Re: [Haskell-cafe] A first glimps on the {-# NOUPDATE #-} pragma

Hi,

upd_noupd n = let l = myenum' 0 n in last l + length l

This could be rewritten as

upd_noupd n = let l n = myenum' 0 n in last (l n) + length (l n)

Or a special form of let could be introduced to define locally-scoped macros:

upd_noupd n = let# l = myenum' 0 n in last l + length l

What's the strength of the {-# NOUPDATE #-} approach? Regards, Facundo

Date: Wed, 29 Aug 2012 10:20:21 +0200 From: Joachim Breitner Subject: Re: [Haskell-cafe] A first glimps on the {-# NOUPDATE #-} pragma To: haskell-cafe@haskell.org Message-ID: <1346228421.4271.9.camel@kirk> Content-Type: text/plain; charset="iso-8859-15"

Hi,

Am Dienstag, den 28.08.2012, 18:16 -0400 schrieb Carter Schonwald:

...

On Tuesday, August 28, 2012, Yves Par?s wrote: Monad? Simple strictness anotation is enough in that case:

upd_noupd n = let l = myenum' 0 n h = head l in h `seq` last l + h

darn, I though I changed my examples before posting to:

upd_noupd n = let l = myenum' 0 n in last l + length l

("head" was a bad example because actually due to strictness analysis and worker/wrapper transformation, GHC would yield good code even without "`seq`").

In this case (which is actually the benchmarked case), reordering or strictness annotations do not help.

Greetings and sorry for the confusion, Joachim

-- Dipl.-Math. Dipl.-Inform. Joachim Breitner Wissenschaftlicher Mitarbeiter http://pp.info.uni-karlsruhe.de/~breitner