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
