callable.hpp

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<>.

Features

Callables

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.

Traits

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
  

Example

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

Compilation

Library

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

Test cases

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

License

MIT. See LICENSE.txt for more details.