buttons").append('<img src="assets/img/loading.gif" alt="Loading..." id="loading" />');
        $.post("sendmail.php",
                {emailFrom: nameVal, subject: subjectVal, message: messageVal},
                function(data){
                    jQuery("#form").slideUp("normal", function() {                 
                        $("#form").before('<h1>Success</h1><p>Your email was sent.</p>');
                    });
                }
        );
    });
});

Moving Panel in Visual Studio Code to right side

As of June 2019 this setting can be found through searching 'Panel' - if you want to change the default there is an option for it as shown in the screenshot:enter image description here

Powershell send-mailmessage - email to multiple recipients

to send a .NET / C# powershell eMail use such a structure:

for best behaviour create a class with a method like this

 using (PowerShell PowerShellInstance = PowerShell.Create())
            {
                PowerShellInstance.AddCommand("Send-MailMessage")
                                  .AddParameter("SMTPServer", "smtp.xxx.com")
                                  .AddParameter("From", "[email protected]")
                                  .AddParameter("Subject", "xxx Notification")
                                  .AddParameter("Body", body_msg)
                                  .AddParameter("BodyAsHtml")
                                  .AddParameter("To", recipients);

                // invoke execution on the pipeline (ignore output) --> nothing will be displayed
                PowerShellInstance.Invoke();
            }              

Whereby these instance is called in a function like:

        public void sendEMailPowerShell(string body_msg, string[] recipients)

Never forget to use a string array for the recepients, which can be look like this:

string[] reportRecipient = { 
                        "xxx <[email protected]>",
                        "xxx <[email protected]>"
                        };

body_msg

this message can be overgiven as parameter to the method itself, HTML coding enabled!!

recipients

never forget to use a string array in case of multiple recipients, otherwise only the last address in the string will be used!!!

calling the function can look like this:

        mail reportMail = new mail(); //instantiate from class
        reportMail.sendEMailPowerShell(reportMessage, reportRecipient); //msg + email addresses

ThumbUp

JSONDecodeError: Expecting value: line 1 column 1

If you look at the output you receive from print() and also in your Traceback, you'll see the value you get back is not a string, it's a bytes object (prefixed by b):

b'{\n  "note":"This file    .....

If you fetch the URL using a tool such as curl -v, you will see that the content type is

Content-Type: application/json; charset=utf-8

So it's JSON, encoded as UTF-8, and Python is considering it a byte stream, not a simple string. In order to parse this, you need to convert it into a string first.

Change the last line of code to this:

info = json.loads(js.decode("utf-8"))

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

new / delete

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

malloc / free

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

Table comparison of the features:

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

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

How to make a div fill a remaining horizontal space?

The solution comes from the display property.

Basically you need to make the two divs act like table cells. So instead of using float:left, you'll have to use display:table-cell on both divs, and for the dynamic width div you need to set width:auto; also. The both divs should be placed into a 100% width container with the display:table property.

Here is the css:

.container {display:table;width:100%}
#search {
  width: 160px;
  height: 25px;
  display:table-cell;
  background-color: #FFF;
}
#navigation {
  width: auto;
  display:table-cell;
  /*background-color: url('../images/transparent.png') ;*/
  background-color: #A53030;
}

*html #navigation {float:left;}

And the HTML:

<div class="container">
   <div id="search"></div>
   <div id="navigation"></div>
</div>

IMPORTANT:For Internet Explorer you need to specify the float property on the dynamic width div, otherwise the space will not be filled.

I hope that this will solve your problem. If you want, you can read the full article I wrote about this on my blog.

How to JSON decode array elements in JavaScript?

If the object element you get is a function, you can try this:

var url = myArray[i]();

What happened to console.log in IE8?

if (window.console && 'function' === typeof window.console.log) {
    window.console.log(o);
}

Chrome - ERR_CACHE_MISS

This is a known issue in Chrome and resolved in latest versions. Please refer https://bugs.chromium.org/p/chromium/issues/detail?id=942440 for more details.

How to implement debounce in Vue2?

We can do with by using few lines of JS code:

if(typeof window.LIT !== 'undefined') {
      clearTimeout(window.LIT);
}

window.LIT = setTimeout(() => this.updateTable(), 1000);

Simple solution! Work Perfect! Hope, will be helpful for you guys.

