Extract the return type of a function without calling it (using templates?)

Question

I\'m looking for a way in C++ to extract the return type of a function (without calling it). I presume this will require some template magic.

float Foo();
i         


        

Answer 1

Foo and Bar are functions, not function types, so you need to do a bit of extra work.

Here's a solution using a combination of boost::function_traits and BOOST_TYPEOF.

#include 
#include 

float Foo();
int Bar();

int main()
{
  boost::function_traits::result_type f = 5.0f;
  boost::function_traits::result_type i = 1;
  return i;
}

Edit:

• This will work for functions of any arity up to 10, which should be enough for most sensible uses.
• This use of BOOST_TYPEOF works on platforms that do not supply a native typeof, so it's reasonably portable.