From: Johann Hibschman <johannh@...>
Date: 2002-02-07T04:02:12+09:00
Subject: Re: Call/CC and Ruby iterators.

timsuth@ihug.co.nz (Tim Sutherland) writes:

> No. Ruby's ``iterators'' just call a closure repeatedly. The 'callcc' method
> in Ruby is equivalent to Scheme's call/cc.
> 
> Ruby
> 	[1, 2, 3].map { |x| x+1 }
> Scheme
> 	(map (lambda (x) (+ x 1)) (list 1 2 3))

No, this isn't quite true.  Ruby iterators define "break" (to stop the
iteration) and "next" to skip to the next iteration.  This is harder
to do with continuations.

i.e.

> 10.times {|i| puts i; next if i == 2; break if i == 4; puts 'foo'}
0
foo
1
foo
2
3
foo
4
nil

How would you do this in Scheme?

--Johann