Have you looked at the [comparison][1] in the variant library already?

(Not sure what states from external sources are, so it&#39;s kind of hard to say what&#39;s more appropriate for you.)

  [1]: http://www.boost.org/doc/html/variant/misc.html#variant.versus-any

I&#39;m trying to add _simple_ Authentication and Authorization to an ASP.NET MVC application.

I&#39;m just trying to tack on some added functionality to the basic Forms Authentication (due to simplicity and custom database structure)


Assuming this is my database structure:
User:
  username
  password
  role (ideally some enum. Strings if need be. Currently, user only has ONE role, but this might change)

High Level Problem:
Given the above database structure, I would like to be able to do the following:

 - Simple Login using Forms Authentication
 - Decorate my actions with:
   [Authorize(Roles={ MyRoles.Admin, MyRoles.Member})]
 - Use roles in my Views (to determine links to display in some partials)

Currently, all I&#39;m really sure of is how to Authenticate. After that I&#39;m lost. I&#39;m not sure at which point do I grab the user role (login, every authorization?). Since my roles may not be strings, I&#39;m not sure how they will fit in with the User.IsInRole().

Now, I&#39;m asking here because I haven&#39;t found a &quot;simple&quot; accomplish what I need. I have seen multiple examples.

For Authentication:

 - We have simple user validation that checks the database and &quot;SetAuthCookie&quot;
 - Or we override the Membership provider and do this inside of ValidateUser
In either of these, I&#39;m not sure how to tack on my simple user Roles, so that they work with the:
HttpContext.Current.User.IsInRole(&quot;Administrator&quot;)
Furthermore, I&#39;m not sure how to modify this to work with my enum values.

For Authorization, I&#39;ve seen:

 - Deriving AuthorizeAttribute and implementing AuthorizeCore OR OnAuthorization to handle roles?
 - Implementing IPrincipal?


Any assistance would be greatly appreciated. However, I fear I may need a lot of detail, because none of what I&#39;ve Googled seems to fit with what I need to do.

ASP.NET MVC Forms Authentication + Authorize Attribute + Simple Roles

I have a struct as follows, with a pointer to a function called &quot;length&quot; that will return the length of the chars member.

    typedef struct pstring_t {
    	char * chars;
    	int (* length)();
    } PString;

I have a function to return the length of the characters from a pointer to a PString:

    int length(PString * self) {
    	return strlen(self-&gt;chars);
    }


I have a function initializeString() that returns a pointer to a PString:

    PString * initializeString() {
    	PString *str;
    	str-&gt;length = &amp;length;
    	return str;
    }

It is clear that I am doing something very wrong with my pointers here, because the `str-&gt;length = &amp;length` line causes an EXC_BAD_ACCESS signal in my debugger, as does `return strlen(self-&gt;chars). Does anyone have any insights into this problem?

I specifically want to be able have the initializeString() function return a pointer to a PString, and the length function to use a pointer to a PString as input. This is just an experiment in implementing a rudimentary object-oriented system in C, but I don&#39;t have a lot of experience dealing with pointers head-on. Thanks for any help you can give me.

Function pointer as a member of a C struct

I&#39;m having trouble choosing between Boost.Any and Boost.Variant.  
When should I use each one? 

What are the advantages and disadvantages of each?  

I am basically looking to store some states from external sources.  

Boost.Any vs. Boost.Variant

I'm having trouble choosing between Boost.Any and Boost.Variant. 
When should I use each one?
What are the advantages and disadvantages of each?
I am basically looking to store some states from external sources.

I just started using [Qt][1] and noticed that it uses its own make tool, [qmake][2].

- Why does Qt use its own make tool?
- Is there something special that prevents it from using a standard make tool?
- Does qmake call the [GCC][3] C++ compiler?


  [1]: http://en.wikipedia.org/wiki/Qt_%28toolkit%29
  [2]: http://en.wikipedia.org/wiki/Qmake
  [3]: http://en.wikipedia.org/wiki/GNU_Compiler_Collection

Why does Qt use its own make tool, qmake?

I just started using Qt and noticed that all the example class definitions have the macro `Q_OBJECT` as the first line. What is the purpose of this preprocessor macro?

What does the Q_OBJECT macro do? Why do all Qt objects need this macro?

Is there a way of printing arrays in C++?

I&#39;m trying to make a function that reverses a user-input array and then prints it out. I tried Googling this problem and it seemed like C++ can&#39;t print arrays. That can&#39;t be true can it?

Printing an array in C++?

