Re: [boost] [Review] Boost.Type Traits Extension by Frederic Bron

Subject: Re: [boost] [Review] Boost.Type Traits Extension by Frederic Bron
From: Vicente Botet (vicente.botet_at_[hidden])
Date: 2011-03-15 05:28:28

Frédéric Bron wrote:
> 
>> are you saying that you can check if the return type is actually void? I
>> believed that this was not possible, but who knows ...
> 
> If you look at the implementation, I must separate implementation for
> operators returning void and operators returning non-void.
> So I know if the operator returns void or not:
> 
> // this intermediate trait has member value of type bool:
> // - value==true -> operator- returns void
> // - value==false -> operator- does not return void
> template < typename RHS >
> struct operator_unary_minus_returns_void {
>    // overloads of function returns_void make the difference
>    // yes_type and no_type have different size by construction
>    static ::boost::type_traits::yes_type returns_void(returns_void_t);
>    static ::boost::type_traits::no_type returns_void(int);
>    static const bool
> value=(sizeof(::boost::type_traits::yes_type)==sizeof(returns_void((-make(),returns_void_t()))));
> };
> 

I'm not sure this works. Guiven the operator-() overloading for any, the
type of the expression

(-make(),returns_void_t())

is always returns_void_t, isn't it?

so  the following expression would be always true

sizeof(::boost::type_traits::yes_type)==sizeof(returns_void((-make(),returns_void_t())))

Best,
Vicente

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