Rust switches to external iteration

[bearophile]

Jonathan M Davis:

> And given how useless pure input ranges are, I really don't see 
> much value in
> that. About all they give you is the ability to iterate over a 
> set of values
> once. The other range types are _far_ more powerful, and pure 
> input ranges
> should be avoided as much as possible IMHO.

Python generators are essentially input ranges, you can go only 
forward, and they yield their results only once:


>>> g = (i ** 2 for i in xrange(5))
>>> list(g)
[0, 1, 4, 9, 16]
>>> list(g)
[]
>>> def gen():
...     for i in xrange(5):
...         yield i * i
...
>>> g = gen()
>>> list(g)
[0, 1, 4, 9, 16]
>>> list(g)
[]


Yet in Python they are used everywhere. I define input ranges 
often in D and I think they are useful.

Having a built-in "yield" in a language is quite handy. Take a 
look at the Python and the second D solutions here:
http://rosettacode.org/wiki/Same_Fringe

Bye,
bearophile