They both do the same thing, just pick one and stick with it so that you have consistency. There is nothing to gain by using either in the end.

Is there any counter-indication to doing this ? Or is the behavior well specified?

    #pragma omp parallel for
    for(auto x : stl_container)
    {
       ...
    }

Because it seems that OpenMP specification is only valid for c++98 but I guess there might be more incompatibilities due to C++11 threads, which are not used here. I wanted to be sure, still.

Using OpenMP with C++11 range-based for loops?

There is the following code:

    class Product &lt; ActiveRecord::Base
      validates :title, :description, :image_url, presence: true
      validates :price, numericality: {greater_than_or_equal_to: 0.01}
      validates :title, uniqueness: true
      validates :image_url, allow_blank: true, format: {
          with: %r{\.(gif|jpg|png)$}i,
          message: &#39;URL must point to GIT/JPG/PNG pictures&#39;
      }
    end

It works, but when I try to test it using &quot;rake test&quot; I&#39;ll catch this message: 

    rake aborted!
    The provided regular expression is using multiline anchors (^ or $), which may present a security risk. Did you mean to use \A and \z, or forgot to add the :multiline =&gt; true option?

What does it mean? How can I fix it? 



Regular expressions with validations in RoR 4

My question might sound a little foolish but it bugs me every time i face it.
What is the difference between :

    where value.HasValue

and

    where value != null

Does HasValue checks if `value` is null?

C# HasValue vs !=null

My question might sound a little foolish but it bugs me every time i face it.
What is the difference between :
<pre><code class="hljs language-bash">where value.HasValue
</code></pre>
and
<pre><code class="hljs language-csharp">where value != null
</code></pre>
Does HasValue checks if <code>value</code> is null?

I&#39;m trying to parse some XML inside a WiX installer. The XML would be an object of all my errors returned from a web server. I&#39;m getting the error in the question title with this code:

    XmlDocument xml = new XmlDocument();
    try
    {
    	xml.LoadXml(myString);
    }
    catch (Exception ex)
    {
    	System.IO.File.WriteAllText(@&quot;C:\text.txt&quot;, myString + &quot;\r\n\r\n&quot; + ex.Message);
    	throw ex;
    }

`myString` is this (as seen in the output of `text.txt`)

    &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
    &lt;Errors&gt;&lt;/Errors&gt;

`text.txt` comes out looking like this:

    &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
    &lt;Errors&gt;&lt;/Errors&gt;
    
    Data at the root level is invalid. Line 1, position 1.

I need this XML to parse so I can see if I had any errors.

xml.LoadData - Data at the root level is invalid. Line 1, position 1

I want to serialize objects to strings, and back.

We use protobuf-net to turn an object into a Stream and back, successfully.

However, Stream to string and back... not so successful. After going through `StreamToString` and `StringToStream`, the new `Stream `isn&#39;t
deserialized by protobuf-net; it raises an `Arithmetic Operation resulted in an Overflow` exception.  If we deserialize the original stream, it works.

Our methods:

    public static string StreamToString(Stream stream)
    {
        stream.Position = 0;
        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
        {
            return reader.ReadToEnd();
        }
    }

    public static Stream StringToStream(string src)
    {
        byte[] byteArray = Encoding.UTF8.GetBytes(src);
        return new MemoryStream(byteArray);
    }

Our example code using these two:

    MemoryStream stream = new MemoryStream();
    Serializer.Serialize&lt;SuperExample&gt;(stream, test);
    stream.Position = 0;
    string strout = StreamToString(stream);
    MemoryStream result = (MemoryStream)StringToStream(strout);
    var other = Serializer.Deserialize&lt;SuperExample&gt;(result);


Converting Stream to String and back...what are we missing?

I&#39;m a bit confused about how to best refactor my code into something more readable.

Consider this piece of code:

    var foo = getfoo();
    if(foo!=null)
    {
        var bar = getbar(foo);
        if(bar!=null)
        {
            var moo = getmoo(bar);
            if(moo!=null)
            {
                var cow = getcow(moo);
                ...
            }
        }
    }
    return;

As you can see, lots of nested `if` blocks, needed because each nested if is dependent on the previous values.

Now I was wondering how to make my code a bit cleaner in this regard.

Some options I have thought of myself would be to:

 - return after each if clause, meaning I&#39;d have multiple places where I leave my method
 - throw `ArgumentNullException`s, after which I&#39;d catch them in the end and place the return statement in my finally clause (or outside the try/catch block)
 - work with a label and `goto:`

Most of these options seem a bit &quot;dirty&quot; to me, so I was wondering if there was a good way to clean up this mess that I&#39;ve created.


How to prevent the arrowhead anti-pattern

I&#39;ve programmatically created a new document collection using the MongoDB C# driver.

At this point I want to create and build indexes programmatically. How can I do that?

How to create indexes in MongoDB via .NET

I&#39;m trying to create this generic method to simplify things but I think I messed it up! Can you help with my problem?

