Programs & Examples On #Quantile

Quantiles are points taken at regular intervals from the cumulative distribution function (CDF) of a random variable.

How to get coordinates of an svg element?

svg.selectAll("rect")
.attr('x',function(d,i){
    // get x coord
    console.log(this.getBBox().x, 'or', d3.select(this).attr('x'))
})
.attr('y',function(d,i){
    // get y coord
    console.log(this.getBBox().y)
})
.attr('dx',function(d,i){
    // get dx coord
    console.log(parseInt(d3.select(this).attr('dx')))
})

Quantile-Quantile Plot using SciPy

If you need to do a QQ plot of one sample vs. another, statsmodels includes qqplot_2samples(). Like Ricky Robinson in a comment above, this is what I think of as a QQ plot vs a probability plot which is a sample against a theoretical distribution.

http://statsmodels.sourceforge.net/devel/generated/statsmodels.graphics.gofplots.qqplot_2samples.html

Correct way to create rounded corners in Twitter Bootstrap

What you want is a Bootstrap panel. Just add the panel class, and your header will look uniform. You can also add classes panel panel-info, panel panel-success, etc. It works for pretty much any block element, and should work with <header>, but I expect it would be used mostly with <div>s.

CSS Div width percentage and padding without breaking layout

You can also use the CSS calc() function to subtract the width of your padding from the percentage of your container's width.

An example:

width: calc((100%) - (32px))

Just be sure to make the subtracted width equal to the total padding, not just one half. If you pad both sides of the inner div with 16px, then you should subtract 32px from the final width, assuming that the example below is what you want to achieve.

_x000D_
_x000D_
.outer {_x000D_
  width: 200px;_x000D_
  height: 120px;_x000D_
  background-color: black;_x000D_
}_x000D_
_x000D_
.inner {_x000D_
  height: 40px;_x000D_
  top: 30px;_x000D_
  position: relative;_x000D_
  padding: 16px;_x000D_
  background-color: teal;_x000D_
}_x000D_
_x000D_
#inner-1 {_x000D_
  width: 100%;_x000D_
}_x000D_
_x000D_
#inner-2 {_x000D_
  width: calc((100%) - (32px));_x000D_
}
_x000D_
<div class="outer" id="outer-1">_x000D_
  <div class="inner" id="inner-1"> width of 100% </div>_x000D_
</div>_x000D_
_x000D_
<br>_x000D_
<br>_x000D_
_x000D_
<div class="outer" id="outer-2">_x000D_
  <div class="inner" id="inner-2"> width of 100% - 16px </div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

Right query to get the current number of connections in a PostgreSQL DB

Those two requires aren't equivalent. The equivalent version of the first one would be:

SELECT sum(numbackends) FROM pg_stat_database;

In that case, I would expect that version to be slightly faster than the second one, simply because it has fewer rows to count. But you are not likely going to be able to measure a difference.

Both queries are based on exactly the same data, so they will be equally accurate.

How do I limit the number of decimals printed for a double?

okay one other solution that I thought of just for the fun of it would be to turn your decimal into a string and then cut the string into 2 strings, one containing the point and the decimals and the other containing the Int to the left of the point. after that you limit the String of the point and decimals to 3 chars, one for the decimal point and the others for the decimals. then just recombine.

double shippingCost = ((nCartons * 1.44) + (lbs + 1) * 0.96) + 3.0;
String ShippingCost = (String) shippingCost;
String decimalCost = ShippingCost.subString(indexOf('.'),ShippingCost.Length());
ShippingCost = ShippingCost.subString(0,indexOf('.'));
ShippingCost = ShippingCost + decimalCost;

There! Simple, right?

Lodash remove duplicates from array

With lodash version 4+, you would remove duplicate objects either by specific property or by the entire object like so:

var users = [
  {id:1,name:'ted'},
  {id:1,name:'ted'},
  {id:1,name:'bob'},
  {id:3,name:'sara'}
];
var uniqueUsersByID = _.uniqBy(users,'id'); //removed if had duplicate id
var uniqueUsers = _.uniqWith(users, _.isEqual);//removed complete duplicates

Source:https://www.codegrepper.com/?search_term=Lodash+remove+duplicates+from+array

How can I write data attributes using Angular?

About access

<ol class="viewer-nav">
    <li *ngFor="let section of sections" 
        [attr.data-sectionvalue]="section.value"
        (click)="get_data($event)">
        {{ section.text }}
    </li>  
</ol>

And

get_data(event) {
   console.log(event.target.dataset.sectionvalue)
}

How to create .pfx file from certificate and private key?

In most of the cases, if you are unable to export the certificate as a PFX (including the private key) is because MMC/IIS cannot find/don't have access to the private key (used to generate the CSR). These are the steps I followed to fix this issue:

  • Run MMC as Admin
    • Generate the CSR using MMC. Follow this instructions to make the certificate exportable.
  • Once you get the certificate from the CA (crt + p7b), import them (Personal\Certificates, and Intermediate Certification Authority\Certificates)
  • IMPORTANT: Right-click your new certificate (Personal\Certificates) All Tasks..Manage Private Key, and assign permissions to your account or Everyone (risky!). You can go back to previous permissions once you have finished.
  • Now, right-click the certificate and select All Tasks..Export, and you should be able to export the certificate including the private key as a PFX file, and you can upload it to Azure!

Hope this helps!

Export to CSV using jQuery and html

Demo

See below for an explanation.

_x000D_
_x000D_
$(document).ready(function() {_x000D_
_x000D_
  function exportTableToCSV($table, filename) {_x000D_
_x000D_
    var $rows = $table.find('tr:has(td)'),_x000D_
_x000D_
      // Temporary delimiter characters unlikely to be typed by keyboard_x000D_
      // This is to avoid accidentally splitting the actual contents_x000D_
      tmpColDelim = String.fromCharCode(11), // vertical tab character_x000D_
      tmpRowDelim = String.fromCharCode(0), // null character_x000D_
_x000D_
      // actual delimiter characters for CSV format_x000D_
      colDelim = '","',_x000D_
      rowDelim = '"\r\n"',_x000D_
_x000D_
      // Grab text from table into CSV formatted string_x000D_
      csv = '"' + $rows.map(function(i, row) {_x000D_
        var $row = $(row),_x000D_
          $cols = $row.find('td');_x000D_
_x000D_
        return $cols.map(function(j, col) {_x000D_
          var $col = $(col),_x000D_
            text = $col.text();_x000D_
_x000D_
          return text.replace(/"/g, '""'); // escape double quotes_x000D_
_x000D_
        }).get().join(tmpColDelim);_x000D_
_x000D_
      }).get().join(tmpRowDelim)_x000D_
      .split(tmpRowDelim).join(rowDelim)_x000D_
      .split(tmpColDelim).join(colDelim) + '"';_x000D_
_x000D_
    // Deliberate 'false', see comment below_x000D_
    if (false && window.navigator.msSaveBlob) {_x000D_
_x000D_
      var blob = new Blob([decodeURIComponent(csv)], {_x000D_
        type: 'text/csv;charset=utf8'_x000D_
      });_x000D_
_x000D_
      // Crashes in IE 10, IE 11 and Microsoft Edge_x000D_
      // See MS Edge Issue #10396033_x000D_
      // Hence, the deliberate 'false'_x000D_
      // This is here just for completeness_x000D_
      // Remove the 'false' at your own risk_x000D_
      window.navigator.msSaveBlob(blob, filename);_x000D_
_x000D_
    } else if (window.Blob && window.URL) {_x000D_
      // HTML5 Blob        _x000D_
      var blob = new Blob([csv], {_x000D_
        type: 'text/csv;charset=utf-8'_x000D_
      });_x000D_
      var csvUrl = URL.createObjectURL(blob);_x000D_
_x000D_
      $(this)_x000D_
        .attr({_x000D_
          'download': filename,_x000D_
          'href': csvUrl_x000D_
        });_x000D_
    } else {_x000D_
      // Data URI_x000D_
      var csvData = 'data:application/csv;charset=utf-8,' + encodeURIComponent(csv);_x000D_
_x000D_
      $(this)_x000D_
        .attr({_x000D_
          'download': filename,_x000D_
          'href': csvData,_x000D_
          'target': '_blank'_x000D_
        });_x000D_
    }_x000D_
  }_x000D_
_x000D_
  // This must be a hyperlink_x000D_
  $(".export").on('click', function(event) {_x000D_
    // CSV_x000D_
    var args = [$('#dvData>table'), 'export.csv'];_x000D_
_x000D_
    exportTableToCSV.apply(this, args);_x000D_
_x000D_
    // If CSV, don't do event.preventDefault() or return false_x000D_
    // We actually need this to be a typical hyperlink_x000D_
  });_x000D_
});
_x000D_
a.export,_x000D_
a.export:visited {_x000D_
  display: inline-block;_x000D_
  text-decoration: none;_x000D_
  color: #000;_x000D_
  background-color: #ddd;_x000D_
  border: 1px solid #ccc;_x000D_
  padding: 8px;_x000D_
}
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<a href="#" class="export">Export Table data into Excel</a>_x000D_
<div id="dvData">_x000D_
  <table>_x000D_
    <tr>_x000D_
      <th>Column One</th>_x000D_
      <th>Column Two</th>_x000D_
      <th>Column Three</th>_x000D_
    </tr>_x000D_
    <tr>_x000D_
      <td>row1 Col1</td>_x000D_
      <td>row1 Col2</td>_x000D_
      <td>row1 Col3</td>_x000D_
    </tr>_x000D_
    <tr>_x000D_
      <td>row2 Col1</td>_x000D_
      <td>row2 Col2</td>_x000D_
      <td>row2 Col3</td>_x000D_
    </tr>_x000D_
    <tr>_x000D_
      <td>row3 Col1</td>_x000D_
      <td>row3 Col2</td>_x000D_
      <td>row3 Col3</td>_x000D_
    </tr>_x000D_
    <tr>_x000D_
      <td>row4 'Col1'</td>_x000D_
      <td>row4 'Col2'</td>_x000D_
      <td>row4 'Col3'</td>_x000D_
    </tr>_x000D_
    <tr>_x000D_
      <td>row5 &quot;Col1&quot;</td>_x000D_
      <td>row5 &quot;Col2&quot;</td>_x000D_
      <td>row5 &quot;Col3&quot;</td>_x000D_
    </tr>_x000D_
    <tr>_x000D_
      <td>row6 "Col1"</td>_x000D_
      <td>row6 "Col2"</td>_x000D_
      <td>row6 "Col3"</td>_x000D_
    </tr>_x000D_
  </table>_x000D_
</div>
_x000D_
_x000D_
_x000D_


As of 2017

Now uses HTML5 Blob and URL as the preferred method with Data URI as a fallback.

On Internet Explorer

Other answers suggest window.navigator.msSaveBlob; however, it is known to crash IE10/Window 7 and IE11/Windows 10. Whether it works using Microsoft Edge is dubious (see Microsoft Edge issue ticket #10396033).

Merely calling this in Microsoft's own Developer Tools / Console causes the browser to crash:

navigator.msSaveBlob(new Blob(["hello"], {type: "text/plain"}), "test.txt");

?Four years after my first answer, new IE versions include IE10, IE11, and Edge. They all crash on a function that Microsoft invented (slow clap).

Add navigator.msSaveBlob support at your own risk.


As of 2013

Typically this would be performed using a server-side solution, but this is my attempt at a client-side solution. Simply dumping HTML as a Data URI will not work, but is a helpful step. So:

  1. Convert the table contents into a valid CSV formatted string. (This is the easy part.)
  2. Force the browser to download it. The window.open approach would not work in Firefox, so I used <a href="{Data URI here}">.
  3. Assign a default file name using the <a> tag's download attribute, which only works in Firefox and Google Chrome. Since it is just an attribute, it degrades gracefully.

Notes

Compatibility

Browsers testing includes:

  • Firefox 20+, Win/Mac (works)
  • Google Chrome 26+, Win/Mac (works)
  • Safari 6, Mac (works, but filename is ignored)
  • IE 9+ (fails)

Content Encoding

The CSV is exported correctly, but when imported into Excel, the character ü is printed out as ä. Excel interprets the value incorrectly.

Introduce var csv = '\ufeff'; and then Excel 2013+ interprets the values correctly.

If you need compatibility with Excel 2007, add UTF-8 prefixes at each data value. See also:

Python Create unix timestamp five minutes in the future

The following is based on the answers above (plus a correction for the milliseconds) and emulates datetime.timestamp() for Python 3 before 3.3 when timezones are used.

def datetime_timestamp(datetime):
    '''
    Equivalent to datetime.timestamp() for pre-3.3
    '''
    try:
        return datetime.timestamp()
    except AttributeError:
        utc_datetime = datetime.astimezone(utc)
        return timegm(utc_datetime.timetuple()) + utc_datetime.microsecond / 1e6

To strictly answer the question as asked, you'd want:

datetime_timestamp(my_datetime) + 5 * 60

datetime_timestamp is part of simple-date. But if you were using that package you'd probably type:

SimpleDate(my_datetime).timestamp + 5 * 60

which handles many more formats / types for my_datetime.

How to add text to an existing div with jquery

_x000D_
_x000D_
$(function () {_x000D_
  $('#Add').click(function () {_x000D_
    $('<p>Text</p>').appendTo('#Content');_x000D_
  });_x000D_
}); 
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>_x000D_
 <div id="Content">_x000D_
    <button id="Add">Add<button>_x000D_
 </div>
_x000D_
_x000D_
_x000D_

Entity Framework: "Store update, insert, or delete statement affected an unexpected number of rows (0)."

One way to debug this problem in an Sql Server environment is to use the Sql Profiler included with your copy of SqlServer, or if using the Express version get a copy of Express Profiler for free off from CodePlex by the following the link below:

Express Profiler

By using Sql Profiler you can get access to whatever is being sent by EF to the DB. In my case this amounted to:

exec sp_executesql N'UPDATE [dbo].[Category]
SET [ParentID] = @0, [1048] = NULL, [1033] = @1, [MemberID] = @2, [AddedOn] = @3
WHERE ([CategoryID] = @4)
',N'@0 uniqueidentifier,@1 nvarchar(50),@2 uniqueidentifier,@3 datetime2(7),@4 uniqueidentifier',
@0='E060F2CA-433A-46A7-86BD-80CD165F5023',@1=N'I-Like-Noodles-Do-You',@2='EEDF2C83-2123-4B1C-BF8D-BE2D2FA26D09',
@3='2014-01-29 15:30:27.0435565',@4='3410FD1E-1C76-4D71-B08E-73849838F778'
go

I copy pasted this into a query window in Sql Server and executed it. Sure enough, although it ran, 0 records were affected by this query hence the error being returned by EF.

In my case the problem was caused by the CategoryID.

There was no CategoryID identified by the ID EF sent to the database hence 0 records being affected.

This was not EF's fault though but rather a buggy null coalescing "??" statement up in a View Controller that was sending nonsense down to data tier.

How to do a SUM() inside a case statement in SQL server

If you're using SQL Server 2005 or above, you can use the windowing function SUM() OVER ().

case 
when test1.TotalType = 'Average' then Test2.avgscore
when test1.TotalType = 'PercentOfTot' then (cnt/SUM(test1.qrank) over ())
else cnt
end as displayscore

But it'll be better if you show your full query to get context of what you actually need.

Execute bash script from URL

You can also do this:

wget -O - https://raw.github.com/luismartingil/commands/master/101_remote2local_wireshark.sh | bash

Joining pandas dataframes by column names

you need to make county_ID as index for the right frame:

frame_2.join ( frame_1.set_index( [ 'county_ID' ], verify_integrity=True ),
               on=[ 'countyid' ], how='left' )

for your information, in pandas left join breaks when the right frame has non unique values on the joining column. see this bug.

so you need to verify integrity before joining by , verify_integrity=True

Capture characters from standard input without waiting for enter to be pressed

The closest thing to portable is to use the ncurses library to put the terminal into "cbreak mode". The API is gigantic; the routines you'll want most are

  • initscr and endwin
  • cbreak and nocbreak
  • getch

Good luck!

View array in Visual Studio debugger?

Are you trying to view an array with memory allocated dynamically? If not, you can view an array for C++ and C# by putting it in the watch window in the debugger, with its contents visible when you expand the array on the little (+) in the watch window by a left mouse-click.

