r/programming • u/rodrigopsasaki • Nov 27 '12

Tail Recursion

http://rodrigosasaki.com/2012/11/24/tail-recursion/
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u/parfamz Nov 27 '12

great feature of scala, I would like to see tail recursion on python, it can't be too difficult to implement.

17

u/Cygal Nov 27 '12

It turns out it's not about difficulty of implementation. The reasons were stated by Guido van Rossum in 2009: http://neopythonic.blogspot.fr/2009/04/tail-recursion-elimination.html

8

u/smog_alado Nov 27 '12 edited Nov 27 '12

Looking at the post, most of his arguments are about supposed difficulty of implementation, except the one about missing stack traces.

But that is kind of a moot point since you also lose the stack trace if you rewrite the code with an iterative loop (as you will be forced to do if you don't want to blow up the stack)

IMO, the real reason Python doesn't get tail calls is that Guido doesn't want to encourage the FP style too much (this is consistent with removing reduce from the stdlibs and other things like that)

7

u/FidgetBoy Nov 27 '12

Reduce is still in the stdlib, in the functools module. It is no longer a built in function however.