How to find the minimum value of a column in R?

df <- read.table(text = 
             "X  Y
             1  2  3
             2  4  5
             3  6  7
             4  8  9
             5 10 11",
             header = TRUE)


y_min <- min(df[,"Y"])

# Corresponding X value
x_val_associated <- df[df$Y == y_min, "X"]

x_val_associated

First, you find the Y min using the min function on the "Y" column only. Notice the returned result is just an integer value. Then, to find the associated X value, you can subset the data.frame to only the rows where the minimum Y value is located and extract just the "X" column.

You now have two integer values for X and Y where Y is the min.

PostgreSQL - fetch the row which has the Max value for a column

On a table with 158k pseudo-random rows (usr_id uniformly distributed between 0 and 10k, trans_id uniformly distributed between 0 and 30),

By query cost, below, I am referring to Postgres' cost based optimizer's cost estimate (with Postgres' default xxx_cost values), which is a weighed function estimate of required I/O and CPU resources; you can obtain this by firing up PgAdminIII and running "Query/Explain (F7)" on the query with "Query/Explain options" set to "Analyze"

  • Quassnoy's query has a cost estimate of 745k (!), and completes in 1.3 seconds (given a compound index on (usr_id, trans_id, time_stamp))
  • Bill's query has a cost estimate of 93k, and completes in 2.9 seconds (given a compound index on (usr_id, trans_id))
  • Query #1 below has a cost estimate of 16k, and completes in 800ms (given a compound index on (usr_id, trans_id, time_stamp))
  • Query #2 below has a cost estimate of 14k, and completes in 800ms (given a compound function index on (usr_id, EXTRACT(EPOCH FROM time_stamp), trans_id))
    • this is Postgres-specific
  • Query #3 below (Postgres 8.4+) has a cost estimate and completion time comparable to (or better than) query #2 (given a compound index on (usr_id, time_stamp, trans_id)); it has the advantage of scanning the lives table only once and, should you temporarily increase (if needed) work_mem to accommodate the sort in memory, it will be by far the fastest of all queries.

All times above include retrieval of the full 10k rows result-set.

Your goal is minimal cost estimate and minimal query execution time, with an emphasis on estimated cost. Query execution can dependent significantly on runtime conditions (e.g. whether relevant rows are already fully cached in memory or not), whereas the cost estimate is not. On the other hand, keep in mind that cost estimate is exactly that, an estimate.

The best query execution time is obtained when running on a dedicated database without load (e.g. playing with pgAdminIII on a development PC.) Query time will vary in production based on actual machine load/data access spread. When one query appears slightly faster (<20%) than the other but has a much higher cost, it will generally be wiser to choose the one with higher execution time but lower cost.

When you expect that there will be no competition for memory on your production machine at the time the query is run (e.g. the RDBMS cache and filesystem cache won't be thrashed by concurrent queries and/or filesystem activity) then the query time you obtained in standalone (e.g. pgAdminIII on a development PC) mode will be representative. If there is contention on the production system, query time will degrade proportionally to the estimated cost ratio, as the query with the lower cost does not rely as much on cache whereas the query with higher cost will revisit the same data over and over (triggering additional I/O in the absence of a stable cache), e.g.:

              cost | time (dedicated machine) |     time (under load) |
-------------------+--------------------------+-----------------------+
some query A:   5k | (all data cached)  900ms | (less i/o)     1000ms |
some query B:  50k | (all data cached)  900ms | (lots of i/o) 10000ms |

Do not forget to run ANALYZE lives once after creating the necessary indices.


Query #1

-- incrementally narrow down the result set via inner joins
--  the CBO may elect to perform one full index scan combined
--  with cascading index lookups, or as hash aggregates terminated
--  by one nested index lookup into lives - on my machine
--  the latter query plan was selected given my memory settings and
--  histogram
SELECT
  l1.*
 FROM
  lives AS l1
 INNER JOIN (
    SELECT
      usr_id,
      MAX(time_stamp) AS time_stamp_max
     FROM
      lives
     GROUP BY
      usr_id
  ) AS l2
 ON
  l1.usr_id     = l2.usr_id AND
  l1.time_stamp = l2.time_stamp_max
 INNER JOIN (
    SELECT
      usr_id,
      time_stamp,
      MAX(trans_id) AS trans_max
     FROM
      lives
     GROUP BY
      usr_id, time_stamp
  ) AS l3
 ON
  l1.usr_id     = l3.usr_id AND
  l1.time_stamp = l3.time_stamp AND
  l1.trans_id   = l3.trans_max

