Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info>:
> I have this snippet of SML code which I'm trying to translate to Python:
>
> fun isqrt n = if n=0 then 0
> else let val r = isqrt (n/4)
> in
> if n < (2*r+1)^2 then 2*r
> else 2*r+1
> end
>
>
> I've tried reading up on SML and can't make heads or tails of the
> "let...in...end" construct.
>
>
> The best I've come up with is this:
>
> def isqrt(n):
> if n == 0:
> return 0
> else:
> r = isqrt(n/4)
> if n < (2*r+1)**2:
> return 2*r
> else:
> return 2*r+1
>
> but I don't understand the let ... in part so I'm not sure if I'm doing
> it right.
You must make sure "r" doesn't leak outside its syntactic context so:
def isqrt(n):
if n == 0:
return 0
else:
def f2398478957():
r = isqrt(n//4)
if n < (2*r+1)**2:
return 2*r
else:
return 2*r+1
return f2398478957()
(Also use // instead of /: isqrt = integer square root.)
Marko
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