Re[2]: [Haskell-cafe] CPS and the product function

Hello michael, Monday, April 20, 2009, 6:32:47 PM, you wrote: something like 0*_ = 0 x*y = x *# y or vice versa _*0 = 0 x*y = x *# y where *# is original (*) definition. current ghc definiton just performs cpu-level operation w/o checking for 0 since this is rarely useful and need some time OTOH, boolean operations are expected to short-circuit, so they are defined properly. try and (iterate [True,False])

Hi Eugene,

Clever solution.

It didn't come right back so I interrupted it. Guess it would do all those multiplies by zero.

Does anyone know how to define it to avoid that?

Thanks.

Michael

--- On Mon, 4/20/09, Eugene Kirpichov wrote:

From: Eugene Kirpichov Subject: Re: [Haskell-cafe] CPS and the product function To: "michael rice" Cc: haskell-cafe@haskell.org Date: Monday, April 20, 2009, 9:40 AM

Check that by experiment in ghci or by looking at the source:

Prelude*>> product [0..]

Or search "product" at http://holumbus.fh-wedel.de/hayoo/hayoo.html and click on one of the Source links.

2009/4/20 michael rice :

...

I've been looking at CPS in Haskell and wondering how many multiplications the product function performs if it encounters a zero somewhere in the input list. Zero?

Does anyone know the definition of the product function?

Michael

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