How do I prevent from including header files twice? The problem is I&#39;m including the **&lt;winsock2.h&gt;** in **MyClass.h** and then I&#39;m including **MyClass.h** in many files, so it includes &lt;winsock2.h&gt; multiple times and redefinition error occurs. How to prevent?

I&#39;m using #pragma once instead of include guards, and I guess that&#39;s fine.

**MyClass.h:**

    // MyClass.h
    #pragma once
    
    #include &lt;winsock2.h&gt;
    
    class MyClass
    {
    
    // methods
    public:
     MyClass(unsigned short port);
     virtual ~MyClass(void);
    };

**EDIT:** Few of the errors I&#39;m getting

    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(91) : warning C4005: &#39;AF_IPX&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(460) : see previous definition of &#39;AF_IPX&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(124) : warning C4005: &#39;AF_MAX&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(479) : see previous definition of &#39;AF_MAX&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(163) : warning C4005: &#39;SO_DONTLINGER&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(402) : see previous definition of &#39;SO_DONTLINGER&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(206) : error C2011: &#39;sockaddr&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(485) : see declaration of &#39;sockaddr&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(384) : error C2143: syntax error : missing &#39;}&#39; before &#39;constant&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(384) : error C2143: syntax error : missing &#39;;&#39; before &#39;constant&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(384) : error C2059: syntax error : &#39;constant&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(437) : error C2143: syntax error : missing &#39;;&#39; before &#39;}&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(437) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(437) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(518) : warning C4005: &#39;IN_CLASSA&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(287) : see previous definition of &#39;IN_CLASSA&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(524) : warning C4005: &#39;IN_CLASSB&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(293) : see previous definition of &#39;IN_CLASSB&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(530) : warning C4005: &#39;IN_CLASSC&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(299) : see previous definition of &#39;IN_CLASSC&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(541) : warning C4005: &#39;INADDR_ANY&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(304) : see previous definition of &#39;INADDR_ANY&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(543) : warning C4005: &#39;INADDR_BROADCAST&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(306) : see previous definition of &#39;INADDR_BROADCAST&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\ws2def.h(577) : error C2011: &#39;sockaddr_in&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(312) : see declaration of &#39;sockaddr_in&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(132) : error C2011: &#39;fd_set&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(68) : see declaration of &#39;fd_set&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(167) : warning C4005: &#39;FD_SET&#39; : macro redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(102) : see previous definition of &#39;FD_SET&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(176) : error C2011: &#39;timeval&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(111) : see declaration of &#39;timeval&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(232) : error C2011: &#39;hostent&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(167) : see declaration of &#39;hostent&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(245) : error C2011: &#39;netent&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(180) : see declaration of &#39;netent&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(252) : error C2011: &#39;servent&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(187) : see declaration of &#39;servent&#39;
    c:\program files\microsoft sdks\windows\v6.0a\include\winsock2.h(264) : error C2011: &#39;protoent&#39; : &#39;struct&#39; type redefinition
            c:\program files\microsoft sdks\windows\v6.0a\include\winsock.h(199) : see declaration of &#39;protoent&#39;


C++ Redefinition Header Files (winsock2.h)

I have the following C++ code:

    #include &lt;math.h&gt;
    #include &lt;cmath.h&gt;      // per http://www.cplusplus.com/reference/clibrary/cmath/abs/

    // snip ...

    if ( (loan_balance &lt; 0) &amp;&amp; (abs(loan_balance) &gt; loan_payment) ) {
        ...
    }


and `make` blows up on:

    error: call of overloaded &#39;abs(double)&#39; is ambiguous

also of interest:

    /usr/include/stdlib.h:785: note: candidates are: int abs(int)

**How can I specify that the compiler needs to call the abs() in cmath.h that can handle floats?**

Compiler info (Not sure if this matters):

    [some_man@some_box ~/some_code]#  gcc -v
    Using built-in specs.
    Target: i386-redhat-linux
    Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr    /share/info --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --enable-plugin --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic --host=i386-redhat-linux
    Thread model: posix
    gcc version 4.1.2 20080704 (Red Hat 4.1.2-44)

Ambiguous overload call to abs(double)

I know this question has been asked before but I still haven&#39;t seen a satisfactory answer, or a definitive &quot;no, this cannot be done&quot;, so I&#39;ll ask again!

All I want to do is get the path to the currently running executable, either as an absolute path or relative to where the executable is invoked from, in a platform-independent fashion. I though boost::filesystem::initial_path was the answer to my troubles but that seems to only handle the &#39;platform-independent&#39; part of the question - it still returns the path from which the application was invoked.

