A C++ 11 template for type traits of callables (like functions, objects with operator(), lambda functions, ...).

The template, callable_traits, can be used to determine useful properties of callable objects, like return type, number of arguments and types of the individual arguments.

It is especially useful in template functions/... that handle callable objects, for example as callbacks. callable_traits allows the code to treat different types of callables uniformly without wrapping them in a std::function<>.

Callables are things that can be called with ():

• Functions
• Function pointers
• Objects with operator()
• std::function<...>
• Lambda functions

callable_traits can be used to treat all these different kinds of callables uniformly in a template function.

callable_traits deduces the following properties from the type T of a callable:

• The return type

    typename callable_traits<T>::return_type
  

• The number of arguments

    callable_traits<T>::argc
  

• The individual argument types

    typename callable_traits<T>::template argument_type<N>
  

• A function type representing the call:

    typename callable_traits<T>::function_type
  

template<typename Callable>
void metainfo(Callable f) {
   std::cout << callable_traits<Callable>::argc << " arguments" << std:endl;
}

The library is header only, so it doesn't need to be compiled. Just include the header file when you need it.

To compile the test cases, you need:

• SCons as a build tool
• Boost.Test for the test cases

With these tools you can compile callable_test by running scons in the main directory:

scons

MIT. See LICENSE.txt for more details.