Use `std::vector`&#39;s range constructor:

    std::vector&lt;int&gt; intVec;
    std::vector&lt;double&gt; doubleVec(intVec.begin(), intVec.end());

Use `std::transform` algorithm:

    std::transform(intVec.begin(), intVec.end(), doubleVec.begin(), [](int x) { return (double)x;});

I&#39;m setting up the Django admin to the following models:
                                          
```python                                    
class Tag(models.Model):                                                 
    name = models.CharField(max_length=100)                                 

class Quote(models.Model):                                                  
    author = models.CharField(max_length=100)                               
    quote = models.CharField(max_length=1000)                               
    tags = models.ManyToManyField(Tag)
```

With the following code:

    class TagInline(admin.TabularInline):                                                                                               
        model = Tag                                                             
                                                                                
    class QuoteAdmin(admin.ModelAdmin):                                         
        list_display = (&#39;author&#39;, &#39;quote&#39;)                                      
        inlines = (TagInline,)                                                  
                                                                                
    class TagAdmin(admin.ModelAdmin):                                           
        pass                                                                    
                                                                                
    admin.site.register(Quote, QuoteAdmin)                                      
    admin.site.register(Tag, TagAdmin)

When trying to view the admin page to add a `Quote`, the page shows an error saying `&lt;class &#39;quotes.models.Tag&#39;&gt; has no ForeignKey to &lt;class &#39;quotes.models.Quote&#39;&gt;`. This didn&#39;t happen before I added an inline. What&#39;s the problem? How do I correctly add a `Tag` as an inline?

*(I spent a good 20 minutes searching for an answer; I found similar questions but none of their answers worked for me.)*

Django admin ManyToMany inline &quot;has no ForeignKey to&quot; error

I have the following Layout which does not work:

&lt;!-- language: lang-xml --&gt;

    &lt;LinearLayout 
        android:orientation=&quot;horizontal&quot; 
        android:layout_width=&quot;match_parent&quot; 
        android:id=&quot;@+id/experienceLayout&quot; 
        android:background=&quot;#ffffff&quot; 
        android:layout_height=&quot;match_parent&quot; 
        android:paddingLeft=&quot;6dp&quot; 
        android:paddingRight=&quot;6dp&quot; 
        android:paddingBottom=&quot;6dp&quot; 
        android:paddingTop=&quot;6dp&quot;&gt;
    
        &lt;TextView 
            android:layout_weight=&quot;1&quot; 
            android:id=&quot;@+id/experienceLabel&quot; 
            android:text=&quot;Experience&quot; 
            android:layout_height=&quot;wrap_content&quot; 
            android:textColor=&quot;#000000&quot; 
            android:layout_width=&quot;wrap_content&quot; 
            android:textStyle=&quot;bold&quot;&gt;
        &lt;/TextView&gt;
    
        &lt;TextView 
            android:id=&quot;@+id/experienceTextView&quot; 
            android:text=&quot;TextView&quot; 
            android:layout_height=&quot;wrap_content&quot; 
            android:textColor=&quot;#000000&quot; 
            android:layout_width=&quot;wrap_content&quot; 
            android:ellipsize=&quot;end&quot; 
            android:lines=&quot;1&quot; 
            android:maxLines=&quot;1&quot; 
            android:singleLine=&quot;true&quot; 
            android:fadeScrollbars=&quot;false&quot;&gt;
        &lt;/TextView&gt;
    
    &lt;/LinearLayout&gt;

How can I show ellipses on my TextView if it is greater than the 1 line?

What is a good clean way to convert a `std::vector&lt;int&gt; intVec` to `std::vector&lt;double&gt; doubleVec`. Or, more generally, to convert two vectors of convertible types?

C++ convert vector&lt;int&gt; to vector&lt;double&gt;

<p>What is a good clean way to convert a <code>std::vector&#x3C;int> intVec</code> to <code>std::vector&#x3C;double> doubleVec</code>. Or, more generally, to convert two vectors of convertible types?</p>


I know that at least one of the changes in C++11 that will cause some old code to stop compiling: the introduction of `explicit operator bool()` in the standard library, replacing old instances of `operator void*()`. Granted, the code that this will break is probably code that should not have been valid in the first place, but it&#39;s still a breaking change nonetheless: programs that used to be valid no longer are.

Are there any other breaking changes?



What breaking changes are introduced in C++11?

I have `.lib` file compiled from C code. How I know if this self-contained static library or just an import lib and DLL will be needed at runtime? Is there some `dumpbin` option I&#39;m missing?


know if .lib is static or import

When exactly are objects destroyed in C++, and what does that mean? Do I have to destroy them manually, since there is no Garbage Collector? How do exceptions come into play?

