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Subject: Re: [Boost-users] Can not compile a program that uses typeof package by gcc?
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-10-20 12:14:23


Peng Yu wrote:
> template <typename T1, typename T2>
> struct multiply_traits;
> template <typename T1, typename T2>
> struct multiply_traits<X<T1>, T2> {
> typedef X<T1> result_type;
> };

The most reliable way to define multiply_traits in general is

template<class T>
T make();

template<class T1, class T2>
struct multiply_traits {
    BOOST_TYPEOF_NESTED_TYPEDEF_TPL(nested, make<T1>() * make<T2>());
    typedef typename nested::type type;

> Y<BOOST_TYPEOF(T1() * T2())> operator*(const Y<T1> &y, const T2 &t)

You need to use BOOST_TYPEOF_TPL.
Some compilers can handle this (I just tried it on msvc 9.0), but I strongly
advise using multiply_traits as defined above for portability.

In Christ,
Steven Watanabe

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