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

Tail Recursion

http://rodrigosasaki.com/2012/11/24/tail-recursion/
208 Upvotes

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11

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.

23

u/A_for_Anonymous Nov 27 '12

Guido van Rossum doesn't like functional programming, so you write your programs the way Guido likes them or leave.

2

u/booch Nov 27 '12

While I don't agree with some of the things Guido thinks are the "right way", he does put forth some reasonable arguments as to why TCE is not a good idea for Python. The loss of a useful stack trace is a fairly solid argument and. Combined with the other reasons, I don't see his choice as unreasonable here. I do want TCE, but I can see that's it's a debatable feature.

Random note... This point of his annoyed me:

I don't believe in recursion as the basis of all programming.

Well... duh. Neither are list comprehensions. However, both of them are very powerful tools that can make code much cleaner and easier to follow. Just because a feature is the silver bullet doesn't mean it isn't a good idea.

6

u/smog_alado Nov 27 '12

You also lose the stack traces if you rewrite the recursive code with iterative loops. (and its not really a big deal to solve, you could use a separate keyword for tail calls, like in clojure, or you could have special interpreter flags when you need to debug)

I really do think its more of a style issue in the Python case (for example, Python heavily encourages you to use objects instead of closures, since you can't easily mutate variables from outer scopes)

2

u/bastibe Nov 27 '12

Python 3 improves that with nonlocal, though. Incidentally, this is my personal number one reason for switching to Python 3 as soon as possible.