[Python-Dev] Re: Proper tail recursion (original) (raw)

Christian Tismer tismer at stackless.com
Mon Jul 19 23:17:36 CEST 2004

David Eppstein wrote:

In article <005701c46db5$764b48d0$6602a8c0 at arkdesktop>, "Andrew Koenig" <ark-mlist at att.net> wrote:

I also haven't seen the use case that requires this and couldn't easily be fixed by changing the data structure or code slightly. (Andrew Koenig's theoretical objections don't count as use cases.) Didn't we just hear that this problem affects pickling? We heard that the recursion limit prevents recursive DFS from being applied to large graphs, and that pickling uses DFS. However, tail recursion wouldn't help in this case -- it's a deep recursion but not a tail recursion.

[dropping interesting details for my brute-force solution]

I went a different and very simple path for Stackless: When cPickle goes too deep, I simply allocate a new C stack and let it continue. That was the simplest possible patch for me, since I only wanted it to no longer crash. Not that this is not needed for unpickling; this structure is as flat as it can be.

ciao - chris

-- Christian Tismer :^) <mailto:tismer at stackless.com> Mission Impossible 5oftware : Have a break! Take a ride on Python's Johannes-Niemeyer-Weg 9a : Starship http://starship.python.net/ 14109 Berlin : PGP key -> http://wwwkeys.pgp.net/ work +49 30 89 09 53 34 home +49 30 802 86 56 mobile +49 173 24 18 776 PGP 0x57F3BF04 9064 F4E1 D754 C2FF 1619 305B C09C 5A3B 57F3 BF04 whom do you want to sponsor today? http://www.stackless.com/

More information about the Python-Dev mailing list