If it's a pointer to a dynamically allocated array, to view N contents of the pointer, type "pointer, N" in the watch window of the debugger. Note, N must be an integer or the debugger will give you an error saying it can't access the contents. Then, left click on the little (+) icon that appears to view the contents.

unable to dequeue a cell with identifier Cell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard

This worked for me, May help you too :

Swift 4+ :

self.tableView.register(UITableViewCell.self, forCellWithReuseIdentifier: "cell")

Swift 3 :

self.tableView.register(UITableViewCell.classForKeyedArchiver(), forCellReuseIdentifier: "Cell")

Swift 2.2 :

self.tableView.registerClass(UITableViewCell.classForKeyedArchiver(), forCellReuseIdentifier: "Cell")

We have to Set Identifier property to Table View Cell as per below image,

enter image description here

$_SERVER['HTTP_REFERER'] missing

From the documentation:

The address of the page (if any) which referred the user agent to the current page. This is set by the user agent. Not all user agents will set this, and some provide the ability to modify HTTP_REFERER as a feature. In short, it cannot really be trusted.

http://php.net/manual/en/reserved.variables.server.php

Issue with Task Scheduler launching a task

As far as I know you will need to give the domain account the proper "User Rights" such as "Log on as a Batch Job". You can check that in your Local Policies. Also, you might have a Domain GPO which is overwriting your local policies. I bet if you add this Domain Account into the local admin group of that machine, your problem will go away. A few articles for you to check:

http://social.technet.microsoft.com/Forums/en/windowsserver2008r2general/thread/9edcb63a-d133-45a0-9e8c-f1b774765531 http://social.technet.microsoft.com/Forums/lv/winservergen/thread/68019b24-78a5-4db0-a150-ada921930924 http://sqlsolace.blogspot.com/2009/08/task-scheduler-task-does-not-run-error.html?m=1 http://technet.microsoft.com/en-us/library/cc722152.aspx

How to remove a character at the end of each line in unix

This Perl code removes commas at the end of the line:

perl -pe 's/,$//' file > file.nocomma

This variation still works if there is whitespace after the comma:

perl -lpe 's/,\s*$//' file > file.nocomma

This variation edits the file in-place:

perl -i -lpe 's/,\s*$//' file

This variation edits the file in-place, and makes a backup file.bak:

perl -i.bak -lpe 's/,\s*$//' file

Using if-else in JSP

It's almost always advisable to not use scriptlets in your JSP. They're considered bad form. Instead, try using JSTL (JSP Standard Tag Library) combined with EL (Expression Language) to run the conditional logic you're trying to do. As an added benefit, JSTL also includes other important features like looping.

Instead of:

<%String user=request.getParameter("user"); %>
<%if(user == null || user.length() == 0){
    out.print("I see! You don't have a name.. well.. Hello no name");   
}
else {%>
    <%@ include file="response.jsp" %>
<% } %>

Use:

<c:choose>
    <c:when test="${empty user}">
        I see!  You don't have a name.. well.. Hello no name
    </c:when>
    <c:otherwise>
        <%@ include file="response.jsp" %>
    </c:otherwise>
</c:choose>

Also, unless you plan on using response.jsp somewhere else in your code, it might be easier to just include the html in your otherwise statement:

<c:otherwise>
    <h1>Hello</h1>
    ${user}
</c:otherwise>

Also of note. To use the core tag, you must import it as follows:

 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

You want to make it so the user will receive a message when the user submits a username. The easiest way to do this is to not print a message at all when the "user" param is null. You can do some validation to give an error message when the user submits null. This is a more standard approach to your problem. To accomplish this:

In scriptlet:

<% String user = request.getParameter("user");
   if( user != null && user.length() > 0 ) {
       <%@ include file="response.jsp" %>
   }
%>

In jstl:

<c:if test="${not empty user}">
    <%@ include file="response.jsp" %>
</c:if>

Build Maven Project Without Running Unit Tests

Run following command:

mvn clean install -DskipTests=true

Easiest way to convert a Blob into a byte array

the mySql blob class has the following function :

blob.getBytes

use it like this:

//(assuming you have a ResultSet named RS)
Blob blob = rs.getBlob("SomeDatabaseField");

int blobLength = (int) blob.length();  
byte[] blobAsBytes = blob.getBytes(1, blobLength);

//release the blob and free up memory. (since JDBC 4.0)
blob.free();

Docker: adding a file from a parent directory

Since -f caused another problem, I developed another solution.

  • Create a base image in the parent folder
  • Added the required files.
  • Used this image as a base image for the project which in a descendant folder.

The -f flag does not solved my problem because my onbuild image looks for a file in a folder and had to call like this:

-f foo/bar/Dockerfile foo/bar

instead of

-f foo/bar/Dockerfile .

Also note that this is only solution for some cases as -f flag

Implementing autocomplete

I think you can use typeahead.js. There are typescript definitions for it. so it'll be easy to use it i guess if you are using typescript for development.

How to downgrade Node version

This may be due to version incompatibility between your code and the version you have installed.

In my case I was using v8.12.0 for development (locally) and installed latest version v13.7.0 on the server.

So using nvm I switched the node version to v8.12.0 with the below command:

> nvm install 8.12.0 // to install the version I wanted

> nvm use 8.12.0  // use the installed version

NOTE: You need to install nvm on your system to use nvm.

You should try this solution before trying solutions like installing build-essentials or uninstalling the current node version because you could switch between versions easily than reverting all the installations/uninstallations that you've done.

How to create a sticky left sidebar menu using bootstrap 3?

Bootstrap 3

Here is a working left sidebar example:

http://bootply.com/90936 (similar to the Bootstrap docs)

The trick is using the affix component along with some CSS to position it:

  #sidebar.affix-top {
    position: static;
    margin-top:30px;
    width:228px;
  }

  #sidebar.affix {
    position: fixed;
    top:70px;
    width:228px;
  }

EDIT- Another example with footer and affix-bottom


Bootstrap 4

The Affix component has been removed in Bootstrap 4, so to create a sticky sidebar, you can use a 3rd party Affix plugin like this Bootstrap 4 sticky sidebar example, or use the sticky-top class is explained in this answer.

Related: Create a responsive navbar sidebar "drawer" in Bootstrap 4?

How to draw a custom UIView that is just a circle - iPhone app

Would I just override the drawRect method?

Yes:

- (void)drawRect:(CGRect)rect
{
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextAddEllipseInRect(ctx, rect);
    CGContextSetFillColor(ctx, CGColorGetComponents([[UIColor blueColor] CGColor]));
    CGContextFillPath(ctx);
}

Also, would it be okay to change the frame of that view within the class itself?

Ideally not, but you could.

Or do I need to change the frame from a different class?

I'd let the parent control that.

Convert a Map<String, String> to a POJO

I have tested both Jackson and BeanUtils and found out that BeanUtils is much faster.
In my machine(Windows8.1 , JDK1.7) I got this result.

BeanUtils t2-t1 = 286
Jackson t2-t1 = 2203


public class MainMapToPOJO {

public static final int LOOP_MAX_COUNT = 1000;

public static void main(String[] args) {
    Map<String, Object> map = new HashMap<>();
    map.put("success", true);
    map.put("data", "testString");

    runBeanUtilsPopulate(map);

    runJacksonMapper(map);
}

private static void runBeanUtilsPopulate(Map<String, Object> map) {
    long t1 = System.currentTimeMillis();
    for (int i = 0; i < LOOP_MAX_COUNT; i++) {
        try {
            TestClass bean = new TestClass();
            BeanUtils.populate(bean, map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }
    long t2 = System.currentTimeMillis();
    System.out.println("BeanUtils t2-t1 = " + String.valueOf(t2 - t1));
}

private static void runJacksonMapper(Map<String, Object> map) {
    long t1 = System.currentTimeMillis();
    for (int i = 0; i < LOOP_MAX_COUNT; i++) {
        ObjectMapper mapper = new ObjectMapper();
        TestClass testClass = mapper.convertValue(map, TestClass.class);
    }
    long t2 = System.currentTimeMillis();
    System.out.println("Jackson t2-t1 = " + String.valueOf(t2 - t1));
}}

jQuery Set Cursor Position in Text Area

I had to get this working for contenteditable elements and jQuery and tought someone might want it ready to use:

$.fn.getCaret = function(n) {
    var d = $(this)[0];
    var s, r;
    r = document.createRange();
    r.selectNodeContents(d);
    s = window.getSelection();
    console.log('position: '+s.anchorOffset+' of '+s.anchorNode.textContent.length);
    return s.anchorOffset;
};

$.fn.setCaret = function(n) {
    var d = $(this)[0];
    d.focus();
    var r = document.createRange();
    var s = window.getSelection();
    r.setStart(d.childNodes[0], n);
    r.collapse(true);
    s.removeAllRanges();
    s.addRange(r);
    console.log('position: '+s.anchorOffset+' of '+s.anchorNode.textContent.length);
    return this;
};

Usage $(selector).getCaret() returns the number offset and $(selector).setCaret(num) establishes the offeset and sets focus on element.

Also a small tip, if you run $(selector).setCaret(num) from console it will return the console.log but you won't visualize the focus since it is established at the console window.

Bests ;D

Failed to Connect to MySQL at localhost:3306 with user root

It worked for me this way:

Step1: Open System Preference > MySQL > Initialize Database.

Step2: Put password you used while installing MySQL.

Step3: Start MySQL server.

Step4: Come back to MySQL Workbench and double connect/ create a new one.

How to pass ArrayList of Objects from one to another activity using Intent in android?

You must need to also implement Parcelable interface and must add writeToParcel method to your Questions class with Parcel argument in Constructor in addition to Serializable. otherwise app will crash.

How to install a specific version of Node on Ubuntu?

Try this way. This worked me.

  1. wget nodejs.org/dist/v0.10.36/node-v0.10.36-linux-x64.tar.gz(download file)

  2. Go to the directory where the Node.js binary was downloaded to, and then run command i.e, sudo tar -C /usr/local --strip-components 1 -xzf node-v0.10.36-linux-x64.tar.gz to install the Node.js binary package in “/usr/local/”.

  3. You can check:-

    $ node -v
     v0.10.36 
    $ npm -v
     1.4.28
    

Error checking for NULL in VBScript

I will just add a blank ("") to the end of the variable and do the comparison. Something like below should work even when that variable is null. You can also trim the variable just in case of spaces.

If provider & "" <> "" Then 
    url = url & "&provider=" & provider 
End if

How to calculate date difference in JavaScript?

Assuming you have two Date objects, you can just subtract them to get the difference in milliseconds:

var difference = date2 - date1;

From there, you can use simple arithmetic to derive the other values.

Math constant PI value in C

Just define:

#define M_PI acos(-1.0)

It should give you exact PI number that math functions are working with. So if they change PI value they are working with in tangent or cosine or sine, then your program should be always up-to-dated ;)

How can I calculate the time between 2 Dates in typescript

In order to calculate the difference you have to put the + operator,

that way typescript converts the dates to numbers.

+new Date()- +new Date("2013-02-20T12:01:04.753Z")

From there you can make a formula to convert the difference to minutes or hours.

How to check identical array in most efficient way?

So, what's wrong with checking each element iteratively?

function arraysEqual(arr1, arr2) {
    if(arr1.length !== arr2.length)
        return false;
    for(var i = arr1.length; i--;) {
        if(arr1[i] !== arr2[i])
            return false;
    }

    return true;
}

How to iterate object keys using *ngFor

You have to create custom pipe.

import { Injectable, Pipe } from '@angular/core';
@Pipe({
   name: 'keyobject'
})
@Injectable()
export class Keyobject {

transform(value, args:string[]):any {
    let keys = [];
    for (let key in value) {
        keys.push({key: key, value: value[key]});
    }
    return keys;
}}

And then use it in your *ngFor

*ngFor="let item of data | keyobject"

How do I specify unique constraint for multiple columns in MySQL?

Multi column unique indexes do not work in MySQL if you have a NULL value in row as MySQL treats NULL as a unique value and at least currently has no logic to work around it in multi-column indexes. Yes the behavior is insane, because it limits a lot of legitimate applications of multi-column indexes, but it is what it is... As of yet, it is a bug that has been stamped with "will not fix" on the MySQL bug-track...

Convert bytes to int?

Assuming you're on at least 3.2, there's a built in for this:

int.from_bytes( bytes, byteorder, *, signed=False )

...

The argument bytes must either be a bytes-like object or an iterable producing bytes.

The byteorder argument determines the byte order used to represent the integer. If byteorder is "big", the most significant byte is at the beginning of the byte array. If byteorder is "little", the most significant byte is at the end of the byte array. To request the native byte order of the host system, use sys.byteorder as the byte order value.

The signed argument indicates whether two’s complement is used to represent the integer.


## Examples:
int.from_bytes(b'\x00\x01', "big")                         # 1
int.from_bytes(b'\x00\x01', "little")                      # 256

int.from_bytes(b'\x00\x10', byteorder='little')            # 4096
int.from_bytes(b'\xfc\x00', byteorder='big', signed=True)  #-1024

Get current time in seconds since the Epoch on Linux, Bash

Just to add.

Get the seconds since epoch(Jan 1 1970) for any given date(e.g Oct 21 1973).

date -d "Oct 21 1973" +%s


Convert the number of seconds back to date

date --date @120024000


The command date is pretty versatile. Another cool thing you can do with date(shamelessly copied from date --help). Show the local time for 9AM next Friday on the west coast of the US

date --date='TZ="America/Los_Angeles" 09:00 next Fri'

Better yet, take some time to read the man page http://man7.org/linux/man-pages/man1/date.1.html

SSL Error: unable to get local issuer certificate

If you are a linux user Update node to a later version by running

sudo apt update

 sudo apt install build-essential checkinstall libssl-dev

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.35.1/install.sh | bash

nvm --version

nvm ls

nvm ls-remote

nvm install [version.number]

this should solve your problem

Check if string contains only letters in javascript

try to add \S at your pattern

^[A-Za-z]\S*$

Ruby: Calling class method from instance

Similar your question, you could use:

class Truck
  def default_make
    # Do something
  end

  def initialize
    super
    self.default_make
  end
end

Object passed as parameter to another class, by value or reference?

If you need to copy object please refer to object cloning, because objects are passed by reference, which is good for performance by the way, object creation is expensive.

Here is article to refer to: Deep cloning objects

How to add a constant column in a Spark DataFrame?

In spark 2.2 there are two ways to add constant value in a column in DataFrame:

1) Using lit

2) Using typedLit.

The difference between the two is that typedLit can also handle parameterized scala types e.g. List, Seq, and Map

Sample DataFrame:

val df = spark.createDataFrame(Seq((0,"a"),(1,"b"),(2,"c"))).toDF("id", "col1")

+---+----+
| id|col1|
+---+----+
|  0|   a|
|  1|   b|
+---+----+

1) Using lit: Adding constant string value in new column named newcol:

import org.apache.spark.sql.functions.lit
val newdf = df.withColumn("newcol",lit("myval"))

Result:

+---+----+------+
| id|col1|newcol|
+---+----+------+
|  0|   a| myval|
|  1|   b| myval|
+---+----+------+

2) Using typedLit:

import org.apache.spark.sql.functions.typedLit
df.withColumn("newcol", typedLit(("sample", 10, .044)))

Result:

+---+----+-----------------+
| id|col1|           newcol|
+---+----+-----------------+
|  0|   a|[sample,10,0.044]|
|  1|   b|[sample,10,0.044]|
|  2|   c|[sample,10,0.044]|
+---+----+-----------------+

setTimeout / clearTimeout problems

Not sure if this violates some good practice coding rule but I usually come out with this one:

if(typeof __t == 'undefined')
        __t = 0;
clearTimeout(__t);
__t = setTimeout(callback, 1000);

This prevent the need to declare the timer out of the function.

EDIT: this also don't declare a new variable at each invocation, but always recycle the same.

Hope this helps.

Replace negative values in an numpy array

You are halfway there. Try:

In [4]: a[a < 0] = 0

In [5]: a
Out[5]: array([1, 2, 3, 0, 5])

View's getWidth() and getHeight() returns 0

We need to wait for view will be drawn. For this purpose use OnPreDrawListener. Kotlin example:

val preDrawListener = object : ViewTreeObserver.OnPreDrawListener {

                override fun onPreDraw(): Boolean {
                    view.viewTreeObserver.removeOnPreDrawListener(this)

                    // code which requires view size parameters

                    return true
                }
            }

            view.viewTreeObserver.addOnPreDrawListener(preDrawListener)

Combining two sorted lists in Python

def merge_sort(a,b):

    pa = 0
    pb = 0
    result = []

    while pa < len(a) and pb < len(b):
        if a[pa] <= b[pb]:
            result.append(a[pa])
            pa += 1
        else:
            result.append(b[pb])
            pb += 1

    remained = a[pa:] + b[pb:]
    result.extend(remained)


return result

Angular error: "Can't bind to 'ngModel' since it isn't a known property of 'input'"

In my case, during a lazy-loading conversion of my application I had incorrectly imported the RoutingModule instead of my ComponentModule inside app-routing.module.ts

Which MySQL datatype to use for an IP address?