&lt;sub&gt;&lt;i&gt;
(Note: This is meant to be an entry to [Stack Overflow&#39;s C++ FAQ](https://stackoverflow.com/questions/tagged/c++-faq). If you want to critique the idea of providing an FAQ in this form, then [the posting on meta that started all this](https://meta.stackexchange.com/questions/68647/setting-up-a-faq-for-the-c-tag) would be the place to do that. Answers to that question are monitored in the [C++ chatroom](https://chat.stackoverflow.com/rooms/10/c-lounge), where the FAQ idea started out in the first place, so your answer is very likely to get read by those who came up with the idea.)
&lt;/i&gt;&lt;/sub&gt;


Object destruction in C++

I have been working on a project (a game to be specific) and I feel that I should start over with different libraries. So when doing this I reinstalled [Code::Blocks](http://codeblocks.org) and setup my new libraries and includes. 

But as of now Im having a problem starting u[ my new project to test if all of the includes work. This problem is: `libstdc++-6.dll was not found.` At first i wondered if I could just find this file online, but its nowhere to be found(or at least the many places I have searched...) Soon after, I tried loading up my old project, and the same problem happened again(wierd... ._.) I was thinking its maybe my compiler, so I used my older compiler and it did the same thing! At this moment I held the problem off for tomorrow(which is today)

So my question is: If anyone else had this problem, how would you solve it?

Im using Code::Blocks with MinGW as the compiler on Windows Vista 32 bit.


*****EDIT*****

Here are the Build options in my project. Note that these are the settings in the Project, not the global compiler:

In (project name)-&gt;Compiler settings-&gt;Otehr options:

(I use `//` to seperate the commands)

    -mthreads//
    -fmessage-length=0//
    -fexceptions//
    -fident//

In (project name)-&gt;Compiler settings-&gt;#define:


    WIN32//
    _WINDOWS//

In (project name)-&gt;Linker settings-&gt;Other linker options:

    -static-libstdc++//
    -static-libgcc//
    -Wl,--enable-auto-image-base//
    -Wl,--add-stdcall-alias//
    -Wl,--enable-auto-import//

In linker-&gt;link libraries i have various links to files with a `.a` extension, these files include Bullet PHysics, Ogre3D, and SFML

In the search directories i have links to the MinGW/bin, and the MinGW/lib directories, along with other links to different libraries.


My Compiler is MinGW, a GNU GCC compiler for windows 32 bit. and the IDE is Codeblocks. Also note that in Debug and Release settings on the project, there is nothing.

Most of these setings are also pieces that i got from the [Ogre3D Application setup tutorial](http://www.ogre3d.org/tikiwiki/Setting+Up+An+Application+-+CodeBlocks) if that is of any help.



libstdc++-6.dll not found

Is there a difference between declaring a friend function/class as private or public? I can&#39;t seem to find anything about this online.

I mean the difference between:

    class A
    {
     public: 
          friend class B;
     };


and

    class A
    {
     private: //or nothing as the default is private
          friend class B;
     };

Is there a difference?

Friend declaration in C++ - difference between public and private

Compare

    double average = CalculateAverage(values.begin(), values.end());

with

    double average = std::for_each(values.begin(), values.end(), CalculateAverage());


What are the benefits of using a functor over a function?  Isn&#39;t the first a lot easier to read (even before the implementation is added)?

Assume the functor is defined like this:

    class CalculateAverage
    {
    private:
       std::size_t num;
       double sum;
    public:
    
       CalculateAverage() : num (0) , sum (0)
       {
       }
    
       void operator () (double elem) 
       {
          num++; 
          sum += elem;
       }
    
       operator double() const
       {
    	   return sum / num;
       }
    };

Why use functors over functions?

I&#39;m trying to use `std::vector` as a `char` array.

My function takes in a void pointer:

    void process_data(const void *data);

Before I simply just used this code:

    char something[] = &quot;my data here&quot;;
    process_data(something);

Which worked as expected.

But now I need the dynamicity of `std::vector`, so I tried this code instead:

    vector&lt;char&gt; something;
    *cut*
    process_data(something);

The question is, how do I pass the char vector to my function so I can access the vector raw data (no matter which format it is – floats, etc.)?

I tried this:

    process_data(&amp;something);

And this:

    process_data(&amp;something.begin());

But it returned a pointer to gibberish data, and the latter gave warning: `warning C4238: nonstandard extension used : class rvalue used as lvalue`.


How to get std::vector pointer to the raw data?

I want to map objects of a given class to objects of another. The class I want to use as key, however, was not written by me and is a simple `struct` with a few values. std::map orders it&#39;s contents, and I was wondering how it does it, and if any arbitrary class can be used as a key or if there&#39;s a set of requirements (operators and what not) that need to be defined.