Query #2

-- cheat to obtain a max of the (time_stamp, trans_id) tuple in one pass
-- this results in a single table scan and one nested index lookup into lives,
--  by far the least I/O intensive operation even in case of great scarcity
--  of memory (least reliant on cache for the best performance)
SELECT
  l1.*
 FROM
  lives AS l1
 INNER JOIN (
   SELECT
     usr_id,
     MAX(ARRAY[EXTRACT(EPOCH FROM time_stamp),trans_id])
       AS compound_time_stamp
    FROM
     lives
    GROUP BY
     usr_id
  ) AS l2
ON
  l1.usr_id = l2.usr_id AND
  EXTRACT(EPOCH FROM l1.time_stamp) = l2.compound_time_stamp[1] AND
  l1.trans_id = l2.compound_time_stamp[2]

2013/01/29 update

Finally, as of version 8.4, Postgres supports Window Function meaning you can write something as simple and efficient as:

Query #3

-- use Window Functions
-- performs a SINGLE scan of the table
SELECT DISTINCT ON (usr_id)
  last_value(time_stamp) OVER wnd,
  last_value(lives_remaining) OVER wnd,
  usr_id,
  last_value(trans_id) OVER wnd
 FROM lives
 WINDOW wnd AS (
   PARTITION BY usr_id ORDER BY time_stamp, trans_id
   ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
 );

How can I exclude one word with grep?

I excluded the root ("/") mount point by using grep -vw "^/".

# cat /tmp/topfsfind.txt| head -4 |awk '{print $NF}'
/
/root/.m2
/root
/var

# cat /tmp/topfsfind.txt| head -4 |awk '{print $NF}' | grep -vw "^/"
/root/.m2
/root
/var

HTML combo box with option to type an entry

Before datalist (see note below), you would supply an additional input element for people to type in their own option.

_x000D_
_x000D_
<select name="example">
  <option value="A">A</option>
  <option value="B">B</option>
  <option value="-">Other</option>
</select>

<input type="text" name="other">
_x000D_
_x000D_
_x000D_

This mechanism works in all browsers and requires no JavaScript.

You could use a little JavaScript to be clever about only showing the input if the "Other" option was selected.

datalist Element

The datalist element is intended to provide a better mechanism for this concept. In some browsers, e.g. iOS Safari < 12.2, this was not supported or the implementation had issues. Check the Can I Use page to see current datalist support.

_x000D_
_x000D_
<input type="text" name="example" list="exampleList">
<datalist id="exampleList">
  <option value="A">  
  <option value="B">
</datalist>
_x000D_
_x000D_
_x000D_

Java collections convert a string to a list of characters

IntStream can be used to access each character and add them to the list.

String str = "abc";
List<Character> charList = new ArrayList<>();
IntStream.range(0,str.length()).forEach(i -> charList.add(str.charAt(i)));

What's the best way to add a drop shadow to my UIView

You can create an extension for UIView to access these values in the design editor

Shadow options in design editor

extension UIView{

    @IBInspectable var shadowOffset: CGSize{
        get{
            return self.layer.shadowOffset
        }
        set{
            self.layer.shadowOffset = newValue
        }
    }

    @IBInspectable var shadowColor: UIColor{
        get{
            return UIColor(cgColor: self.layer.shadowColor!)
        }
        set{
            self.layer.shadowColor = newValue.cgColor
        }
    }

    @IBInspectable var shadowRadius: CGFloat{
        get{
            return self.layer.shadowRadius
        }
        set{
            self.layer.shadowRadius = newValue
        }
    }

    @IBInspectable var shadowOpacity: Float{
        get{
            return self.layer.shadowOpacity
        }
        set{
            self.layer.shadowOpacity = newValue
        }
    }
}

Convert float to std::string in C++

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

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

$http get parameters does not work

From $http.get docs, the second parameter is a configuration object:

get(url, [config]);

Shortcut method to perform GET request.

You may change your code to:

$http.get('accept.php', {
    params: {
        source: link, 
        category_id: category
    }
});

Or:

$http({
    url: 'accept.php', 
    method: 'GET',
    params: { 
        source: link, 
        category_id: category
    }
});

As a side note, since Angular 1.6: .success should not be used anymore, use .then instead:

$http.get('/url', config).then(successCallback, errorCallback);

Sort rows in data.table in decreasing order on string key `order(-x,v)` gives error on data.table 1.9.4 or earlier

You can only use - on the numeric entries, so you can use decreasing and negate the ones you want in increasing order:

DT[order(x,-v,decreasing=TRUE),]
      x y v
 [1,] c 1 7
 [2,] c 3 8
 [3,] c 6 9
 [4,] b 1 1
 [5,] b 3 2
 [6,] b 6 3
 [7,] a 1 4
 [8,] a 3 5
 [9,] a 6 6