You have two possibilities (for an IPv4 address) :

  • a varchar(15), if your want to store the IP address as a string
    • 192.128.0.15 for instance
  • an integer (4 bytes), if you convert the IP address to an integer
    • 3229614095 for the IP I used before


The second solution will require less space in the database, and is probably a better choice, even if it implies a bit of manipulations when storing and retrieving the data (converting it from/to a string).

About those manipulations, see the ip2long() and long2ip() functions, on the PHP-side, or inet_aton() and inet_ntoa() on the MySQL-side.

Could pandas use column as index?

You can change the index as explained already using set_index. You don't need to manually swap rows with columns, there is a transpose (data.T) method in pandas that does it for you:

> df = pd.DataFrame([['ABBOTSFORD', 427000, 448000],
                    ['ABERFELDIE', 534000, 600000]],
                    columns=['Locality', 2005, 2006])

> newdf = df.set_index('Locality').T
> newdf

Locality    ABBOTSFORD  ABERFELDIE
2005        427000      534000
2006        448000      600000

then you can fetch the dataframe column values and transform them to a list:

> newdf['ABBOTSFORD'].values.tolist()

[427000, 448000]

WPF Binding to parent DataContext

I dont know about XamGrid but that's what i'll do with a standard wpf DataGrid:

<DataGrid>
    <DataGrid.Columns>
        <DataGridTemplateColumn>
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding DataContext.MyProperty, RelativeSource={RelativeSource AncestorType=MyUserControl}}"/>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
            <DataGridTemplateColumn.CellEditingTemplate>
                <DataTemplate>
                    <TextBox Text="{Binding DataContext.MyProperty, RelativeSource={RelativeSource AncestorType=MyUserControl}}"/>
                </DataTemplate>
            </DataGridTemplateColumn.CellEditingTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

Since the TextBlock and the TextBox specified in the cell templates will be part of the visual tree, you can walk up and find whatever control you need.

How to add items into a numpy array

np.insert can also be used for the purpose

import numpy as np
a = np.array([[1, 3, 4],
              [1, 2, 3],
              [1, 2, 1]])
x = 5
index = 3 # the position for x to be inserted before
np.insert(a, index, x, axis=1)
array([[1, 3, 4, 5],
       [1, 2, 3, 5],
       [1, 2, 1, 5]])

index can also be a list/tuple

>>> index = [1, 1, 3] # equivalently (1, 1, 3)
>>> np.insert(a, index, x, axis=1)
array([[1, 5, 5, 3, 4, 5],
       [1, 5, 5, 2, 3, 5],
       [1, 5, 5, 2, 1, 5]])

or a slice

>>> index = slice(0, 3)
>>> np.insert(a, index, x, axis=1)
array([[5, 1, 5, 3, 5, 4],
       [5, 1, 5, 2, 5, 3],
       [5, 1, 5, 2, 5, 1]])

Recursive file search using PowerShell

When searching folders where you might get an error based on security (e.g. C:\Users), use the following command:

Get-ChildItem -Path V:\Myfolder -Filter CopyForbuild.bat -Recurse -ErrorAction SilentlyContinue -Force

Generator expressions vs. list comprehensions

The important point is that the list comprehension creates a new list. The generator creates a an iterable object that will "filter" the source material on-the-fly as you consume the bits.

Imagine you have a 2TB log file called "hugefile.txt", and you want the content and length for all the lines that start with the word "ENTRY".

So you try starting out by writing a list comprehension:

logfile = open("hugefile.txt","r")
entry_lines = [(line,len(line)) for line in logfile if line.startswith("ENTRY")]

This slurps up the whole file, processes each line, and stores the matching lines in your array. This array could therefore contain up to 2TB of content. That's a lot of RAM, and probably not practical for your purposes.

So instead we can use a generator to apply a "filter" to our content. No data is actually read until we start iterating over the result.

logfile = open("hugefile.txt","r")
entry_lines = ((line,len(line)) for line in logfile if line.startswith("ENTRY"))

Not even a single line has been read from our file yet. In fact, say we want to filter our result even further:

long_entries = ((line,length) for (line,length) in entry_lines if length > 80)

Still nothing has been read, but we've specified now two generators that will act on our data as we wish.

Lets write out our filtered lines to another file:

outfile = open("filtered.txt","a")
for entry,length in long_entries:
    outfile.write(entry)

Now we read the input file. As our for loop continues to request additional lines, the long_entries generator demands lines from the entry_lines generator, returning only those whose length is greater than 80 characters. And in turn, the entry_lines generator requests lines (filtered as indicated) from the logfile iterator, which in turn reads the file.

So instead of "pushing" data to your output function in the form of a fully-populated list, you're giving the output function a way to "pull" data only when its needed. This is in our case much more efficient, but not quite as flexible. Generators are one way, one pass; the data from the log file we've read gets immediately discarded, so we can't go back to a previous line. On the other hand, we don't have to worry about keeping data around once we're done with it.

SHA1 vs md5 vs SHA256: which to use for a PHP login?

I think using md5 or sha256 or any hash optimized for speed is perfectly fine and am very curious to hear any rebuttle other users might have. Here are my reasons

  1. If you allow users to use weak passwords such as God, love, war, peace then no matter the encryption you will still be allowing the user to type in the password not the hash and these passwords are often used first, thus this is NOT going to have anything to do with encryption.

  2. If your not using SSL or do not have a certificate then attackers listening to the traffic will be able to pull the password and any attempts at encrypting with javascript or the like is client side and easily cracked and overcome. Again this is NOT going to have anything to do with data encryption on server side.

  3. Brute force attacks will take advantage weak passwords and again because you allow the user to enter the data if you do not have the login limitation of 3 or even a little more then the problem will again NOT have anything to do with data encryption.

  4. If your database becomes compromised then most likely everything has been compromised including your hashing techniques no matter how cryptic you've made it. Again this could be a disgruntled employee XSS attack or sql injection or some other attack that has nothing to do with your password encryption.

I do believe you should still encrypt but the only thing I can see the encryption does is prevent people that already have or somehow gained access to the database from just reading out loud the password. If it is someone unauthorized to on the database then you have bigger issues to worry about that's why Sony got took because they thought an encrypted password protected everything including credit card numbers all it does is protect that one field that's it.

The only pure benefit I can see to complex encryptions of passwords in a database is to delay employees or other people that have access to the database from just reading out the passwords. So if it's a small project or something I wouldn't worry to much about security on the server side instead I would worry more about securing anything a client might send to the server such as sql injection, XSS attacks or the plethora of other ways you could be compromised. If someone disagrees I look forward to reading a way that a super encrypted password is a must from the client side.

The reason I wanted to try and make this clear is because too often people believe an encrypted password means they don't have to worry about it being compromised and they quit worrying about securing the website.

How can I match on an attribute that contains a certain string?

EDIT: see bobince's solution which uses contains rather than start-with, along with a trick to ensure the comparison is done at the level of a complete token (lest the 'atag' pattern be found as part of another 'tag').

"atag btag" is an odd value for the class attribute, but never the less, try:

//*[starts-with(@class,"atag")]

Using boolean values in C

If you are using C99 then you can use the _Bool type. No #includes are necessary. You do need to treat it like an integer, though, where 1 is true and 0 is false.

You can then define TRUE and FALSE.

_Bool this_is_a_Boolean_var = 1;


//or using it with true and false
#define TRUE 1
#define FALSE 0
_Bool var = TRUE;

HttpClient does not exist in .net 4.0: what can I do?

Agreeing with TrueWill's comment on a separate answer, the best way I've seen to use system.web.http on a .NET 4 targeted project under current Visual Studio is Install-Package Microsoft.AspNet.WebApi.Client -Version 4.0.30506

Conditionally formatting if multiple cells are blank (no numerics throughout spreadsheet )

If you place the dollar sign before the letter, you will affect only the column, not the row. If you want to have it affect only a row, place the dollar before the number.

You may want to use =isblank() rather than =""

I'm also confused by your comment "no values throughout spreadsheet - just text" - text is a value.

One more hint - excel has a habit of rewriting rules - I don't know how many rules I've written only to discover that excel has changed the values in the "apply to" or formula entry fields.

If you could post an example, I'll revise the answer. Conditional formatting is very finicky.

Selected tab's color in Bottom Navigation View

If you want to change icons' and texts' colors programmatically:

ColorStateList iconsColorStates = new ColorStateList(
            new int[][]{
                    new int[]{-android.R.attr.state_checked},
                    new int[]{android.R.attr.state_checked}
            },
            new int[]{
                    Color.parseColor("#123456"),
                    Color.parseColor("#654321")
            });

    ColorStateList textColorStates = new ColorStateList(
            new int[][]{
                    new int[]{-android.R.attr.state_checked},
                    new int[]{android.R.attr.state_checked}
            },
            new int[]{
                    Color.parseColor("#123456"),
                    Color.parseColor("#654321")
            });

    navigation.setItemIconTintList(iconsColorStates);
    navigation.setItemTextColor(textColorStates);

Display tooltip on Label's hover?

You could use the title attribute in html :)

<label title="This is the full title of the label">This is the...</label>

When you keep the mouse over for a brief moment, it should pop up with a box, containing the full title.

If you want more control, I suggest you look into the Tipsy Plugin for jQuery - It can be found at http://onehackoranother.com/projects/jquery/tipsy/ and is fairly simple to get started with.

How to get source code of a Windows executable?

I would (and have) used IDA Pro to decompile executables. It creates semi-complete code, you can decompile to assembly or C.

If you have a copy of the debug symbols around, load those into IDA before decompiling and it will be able to name many of the functions, parameters, etc.

Calling functions in a DLL from C++

You can either go the LoadLibrary/GetProcAddress route (as Harper mentioned in his answer, here's link to the run-time dynamic linking MSDN sample again) or you can link your console application to the .lib produced from the DLL project and include the hea.h file with the declaration of your function (as described in the load-time dynamic linking MSDN sample)

In both cases, you need to make sure your DLL exports the function you want to call properly. The easiest way to do it is by using __declspec(dllexport) on the function declaration (as shown in the creating a simple dynamic-link library MSDN sample), though you can do it also through the corresponding .def file in your DLL project.

For more information on the topic of DLLs, you should browse through the MSDN About Dynamic-Link Libraries topic.

What is the size of a boolean variable in Java?

Size of the boolean in java is virtual machine dependent. but Any Java object is aligned to an 8 bytes granularity. A Boolean has 8 bytes of header, plus 1 byte of payload, for a total of 9 bytes of information. The JVM then rounds it up to the next multiple of 8. so the one instance of java.lang.Boolean takes up 16 bytes of memory.

Docker-Compose persistent data MySQL

first, you need to delete all old mysql data using

docker-compose down -v

after that add two lines in your docker-compose.yml

volumes:
  - mysql-data:/var/lib/mysql

and

volumes:
  mysql-data:

your final docker-compose.yml will looks like

version: '3.1'

services:
  php:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - 80:80
    volumes:
      - ./src:/var/www/html/
  db:
    image: mysql
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example
    volumes:
      - mysql-data:/var/lib/mysql

  adminer:
    image: adminer
    restart: always
    ports:
      - 8080:8080
volumes:
  mysql-data:

after that use this command

docker-compose up -d

now your data will persistent and will not be deleted even after using this command

docker-compose down

extra:- but if you want to delete all data then you will use

docker-compose down -v

Pass in an enum as a method parameter

public string CreateFile(string id, string name, string description, SupportedPermissions supportedPermissions)
{
    file = new File
    {  
       Name = name,
        Id = id,
        Description = description,
        SupportedPermissions = supportedPermissions
    };

    return file.Id;
}

How to echo JSON in PHP

if you want to encode or decode an array from or to JSON you can use these functions

$myJSONString = json_encode($myArray);
$myArray = json_decode($myString);

json_encode will result in a JSON string, built from an (multi-dimensional) array. json_decode will result in an Array, built from a well formed JSON string

with json_decode you can take the results from the API and only output what you want, for example:

echo $myArray['payload']['ign'];

Meaning of "[: too many arguments" error from if [] (square brackets)

Just bumped into this post, by getting the same error, trying to test if two variables are both empty (or non-empty). That turns out to be a compound comparison - 7.3. Other Comparison Operators - Advanced Bash-Scripting Guide; and I thought I should note the following:

  • I used -e thinking it means "empty" at first; but that means "file exists" - use -z for testing empty variable (string)
  • String variables need to be quoted
  • For compound logical AND comparison, either:
    • use two tests and && them: [ ... ] && [ ... ]
    • or use the -a operator in a single test: [ ... -a ... ]

Here is a working command (searching through all txt files in a directory, and dumping those that grep finds contain both of two words):

find /usr/share/doc -name '*.txt' | while read file; do \
  a1=$(grep -H "description" $file); \
  a2=$(grep -H "changes" $file); \
  [ ! -z "$a1" -a ! -z "$a2"  ] && echo -e "$a1 \n $a2" ; \
done

Edit 12 Aug 2013: related problem note:

Note that when checking string equality with classic test (single square bracket [), you MUST have a space between the "is equal" operator, which in this case is a single "equals" = sign (although two equals' signs == seem to be accepted as equality operator too). Thus, this fails (silently):

$ if [ "1"=="" ] ; then echo A; else echo B; fi 
A
$ if [ "1"="" ] ; then echo A; else echo B; fi 
A
$ if [ "1"="" ] && [ "1"="1" ] ; then echo A; else echo B; fi 
A
$ if [ "1"=="" ] && [ "1"=="1" ] ; then echo A; else echo B; fi 
A

... but add the space - and all looks good:

$ if [ "1" = "" ] ; then echo A; else echo B; fi 
B
$ if [ "1" == "" ] ; then echo A; else echo B; fi 
B
$ if [ "1" = "" -a "1" = "1" ] ; then echo A; else echo B; fi 
B
$ if [ "1" == "" -a "1" == "1" ] ; then echo A; else echo B; fi 
B

is inaccessible due to its protection level

myClub.distance = Console.ReadLine();

should be

myClub.mydistance = Console.ReadLine(); 

use your public properties that you have defined for others as well instead of the protected field members.

Better way to sort array in descending order

Depending on the sort order, you can do this :

    int[] array = new int[] { 3, 1, 4, 5, 2 };
    Array.Sort<int>(array,
                    new Comparison<int>(
                            (i1, i2) => i2.CompareTo(i1)
                    ));

... or this :

    int[] array = new int[] { 3, 1, 4, 5, 2 };
    Array.Sort<int>(array,
                    new Comparison<int>(
                            (i1, i2) => i1.CompareTo(i2)
                    ));

i1 and i2 are just reversed.

What's the difference between git reset --mixed, --soft, and --hard?

Three types of regret

A lot of the existing answers don't seem to answer the actual question. They are about what the commands do, not about what you (the user) want — the use case. But that is what the OP asked about!

It might be more helpful to couch the description in terms of what it is precisely that you regret at the time you give a git reset command. Let's say we have this:

A - B - C - D <- HEAD

Here are some possible regrets and what to do about them:

1. I regret that B, C, and D are not one commit.

git reset --soft A. I can now immediately commit and presto, all the changes since A are one commit.

2. I regret that B, C, and D are not ten commits.

git reset --mixed A. The commits are gone and the index is back at A, but the work area still looks as it did after D. So now I can add-and-commit in a whole different grouping.

3. I regret that B, C, and D happened on this branch; I wish I had branched after A and they had happened on that other branch.

Make a new branch otherbranch, and then git reset --hard A. The current branch now ends at A, with otherbranch stemming from it.

(Of course you could also use a hard reset because you wish B, C, and D had never happened at all.)

How to validate a url in Python? (Malformed or not)

Nowadays, I use the following, based on the Padam's answer:

$ python --version
Python 3.6.5

And this is how it looks:

from urllib.parse import urlparse

def is_url(url):
  try:
    result = urlparse(url)
    return all([result.scheme, result.netloc])
  except ValueError:
    return False

Just use is_url("http://www.asdf.com").

Hope it helps!

Insert Unicode character into JavaScript

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

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

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

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

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

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

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

How to disable horizontal scrolling of UIScrollView?