If so, I could create a wrapper for the class implementing the operators map uses. I just need to know what I need to implement first, and none of the references for the class I [found online][1] specify them.


  [1]: http://en.cppreference.com/w/cpp/container/map

What requirements must std::map key classes meet to be valid keys?

I&#39;m used to writing loops like this:

    for (std::size_t index = 0; index &lt; foo.size(); index++)
    {
        // Do stuff with foo[index].
    }

But when I see iterator loops in others&#39;  code, they look like this:

    for (Foo::Iterator iterator = foo.begin(); iterator != foo.end(); iterator++)
    {
        // Do stuff with *Iterator.
    }

I find the `iterator != foo.end()` to be offputting.  It can also be dangerous if `iterator` is incremented by more than one.

It seems more &quot;correct&quot; to use `iterator &lt; foo.end()`, but I never see that in real code.  Why not?

Why is &quot;!=&quot; used with iterators instead of &quot;&lt;&quot;?

I want to replace an element into a specific position of a vector, can I just use an assignment:

    // vec1 and 2 have the same length &amp; filled in somehow
    vec1;
    vec2;

    vec1[i] = vec2[i] // insert vec2[i] at position i of vec1

or I have to use insert():

    vector&lt;sometype&gt;::iterator iterator = vec1.begin();

    vec1.insert(iterator+(i+1), vec2[i]);


Replace an element into a specific position of a vector

I have a list of integers that I need to iterate over but an array is inadequate.
What are the differences between `vectors` and `lists` and is there anything I need to know before I pick a type?

Just to be clear, I&#39;ve read the QT docs but this is the extent of what I know:

&gt;  `QList&lt;T&gt;`, `QLinkedList&lt;T&gt;`, and `QVector&lt;T&gt;` provide similar functionality. Here&#39;s an overview:
&gt;
 - For most purposes, `QList` is the right class to use. Its index-based API is more convenient than `QLinkedList&#39;s` iterator-based API, and it is usually faster than `QVector` because of the way it stores its items in memory. It also expands to less code in your executable.
 - If you need a real linked list, with guarantees of constant time insertions in the middle of the list and iterators to items rather than indexes, use `QLinkedList`.
 - If you want the items to occupy adjacent memory positions, use `QVector`.


QVector vs QList

What is the difference between `std::array` and `std::vector`? When do you use one over other?

I have always used and considered `std:vector` as an C++ way of using C arrays, so what is the difference?


What is the difference between std::array and std::vector? When do you use one over other?

I know that when we are using template inside another template, we should write it like this:

`vector&lt;pair&lt;int,int&gt; &gt; s;`

and if we write it without the whitespace:

`vector&lt;pair&lt;int,int&gt;&gt; s;`

we will get an error:

&gt; \`&gt;&gt;&#39; should be \`&gt; &gt;&#39; within a nested template argument list

I see this is understandable, but I just can&#39;t help but wondering, in which cases will this be really ambiguous?

Template within template: why &quot;`&gt;&gt;&#39; should be `&gt; &gt;&#39; within a nested template argument list&quot;

How can I convert a string like `123,456.908` to float `123456.908` in Python?

How can I convert a string with dot and comma into a float in Python

I have a variable that can either be boolean `false`, or an integer (including 0). I want to put it in a switch statement like:

    switch(my_var){
        case 0:
             // Do something
             break;
        case 1:
             // Do something else
             break;
        case false:
             // Some other code
    }

In my tests in Google Chrome, it seems to work perfectly, but I&#39;m a little nervous to use it because I&#39;m afraid that in some browsers, if `my_var` is `false`, it might execute the first case since `0 == false`.

I&#39;m just wondering if there is anything official in JavaScript that says the switch statement will use strict comparison such that `0 !== false`, but I can&#39;t find anything myself, and I&#39;m not sure if this will work well in different JavaScript engines. Does anybody know if the comparison done by a switch statement is guaranteed to be strict?

Is it safe to assume strict comparison in a JavaScript switch statement?

I have an array:

    $a = array(&#39;foo&#39; =&gt; &#39;fooMe&#39;);

and I do:

    print_r($a);

which prints:

    Array ( [foo] =&gt; printme )

Is there a function, so when doing:

    needed_function(&#39;    Array ( [foo] =&gt; printme )&#39;);

I will get the array `array(&#39;foo&#39; =&gt; &#39;fooMe&#39;);` back?

How create an array from the output of an array printed with print_r?

