PEP 276 Simple Iterator for ints (fwd)

David Eppstein eppstein at ics.uci.edu
Thu Dec 6 04:21:43 CET 2001


In article <mailman.1007602329.14054.python-list at python.org>,
 "Delaney, Timothy" <tdelaney at avaya.com> wrote:

> > I meant translating
> > 
> >     for 0 <= i < 10:
> >         print i
> > 
> > into
> > 
> >     i = 0
> >     while i < 10:
> >         print i
> >         i += 1
> > 
> > There is no iterator here.
> 
> This would not work with either the old or the new semantics of for loops.
> It would mean that you would have for loops which in this one particular
> case behaved differently to all other cases. That would classify as a severe
> wart.

I agree: if "for x in list" doesn't change subsequent iterations if you 
rebind x or list within the loop body, neither should "for x <= i < y" 
or whatever similar syntax one uses. So that means, it should construct an 
iterator and then act as if it were called by "for i in iterator" (I 
hesitate to write an explicit formula for the iterator because of 
difficulty getting it right when x or y may be non-integer).
-- 
David Eppstein       UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/



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