Rust switches to external iteration

[Jonathan M Davis]

On Thursday, July 04, 2013 21:40:23 w0rp wrote:
> On Thursday, 4 July 2013 at 19:26:43 UTC, Jonathan M Davis wrote:
> > Sometimes, you're stuck, because the nature of the type that
> > you're dealing
> > with forces it to be a pure input range, but you just can't
> > take advantage of
> > many algorithms with pure input ranges, which means that you
> > have to write a
> > lot more code or use std.array.array in order to use the
> > various algorithms,
> > forcing you to allocate when it should be completely
> > unnecessary.
> 
> That is exactly why yield is useful, because without yield, you
> have two options.
> 
> 1. Write a lot of code to create an InputRange. (Cost in time
> taken to write it.)
> 2. Allocate and lose on performance. (Cost in runtime
> performance.)
> 
> Yield gives you option 3.
> 
> 3. Write very little code while also saving on performance.

Except that in most cases, you should have been writing a range type with more 
capabilites than an input range. IMHO, something like yield would pretty much 
only be of value in situations where you just need to iterate over something 
(so you're not taking advantage of much in the way of algorithms) and where 
you need a range type specific to your program which will never be reused 
anywhere. And that implies that you're not writing very reusable code. 
Sometimes, that's the way things go, but ranges and algorithms are such that 
most of the time, you should be able to write range-based functions which are 
reusable. And if you're doing that, you should be writing ranges with the full 
set of capabilites that they can have, not just input ranges.

- Jonathan M Davis