Re: container design (Was: std::complex design (Was: N-Dimensional array))

From: rwgk (rwgk_at_[hidden])
Date: 2002-03-10 02:20:07

--- In boost_at_y..., Howard Hinnant <hinnant_at_t...> wrote:
> A typical implementation might look something like (warning, 
unchecked 
> pseudo code):
> 
> template <class F>
> vector(size_type n, F init, const Allocator& a = Allocator())
> {
> 	choose_F_init(n, init, a, int2type<!is_convertible<F, 
> value_type>::value>());
> }
> 
> Then you've got two overloads for choose_F_init:
> 
> 1.  Takes a int2type<false>.  F *is* convertible to value_type.  
This is 
> a mistaken binding.  Redirect to the code that implements 
> vector(size_type, value_type, allocator); (converting init to a 
> value_type of course).
> 
> 2.  Takes a int2type<true>.  F will not convert to value_type.  
This is 
> the real deal, do whatever you were going to do in the first place 
with 
> (n, init, a).

Thanks a lot for this!

> Now isn't:
> 
> template <class F : !is_convertible<F, value_type>::value>
> vector(size_type n, F init, const Allocator& = Allocator());
> 
> *much* easier?! :-)  The compiler does the redirecting for you, but 
> under your precise instructions.

I am 100% with you. Remember the thread starting with message 23337?
Ralf