Try This:

CGSize scrollSize = CGSizeMake([UIScreen mainScreen].bounds.size.width, scrollHeight);
[scrollView setContentSize: scrollSize];

Given final block not properly padded

I met this issue due to operation system, simple to different platform about JRE implementation.

new SecureRandom(key.getBytes())

will get the same value in Windows, while it's different in Linux. So in Linux need to be changed to

SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
secureRandom.setSeed(key.getBytes());
kgen.init(128, secureRandom);

"SHA1PRNG" is the algorithm used, you can refer here for more info about algorithms.

Convert a string date into datetime in Oracle

You can use a cast to char to see the date results

_x000D_
_x000D_
 select to_char(to_date('17-MAR-17 06.04.54','dd-MON-yy hh24:mi:ss'), 'mm/dd/yyyy hh24:mi:ss') from dual;
_x000D_
_x000D_
_x000D_

CSS display: inline vs inline-block

Inline elements:

  1. respect left & right margins and padding, but not top & bottom
  2. cannot have a width and height set
  3. allow other elements to sit to their left and right.
  4. see very important side notes on this here.

Block elements:

  1. respect all of those
  2. force a line break after the block element
  3. acquires full-width if width not defined

Inline-block elements:

  1. allow other elements to sit to their left and right
  2. respect top & bottom margins and padding
  3. respect height and width

From W3Schools:

  • An inline element has no line break before or after it, and it tolerates HTML elements next to it.

  • A block element has some whitespace above and below it and does not tolerate any HTML elements next to it.

  • An inline-block element is placed as an inline element (on the same line as adjacent content), but it behaves as a block element.

When you visualize this, it looks like this:

CSS block vs inline vs inline-block

The image is taken from this page, which also talks some more about this subject.

UITableview: How to Disable Selection for Some Rows but Not Others

For Xcode 6.3:

 cell.selectionStyle = UITableViewCellSelectionStyle.None;

delete map[key] in go?

From Effective Go:

To delete a map entry, use the delete built-in function, whose arguments are the map and the key to be deleted. It's safe to do this even if the key is already absent from the map.

delete(timeZone, "PDT")  // Now on Standard Time

Flask example with POST

Before actually answering your question:

Parameters in a URL (e.g. key=listOfUsers/user1) are GET parameters and you shouldn't be using them for POST requests. A quick explanation of the difference between GET and POST can be found here.

In your case, to make use of REST principles, you should probably have:

http://ip:5000/users
http://ip:5000/users/<user_id>

Then, on each URL, you can define the behaviour of different HTTP methods (GET, POST, PUT, DELETE). For example, on /users/<user_id>, you want the following:

GET /users/<user_id> - return the information for <user_id>
POST /users/<user_id> - modify/update the information for <user_id> by providing the data
PUT - I will omit this for now as it is similar enough to `POST` at this level of depth
DELETE /users/<user_id> - delete user with ID <user_id> 

So, in your example, you want do a POST to /users/user_1 with the POST data being "John". Then the XPath expression or whatever other way you want to access your data should be hidden from the user and not tightly couple to the URL. This way, if you decide to change the way you store and access data, instead of all your URL's changing, you will simply have to change the code on the server-side.

Now, the answer to your question: Below is a basic semi-pseudocode of how you can achieve what I mentioned above:

from flask import Flask
from flask import request

app = Flask(__name__)

@app.route('/users/<user_id>', methods = ['GET', 'POST', 'DELETE'])
def user(user_id):
    if request.method == 'GET':
        """return the information for <user_id>"""
        .
        .
        .
    if request.method == 'POST':
        """modify/update the information for <user_id>"""
        # you can use <user_id>, which is a str but could
        # changed to be int or whatever you want, along
        # with your lxml knowledge to make the required
        # changes
        data = request.form # a multidict containing POST data
        .
        .
        .
    if request.method == 'DELETE':
        """delete user with ID <user_id>"""
        .
        .
        .
    else:
        # POST Error 405 Method Not Allowed
        .
        .
        .

There are a lot of other things to consider like the POST request content-type but I think what I've said so far should be a reasonable starting point. I know I haven't directly answered the exact question you were asking but I hope this helps you. I will make some edits/additions later as well.

Thanks and I hope this is helpful. Please do let me know if I have gotten something wrong.

including parameters in OPENQUERY

From the MSDN page:

OPENQUERY does not accept variables for its arguments

Fundamentally, this means you cannot issue a dynamic query. To achieve what your sample is attempting, try this:

SELECT * FROM 
   OPENQUERY([NameOfLinkedSERVER], 'SELECT * FROM TABLENAME') T1 
   INNER JOIN 
   MYSQLSERVER.DATABASE.DBO.TABLENAME T2 ON T1.PK = T2.PK 
where
   T1.field1 = @someParameter

Clearly if your TABLENAME table contains a large amount of data, this will go across the network too and performance might be poor. On the other hand, for a small amount of data, this works well and avoids the dynamic sql construction overheads (sql injection, escaping quotes) that an exec approach might require.

Insert, on duplicate update in PostgreSQL?

Warning: this is not safe if executed from multiple sessions at the same time (see caveats below).


Another clever way to do an "UPSERT" in postgresql is to do two sequential UPDATE/INSERT statements that are each designed to succeed or have no effect.

UPDATE table SET field='C', field2='Z' WHERE id=3;
INSERT INTO table (id, field, field2)
       SELECT 3, 'C', 'Z'
       WHERE NOT EXISTS (SELECT 1 FROM table WHERE id=3);

The UPDATE will succeed if a row with "id=3" already exists, otherwise it has no effect.

The INSERT will succeed only if row with "id=3" does not already exist.

You can combine these two into a single string and run them both with a single SQL statement execute from your application. Running them together in a single transaction is highly recommended.

This works very well when run in isolation or on a locked table, but is subject to race conditions that mean it might still fail with duplicate key error if a row is inserted concurrently, or might terminate with no row inserted when a row is deleted concurrently. A SERIALIZABLE transaction on PostgreSQL 9.1 or higher will handle it reliably at the cost of a very high serialization failure rate, meaning you'll have to retry a lot. See why is upsert so complicated, which discusses this case in more detail.

This approach is also subject to lost updates in read committed isolation unless the application checks the affected row counts and verifies that either the insert or the update affected a row.

mongodb/mongoose findMany - find all documents with IDs listed in array

Use this format of querying

let arr = _categories.map(ele => new mongoose.Types.ObjectId(ele.id));

Item.find({ vendorId: mongoose.Types.ObjectId(_vendorId) , status:'Active'})
  .where('category')
  .in(arr)
  .exec();

'Static readonly' vs. 'const'

There is a minor difference between const and static readonly fields in C#.Net

const must be initialized with value at compile time.

const is by default static and needs to be initialized with constant value, which can not be modified later on. It can not be used with all datatypes. For ex- DateTime. It can not be used with DateTime datatype.

public const DateTime dt = DateTime.Today;  //throws compilation error
public const string Name = string.Empty;    //throws compilation error
public static readonly string Name = string.Empty; //No error, legal

readonly can be declared as static, but not necessary. No need to initialize at the time of declaration. Its value can be assigned or changed using constructor once. So there is a possibility to change value of readonly field once (does not matter, if it is static or not), which is not possible with const.

jquery json to string?

Edit: You should use the json2.js library from Douglas Crockford instead of implementing the code below. It provides some extra features and better/older browser support.

Grab the json2.js file from: https://github.com/douglascrockford/JSON-js


// implement JSON.stringify serialization
JSON.stringify = JSON.stringify || function (obj) {
    var t = typeof (obj);
    if (t != "object" || obj === null) {
        // simple data type
        if (t == "string") obj = '"'+obj+'"';
        return String(obj);
    }
    else {
        // recurse array or object
        var n, v, json = [], arr = (obj && obj.constructor == Array);
        for (n in obj) {
            v = obj[n]; t = typeof(v);
            if (t == "string") v = '"'+v+'"';
            else if (t == "object" && v !== null) v = JSON.stringify(v);
            json.push((arr ? "" : '"' + n + '":') + String(v));
        }
        return (arr ? "[" : "{") + String(json) + (arr ? "]" : "}");
    }
};

var tmp = {one: 1, two: "2"};
JSON.stringify(tmp); // '{"one":1,"two":"2"}'

Code from: http://www.sitepoint.com/blogs/2009/08/19/javascript-json-serialization/

MySQL - Cannot add or update a child row: a foreign key constraint fails

Even though this is pretty old, just chiming in to say that what is useful in @Sidupac's answer is the FOREIGN_KEY_CHECKS=0.

This answer is not an option when you are using something that manages the database schema for you (JPA in my case) but the problem may be that there are "orphaned" entries in your table (referencing a foreign key that might not exist).

This can often happen when you convert a MySQL table from MyISAM to InnoDB since referential integrity isn't really a thing with the former.

This project references NuGet package(s) that are missing on this computer

One solution would be to remove from the .csproj file the following:

<Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$(SolutionDir)\.nuget\NuGet.targets')" />

This project references NuGet package(s) that are missing on this computer. Enable NuGet Package Restore to download them. For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.

How to calculate a Mod b in Casio fx-991ES calculator

There is a switch a^b/c

If you want to calculate

491 mod 12

then enter 491 press a^b/c then enter 12. Then you will get 40, 11, 12. Here the middle one will be the answer that is 11.

Similarly if you want to calculate 41 mod 12 then find 41 a^b/c 12. You will get 3, 5, 12 and the answer is 5 (the middle one). The mod is always the middle value.

Using sessions & session variables in a PHP Login Script

Firstly, the PHP documentation has some excellent information on sessions.

Secondly, you will need some way to store the credentials for each user of your website (e.g. a database). It is a good idea not to store passwords as human-readable, unencrypted plain text. When storing passwords, you should use PHP's crypt() hashing function. This means that if any credentials are compromised, the passwords are not readily available.

Most log-in systems will hash/crypt the password a user enters then compare the result to the hash in the storage system (e.g. database) for the corresponding username. If the hash of the entered password matches the stored hash, the user has entered the correct password.

You can use session variables to store information about the current state of the user - i.e. are they logged in or not, and if they are you can also store their unique user ID or any other information you need readily available.

To start a PHP session, you need to call session_start(). Similarly, to destroy a session and its data, you need to call session_destroy() (for example, when the user logs out):

// Begin the session
session_start();

// Use session variables
$_SESSION['userid'] = $userid;

// E.g. find if the user is logged in
if($_SESSION['userid']) {
    // Logged in
}
else {
    // Not logged in
}

// Destroy the session
if($log_out)
    session_destroy();

I would also recommend that you take a look at this. There's some good, easy to follow information on creating a simple log-in system there.

How do I raise the same Exception with a custom message in Python?

The current answer did not work good for me, if the exception is not re-caught the appended message is not shown.

But doing like below both keeps the trace and shows the appended message regardless if the exception is re-caught or not.

try:
  raise ValueError("Original message")
except ValueError as err:
  t, v, tb = sys.exc_info()
  raise t, ValueError(err.message + " Appended Info"), tb

( I used Python 2.7, have not tried it in Python 3 )

What does this symbol mean in IntelliJ? (red circle on bottom-left corner of file name, with 'J' in it)

This situation happens when the IDE looks for src folder, and it cannot find it in the path. Select the project root (F4 in windows) > Go to Modules on Side Tab > Select Sources > Select appropriate folder with source files in it> Click on the blue sources folder icon (for adding sources) > Click on Green Test Sources folder ( to add Unit test folders).

Where can I get a list of Ansible pre-defined variables?

Argh! From the FAQ:

How do I see a list of all of the ansible_ variables? Ansible by default gathers “facts” about the machines under management, and these facts can be accessed in Playbooks and in templates. To see a list of all of the facts that are available about a machine, you can run the “setup” module as an ad-hoc action:

ansible -m setup hostname

This will print out a dictionary of all of the facts that are available for that particular host.

Here is the output for my vagrant virtual machine called scdev:

scdev | success >> {
    "ansible_facts": {                                                                                                 
        "ansible_all_ipv4_addresses": [                                                                                
            "10.0.2.15",                                                                                               
            "192.168.10.10"                                                                                            
        ],                                                                                                             
        "ansible_all_ipv6_addresses": [                                                                                
            "fe80::a00:27ff:fe12:9698",                                                                                
            "fe80::a00:27ff:fe74:1330"                                                                                 
        ],                                                                                                             
        "ansible_architecture": "i386",                                                                                
        "ansible_bios_date": "12/01/2006",                                                                             
        "ansible_bios_version": "VirtualBox",                                                                          
        "ansible_cmdline": {                                                                                           
            "BOOT_IMAGE": "/vmlinuz-3.2.0-23-generic-pae",                                                             
            "quiet": true,                                                                                             
            "ro": true,                                                                                                
            "root": "/dev/mapper/precise32-root"                                                                       
        },                                                                                                             
        "ansible_date_time": {                                                                                         
            "date": "2013-09-17",                                                                                      
            "day": "17",                                                                                               
            "epoch": "1379378304",                                                                                     
            "hour": "00",                                                                                              
            "iso8601": "2013-09-17T00:38:24Z",                                                                         
            "iso8601_micro": "2013-09-17T00:38:24.425092Z",                                                            
            "minute": "38",                                                                                            
            "month": "09",                                                                                             
            "second": "24",                                                                                            
            "time": "00:38:24",                                                                                        
            "tz": "UTC",                                                                                               
            "year": "2013"                                                                                             
        },                                                                                                             
        "ansible_default_ipv4": {                                                                                      
            "address": "10.0.2.15",                                                                                    
            "alias": "eth0",                                                                                           
            "gateway": "10.0.2.2",                                                                                     
            "interface": "eth0",                                                                                       
            "macaddress": "08:00:27:12:96:98",                                                                         
            "mtu": 1500,                                                                                               
            "netmask": "255.255.255.0",                                                                                
            "network": "10.0.2.0",                                                                                     
            "type": "ether"                                                                                            
        },                                                                                                             
        "ansible_default_ipv6": {},                                                                                    
        "ansible_devices": {                                                                                           
            "sda": {                                                                                                   
                "holders": [],                                                                                         
                "host": "SATA controller: Intel Corporation 82801HM/HEM (ICH8M/ICH8M-E) SATA Controller [AHCI mode] (rev 02)",                                                                                                                
                "model": "VBOX HARDDISK",                                                                              
                "partitions": {                                                                                        
                    "sda1": {                                                                                          
                        "sectors": "497664",                                                                           
                        "sectorsize": 512,                                                                             
                        "size": "243.00 MB",                                                                           
                        "start": "2048"                                                                                
                    },                                                                                                 
                    "sda2": {                                                                                          
                        "sectors": "2",                                                                                
                        "sectorsize": 512,                                                                             
                        "size": "1.00 KB",                                                                             
                        "start": "501758"                                                                              
                    },                                                                                                 
                },                                                                                                     
                "removable": "0",                                                                                      
                "rotational": "1",                                                                                     
                "scheduler_mode": "cfq",                                                                               
                "sectors": "167772160",                                                                                
                "sectorsize": "512",                                                                                   
                "size": "80.00 GB",                                                                                    
                "support_discard": "0",                                                                                
                "vendor": "ATA"                                                                                        
            },                                                                                                         
            "sr0": {                                                                                                   
                "holders": [],                                                                                         
                "host": "IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)",                           
                "model": "CD-ROM",                                                                                     
                "partitions": {},                                                                                      
                "removable": "1",                                                                                      
                "rotational": "1",                                                                                     
                "scheduler_mode": "cfq",                                                                               
                "sectors": "2097151",                                                                                  
                "sectorsize": "512",                                                                                   
                "size": "1024.00 MB",                                                                                  
                "support_discard": "0",                                                                                
                "vendor": "VBOX"                                                                                       
            },                                                                                                         
            "sr1": {                                                                                                   
                "holders": [],                                                                                         
                "host": "IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)",                           
                "model": "CD-ROM",                                                                                     
                "partitions": {},                                                                                      
                "removable": "1",                                                                                      
                "rotational": "1",                                                                                     
                "scheduler_mode": "cfq",                                                                               
                "sectors": "2097151",                                                                                  
                "sectorsize": "512",                                                                                   
                "size": "1024.00 MB",                                                                                  
                "support_discard": "0",                                                                                
                "vendor": "VBOX"                                                                                       
            }                                                                                                          
        },                                                                                                             
        "ansible_distribution": "Ubuntu",                                                                              
        "ansible_distribution_release": "precise",                                                                     
        "ansible_distribution_version": "12.04",                                                                       
        "ansible_domain": "",                                                                                          
        "ansible_eth0": {                                                                                              
            "active": true,                                                                                            
            "device": "eth0",                                                                                          
            "ipv4": {                                                                                                  
                "address": "10.0.2.15",                                                                                
                "netmask": "255.255.255.0",                                                                            
                "network": "10.0.2.0"                                                                                  
            },                                                                                                         
            "ipv6": [                                                                                                  
                {                                                                                                      
                    "address": "fe80::a00:27ff:fe12:9698",                                                             
                    "prefix": "64",                                                                                    
                    "scope": "link"                                                                                    
                }                                                                                                      
            ],                                                                                                         
            "macaddress": "08:00:27:12:96:98",                                                                         
            "module": "e1000",                                                                                         
            "mtu": 1500,                                                                                               
            "type": "ether"                                                                                            
        },                                                                                                             
        "ansible_eth1": {                                                                                              
            "active": true,                                                                                            
            "device": "eth1",                                                                                          
            "ipv4": {                                                                                                  
                "address": "192.168.10.10",                                                                            
                "netmask": "255.255.255.0",                                                                            
                "network": "192.168.10.0"                                                                              
            },                                                                                                         
            "ipv6": [                                                                                                  
                {                                                                                                      
                    "address": "fe80::a00:27ff:fe74:1330",                                                             
                    "prefix": "64",                                                                                    
                    "scope": "link"                                                                                    
                }                                                                                                      
            ],                                                                                                         
            "macaddress": "08:00:27:74:13:30",                                                                         
            "module": "e1000",                                                                                         
            "mtu": 1500,                                                                                               
            "type": "ether"                                                                                            
        },                                                                                                             
        "ansible_form_factor": "Other",                                                                                
        "ansible_fqdn": "scdev",                                                                                       
        "ansible_hostname": "scdev",                                                                                   
        "ansible_interfaces": [                                                                                        
            "lo",                                                                                                      
            "eth1",                                                                                                    
            "eth0"                                                                                                     
        ],                                                                                                             
        "ansible_kernel": "3.2.0-23-generic-pae",                                                                      
        "ansible_lo": {                                                                                                
            "active": true,                                                                                            
            "device": "lo",                                                                                            
            "ipv4": {                                                                                                  
                "address": "127.0.0.1",                                                                                
                "netmask": "255.0.0.0",                                                                                
                "network": "127.0.0.0"                                                                                 
            },                                                                                                         
            "ipv6": [                                                                                                  
                {                                                                                                      
                    "address": "::1",                                                                                  
                    "prefix": "128",                                                                                   
                    "scope": "host"                                                                                    
                }                                                                                                      
            ],                                                                                                         
            "mtu": 16436,                                                                                              
            "type": "loopback"                                                                                         
        },                                                                                                             
        "ansible_lsb": {                                                                                               
            "codename": "precise",                                                                                     
            "description": "Ubuntu 12.04 LTS",                                                                         
            "id": "Ubuntu",                                                                                            
            "major_release": "12",                                                                                     
            "release": "12.04"                                                                                         
        },                                                                                                             
        "ansible_machine": "i686",                                                                                     
        "ansible_memfree_mb": 23,                                                                                      
        "ansible_memtotal_mb": 369,                                                                                    
        "ansible_mounts": [                                                                                            
            {                                                                                                          
                "device": "/dev/mapper/precise32-root",                                                                
                "fstype": "ext4",                                                                                      
                "mount": "/",                                                                                          
                "options": "rw,errors=remount-ro",                                                                     
                "size_available": 77685088256,                                                                         
                "size_total": 84696281088                                                                              
            },                                                                                                         
            {                                                                                                          
                "device": "/dev/sda1",                                                                                 
                "fstype": "ext2",                                                                                      
                "mount": "/boot",                                                                                      
                "options": "rw",                                                                                       
                "size_available": 201044992,                                                                           
                "size_total": 238787584                                                                                
            },                                                                                                         
            {                                                                                                          
                "device": "/vagrant",                                                                                  
                "fstype": "vboxsf",                                                                                    
                "mount": "/vagrant",                                                                                   
                "options": "uid=1000,gid=1000,rw",                                                                     
                "size_available": 42013151232,                                                                         
                "size_total": 484145360896                                                                             
            }                                                                                                          
        ],                                                                                                             
        "ansible_os_family": "Debian",                                                                                 
        "ansible_pkg_mgr": "apt",                                                                                      
        "ansible_processor": [                                                                                         
            "Pentium(R) Dual-Core  CPU      E5300  @ 2.60GHz"                                                          
        ],                                                                                                             
        "ansible_processor_cores": "NA",                                                                               
        "ansible_processor_count": 1,                                                                                  
        "ansible_product_name": "VirtualBox",                                                                          
        "ansible_product_serial": "NA",                                                                                
        "ansible_product_uuid": "NA",                                                                                  
        "ansible_product_version": "1.2",                                                                              
        "ansible_python_version": "2.7.3", 
        "ansible_selinux": false, 
        "ansible_swapfree_mb": 766, 
        "ansible_swaptotal_mb": 767, 
        "ansible_system": "Linux", 
        "ansible_system_vendor": "innotek GmbH", 
        "ansible_user_id": "neves", 
        "ansible_userspace_architecture": "i386", 
        "ansible_userspace_bits": "32", 
        "ansible_virtualization_role": "guest", 
        "ansible_virtualization_type": "virtualbox"
    }, 
    "changed": false
}

The current documentation now has a complete chapter listing all Variables and Facts

iPhone - Grand Central Dispatch main thread

Swift 3, 4 & 5

Running code on the main thread

DispatchQueue.main.async {
    // Your code here
}

How to get the <html> tag HTML with JavaScript / jQuery?

In jQuery:

var html_string = $('html').outerHTML()

In plain Javascript:

var html_string = document.documentElement.outerHTML

What is Func, how and when is it used

Think of it as a placeholder. It can be quite useful when you have code that follows a certain pattern but need not be tied to any particular functionality.

For example, consider the Enumerable.Select extension method.

  • The pattern is: for every item in a sequence, select some value from that item (e.g., a property) and create a new sequence consisting of these values.
  • The placeholder is: some selector function that actually gets the values for the sequence described above.

This method takes a Func<T, TResult> instead of any concrete function. This allows it to be used in any context where the above pattern applies.

So for example, say I have a List<Person> and I want just the name of every person in the list. I can do this:

var names = people.Select(p => p.Name);

Or say I want the age of every person:

var ages = people.Select(p => p.Age);

Right away, you can see how I was able to leverage the same code representing a pattern (with Select) with two different functions (p => p.Name and p => p.Age).

The alternative would be to write a different version of Select every time you wanted to scan a sequence for a different kind of value. So to achieve the same effect as above, I would need:

// Presumably, the code inside these two methods would look almost identical;
// the only difference would be the part that actually selects a value
// based on a Person.
var names = GetPersonNames(people);
var ages = GetPersonAges(people);

With a delegate acting as placeholder, I free myself from having to write out the same pattern over and over in cases like this.

Getting list of files in documents folder

Apple states about NSSearchPathForDirectoriesInDomains(_:_:_:):

You should consider using the FileManager methods urls(for:in:) and url(for:in:appropriateFor:create:) which return URLs, which are the preferred format.


With Swift 5, FileManager has a method called contentsOfDirectory(at:includingPropertiesForKeys:options:). contentsOfDirectory(at:includingPropertiesForKeys:options:) has the following declaration:

Performs a shallow search of the specified directory and returns URLs for the contained items.

func contentsOfDirectory(at url: URL, includingPropertiesForKeys keys: [URLResourceKey]?, options mask: FileManager.DirectoryEnumerationOptions = []) throws -> [URL]

Therefore, in order to retrieve the urls of the files contained in documents directory, you can use the following code snippet that uses FileManager's urls(for:in:) and contentsOfDirectory(at:includingPropertiesForKeys:options:) methods:

guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }

do {
    let directoryContents = try FileManager.default.contentsOfDirectory(at: documentsDirectory, includingPropertiesForKeys: nil, options: [])

    // Print the urls of the files contained in the documents directory
    print(directoryContents)
} catch {
    print("Could not search for urls of files in documents directory: \(error)")
}

As an example, the UIViewController implementation below shows how to save a file from app bundle to documents directory and how to get the urls of the files saved in documents directory:

import UIKit

class ViewController: UIViewController {

    @IBAction func copyFile(_ sender: UIButton) {
        // Get file url
        guard let fileUrl = Bundle.main.url(forResource: "Movie", withExtension: "mov") else { return }

        // Create a destination url in document directory for file
        guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }
        let documentDirectoryFileUrl = documentsDirectory.appendingPathComponent("Movie.mov")

        // Copy file to document directory
        if !FileManager.default.fileExists(atPath: documentDirectoryFileUrl.path) {
            do {
                try FileManager.default.copyItem(at: fileUrl, to: documentDirectoryFileUrl)
                print("Copy item succeeded")
            } catch {
                print("Could not copy file: \(error)")
            }
        }
    }

    @IBAction func displayUrls(_ sender: UIButton) {
        guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }

        do {
            let directoryContents = try FileManager.default.contentsOfDirectory(at: documentsDirectory, includingPropertiesForKeys: nil, options: [])

            // Print the urls of the files contained in the documents directory
            print(directoryContents) // may print [] or [file:///private/var/mobile/Containers/Data/Application/.../Documents/Movie.mov]
        } catch {
            print("Could not search for urls of files in documents directory: \(error)")
        }
    }

}

C++ preprocessor __VA_ARGS__ number of arguments

Boost Preprocessor actually has this as of Boost 1.49, as BOOST_PP_VARIADIC_SIZE(...). It works up to size 64.

Under the hood, it's basically the same as Kornel Kisielewicz's answer.

Unable to read repository at http://download.eclipse.org/releases/indigo

I spent whole my day figuring out this and found the following. And it works great now.

This is basically an issue with your gateway or proxy, If you are under proxy network, Please go to the network settings and set the proxy server settings(server, port , user name and password). If you are under direct gateway network, your firewall may be blocking the http get request from your eclipse.

How can I delete a newline if it is the last character in a file?

Assuming Unix file type and you only want the last newline this works.

sed -e '${/^$/d}'

It will not work on multiple newlines...

* Works only if the last line is a blank line.

How to disable Google Chrome auto update?

The simplest method on Windows 10 with recent versions of Chrome as of early 2020. No registry hack, Powershell or GPO required :

  1. Open the Computer Management app with elevated rights: type it in the taskbar search, then click Run as administrator on the menu
  2. Go to Service and Applications -> Services
  3. Find Google Update Service (gupdate) and Google Update Service (gupdatem)
  4. For both services, right-click, select Properties and set Startup type: to Disabled.

Tested and working on Google Chrome v 80, Win 10 / 1909 / 18363.592, as of March 2020.

How do you import classes in JSP?

In case you use JSTL and you wish to import a class in a tag page instead of a jsp page, the syntax is a little bit different. Replace the word 'page' with the word 'tag'.

Instead of Sandman's correct answer

<%@page import="path.to.your.class"%>

use

<%@tag import="path.to.your.class"%>

Curl setting Content-Type incorrectly

I think you want to specify

-H "Content-Type:text/xml"

with a colon, not an equals.

How to update two tables in one statement in SQL Server 2005?

The short answer to that is no. While you can enter multiple tables in the from clause of an update statement, you can only specify a single table after the update keyword. Even if you do write a "updatable" view (which is simply a view that follows certain restrictions), updates like this will fail. Here are the relevant clips from the MSDN documentation (emphasis is mine).

UPDATE (Transact-SQL)

The view referenced by table_or_view_name must be updatable and reference exactly one base table in the FROM clause of the view. For more information about updatable views, see CREATE VIEW (Transact-SQL).

CREATE VIEW (Transact-SQL)

You can modify the data of an underlying base table through a view, as long as the following conditions are true:

  • Any modifications, including UPDATE, INSERT, and DELETE statements, must reference columns from only one base table.
  • The columns being modified in the view must directly reference the underlying data in the table columns. The columns cannot be derived in any other way, such as through the following:
    • An aggregate function: AVG, COUNT, SUM, MIN, MAX, GROUPING, STDEV, STDEVP, VAR, and VARP.
    • A computation. The column cannot be computed from an expression that uses other columns. Columns that are formed by using the set operators UNION, UNION ALL, CROSSJOIN, EXCEPT, and INTERSECT amount to a computation and are also not updatable.
  • The columns being modified are not affected by GROUP BY, HAVING, or DISTINCT clauses.
  • TOP is not used anywhere in the select_statement of the view together with the WITH CHECK OPTION clause.

In all honesty, though, you should consider using two different SQL statements within a transaction as per LBushkin's example.

UPDATE: My original assertion that you could update multiple tables in an updatable view was wrong. On SQL Server 2005 & 2012, it will generate the following error. I have corrected my answer to reflect this.

Msg 4405, Level 16, State 1, Line 1

View or function 'updatable_view' is not updatable because the modification affects multiple base tables.

Get specific line from text file using just shell script

Assuming line is a variable which holds your required line number, if you can use head and tail, then it is quite simple:

head -n $line file | tail -1

If not, this should work:

x=0
want=5
cat lines | while read line; do
  x=$(( x+1 ))
  if [ $x -eq "$want" ]; then
    echo $line
    break
  fi
done

Hiding elements in responsive layout?

Bootstrap 4.x answer

hidden-* classes are removed from Bootstrap 4 beta onward.

If you want to show on medium and up use the d-* classes, e.g.:

<div class="d-none d-md-block">This will show in medium and up</div>

If you want to show only in small and below use this:

<div class="d-block d-md-none"> This will show only in below medium form factors</div>

Screen size and class chart

| Screen Size        | Class                          |
|--------------------|--------------------------------|
| Hidden on all      | .d-none                        |
| Hidden only on xs  | .d-none .d-sm-block            |
| Hidden only on sm  | .d-sm-none .d-md-block         |
| Hidden only on md  | .d-md-none .d-lg-block         |
| Hidden only on lg  | .d-lg-none .d-xl-block         |
| Hidden only on xl  | .d-xl-none                     |
| Visible on all     | .d-block                       |
| Visible only on xs | .d-block .d-sm-none            |
| Visible only on sm | .d-none .d-sm-block .d-md-none |
| Visible only on md | .d-none .d-md-block .d-lg-none |
| Visible only on lg | .d-none .d-lg-block .d-xl-none |
| Visible only on xl | .d-none .d-xl-block            |

Rather than using explicit .visible-* classes, you make an element visible by simply not hiding it at that screen size. You can combine one .d-*-none class with one .d-*-block class to show an element only on a given interval of screen sizes (e.g. .d-none.d-md-block.d-xl-none shows the element only on medium and large devices).

Documentation

Java: How To Call Non Static Method From Main Method?

A static method means that you don't need to invoke the method on an instance. A non-static (instance) method requires that you invoke it on an instance. So think about it: if I have a method changeThisItemToTheColorBlue() and I try to run it from the main method, what instance would it change? It doesn't know. You can run an instance method on an instance, like someItem.changeThisItemToTheColorBlue().

More information at http://en.wikipedia.org/wiki/Method_(computer_programming)#Static_methods.

std::enable_if to conditionally compile a member function

SFINAE only works if substitution in argument deduction of a template argument makes the construct ill-formed. There is no such substitution.

I thought of that too and tried to use std::is_same< T, int >::value and ! std::is_same< T, int >::value which gives the same result.

That's because when the class template is instantiated (which happens when you create an object of type Y<int> among other cases), it instantiates all its member declarations (not necessarily their definitions/bodies!). Among them are also its member templates. Note that T is known then, and !std::is_same< T, int >::value yields false. So it will create a class Y<int> which contains

class Y<int> {
    public:
        /* instantiated from
        template < typename = typename std::enable_if< 
          std::is_same< T, int >::value >::type >
        T foo() {
            return 10;
        }
        */

        template < typename = typename std::enable_if< true >::type >
        int foo();

        /* instantiated from

        template < typename = typename std::enable_if< 
          ! std::is_same< T, int >::value >::type >
        T foo() {
            return 10;
        }
        */

        template < typename = typename std::enable_if< false >::type >
        int foo();
};

The std::enable_if<false>::type accesses a non-existing type, so that declaration is ill-formed. And thus your program is invalid.

You need to make the member templates' enable_if depend on a parameter of the member template itself. Then the declarations are valid, because the whole type is still dependent. When you try to call one of them, argument deduction for their template arguments happen and SFINAE happens as expected. See this question and the corresponding answer on how to do that.

iOS for VirtualBox

Additional to the above - the QEMU website has good documentation about setting up an ARM based emulator: http://qemu.weilnetz.de/qemu-doc.html#ARM-System-emulator

Adding values to Arraylist

Two last variants are the same, int is wrapped to Integer automatically where you need an Object. If you not write any class in <> it will be Object by default. So there is no difference, but it will be better to understanding if you write Object.

