< cpp‎ | types
Revision as of 20:24, 15 April 2013 by Cubbi (Talk | contribs)

Type support
Type properties
Supported operations
Relationships and property queries
Type modifications
Type transformations
Type trait constants

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Defined in header <type_traits>

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<td >
template< class >
class result_of; //not defined

<td > (1) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >
template< class F, class... ArgTypes >
class result_of<F(ArgTypes...)>;

<td > (2) </td> <td > (since C++11) </td> </tr> Template:ddcl list end

Deduces the return type of a function call expression at compile time.


Member types

Member type Definition
type the return type of the function F if called with the arguments ArgTypes...

Possible implementation

struct result_of;
template<class F, class... ArgTypes>
struct result_of<F(ArgTypes...)>
    typedef decltype(
                    ) type;


std::result_of can be used to determine the result of invoking a functor, in particular if the result type is different for different sets of arguments:

#include <type_traits>
struct S {
    double operator()(char, int&);
    float operator()(int);
struct C {
    double Func(char, int&);
int main()
    // the result of invoking S with char and int& arguments is double
    std::result_of<S(char, int&)>::type f = 3.14; // f has type double
    static_assert(std::is_same<decltype(f), double>::value, "");
    // the result of invoking S with int argument is float
    std::result_of<S(int)>::type d = 3.14; // f has type float
    static_assert(std::is_same<decltype(d), float>::value, "");
    // result_of can be used with a pointer to member function as follows
    std::result_of<decltype(&C::Func)(C, char, int&)>::type g = 3.14;
    static_assert(std::is_same<decltype(g), double>::value, "");

See also

obtains the type of expression in unevaluated context
(function template) [edit]