Avoiding argument checking in recursive calls

[Paul Rubin]

Paul Rubin <http://phr.cx@NOSPAM.invalid> writes:
> I'd write nested functions:
> 
>     def fact(n):
>        if n < 0: raise ValueError
>        def f1(n):
>           return 1 if n==0 else n*f1(n-1)
>        return f1(n)

I forgot to add: all these versions except your original one should
add a type check if you are trying to program defensively.  Otherwise
they can recurse infinitely if you give a positive non-integer arg like
fact(3.5).