Declare variable in table valued function

There are two flavors of table valued functions. One that is just a select statement and one that can have more rows than just a select statement.

This can not have a variable:

create function Func() returns table
as
return
select 10 as ColName

You have to do like this instead:

create function Func()
returns @T table(ColName int)
as
begin
  declare @Var int
  set @Var = 10
  insert into @T(ColName) values (@Var)
  return
end

Writing a dict to txt file and reading it back?

I created my own functions which work really nicely:

def writeDict(dict, filename, sep):
    with open(filename, "a") as f:
        for i in dict.keys():            
            f.write(i + " " + sep.join([str(x) for x in dict[i]]) + "\n")

It will store the keyname first, followed by all values. Note that in this case my dict contains integers so that's why it converts to int. This is most likely the part you need to change for your situation.

def readDict(filename, sep):
    with open(filename, "r") as f:
        dict = {}
        for line in f:
            values = line.split(sep)
            dict[values[0]] = {int(x) for x in values[1:len(values)]}
        return(dict)

Using BigDecimal to work with currencies

Here are a few hints:

  1. Use BigDecimal for computations if you need the precision that it offers (Money values often need this).
  2. Use the NumberFormat class for display. This class will take care of localization issues for amounts in different currencies. However, it will take in only primitives; therefore, if you can accept the small change in accuracy due to transformation to a double, you could use this class.
  3. When using the NumberFormat class, use the scale() method on the BigDecimal instance to set the precision and the rounding method.

PS: In case you were wondering, BigDecimal is always better than double, when you have to represent money values in Java.

PPS:

Creating BigDecimal instances

This is fairly simple since BigDecimal provides constructors to take in primitive values, and String objects. You could use those, preferably the one taking the String object. For example,

BigDecimal modelVal = new BigDecimal("24.455");
BigDecimal displayVal = modelVal.setScale(2, RoundingMode.HALF_EVEN);

Displaying BigDecimal instances

You could use the setMinimumFractionDigits and setMaximumFractionDigits method calls to restrict the amount of data being displayed.

NumberFormat usdCostFormat = NumberFormat.getCurrencyInstance(Locale.US);
usdCostFormat.setMinimumFractionDigits( 1 );
usdCostFormat.setMaximumFractionDigits( 2 );
System.out.println( usdCostFormat.format(displayVal.doubleValue()) );

Loop over html table and get checked checkboxes (JQuery)

use .filter(':has(:checkbox:checked)' ie:

$('#mytable tr').filter(':has(:checkbox:checked)').each(function() {
 $('#out').append(this.id);
});

How to fix a locale setting warning from Perl

sudo nano /etc/locale.gen

Uncomment the locales you want to use (e.g. en_US.UTF-8 UTF-8):

Then run:

sudo /usr/sbin/locale-gen

Source: Configuring Locales

Test a string for a substring

if "ABCD" in "xxxxABCDyyyy":
    # whatever

Append an object to a list in R in amortized constant time, O(1)?

If you pass in the list variable as a quoted string, you can reach it from within the function like:

push <- function(l, x) {
  assign(l, append(eval(as.name(l)), x), envir=parent.frame())
}

so:

> a <- list(1,2)
> a
[[1]]
[1] 1

[[2]]
[1] 2

> push("a", 3)
> a
[[1]]
[1] 1

[[2]]
[1] 2

[[3]]
[1] 3

> 

or for extra credit:

> v <- vector()
> push("v", 1)
> v
[1] 1
> push("v", 2)
> v
[1] 1 2
> 

C multi-line macro: do/while(0) vs scope block

Andrey Tarasevich provides the following explanation:

  1. On Google Groups
  2. On bytes.com

[Minor changes to formatting made. Parenthetical annotations added in square brackets []].

The whole idea of using 'do/while' version is to make a macro which will expand into a regular statement, not into a compound statement. This is done in order to make the use of function-style macros uniform with the use of ordinary functions in all contexts.

Consider the following code sketch:

if (<condition>)
  foo(a);
else
  bar(a);

where foo and bar are ordinary functions. Now imagine that you'd like to replace function foo with a macro of the above nature [named CALL_FUNCS]:

if (<condition>)
  CALL_FUNCS(a);
else
  bar(a);

Now, if your macro is defined in accordance with the second approach (just { and }) the code will no longer compile, because the 'true' branch of if is now represented by a compound statement. And when you put a ; after this compound statement, you finished the whole if statement, thus orphaning the else branch (hence the compilation error).

One way to correct this problem is to remember not to put ; after macro "invocations":

if (<condition>)
  CALL_FUNCS(a)
else
  bar(a);

This will compile and work as expected, but this is not uniform. The more elegant solution is to make sure that macro expand into a regular statement, not into a compound one. One way to achieve that is to define the macro as follows:

#define CALL_FUNCS(x) \
do { \
  func1(x); \
  func2(x); \
  func3(x); \
} while (0)

Now this code:

if (<condition>)
  CALL_FUNCS(a);
else
  bar(a);

will compile without any problems.

However, note the small but important difference between my definition of CALL_FUNCS and the first version in your message. I didn't put a ; after } while (0). Putting a ; at the end of that definition would immediately defeat the entire point of using 'do/while' and make that macro pretty much equivalent to the compound-statement version.

I don't know why the author of the code you quoted in your original message put this ; after while (0). In this form both variants are equivalent. The whole idea behind using 'do/while' version is not to include this final ; into the macro (for the reasons that I explained above).

Command to collapse all sections of code?

In Visual Studio 2017, It seems that this behavior is turned off by default. It can be enabled under Tools > Options > Text Editors > C# > Advanced > Outlining > "Collapse #regions when collapsing to definitions"

Angular directive how to add an attribute to the element?

You can try this:

<div ng-app="app">
    <div ng-controller="AppCtrl">
        <a my-dir ng-repeat="user in users" ng-click="fxn()">{{user.name}}</a>
    </div>
</div>

<script>
var app = angular.module('app', []);

function AppCtrl($scope) {
        $scope.users = [{ name: 'John', id: 1 }, { name: 'anonymous' }];
        $scope.fxn = function () {
            alert('It works');
        };
    }

app.directive("myDir", function ($compile) {
    return {
        scope: {ngClick: '='}
    };
});
</script>

Cannot get Kerberos service ticket: KrbException: Server not found in Kerberos database (7)

This exception comes from the client, right? Please perform a forward and reverse DNS lookup of the server hostname. Your server has incorrect DNS entries. They are absolutely crucial for Kerberos. The proper place is your DNS server, in your case: domain controller. Figure out the IP address of your DNS server and contact your admin. The other option is a missing SPN, please check that too.

How to implement history.back() in angular.js

Angular 4:

/* typescript */
import { Location } from '@angular/common';
// ...

@Component({
  // ...
})
export class MyComponent {

  constructor(private location: Location) { } 

  goBack() {
    this.location.back(); // go back to previous location
  }
}

How to move certain commits to be based on another branch in git?

I believe it's:

git checkout master
git checkout -b good_quickfix2
git cherry-pick quickfix2^
git cherry-pick quickfix2

How to approach a "Got minus one from a read call" error when connecting to an Amazon RDS Oracle instance

I got this error message from using an oracle database in a docker despite the fact i had publish port to host option "-p 1521:1521". I was using jdbc url that was using ip address 127.0.0.1, i changed it to the host machine real ip address and everything worked then.

error: RPC failed; curl transfer closed with outstanding read data remaining

Usually it happen because of one of the below reasone:

  1. Slow Internet.
  • Switching to LAN cable with stable network connection helps in many cases. Avoid doing any parallel network intensive task while you are fetching.
  1. Small TCP/IP connection time out on Server side from where you are trying to fetch.
  • Not much you can do about. All you can do is request your System Admin or CI/CD Team responsible to increaseTCP/IP Timeout and wait.
  1. Heavy Load on Server.
  • Due to heavy server load during work hour downloading a large file can fail constantly.Leave your machine after starting download for night.
  1. Small HTTPS Buffer on Client machine.
  • Increasing buffer size for post and request might help but not guaranteed

git config --global http.postBuffer 524288000

git config --global http.maxRequestBuffer 524288000

git config --global core.compression 0

Multiple HttpPost method in Web API controller

You can use this approach :

public class VTRoutingController : ApiController
{
    [HttpPost("Route")]
    public MyResult Route(MyRequestTemplate routingRequestTemplate)
    {
        return null;
    }

    [HttpPost("TSPRoute")]
    public MyResult TSPRoute(MyRequestTemplate routingRequestTemplate)
    {
        return null;
    }
}

Changing file extension in Python

import os
thisFile = "mysequence.fasta"
base = os.path.splitext(thisFile)[0]
os.rename(thisFile, base + ".aln")

Where thisFile = the absolute path of the file you are changing

How do I remove an item from a stl vector with a certain value?

If you have an unsorted vector, then you can simply swap with the last vector element then resize().

With an ordered container, you'll be best off with ?std::vector::erase(). Note that there is a std::remove() defined in <algorithm>, but that doesn't actually do the erasing. (Read the documentation carefully).

How to remove an item from an array in AngularJS scope?

You'll have to find the index of the person in your persons array, then use the array's splice method:

$scope.persons.splice( $scope.persons.indexOf(person), 1 );

The most sophisticated way for creating comma-separated Strings from a Collection/Array/List?

What makes the code ugly is the special-handling for the first case. Most of the lines in this small snippet are devoted, not to doing the code's routine job, but to handling that special case. And that's what alternatives like gimel's solve, by moving the special handling outside the loop. There is one special case (well, you could see both start and end as special cases - but only one of them needs to be treated specially), so handling it inside the loop is unnecessarily complicated.

Finding non-numeric rows in dataframe in pandas?

I'm thinking something like, just give an idea, to convert the column to string, and work with string is easier. however this does not work with strings containing numbers, like bad123. and ~ is taking the complement of selection.

df['a'] = df['a'].astype(str)
df[~df['a'].str.contains('0|1|2|3|4|5|6|7|8|9')]
df['a'] = df['a'].astype(object)

and using '|'.join([str(i) for i in range(10)]) to generate '0|1|...|8|9'

or using np.isreal() function, just like the most voted answer

df[~df['a'].apply(lambda x: np.isreal(x))]

How can I convert radians to degrees with Python?

-fix- because you want to change from radians to degrees, it is actually rad=deg * math.pi /180 and not deg*180/math.pi

import math
x=1                # in deg
x = x*math.pi/180  # convert to rad
y = math.cos(x)    # calculate in rad

print y

in 1 line it can be like this

y=math.cos(1*math.pi/180)

Should I use scipy.pi, numpy.pi, or math.pi?

One thing to note is that not all libraries will use the same meaning for pi, of course, so it never hurts to know what you're using. For example, the symbolic math library Sympy's representation of pi is not the same as math and numpy:

import math
import numpy
import scipy
import sympy

print(math.pi == numpy.pi)
> True
print(math.pi == scipy.pi)
> True
print(math.pi == sympy.pi)
> False

Make Vim show ALL white spaces as a character

As of patch 7.4.710 you can now set a character to show in place of space using listchars!

:set listchars+=space:?

So, to show ALL white space characters as a character you can do the following:

:set listchars=eol:¬,tab:>·,trail:~,extends:>,precedes:<,space:?
:set list

Discussion on mailing list: https://groups.google.com/forum/?fromgroups#!topic/vim_dev/pjmW6wOZW_Q

When should I use the Visitor Design Pattern?

As Konrad Rudolph already pointed out, it is suitable for cases where we need double dispatch

Here is an example to show a situation where we need double dispatch & how visitor helps us in doing so.

Example :

Lets say I have 3 types of mobile devices - iPhone, Android, Windows Mobile.

All these three devices have a Bluetooth radio installed in them.

Lets assume that the blue tooth radio can be from 2 separate OEMs – Intel & Broadcom.

Just to make the example relevant for our discussion, lets also assume that the APIs exposes by Intel radio are different from the ones exposed by Broadcom radio.

This is how my classes look –

enter image description here enter image description here

Now, I would like to introduce an operation – Switching On the Bluetooth on mobile device.

Its function signature should like something like this –

 void SwitchOnBlueTooth(IMobileDevice mobileDevice, IBlueToothRadio blueToothRadio)

So depending upon Right type of device and Depending upon right type of Bluetooth radio, it can be switched on by calling appropriate steps or algorithm.

In principal, it becomes a 3 x 2 matrix, where-in I’m trying to vector the right operation depending upon the right type of objects involved.

A polymorphic behaviour depending upon the type of both the arguments.

enter image description here

Now, Visitor pattern can be applied to this problem. Inspiration comes from the Wikipedia page stating – “In essence, the visitor allows one to add new virtual functions to a family of classes without modifying the classes themselves; instead, one creates a visitor class that implements all of the appropriate specializations of the virtual function. The visitor takes the instance reference as input, and implements the goal through double dispatch.”

Double dispatch is a necessity here due to the 3x2 matrix

Here is how the set up will look like - enter image description here

I wrote the example to answer another question, the code & its explanation is mentioned here.

How can I get the height and width of an uiimage?

let heightInPoints = image.size.height
let heightInPixels = heightInPoints * image.scale

let widthInPoints = image.size.width
let widthInPixels = widthInPoints * image.scale

Call to a member function on a non-object

you can use 'use' in function like bellow example

function page_properties($objPortal) use($objPage){    
    $objPage->set_page_title($myrow['title']);
}

How can I open a .tex file?

A .tex file should be a LaTeX source file.

If this is the case, that file contains the source code for a LaTeX document. You can open it with any text editor (notepad, notepad++ should work) and you can view the source code. But if you want to view the final formatted document, you need to install a LaTeX distribution and compile the .tex file.

Of course, any program can write any file with any extension, so if this is not a LaTeX document, then we can't know what software you need to install to open it. Maybe if you upload the file somewhere and link it in your question we can see the file and provide more help to you.


Yes, this is the source code of a LaTeX document. If you were able to paste it here, then you are already viewing it. If you want to view the compiled document, you need to install a LaTeX distribution. You can try to install MiKTeX then you can use that to compile the document to a .pdf file.

You can also check out this question and answer for how to do it: How to compile a LaTeX document?

Also, there's an online LaTeX editor and you can paste your code in there to preview the document: https://www.overleaf.com/.

numpy max vs amax vs maximum

For completeness, in Numpy there are four maximum related functions. They fall into two different categories:

  • np.amax/np.max, np.nanmax: for single array order statistics
  • and np.maximum, np.fmax: for element-wise comparison of two arrays

I. For single array order statistics

NaNs propagator np.amax/np.max and its NaN ignorant counterpart np.nanmax.

  • np.max is just an alias of np.amax, so they are considered as one function.

    >>> np.max.__name__
    'amax'
    >>> np.max is np.amax
    True
    
  • np.max propagates NaNs while np.nanmax ignores NaNs.

    >>> np.max([np.nan, 3.14, -1])
    nan
    >>> np.nanmax([np.nan, 3.14, -1])
    3.14
    

II. For element-wise comparison of two arrays

NaNs propagator np.maximum and its NaNs ignorant counterpart np.fmax.

  • Both functions require two arrays as the first two positional args to compare with.

    # x1 and x2 must be the same shape or can be broadcast
    np.maximum(x1, x2, /, ...);
    np.fmax(x1, x2, /, ...)
    
  • np.maximum propagates NaNs while np.fmax ignores NaNs.

    >>> np.maximum([np.nan, 3.14, 0], [np.NINF, np.nan, 2.72])
    array([ nan,  nan, 2.72])
    >>> np.fmax([np.nan, 3.14, 0], [np.NINF, np.nan, 2.72])
    array([-inf, 3.14, 2.72])
    
  • The element-wise functions are np.ufunc(Universal Function), which means they have some special properties that normal Numpy function don't have.

    >>> type(np.maximum)
    <class 'numpy.ufunc'>
    >>> type(np.fmax)
    <class 'numpy.ufunc'>
    >>> #---------------#
    >>> type(np.max)
    <class 'function'>
    >>> type(np.nanmax)
    <class 'function'>
    

And finally, the same rules apply to the four minimum related functions:

  • np.amin/np.min, np.nanmin;
  • and np.minimum, np.fmin.

In Rails, how do you render JSON using a view?

This is potentially a better option and faster than ERB: https://github.com/dewski/json_builder

What is the "-->" operator in C/C++?

One book I read (I don't remember correctly which book) stated: Compilers try to parse expressions to the biggest token by using the left right rule.

