[Haskell-cafe] curious about sum
keithshep at gmail.com
Sat Jun 13 10:47:46 EDT 2009
That's an interesting example. I guess a lazy number system like that
would work nicely for Deniz's use case.
On Sat, Jun 13, 2009 at 10:26 AM, Stephan
Friedrichs<deduktionstheorem at web.de> wrote:
> 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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