Boost C++ Application Development Cookbook - Second Edition

Getting a function's result type at compile time

Many good features were added to C++11 to simplify the metaprogramming. One such feature is the alternative function syntax. It allows deducing the result type of a template function. Here is an example:

template <class T1, class T2>auto my_function_cpp11(const T1& v1, const T2& v2)    -> decltype(v1 + v2){    return v1 + v2;}

It allows us to write generic functions more easily:

#include <cassert>struct s1 {};struct s2 {};struct s3 {};inline s3 operator + (const s1& /*v1*/, const s2& /*v2*/) {    return s3();}inline s3 operator + (const s2& /*v1*/, const s1& /*v2*/) {    return s3();} int main() {    s1 v1;    s2 v2;    s3 res0 = my_function_cpp11(v1, v2);    assert(my_function_cpp11('\0', 1) == 1);}

But, Boost has ...