Steven D'Aprano <st...@remove-this-cybersource.com.au> writes: > On Fri, 16 Apr 2010 08:48:03 -0700, Aahz wrote: > >>>Nevertheless, it is a common intuition that the list comp variable >>>should *not* be exposed outside of the list comp, and that the for-loop >>>variable should. Perhaps it makes no sense, but it is very common -- >>>I've never heard of anyone being surprised that the for-loop variable is >>>exposed, but I've seen many people surprised by the fact that list-comps >>>do expose their loop variable. >> >> I've definitely seen people surprised by the for-loop behavior. > > What programming languages were they used to (if any)? > > I don't know of any language that creates a new scope for loop variables, > but perhaps that's just my ignorance...
I think Pascal and Modula-2 do this, Fortran does this, as well as Ada. I'm sure derivatives of Ada like Oracle's PL/SQL also enforce this. And of course C/C++/Java if the programmer wants it that way. Actually I think C was the first to consider "for" as some kind of syntactic sugar for "while" (thus blurring the notion of a for-loop forever). Python's for is really a member of the for-each family. May I add that having strict for-loop iterators is a good thing, at least in languages like C/C++/Fortran/etc. Optimizing compilers usually spend some time detecting so-called "induction variables" when they're not given: it helps simplifying loop bodies, it reduces register pressure, and changes many array accesses into pointer increments, among other things. -- Alain. -- http://mail.python.org/mailman/listinfo/python-list