In this case, the expression:

x-->0

Parses to biggest tokens:

token 1: x
token 2: --
token 3: >
token 4: 0
conclude: x-- > 0

The same rule applies to this expression:

a-----b

After parse:

token 1: a
token 2: --
token 3: --
token 4: -
token 5: b
conclude: (a--)-- - b

I hope this helps to understand the complicated expression ^^

Xcode - How to fix 'NSUnknownKeyException', reason: … this class is not key value coding-compliant for the key X" error?

This has already happened to me twice.

The solution was remaking the whole storyboard since I copied it from another one (because it was almost the same)

Matplotlib make tick labels font size smaller

The following worked for me:

ax2.xaxis.set_tick_params(labelsize=7)
ax2.yaxis.set_tick_params(labelsize=7)

The advantage of the above is you do not need to provide the array of labels and works with any data on the axes.

TypeError: 'int' object is not subscriptable

Just to be clear, all the answers so far are correct, but the reasoning behind them is not explained very well.

The sumall variable is not yet a string. Parentheticals will not convert to a string (e.g. summ = (int(birthday[0])+int(birthday[1])) still returns an integer. It looks like you most likely intended to type str((int(sumall[0])+int(sumall[1]))), but forgot to. The reason the str() function fixes everything is because it converts anything in it compatible to a string.

How to set Linux environment variables with Ansible

For persistently setting environment variables, you can use one of the existing roles over at Ansible Galaxy. I recommend weareinteractive.environment.

Using ansible-galaxy:

$ ansible-galaxy install weareinteractive.environment

Using requirements.yml:

- src: franklinkim.environment

Then in your playbook:

- hosts: all
  sudo: yes
  roles:
    - role: franklinkim.environment
      environment_config:
        NODE_ENV: staging
        DATABASE_NAME: staging

How can I account for period (AM/PM) using strftime?

format = '%Y-%m-%d %H:%M %p'

The format is using %H instead of %I. Since %H is the "24-hour" format, it's likely just discarding the %p information. It works just fine if you change the %H to %I.

Spring: How to inject a value to static field?

First of all, public static non-final fields are evil. Spring does not allow injecting to such fields for a reason.

Your workaround is valid, you don't even need getter/setter, private field is enough. On the other hand try this:

@Value("${my.name}")
public void setPrivateName(String privateName) {
    Sample.name = privateName;
}  

(works with @Autowired/@Resource). But to give you some constructive advice: Create a second class with private field and getter instead of public static field.

Get current working directory in a Qt application

I'm running Qt 5.5 under Windows and the default constructor of QDir appears to pick up the current working directory, not the application directory.

I'm not sure if the getenv PWD will work cross-platform and I think it is set to the current working directory when the shell launched the application and doesn't include any working directory changes done by the app itself (which might be why the OP is seeing this behavior).

So I thought I'd add some other ways that should give you the current working directory (not the application's binary location):

// using where a relative filename will end up
QFileInfo fi("temp");
cout << fi.absolutePath() << endl;

// explicitly using the relative name of the current working directory
QDir dir(".");
cout << dir.absolutePath() << endl;

Bootstrap 3 dropdown select

If you want to achieve this just keep you dropdown button and style it like the select box. The code is here and below.

.btn {
    cursor: default;
    background-color: #FFF;
    border-radius: 4px;
    text-align: left;
}

.caret {
    position: absolute;
    right: 16px;
    top: 16px;
}

.btn-default:hover, .btn-default:focus, .btn-default:active, .btn-default.active, .open .dropdown-toggle.btn-default {
    background-color: #FFF;    
}

.btn-group.open .dropdown-toggle {
    box-shadow: 0 1px 1px rgba(0, 0, 0, 0.075) inset, 0 0 8px rgba(102, 175, 233, 0.6)
}

.btn-group {width: 100%}
.dropdown-menu {width: 100%;}

To make the button work like a select box, all you need to add is this tiny javascript code:

$('.dropdown-menu a').on('click', function(){    
    $('.dropdown-toggle').html($(this).html() + '<span class="caret"></span>');    
})

If you have multiple custom dropdowns like this you can use this javascript code:

$('.dropdown-menu a').on('click', function(){    
    $(this).parent().parent().prev().html($(this).html() + '<span class="caret"></span>');    
})

Excel 2013 horizontal secondary axis

You should follow the guidelines on Add a secondary horizontal axis:

Add a secondary horizontal axis

To complete this procedure, you must have a chart that displays a secondary vertical axis. To add a secondary vertical axis, see Add a secondary vertical axis.

  1. Click a chart that displays a secondary vertical axis. This displays the Chart Tools, adding the Design, Layout, and Format tabs.

  2. On the Layout tab, in the Axes group, click Axes.

    enter image description here

  3. Click Secondary Horizontal Axis, and then click the display option that you want.

enter image description here


Add a secondary vertical axis

You can plot data on a secondary vertical axis one data series at a time. To plot more than one data series on the secondary vertical axis, repeat this procedure for each data series that you want to display on the secondary vertical axis.

  1. In a chart, click the data series that you want to plot on a secondary vertical axis, or do the following to select the data series from a list of chart elements:

    • Click the chart.

      This displays the Chart Tools, adding the Design, Layout, and Format tabs.

    • On the Format tab, in the Current Selection group, click the arrow in the Chart Elements box, and then click the data series that you want to plot along a secondary vertical axis.

      enter image description here

  2. On the Format tab, in the Current Selection group, click Format Selection. The Format Data Series dialog box is displayed.

    Note: If a different dialog box is displayed, repeat step 1 and make sure that you select a data series in the chart.

  3. On the Series Options tab, under Plot Series On, click Secondary Axis and then click Close.

    A secondary vertical axis is displayed in the chart.

  4. To change the display of the secondary vertical axis, do the following:

    • On the Layout tab, in the Axes group, click Axes.

    • Click Secondary Vertical Axis, and then click the display option that you want.

  5. To change the axis options of the secondary vertical axis, do the following:

    • Right-click the secondary vertical axis, and then click Format Axis.

    • Under Axis Options, select the options that you want to use.

How to put a component inside another component in Angular2?

You don't put a component in directives

You register it in @NgModule declarations:

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ App , MyChildComponent ],
  bootstrap: [ App ]
})

and then You just put it in the Parent's Template HTML as : <my-child></my-child>

That's it.

lvalue required as left operand of assignment

Change = to == i.e if (strcmp("hello", "hello") == 0)

You want to compare the result of strcmp() to 0. So you need ==. Assigning it to 0 won't work because rvalues cannot be assigned to.

Reloading/refreshing Kendo Grid

In a recent project, I had to update the Kendo UI Grid based on some calls, that were happening on some dropdown selects. Here is what I ended up using:

$.ajax({
        url: '/api/....',
        data: { myIDSArray: javascriptArrayOfIDs },
        traditional: true,
        success: function(result) {
            searchResults = result;
        }
    }).done(function() {
        var dataSource = new kendo.data.DataSource({ data: searchResults });
        var grid = $('#myKendoGrid').data("kendoGrid");
        dataSource.read();
        grid.setDataSource(dataSource);
    });

Hopefully this will save you some time.

Returning an empty array

Both foo() and bar() may generate warnings in some IDEs. For example, IntelliJ IDEA will generate a Allocation of zero-length array warning.

An alternative approach is to use Apache Commons Lang 3 ArrayUtils.toArray() function with empty arguments:

public File[] bazz() {
    return ArrayUtils.toArray();
}

This approach is both performance and IDE friendly, yet requires a 3rd party dependency. However, if you already have commons-lang3 in your classpath, you could even use statically-defined empty arrays for primitive types:

public String[] bazz() {
    return ArrayUtils.EMPTY_STRING_ARRAY;
}

How to change icon on Google map marker

You have to add the targeted map :

var markers = [
            {
            "title": 'This is title',
            "lat": '-37.801578',
            "lng": '145.060508',
            "map":  map,
            "icon": 'http://google-maps-icons.googlecode.com/files/sailboat-tourism.png',
            "description": 'Vikash Rathee. <strong> This is test Description</strong> <br/><a href="http://www.pricingindia.in/pincode.aspx">Pin Code by 

City</a>'
            }
];

AngularJS: how to enable $locationProvider.html5Mode with deeplinking

This problem was due to the use of AngularJS 1.1.5 (which was unstable, and obviously had some bug or different implementation of the routing than it was in 1.0.7)

turning it back to 1.0.7 solved the problem instantly.

have tried the 1.2.0rc1 version, but have not finished testing as I had to rewrite some of the router functionality since they took it out of the core.

anyway, this problem is fixed when using AngularJS vs 1.0.7.

Reading specific XML elements from XML file

You could use linq to xml.

    var xmlStr = File.ReadAllText("fileName.xml");


    var str = XElement.Parse(xmlStr);

    var result = str.Elements("word").
Where(x => x.Element("category").Value.Equals("verb")).ToList();

    Console.WriteLine(result);

How do I find all of the symlinks in a directory tree?

This is the best thing I've found so far - shows you the symlinks in the current directory, recursively, but without following them, displayed with full paths and other information:

find ./ -type l -print0 | xargs -0 ls -plah

outputs looks about like this:

lrwxrwxrwx 1 apache develop 99 Dec  5 12:49 ./dir/dir2/symlink1 -> /dir3/symlinkTarget
lrwxrwxrwx 1 apache develop 81 Jan 10 14:02 ./dir1/dir2/dir4/symlink2 -> /dir5/whatever/symlink2Target
etc...

Easiest way to mask characters in HTML(5) text input

A little late, but a useful plugin that will actually use a mask to give a bit more restriction on user input.

<div class="col-sm-3 col-md-6 col-lg-4">
  <div class="form-group">
     <label for="addPhone">Phone Number *</label>
      <input id="addPhone" name="addPhone" type="text" class="form-control 
       required" data-mask="(999) 999-9999"placeholder>
    <span class="help-block">(999) 999-9999</span>
  </div>
</div>

 <!-- Input Mask -->
 <script src="js/plugins/jasny/jasny-bootstrap.min.js"></script>

enter image description here

More info on the plugin https://www.jasny.net/bootstrap/2.3.1/javascript.html#inputmask

How to get the public IP address of a user in C#

That code gets you the IP address of your server not the address of the client who is accessing your website. Use the HttpContext.Current.Request.UserHostAddress property to the client's IP address.

403 Access Denied on Tomcat 8 Manager App without prompting for user/password

I follwed the same tutorial but after some months I strangely got the error "403 Access Denied" while tryed to use Manager App. In this case I was using the ipaddress:8080 in the address bar and Tomcat Manager App didin't prompting for user/password. In case of localhost:8080 the error was "401", the dialogbox asking for username and password was displayed but the user not recognized.

I tried all the previous suggestions / solutions without lucky. The only way I found is been to repeat again the entire tutorial overwriting also the files. When finished, I found again the old deployed project into the webapps directory. Now Apache Tomcat/8.5.16 Manager App are working again. I do not know what happened I didn't understand also because I'm a newbie in Tomcat user

How to use CSS to surround a number with a circle?

If it's 20 and lower, you can just use the unicode characters ? ? ... ?

http://www.alanwood.net/unicode/enclosed_alphanumerics.html

How do I auto-submit an upload form when a file is selected?

You can put this code to make your code work with just single line of code

<input type="file" onchange="javascript:this.form.submit()">

This will upload the file on server without clicking on submit button

Format y axis as percent

This is a few months late, but I have created PR#6251 with matplotlib to add a new PercentFormatter class. With this class you just need one line to reformat your axis (two if you count the import of matplotlib.ticker):

import ...
import matplotlib.ticker as mtick

ax = df['myvar'].plot(kind='bar')
ax.yaxis.set_major_formatter(mtick.PercentFormatter())

PercentFormatter() accepts three arguments, xmax, decimals, symbol. xmax allows you to set the value that corresponds to 100% on the axis. This is nice if you have data from 0.0 to 1.0 and you want to display it from 0% to 100%. Just do PercentFormatter(1.0).

The other two parameters allow you to set the number of digits after the decimal point and the symbol. They default to None and '%', respectively. decimals=None will automatically set the number of decimal points based on how much of the axes you are showing.

Update

PercentFormatter was introduced into Matplotlib proper in version 2.1.0.

What is an MDF file?

SQL Server databases use two files - an MDF file, known as the primary database file, which contains the schema and data, and a LDF file, which contains the logs. See wikipedia. A database may also use secondary database file, which normally uses a .ndf extension.

As John S. indicates, these file extensions are purely convention - you can use whatever you want, although I can't think of a good reason to do that.

More info on MSDN here and in Beginning SQL Server 2005 Administation (Google Books) here.

Change color of Label in C#

I am going to assume this is a WinForms questions (which it feels like, based on it being a "program" rather than a website/app). In which case you can simple do the following to change the text colour of a label:

myLabel.ForeColor = System.Drawing.Color.Red;

Or any other colour of your choice. If you want to be more specific you can use an RGB value like so:

myLabel.ForeColor = Color.FromArgb(0, 0, 0);//(R, G, B) (0, 0, 0 = black)

Having different colours for different users can be done a number of ways. For example, you could allow each user to specify their own RGB value colours, store these somewhere and then load them when the user "connects".

An alternative method could be to just use 2 colours - 1 for the current user (running the app) and another colour for everyone else. This would help the user quickly identify their own messages above others.

A third approach could be to generate the colour randomly - however you will likely get conflicting values that do not show well against your background, so I would suggest not taking this approach. You could have a pre-defined list of "acceptable" colours and just pop one from that list for each user that joins.

How do I create a dictionary with keys from a list and values defaulting to (say) zero?

In python version >= 2.7 and in python 3:

d = {el:0 for el in a}

SQL Server IF NOT EXISTS Usage?

Have you verified that there is in fact a row where Staff_Id = @PersonID? What you've posted works fine in a test script, assuming the row exists. If you comment out the insert statement, then the error is raised.

set nocount on

create table Timesheet_Hours (Staff_Id int, BookedHours int, Posted_Flag bit)

insert into Timesheet_Hours (Staff_Id, BookedHours, Posted_Flag) values (1, 5.5, 0)

declare @PersonID int
set @PersonID = 1

IF EXISTS    
    (
    SELECT 1    
    FROM Timesheet_Hours    
    WHERE Posted_Flag = 1    
        AND Staff_Id = @PersonID    
    )    
    BEGIN
        RAISERROR('Timesheets have already been posted!', 16, 1)
        ROLLBACK TRAN
    END
ELSE
    IF NOT EXISTS
        (
        SELECT 1
        FROM Timesheet_Hours
        WHERE Staff_Id = @PersonID
        )
        BEGIN
            RAISERROR('Default list has not been loaded!', 16, 1)
            ROLLBACK TRAN
        END
    ELSE
        print 'No problems here'

drop table Timesheet_Hours

Finding the last index of an array

say your array is called arr

do

arr[arr.Length - 1]

How to make a edittext box in a dialog

Wasim's answer lead me in the right direction but I had to make some changes to get it working for my current project. I am using this function in a fragment and calling it on button click.

fun showPostDialog(title: String) {
        val alert =  AlertDialog.Builder(activity)

        val edittext = EditText(activity)
        edittext.hint = "Enter Name"
        edittext.maxLines = 1

        var layout = activity?.let { FrameLayout(it) }

        //set padding in parent layout
//        layout.isPaddingRelative(45,15,45,0)
        layout?.setPadding(45,15,45,0)

        alert.setTitle(title)

        layout?.addView(edittext)

        alert.setView(layout)

        alert.setPositiveButton(getString(R.string.label_save), DialogInterface.OnClickListener {

                dialog, which ->
            run {

                val qName = edittext.text.toString()

                showToast("Posted to leaderboard successfully")

                view?.hideKeyboard()

            }

        })
        alert.setNegativeButton(getString(R.string.label_cancel), DialogInterface.OnClickListener {

                dialog, which ->
            run {
                dialog.dismiss()
            }

        })

        alert.show()
    }

    fun View.hideKeyboard() {
        val imm = context.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
        imm.hideSoftInputFromWindow(windowToken, 0)
    }

    fun showToast(message: String) {
        Toast.makeText(activity, message, Toast.LENGTH_LONG).show()
    }

I hope it helps someone else in the near future. Happy coding!

MySQL Workbench: How to keep the connection alive

If you are using a "Standard TCP/IP over SSH" type of connection, it might be the ssh server that keeps timing out, in which case, you would have to edit TCPKeepAlive related settings in /etc/ssh/sshd_config on your server.

What are the differences between if, else, and else if?

