result_of Class

Determines the return type of the callable type that takes the specified argument types.

Syntax

template<class>  
struct result_of; // Causes a static assert  

template <class Fn, class... ArgTypes>  
struct result_of<Fn(ArgTypes...)>;

// Helper type  
template<class T>
   using result_of_t = typename result_of<T>::type;

Parameters

Fn
The callable type to query.

ArgTypes
The types of the argument list to the callable type to query.

Remarks

Use this template to determine at compile time the result type of Fn(ArgTypes), where Fn is a callable type, reference to function, or reference to callable type, invoked using an argument list of the types in ArgTypes. The type member of the template class names the result type of decltype(std::invoke(declval<Fn>(), declval<ArgTypes>()...)) if the unevaluated expression std::invoke(declval<Fn>(), declval<ArgTypes>()...) is well-formed. Otherwise, the template class has no member type. The type Fn and all types in the parameter pack ArgTypes must be complete types, void, or arrays of unknown bound.

Requirements

Header: <type_traits>

Namespace: std

See Also

<type_traits>