Re: [boost] proposal for metafunction mpl::eval

Subject: Re: [boost] proposal for metafunction mpl::eval
From: Nathan Ridge (zeratul976_at_[hidden])
Date: 2013-09-11 19:01:04

>>> I'm not so much into meta-programming, so I'm not sure whether
>>> there's already an alternative available.
>>>
>>> Nevertheless I'd like to propose a new metafunction that simply
>>> evaluates its argument:
>>>
>>> template<typename F>
>>> struct eval: F::type
>>> {};
>>
>> You can only derive from class types, so this can't be used with
>> metafunctions returning scalar types, references, pointers, arrays, or
>> functions.
>
> I'm aware of this, however the implementation could be different:
>
> template<typename F>
> struct eval
> {
> typedef typename F::type type;
> }

This is now a different metafunction - you have to write

typename eval<F>::type

to get at the type (rather than just eval<F>), which is no better than

typename F::type

Regards,
Nate