[Haskell-cafe] curious about sum

Stephan Friedrichs deduktionstheorem at web.de
Sat Jun 13 10:26:49 EDT 2009

Jochem Berndsen wrote:
> Keith Sheppard wrote:
>> Is there any reason that sum isn't strict? I can't think of any case
>> where that is a good thing.
>> Prelude> sum [0 .. 1000000]
>> *** Exception: stack overflow
> It is useful if the (+) is nonstrict; although I cannot think of any
> useful mathematical structure where (+) would be nonstrict.

What about some numeric representations?

type MyNum = [()]

instance Num MyNum where
  (+) = (++)



Früher hieß es ja: Ich denke, also bin ich.
Heute weiß man: Es geht auch so.

 - Dieter Nuhr

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