Steven D'Aprano wrote:
I sometimes write recursive functions like this simple factorial:
def fact(n):
if n < 0: raise ValueError
if n = 0: return 1
return fact(n-1)*n
At the risk of premature optimization, I wonder if there is an idiom for
avoiding the unnecessary test for n <= 0 in the subsequent recursive
calls? For the sake of the argument, let's pretend the test is expensive
and I have a good reason for wanting to avoid it on subsequent calls :)
How about:
def fact(n):
if n < 2:
if n < 0:
raise ValueError
return 1
return fact(n - 1) * n
But really, iteration is the solution to this, and avoiding the
right answer is a mistake. I couldn't resist fixing your test
so you do one less layer of recursion.
--Scott David Daniels
scott.dani...@acm.org
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