[Haskell-cafe] Flattening tail recursion?
jules at jellybean.co.uk
Fri Dec 10 14:04:02 EST 2004
On 10 Dec 2004, at 16:35, Ben Rudiak-Gould wrote:
> Jules Bean wrote:
>> On 10 Dec 2004, at 15:34, Robert Dockins wrote:
>>> So it should get "flattened," but it still doesn't run in constant
>>> space because the "x" parmeter isn't strict, so it will accumulate a
>>> bunch of closures like (((((((0)+1)+1)+1)+1)+1).... To make it
>>> strict, do something like this:
>> Isn't this what the strictness analyser is for? Doesn't GHC know that
>> + for Int is strict in both arguments, and therefore it shouldn't
>> accumulate a great big thunk like that?
> It doesn't know that about (+) :: Num a => a -> a -> a. The original
> poster's code didn't mention Int anywhere, so GHC probably had to
> assume the worst.
Forcing it to Int doesn't help though :(
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