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From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2007-06-05 09:47:22

"Atry" <pop.atry_at_[hidden]> wrote
> Hi everybody, I have an template function, and I want to know if it return
> void, but it does not work:
> template<typename T>
> struct is_foo_void : boost::is_void<BOOST_TYPEOF(T::foo(123))>{};
> struct foo_struct
> {
> template<typename T>
> static void foo(T){}
> };
> BOOST_STATIC_ASSERT(is_foo_return_void<foo_struct>::value);
> ////////////////////////////////////////////////////////////
> Yes, I know funtion_traits would be help if I have a non-template
> function,
> but in this case I can't, what should I do?

Boost.Typeof is unable to deduce the "void" type. This is because typeof is
ultimately beased on the type deduction mechanism provided by C++ when
passing an expression to a template function, such as:

template<class T>
<size-of-return-type-depends-on-T> foo(const T&);

Since it's not possible to pass a void expression to a function,
Boost.Typeof can't handle this type.

An idea of how to handle void inside typeof was suggested by Alexander
Nasonov in the past, but it has not been implemented so far.


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