claus.reinke:
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.
nope!-) -fglasgow-exts is sufficient for the RULE to be parsed and applied in Lennart's code, -frewrite-rules doesn't seem to serve any noticable purpose.
Well, if -O is on, -frewrite-rules is already on by default. Try -fno-rewrite-rules with -O to turn them off specifically, or in ghci, -frewrite-rules can be used to help them fire even on bytecode.
but i see now this is under re-evaluation, aptly titled:
"Confusing flags for rewrite rules" http://hackage.haskell.org/trac/ghc/ticket/2213 (see simonpj's comment at the end)
Right. -- Don