For a bit of background, this is a game using Ogre, which I&#39;m trying to profile using Very Sleepy, which runs the target executable from its own directory, so of course on load the game finds no configuration files etc. and promptly crashes. I want to be able to pass it an absolute path to the configuration files, which I know will always live alongside the executable. The same goes for debugging in Visual Studio - I&#39;d like to be able to run $(TargetPath) without having to set the working directory.

Get path of executable

I need to execute a program and retrieve its stdout output in c++. I&#39;d like my code to be cross-platform too.

Having recently discovered the wonderful world of the Boost c++ libraries for all your cross platform needs, I figured I&#39;d just go to boost.org and read up on the documentation of Boost.Process. Much to my surprise, it wasn&#39;t there! I then proceeded to figure out what name Boost gave their cross-platform library to start external processes, but haven&#39;t managed to find it so far.

A Google search brought me to Julio M. Merino Vidal&#39;s [Boost.Process][1], which seems to be the unofficial Boost library I was looking for. Strangely enough, I cannot seem to find a download link on that website. It also seems like there haven&#39;t been any recent developments regarding the project.

I was finally able to find a download link for Vidal&#39;s Boost.Process on an [external site][2] and will use that for now, but I&#39;m quite amazed at the effort I had to put in to get my hands on a cross platform c++ library to interact with external processes.

So, why is there no official Boost.Process? It seems like it would be a very valuable addition. Or am I totally overlooking the obvious solution here? Could you perhaps suggest other cross-platform libraries for managing simple starting of and interation with external processes?

  [1]: http://www.netbsd.org/~jmmv/process/
  [2]: http://www.highscore.de/boost/process/

Where is Boost.Process?

I&#39;m trying to implement a weighted random numbers. I&#39;m currently just banging my head against the wall and cannot figure this out.

In my project (Hold&#39;em hand-ranges, subjective all-in equity analysis), I&#39;m using Boost&#39;s random -functions. So, let&#39;s say I want to pick a random number between 1 and 3 (so either 1, 2 or 3). Boost&#39;s mersenne twister generator works like a charm for this. However, I want the pick to be weighted for example like this:

&lt;pre&gt;&lt;code&gt;1 (weight: 90)
2 (weight: 56)
3 (weight:  4)&lt;/code&gt;&lt;/pre&gt;

Does Boost have some sort of functionality for this?

Weighted random numbers

I recently wanted to use &lt;a href=&quot;http://www.boost.org/doc/libs/1_41_0/doc/html/string_algo/reference.html#header.boost.algorithm.string.join_hpp&quot;&gt; boost::algorithm::join &lt;/a&gt;but I couldn&#39;t find any usage examples and I didn&#39;t want to invest a lot of time learning the Boost Range library just to use this one function.  

Can anyone provide a good example of how to use join on a container of strings?  Thanks.

A good example for boost::algorithm::join

I find [boost::foreach][1] very useful as it saves me a lot of writing. For example, let&#39;s say I want to print all the elements in a list:

    std::list&lt;int&gt; numbers = { 1, 2, 3, 4 };
    for (std::list&lt;int&gt;::iterator i = numbers.begin(); i != numbers.end(); ++i)
       cout &lt;&lt; *i &lt;&lt; &quot; &quot;;

boost::foreach makes the code above much simplier:

    std::list&lt;int&gt; numbers = { 1, 2, 3, 4 };
    BOOST_FOREACH (int i, numbers)
       cout &lt;&lt; i &lt;&lt; &quot; &quot;;

Much better! However I never figured out a way (if it&#39;s at all possible) to use it for `std::map`s. The documentation only has examples with types such as `vector` or `string`.

[1]: http://www.boost.org/doc/libs/1_35_0/doc/html/foreach.html

Is it possible to use boost::foreach with std::map?

How do variant and any from the boost library work internally? In a project I am working on, I currently use a tagged union. I want to use something else, because unions in C++ don&#39;t let you use objects with constructors, destructors or overloaded assignment operators.

I queried the size of any and variant, and did some experiments with them. In my platform, variant takes the size of its longest possible type plus 8 bytes: I think it my just be 8 bytes o type information and the rest being the stored value. On the other hand, any just takes 8 bytes. Since i&#39;m on a 64-bit platform, I guess any just holds a pointer.

How does Any know what type it holds? How does Variant achieve what it does through templates? I would like to know more about these classes before using them.

Content Type	Original Author	Original Content on Stackoverflow
Question	the_drow	View Question on Stackoverflow
Solution 1 - C++	drby	View Answer on Stackoverflow

Boost.Any vs. Boost.Variant

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Function pointer as a member of a C struct

ASP.NET MVC Forms Authentication + Authorize Attribute + Simple Roles

Attributions