# New Ticket Created by Siddhant Saraf # Please include the string: [perl #113026] # in the subject line of all future correspondence about this issue. # <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=113026 >
$ perl6 -v This is perl6 version 2012.05-15-gdca0fa6 built on parrot 4.4.0 revision RELEASE_4_4_0 <sisar> so here is the same code in perl6 and python: https://gist.github.com/2762953. While the perl6 the loop terminates, in pyhton it is an infinite loop. Though both behaviour have their reasons, I can't decide which is better. <sisar> why python's behaviour is logical, perl6's behaviour is trying to prevent one from potentially infinite loops ... <sisar> so, perl6 makes a temporary copy of @array before it even starts looping. Why ? ... <flussence> it counts the array then iterates over it ... <flussence> copying every array just to loop over it would be crazy inefficient, I think only PHP does that (and only because it uses copy on write) <sisar> flussence: what are merits of that, counting before iterating ? <sisar> flussence: aye, making a copy would be super inefficient. <flussence> if you have an SQL result pretending to be an array, you don't want it going off and calling a .count that does "select count(*)" on every iteration <sisar> flussence: i'm sorry i'm not familiar with SQL <geekosaur> don't worry about it. point is that an array might not be an array, it might be a big chunk of code pretending to be an array <geekosaur> and you don't want to hammer that big chunk of code pointlessly <flussence> it'd be like calling strlen() in C on a really big string ... <TimToady> the whole point of lazy lists is that you never ask for the size of something you're iterating over if you can help it <TimToady> and I think an array iterator should be able to track a growing array without snapshotting the old length <flussence> that makes sense, but I can't imagine it being fun to implement :) ... <sisar> TimToady: so it is a genuine bug? fwiw, both niecza and rakudo iterate only twice. <TimToady> I think so
