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godmodder

decltype on std::async

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Hello,

 

I was experimenting with some C++11. I want to create std::vectors of std::futures that come from std::async.

When using decltype(), this works for lambdas and functors, but not for regular functions:

 

[source]

unsigned int m()
{
    return 1;
}

class n {
public:
    unsigned int operator()() { return 1; }
};

int main() {

    auto l = []() -> unsigned int { return 1; };
    std::vector < decltype( std::async(l) ) > r1;
    std::vector < decltype( std::async(n())  ) > r2;
    std::vector < decltype( std::async(m) ) > r3;                  -> this line fails to compile

 

    return 0;

}

[/source]

 

But the line I indicated fails with the following compile errors:

 

Error    1    error C2780: 'std::future<result_of<enable_if<std::_Is_launch_type<_Fty>::value,_Fty>::type(_ArgTypes...)>::type> std::async(_Policy_type,_Fty &&,_ArgTypes &&...)' : expects 3 arguments - 1 provided    c:\users\jeroen\documents\visual studio 2013\projects\threading\threading\main.cpp    38
Error    2    error C2893: Failed to specialize function template 'std::future<result_of<enable_if<!std::_Is_launch_type<decay<_Ty>::type>::value,_Fty>::type(_ArgTypes...)>::type> std::async(_Fty &&,_ArgTypes &&...)'    c:\users\jeroen\documents\visual studio 2013\projects\threading\threading\main.cpp    38
 

 

Can somebody help me make sense of these errors?

 

Regards,

Jeroen

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Your code compiles with GCC 4.8 and Clang 3.2. I'd say it's your compiler at a fault here.

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Hmm, strange. I am using the MSVC 2013 compiler.

I wonder what the reason is it does not compile.

 

Anyway, thank you for your help :)

Edited by godmodder

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I am using the MSVC 2013

MSVC 2013 only partially supports C++11, and there are some bugs in the features it does support.

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