Re: [boost] [range] [extensions] Default values for range access adaptors?

Subject: Re: [boost] [range] [extensions] Default values for range access adaptors?
From: Akira Takahashi (faithandbrave_at_[hidden])
Date: 2013-06-06 00:35:36

Hi Michel,

2013/6/6 Michel Morin <mimomorin_at_[hidden]>

> Akira Takahashi wrote:
> > My Boost.Range Extension has `front` accessor.
>
> "Range Access" adaptors in your extensions are interesting.
> For the consistency of range adaptors, shouldn't `front` adaptor
> return `single` range?
>

I see. `optional_front` usage is following:

if (optional<T> x = r | optional_front()) {
  std::cout << x.get() << std::endl;
}

If `front` return signle range, the usage is following:

for (T x : x | front) {
  std::cout << x << std::endl;
}

If `front` is error, the return value is empty range.
I think single range approach is better. However, I think now `front` and
`optional_front` is useful.

I would like to add `optional_front` and `front_range`.

Thanks!
Akira