With ARC, I can no longer cast `CGColorRef` to `id`. I learned that I need to do a bridged cast. According [clang docs][1]:

&gt; A **bridged cast** is a C-style cast annotated with one of three keywords:
&gt; 
&gt; `(__bridge T) op` casts the operand to the destination type `T`. If `T`
&gt; is a retainable object pointer type, then `op` must have a
&gt; non-retainable pointer type. If `T` is a non-retainable pointer type,
&gt; then op must have a retainable object pointer type. Otherwise the cast
&gt; is ill-formed. There is no transfer of ownership, and ARC inserts no
&gt; retain operations.
&gt;
&gt; `(__bridge_retained T) op` casts the operand, which must have
&gt; retainable object pointer type, to the destination type, which must be
&gt; a non-retainable pointer type. ARC retains the value, subject to the
&gt; usual optimizations on local values, and the recipient is responsible
&gt; for balancing that +1.
&gt; 
&gt; `(__bridge_transfer T) op` casts the operand, which must have
&gt; non-retainable pointer type, to the destination type, which must be a
&gt; retainable object pointer type. ARC will release the value at the end
&gt; of the enclosing full-expression, subject to the usual optimizations
&gt; on local values.
&gt; 
&gt; These casts are required in order to transfer objects in and out of
&gt; ARC control; see the rationale in the section on conversion of
&gt; retainable object pointers.
&gt; 
&gt; Using a `__bridge_retained` or `__bridge_transfer` cast purely to convince
&gt; ARC to emit an unbalanced retain or release, respectively, is poor
&gt; form.

In what kind of situations would I use each?

For example, `CAGradientLayer` has a `colors` property which accepts an array of `CGColorRef`s. My guess is that I should use `__brige` here, but exactly why I should (or should not) is unclear.

  [1]: http://clang.llvm.org/docs/AutomaticReferenceCounting.html#bridged-casts

ARC and bridged cast

I am trying to verify whether a variable that is passed can be converted to a specific type.  I have tried the following but can&#39;t get it to compile so I assume I&#39;m going about it the wrong way (I&#39;m new to C#)

    string myType = &quot;System.Int32&quot;;
    string myValue = &quot;42&quot;;
    
    bool canBeCast = false;
    
    try
    {
      // try to convert the value to it&#39;s intended type to see if it&#39;s valid.
      var result = (Type.GetType(typeString))dataValue;
      canBeCast = true;
    }
    catch
    {
      canBeCast = false;
    }

I&#39;m basically trying to avoid a massive switch statement along the lines of

      switch(myType){
        case &quot;System.Int32&quot;:
          try
          {
            var convertedValue = Convert.ToInt32(myValue);
          }
          catch (Exception)
          {
            canBeConverted = false;
          }
          break;
        case &quot;another type&quot;:
          ...
      }

EDIT:

Ok, basically I have a db table of known input types that looks like:

    CREATE TABLE [dbo].[MetadataTypes] (
        [typeName]  VARCHAR (50)  NOT NULL,
        [dataType]  VARCHAR (50)  NOT NULL,
        [typeRegex] VARCHAR (255) NULL
    );

which may have data such as 

    &quot;StartTime&quot;,&quot;System.DateTime&quot;,null
    &quot;TicketId&quot;,&quot;System.String&quot;,&quot;$[Ff][0-9]{7}^&quot;

And the input to my function would be a KeyValuePair&lt;string,string&gt; along the lines of 

    myInput = new KeyValuePair&lt;string,string&gt;(&quot;StartTime&quot;,&quot;31/12/2010 12:00&quot;);

I need to check that the value of the KeyValuePair is of the correct datatype expected by the MetaDataType.


EDIT FOR ANSWER:

Leon got really close to the solution I finally came up with.

For reference my function now looks like this:

    public Boolean ValidateMetadata(KeyValuePair&lt;string, string&gt; dataItem)
    {

      // Look for known metadata with name match
      MetadataType type = _repository.GetMetadataTypes().SingleOrDefault(t =&gt; t.typeName == dataItem.Key);
      if (type == null) { return false; }

      // Get the data type and try to match to the passed in data item.
      Boolean isCorrectType = false;
      string typeString = type.dataType;
      string dataValue = dataItem.Value;

      try
      {
        var cValue = Convert.ChangeType(dataValue, Type.GetType(typeString));
        isCorrectType = true;
      }
      catch
      {
        isCorrectType = false;
      }

      //TODO: Validate against possible regex here....            
            
      return isCorrectType;

    }


Content Type	Original Author	Original Content on Stackoverflow
Question	Alan Turing	View Question on Stackoverflow
Solution 1 - C++	James McNellis	View Answer on Stackoverflow
Solution 2 - C++	Yas	View Answer on Stackoverflow

C++ convert vector<int> to vector<double>

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

How can I show ellipses on my TextView if it is greater than the 1 line?

Django admin ManyToMany inline "has no ForeignKey to" error

Attributions