This compiles:

    private string ConcatenateText&lt;T1, T2&gt;(MyEntity myEntity) 
        where T1 : Supplier, new()
        where T1 : Employee, new()
        where T2 : SupplierDepartment, new()
        where T2 : EmployeeDepartment, new()
    {
        T1 p = new T1();
        T2 r = new T2();
        //Code here for myEntity treatment
        return mystring;
    }

While this does not compile:

    protected void mybutton1_Click(object sender, EventArgs e)
    {
       string mystring = ConcatenaText&lt;Supplier, SupplierDepartment&gt;(myEntity);
    }
    
    //This does not compile
    protected void mybutton2_Click(object sender, EventArgs e)
    {
       string mystring = ConcatenaText&lt;Employee, EmployeeDepartment&gt;(myEntity);
    }

**Message: The type Supplier cannot be used as type parameter T1 in the generic type or method ConcatenateText&lt;T1, T2&gt;(MyEntity myEntity). There is no implicit reference conversion from Supplier to Employee**

Can this be done? What am I doing wrong? Can it be improved?


**EDIT:**

And MyEntity is just another class in order to process it inside this generic method! It&#39;s not related to the types T. It just an argument. But it&#39;s clear that I can&#39;t do that, using 2 types like that. I thought that I could assign one or another and the CLR independently of my initialization could react as I wanted. I gonna accept the answer who share a little bit more information about it.

Generic with multiple classes

I ran a program on Windows 7 that was compiled under Cygwin and passed &quot;NUL&quot; as an output file name. Instead of suppressing output it actually created a file named &quot;NUL&quot; in the current directory. (Apparently it expects &quot;/dev/null&quot;, even on Windows.) Now I&#39;m stuck with this &quot;NUL&quot; file that I cannot delete!

I&#39;ve already tried:

 - Windows Explorer - error: &quot;Invalid MS-DOS function&quot; (yes, that is seriously what it says!)
 - Command prompt using &quot;del NUL&quot; - error: &quot;The filename, directory name, or volume
   label syntax is incorrect.&quot;
 - Deleting the entire directory - same deal as just deleting the file
 - `remove()` in a C program - also fails

How can I get rid of these NUL files (I have several by now), short of installing the full Cygwin environment and compiling a C program under Cygwin to do it?

Delete a file named &quot;NUL&quot; on Windows

When I write watch handling functions I check newVal param on `undefined` and `null`. Why does AngularJS have such a behavior, but doesn&#39;t have particular utility method? So there is `angular.isUndefined` but not `angular.isUndefinedOrNull`. It isn&#39;t hard to implement that by hand but how extend angular to have that function in each controller? Tnx.

**Edit**:

The example:

    $scope.$watch(&quot;model&quot;, function(newVal) {
        if (angular.isUndefined(newVal) || newVal == null) return;
        // do somethings with newVal
    }

Is it common accepted practice to handle such a way?

**Edit 2**:

The JSFiddle example ([http://jsfiddle.net/ubA9r/][1]):

    &lt;div ng-app=&quot;App&quot;&gt;
      &lt;div ng-controller=&quot;MainCtrl&quot;&gt; 
          &lt;select ng-model=&quot;model&quot; ng-options=&quot;m for m in models&quot;&gt;
              &lt;option value=&quot;&quot; class=&quot;ng-binding&quot;&gt;Choose model&lt;/option&gt;
          &lt;/select&gt;
          {{model}}
      &lt;/div&gt;
    &lt;/div&gt;

    var app = angular.module(&quot;App&quot;, []);
    
    var MainCtrl = function($scope) {
        $scope.models = [&#39;Apple&#39;, &#39;Banana&#39;];
        $scope.$watch(&quot;model&quot;, function(newVal) {
            console.log(newVal);
        });
    };


  [1]: http://jsfiddle.net/ubA9r/

Undefined or null for AngularJS

What is the most efficient of way of checking if a database will return a record before processing it.  Example: `Truck.where(&quot;id = ?&quot;, id).select(&#39;truck_no&#39;).first.truck_no`

This may or may not return a truck if the truck exists.  What is the most efficient way for me to ensure the page will not crash when processing this request.  How would I handle this both in the view and the controller if lets say I was using a loop to go through each truck and print out its number.

If the record does not exist I would like to be able to print out a message instead saying no records found.

Rails checking if a record exists in database

PHP trivia here.

If we declare an array like this:

    &lt;?php $arr = [ &#39;foo&#39; =&gt; &#39;bar&#39;, NULL =&gt; &#39;hello&#39; ]; ?&gt;

We can access it like this

    print $arr[NULL];

This will print `hello`. Why is this useful, relevant or necessary? Is it a PHP bug or a feature?

My only idea was that you could declare array with the NULL key being equal to an error message to explain to anyone who uses a NULL key that their key is null:

    $arr[NULL] = &#39;Warning you have used a null key, did you mean to?&#39;;

Has anyone found this useful? Seems to be something to cause more harm than good.

Arrays with NULL keys

Take a look at the following example:

    class nul
    {
      public static void main (String[] args)
      {
        System.out.println (String.valueOf((Object)null));
        System.out.println (String.valueOf(null));
      }
    }

The first `println` writes `null` but the second throws a `NullPointerException`.

Why is only the second line worth an exception? And what is the difference between the two `null`s? Is there a *real* `null` and a *fake* `null` in Java?

Content Type	Original Author	Original Content on Stackoverflow
Question	oimitro	View Question on Stackoverflow
Solution 1 - C#	Derek	View Answer on Stackoverflow

C# HasValue vs !=null

C# Problem Overview

C# Solutions

Solution 1 - C#

Regular expressions with validations in RoR 4

Using OpenMP with C++11 range-based for loops?

Attributions