[Haskell-cafe] CPS and the product function

[Bulat Ziganshin]

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 <ekirpichov at gmail.com> wrote:

> From: Eugene Kirpichov <ekirpichov at gmail.com>
> Subject: Re: [Haskell-cafe] CPS and the product function
> To: "michael rice" <nowgate at yahoo.com>
> Cc: haskell-cafe at 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 <nowgate at yahoo.com>:
>> 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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-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com