Re: desperately seeking RULES help

claus.reinke:

...

Here it is:

{-# OPTIONS_GHC -O2 -Wall -fglasgow-exts -ddump-simpl #-} -- compile with: ghc -fno-method-sharing -c F.hs

thanks! it seems i misread the users guide (or is this a bug?). i used -frewrite-rules ("Switch on all rewrite rules"), which does not(!) work, instead of -fglasgow-exts, which does work (ghc-6.9.20080514, booted from 6.6.1).

i learned something new,-)

Right. There are two things here: 1) -frewrite-rules enables rules to fire. 2) -fglasgow-exts enables parsing of RULES pragmas, and their interpretation. You need both if you wish to both write your own rules, and have them fire. -- Don