[boost] Re: Re: Re: FOREACH / C++ "for" proposal

From: Thorsten Ottosen (nesotto_at_[hidden])
Date: 2005-05-10 15:10:23

"Peter Dimov" <pdimov_at_[hidden]> wrote in message 
news:00c101c55591$877dbab0$6401a8c0_at_pdimov2...
| Thorsten Ottosen wrote:
| > "Peter Dimov" <pdimov_at_[hidden]> wrote in message
| > news:02b001c554cd$47504940$6401a8c0_at_pdimov2...
|
| [...]
|
| >> for( [type] [identifier] : [expr] )
| >>    [statement]
| >>
| >> Let e of type E be the value of [expr]. For each iterator i in the
| >> range
| >>
| >> - [ e.begin(), e.end() ) when E is not an array type;
| >> - [ e, e + N ) when E is T[N],
| >>
| >> executes the compound statement
| >>
| >> {
| >>    [type] [identifier] = *i;
| >>    [statement]
| >> }
| >>
| >>
| >>
| >> doesn't require library support.
| >
| > but it wouldn't work with pair<iterator,iterator> without an adapter.
|
| Correct.

and it also makes it harder to treat const char[N] differently.

| I think that the benefits of not having to include <iterator> and
| confining this to a pure core extension not requiring library support
| outweigh the costs.
|
| pair<iterator, iterator> is not the proper way to express an iterator range
| anyway; its use in the standard library only serves to highlight the lack of
| iterator_range<iterator>, or even range<iterator>, if you prefer.

still, a lot of code depends on it...it seems really silly that this new 
construct
should be made harder to use for those libraries.

An <std> header is the way to go IMO.

anyway, I'll try to get a discussion on this in Quebec.

| >> One reasonable extension
| >
| > perhaps. C++ is typed language.
| >
| >> would be to allow [type] to be omitted, ...
|
| This form is even more typed than the other, because it doesn't let you
| accidentally supply a wrong type.

for( auto i : vec )
       ;

will already work

-Thorsten