range doesn't return a forward iterator. Range<A> also implements DoubleEndedIterator.
On Thu, Apr 10, 2014 at 12:53 AM, Kevin Ballard <ke...@sb.org> wrote: > On Apr 9, 2014, at 9:50 PM, Tommi Tissari <rusty.ga...@icloud.com> wrote: > >>> On 10 Apr 2014, at 00:22, Kevin Ballard <ke...@sb.org> wrote: >>> >>> FWIW, my point about range is it relies on One being the number 1, rather >>> than being the multiplicative identity. AFAIK there's nothing special about >>> 1 in a ring outside of its status as a multiplicative identity. Certainly >>> it's not considered some special value for addition. >> >> Another problem with std::iter::range is that it requires too much from its >> argument type A by saying A must implement Add<A, A> while it only returns a >> forward iterator. >> >> Perhaps, in order to make a more sensible implementation of iter::range, a >> new concept, a trait, is needed to be able to specify that a certain type T >> implements a method 'increment' that modifies a variable of type T from >> value x to value y such that: >> 1) x < y >> 2) there is no valid value z of type T satisfying x < z < y >> >> For integral types there would an implementation of this trait in stdlib >> with 'increment' doing x += 1; >> >> Then, a natural extension to this trait would be a trait that has a method >> 'advance(n: uint)' that would, at constant time, conceptually call the >> 'increment' method n times. >> >> Then there would also be a 'decrement' method for going the other direction. >> >> There probably needs to be some other use cases for this new trait to carry >> its weight though. > > This trait would disallow range(0f32, 10f32) because there are quite a lot of > valid values z of type f32 satisfying 0f32 < z < 1f32. > > -Kevin > _______________________________________________ > Rust-dev mailing list > Rust-dev@mozilla.org > https://mail.mozilla.org/listinfo/rust-dev -- http://octayn.net/ _______________________________________________ Rust-dev mailing list Rust-dev@mozilla.org https://mail.mozilla.org/listinfo/rust-dev
