Re: [Boost-users] boost-users: boost enable_if

what i want to do is if type "T" happens to be a integeral type *or* a class type that inherits from boost::operators than let the function compile otherwise a compile time error appears. Basically T is any integeral type or any class type that derives from boost::operators. On 9/26/07, David Abrahams wrote:

on Wed Sep 26 2007, "chun ping wang" wrote:

...

template <typename T> bool boost::pseudoprime(const T& n, const T& k) { typedef boost::operators<T> operatorT; BOOST_STATIC_ASSERT(is_integral<T>::value); // static assert 1. BOOST_STATIC_ASSERT((is_base_of::value)); // static assert 2. BOOST_ASSERT (n > T(2) && n % T(2) != 0); return modular_expo(k, n-1, n) != T(1) % n ? true : false; }

now in vistual studio 2005 sp1 and visual studio 2008 beta the part "is_base_of::value" does not work if T happens to be an int or long due to "error C2803: 'operator --' must have at least one formal parameter of class type". I want to use enable_if to enable the STATIC_ASSERT only if T is NOT an arithmetic type for static assert 2.

enable_if can't "enable static asserts" in any sense that I understand. What are you really trying to do? Try to describe it without mentioning enable_if or STATIC_ASSERT. Just talk about the behavior you want.

-- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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