An if statement follows this sort of structure:

if (condition)
{
    // executed only if "condition" is true
}
else if (other condition)
{
    // executed only if "condition" was false and "other condition" is true
}
else
{
    // executed only if both "condition" and "other condition" were false
}

The if portion is the only block that is absolutely mandatory. else if allows you to say "ok, if the previous condition was not true, then if this condition is true...". The else says "if none of the conditions above were true..."

You can have multiple else if blocks, but only one if block and only one (or zero) else blocks.

Converting float to char*

typedef union{
    float a;
    char b[4];
} my_union_t;

You can access to float data value byte by byte and send it through 8-bit output buffer (e.g. USART) without casting.

Django model "doesn't declare an explicit app_label"

I just ran into this issue and figured out what was going wrong. Since no previous answer described the issue as it happened to me, I though I would post it for others:

  • the issue came from using python migrate.py startapp myApp from my project root folder, then move myApp to a child folder with mv myApp myFolderWithApps/.
  • I wrote myApp.models and ran python migrate.py makemigrations. All went well.
  • then I did the same with another app that was importing models from myApp. Kaboom! I ran into this error, while performing makemigrations. That was because I had to use myFolderWithApps.myApp to reference my app, but I had forgotten to update MyApp/apps.py. So I corrected myApp/apps.py, settings/INSTALLED_APPS and my import path in my second app.
  • but then the error kept happening: the reason was that I had migrations trying to import the models from myApp with the wrong path. I tried to correct the migration file, but I went at the point where it was easier to reset the DB and delete the migrations to start from scratch.

So to make a long story short: - the issue was initially coming from the wrong app name in apps.py of myApp, in settings and in the import path of my second app. - but it was not enough to correct the paths in these three places, as migrations had been created with imports referencing the wrong app name. Therefore, the same error kept happening while migrating (except this time from migrations).

So... check your migrations, and good luck!

select count(*) from table of mysql in php

 $howmanyuser_query=$conn->query('SELECT COUNT(uno)  FROM userentry;');
 $howmanyuser=$howmanyuser_query->fetch_array(MYSQLI_NUM); 
 echo $howmanyuser[0];

after the so many hours excellent :)

Get full path of a file with FileUpload Control

Try

Server.MapPath(FileUpload1.FileName);

Edit: This answer describes how to get the path to a file on the server. It does not describe how to get the path to a file on the client, which is what the question asked. The answer to that question is "you can't", because modern browser will not tell you the path on the client, for security reasons.

package R does not exist

For anyone who ran into this, I refactored by renaming the namespace folders. I just forgot to also edit AndroidManifest and that's why I got this error.

Make sure you check this as well.

How to get a subset of a javascript object's properties

While it's a bit more verbose, you can accomplish what everyone else was recommending underscore/lodash for 2 years ago, by using Array.prototype.reduce.

var subset = ['color', 'height'].reduce(function(o, k) { o[k] = elmo[k]; return o; }, {});

This approach solves it from the other side: rather than take an object and pass property names to it to extract, take an array of property names and reduce them into a new object.

While it's more verbose in the simplest case, a callback here is pretty handy, since you can easily meet some common requirements, e.g. change the 'color' property to 'colour' on the new object, flatten arrays, etc. -- any of the things you need to do when receiving an object from one service/library and building a new object needed somewhere else. While underscore/lodash are excellent, well-implemented libs, this is my preferred approach for less vendor-reliance, and a simpler, more consistent approach when my subset-building logic gets more complex.

edit: es7 version of the same:

const subset = ['color', 'height'].reduce((a, e) => (a[e] = elmo[e], a), {});

edit: A nice example for currying, too! Have a 'pick' function return another function.

const pick = (...props) => o => props.reduce((a, e) => ({ ...a, [e]: o[e] }), {});

The above is pretty close to the other method, except it lets you build a 'picker' on the fly. e.g.

pick('color', 'height')(elmo);

What's especially neat about this approach, is you can easily pass in the chosen 'picks' into anything that takes a function, e.g. Array#map:

[elmo, grover, bigBird].map(pick('color', 'height'));
// [
//   { color: 'red', height: 'short' },
//   { color: 'blue', height: 'medium' },
//   { color: 'yellow', height: 'tall' },
// ]

LINQ Aggregate algorithm explained

Super short Aggregate works like fold in Haskell/ML/F#.

Slightly longer .Max(), .Min(), .Sum(), .Average() all iterates over the elements in a sequence and aggregates them using the respective aggregate function. .Aggregate () is generalized aggregator in that it allows the developer to specify the start state (aka seed) and the aggregate function.

I know you asked for a short explaination but I figured as others gave a couple of short answers I figured you would perhaps be interested in a slightly longer one

Long version with code One way to illustrate what does it could be show how you implement Sample Standard Deviation once using foreach and once using .Aggregate. Note: I haven't prioritized performance here so I iterate several times over the colleciton unnecessarily

First a helper function used to create a sum of quadratic distances:

static double SumOfQuadraticDistance (double average, int value, double state)
{
    var diff = (value - average);
    return state + diff * diff;
}

Then Sample Standard Deviation using ForEach:

static double SampleStandardDeviation_ForEach (
    this IEnumerable<int> ints)
{
    var length = ints.Count ();
    if (length < 2)
    {
        return 0.0;
    }

    const double seed = 0.0;
    var average = ints.Average ();

    var state = seed;
    foreach (var value in ints)
    {
        state = SumOfQuadraticDistance (average, value, state);
    }
    var sumOfQuadraticDistance = state;

    return Math.Sqrt (sumOfQuadraticDistance / (length - 1));
}

Then once using .Aggregate:

static double SampleStandardDeviation_Aggregate (
    this IEnumerable<int> ints)
{
    var length = ints.Count ();
    if (length < 2)
    {
        return 0.0;
    }

    const double seed = 0.0;
    var average = ints.Average ();

    var sumOfQuadraticDistance = ints
        .Aggregate (
            seed,
            (state, value) => SumOfQuadraticDistance (average, value, state)
            );

    return Math.Sqrt (sumOfQuadraticDistance / (length - 1));
}

Note that these functions are identical except for how sumOfQuadraticDistance is calculated:

var state = seed;
foreach (var value in ints)
{
    state = SumOfQuadraticDistance (average, value, state);
}
var sumOfQuadraticDistance = state;

Versus:

var sumOfQuadraticDistance = ints
    .Aggregate (
        seed,
        (state, value) => SumOfQuadraticDistance (average, value, state)
        );

So what .Aggregate does is that it encapsulates this aggregator pattern and I expect that the implementation of .Aggregate would look something like this:

public static TAggregate Aggregate<TAggregate, TValue> (
    this IEnumerable<TValue> values,
    TAggregate seed,
    Func<TAggregate, TValue, TAggregate> aggregator
    )
{
    var state = seed;

    foreach (var value in values)
    {
        state = aggregator (state, value);
    }

    return state;
}

Using the Standard deviation functions would look something like this:

var ints = new[] {3, 1, 4, 1, 5, 9, 2, 6, 5, 4};
var average = ints.Average ();
var sampleStandardDeviation = ints.SampleStandardDeviation_Aggregate ();
var sampleStandardDeviation2 = ints.SampleStandardDeviation_ForEach ();

Console.WriteLine (average);
Console.WriteLine (sampleStandardDeviation);
Console.WriteLine (sampleStandardDeviation2);

IMHO

So does .Aggregate help readability? In general I love LINQ because I think .Where, .Select, .OrderBy and so on greatly helps readability (if you avoid inlined hierarhical .Selects). Aggregate has to be in Linq for completeness reasons but personally I am not so convinced that .Aggregate adds readability compared to a well written foreach.

Convert base class to derived class

That's not possible. but you can use an Object Mapper like AutoMapper

Example:

class A
{
    public int IntProp { get; set; }
}
class B
{
    public int IntProp { get; set; }
    public string StrProp { get; set; }
}

In global.asax or application startup:

AutoMapper.Mapper.CreateMap<A, B>();

Usage:

var b = AutoMapper.Mapper.Map<B>(a);

It's easily configurable via a fluent API.

Java Map equivalent in C#

Dictionary<,> is the equivalent. While it doesn't have a Get(...) method, it does have an indexed property called Item which you can access in C# directly using index notation:

class Test {
  Dictionary<int,String> entities;

  public String getEntity(int code) {
    return this.entities[code];
  }
}

If you want to use a custom key type then you should consider implementing IEquatable<> and overriding Equals(object) and GetHashCode() unless the default (reference or struct) equality is sufficient for determining equality of keys. You should also make your key type immutable to prevent weird things happening if a key is mutated after it has been inserted into a dictionary (e.g. because the mutation caused its hash code to change).

Display exact matches only with grep

Try this:

Alex Misuno@hp4530s ~
$ cat test.txt
1 OK
2 OK
3 NOTOK
4 OK
5 NOTOK
Alex Misuno@hp4530s ~
$ cat test.txt | grep ".* OK$"
1 OK
2 OK
4 OK

Remove a marker from a GoogleMap

Add the marker to the map like this

Marker markerName = map.addMarker(new MarkerOptions().position(latLng).title("Title"));

Then you'll be able to use the remove method, it will remove only that marker

markerName.remove();

How to copy the first few lines of a giant file, and add a line of text at the end of it using some Linux commands?

I am assuming what you are trying to achieve is to insert a line after the first few lines of of a textfile.

head -n10 file.txt >> newfile.txt
echo "your line >> newfile.txt
tail -n +10 file.txt >> newfile.txt

If you don't want to rest of the lines from the file, just skip the tail part.

How to delete a specific line in a file?

To delete a specific line of a file by its line number:

Replace variables filename and line_to_delete with the name of your file and the line number you want to delete.

filename = 'foo.txt'
line_to_delete = 3
initial_line = 1
file_lines = {}

with open(filename) as f:
    content = f.readlines() 

for line in content:
    file_lines[initial_line] = line.strip()
    initial_line += 1

f = open(filename, "w")
for line_number, line_content in file_lines.items():
    if line_number != line_to_delete:
        f.write('{}\n'.format(line_content))

f.close()
print('Deleted line: {}'.format(line_to_delete))

Example output:

Deleted line: 3

How do I show the changes which have been staged?

If you'd be interested in a visual side-by-side view, the diffuse visual diff tool can do that. It will even show three panes if some but not all changes are staged. In the case of conflicts, there will even be four panes.

Screenshot of diffuse with staged and unstaged edits

Invoke it with

diffuse -m

in your Git working copy.

If you ask me, the best visual differ I've seen for a decade. Also, it is not specific to Git: It interoperates with a plethora of other VCS, including SVN, Mercurial, Bazaar, ...

See also: Show both staged & working tree in git diff?

How to set a variable inside a loop for /F

To expand on the answer I came here to get a better understanding so I wrote this that can explain it and helped me too.

It has the setlocal DisableDelayedExpansion in there so you can locally set this as you wish between the setlocal EnableDelayedExpansion and it.

@echo off
title %~nx0
for /f "tokens=*" %%A in ("Some Thing") do (
  setlocal EnableDelayedExpansion
  set z=%%A
  echo !z!        Echoing the assigned variable in setlocal scope.
  echo %%A        Echoing the variable in local scope.
  setlocal DisableDelayedExpansion
  echo !z!        &rem !z!           Neither of these now work, which makes sense.
  echo %z%        &rem ECHO is off.  Neither of these now work, which makes sense.
  echo %%A        Echoing the variable in its local scope, will always work.
  )

How to call a SOAP web service on Android

Android does not provide any sort of SOAP library. You can either write your own, or use something like kSOAP 2. As you note, others have been able to compile and use kSOAP2 in their own projects, but I haven't had to.

Google has shown, to date, little interest in adding a SOAP library to Android. My suspicion for this is that they'd rather support the current trends in Web Services toward REST-based services, and using JSON as a data encapsulation format. Or, using XMPP for messaging. But that is just conjecture.

XML-based web services are a slightly non-trivial task on Android at this time. Not knowing NetBeans, I can't speak to the tools available there, but I agree that a better library should be available. It is possible that the XmlPullParser will save you from using SAX, but I don't know much about that.

Set Focus on EditText

This works from me:

public void showKeyboard(final EditText ettext){
    ettext.requestFocus();
    ettext.postDelayed(new Runnable(){
            @Override public void run(){
                InputMethodManager keyboard=(InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
                keyboard.showSoftInput(ettext,0);
            }
        }
        ,200);
}

To hide:

private void hideSoftKeyboard(EditText ettext){
    InputMethodManager inputMethodManager = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
    inputMethodManager.hideSoftInputFromWindow(ettext.getWindowToken(), 0);
}

How do you convert epoch time in C#?

If you want better performance you can use this version.

public const long UnixEpochTicks = 621355968000000000;
public const long TicksPerMillisecond = 10000;
public const long TicksPerSecond = TicksPerMillisecond * 1000;

//[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static DateTime FromUnixTimestamp(this long unixTime)
{
    return new DateTime(UnixEpochTicks + unixTime * TicksPerSecond);
}

From a quick benchmark (BenchmarkDotNet) under net471 I get this number:

        Method |     Mean |     Error |    StdDev | Scaled |
-------------- |---------:|----------:|----------:|-------:|
         LukeH | 5.897 ns | 0.0897 ns | 0.0795 ns |   1.00 |
      MyCustom | 3.176 ns | 0.0573 ns | 0.0536 ns |   0.54 |

2x faster against LukeH's version (if the performance mater)

This is similar to how DateTime internally work.

Can media queries resize based on a div element instead of the screen?

The only way I can think that you can accomplish what you want purely with css, is to use a fluid container for your widget. If your container's width is a percentage of the screen then you can use media queries to style depending on your container's width, as you will now know for each screen's dimensions what is your container's dimensions. For example, let's say you decide to make your container's 50% of the screen width. Then for a screen width of 1200px you know that your container is 600px

.myContainer {
  width: 50%;
}

/* you know know that your container is 600px 
 * so you style accordingly
*/
@media (max-width: 1200px) { 
  /* your css for 600px container */
}

How can I define a composite primary key in SQL?

CREATE TABLE `voting` (
  `QuestionID` int(10) unsigned NOT NULL,
  `MemberId` int(10) unsigned NOT NULL,
  `vote` int(10) unsigned NOT NULL,
  PRIMARY KEY  (`QuestionID`,`MemberId`)
);

What does 'synchronized' mean?

What is the synchronized keyword?

Threads communicate primarily by sharing access to fields and the objects reference fields refer to. This form of communication is extremely efficient, but makes two kinds of errors possible: thread interference and memory consistency errors. The tool needed to prevent these errors is synchronization.

Synchronized blocks or methods prevents thread interference and make sure that data is consistent. At any point of time, only one thread can access a synchronized block or method (critical section) by acquiring a lock. Other thread(s) will wait for release of lock to access critical section.

When are methods synchronized?

Methods are synchronized when you add synchronized to method definition or declaration. You can also synchronize a particular block of code with-in a method.

What does it mean pro grammatically and logically?

It means that only one thread can access critical section by acquiring a lock. Unless this thread release this lock, all other thread(s) will have to wait to acquire a lock. They don't have access to enter critical section with out acquiring lock.

This can't be done with a magic. It's programmer responsibility to identify critical section(s) in application and guard it accordingly. Java provides a framework to guard your application, but where and what all sections to be guarded is the responsibility of programmer.

More details from java documentation page

Intrinsic Locks and Synchronization:

Synchronization is built around an internal entity known as the intrinsic lock or monitor lock. Intrinsic locks play a role in both aspects of synchronization: enforcing exclusive access to an object's state and establishing happens-before relationships that are essential to visibility.

Every object has an intrinsic lock associated with it. By convention, a thread that needs exclusive and consistent access to an object's fields has to acquire the object's intrinsic lock before accessing them, and then release the intrinsic lock when it's done with them.

A thread is said to own the intrinsic lock between the time it has acquired the lock and released the lock. As long as a thread owns an intrinsic lock, no other thread can acquire the same lock. The other thread will block when it attempts to acquire the lock.

When a thread releases an intrinsic lock, a happens-before relationship is established between that action and any subsequent acquisition of the same lock.

Making methods synchronized has two effects:

First, it is not possible for two invocations of synchronized methods on the same object to interleave.

When one thread is executing a synchronized method for an object, all other threads that invoke synchronized methods for the same object block (suspend execution) until the first thread is done with the object.

Second, when a synchronized method exits, it automatically establishes a happens-before relationship with any subsequent invocation of a synchronized method for the same object.

This guarantees that changes to the state of the object are visible to all threads.

Look for other alternatives to synchronization in :

Avoid synchronized(this) in Java?