Re: [Boost-users] Determine at compile time whether type has subtraction semantics?

Subject: Re: [Boost-users] Determine at compile time whether type has subtraction semantics?
From: Frédéric Bron (frederic.bron_at_[hidden])
Date: 2011-02-19 01:51:52

> Is it possible to determine at compile-time if a type has subtraction
> semantics? E.g. in struct A<T> I would like to decide at compile-time not to
> execute &A::subtract in the register_fns method. Then the subtract method is
> not instantiated and there is no error.

You can look at the code that will be reviewed soon for an extension
of type traits.

#include <boost/type_traits/has_operator_minus.hpp>

boost::has_operator_minus<T, T, T>::value is what you want:
is true if x-y returns something convertible to T
is false if operator-(T, T) does not exist.

http://www.boostpro.com/vault/index.php?action=downloadfile&filename=type_traits.tar.bz2&directory=Extension&

Frédéric