[jhc] How to fire jhc rules

Facundo Domínguez facundominguez at gmail.com
Mon Jan 17 23:45:33 CET 2011

Dear haskellers,
      In learning to use rules with jhc 0.7.6-3, I am trying to
compile the following test program with flags -f global-optimize -f
rules, but it seems I cannot get rule "hf" to fire. I've compiled the
program with ghc and the rule is applied in that case.

{-# NOINLINE f #-}
f x = x ++ "f"

{-# NOINLINE h #-}
h x = x++"h"

{-# RULES "hf" forall x. h (f x) = x  #-}

main = putStr (h (f "1"))

Rule "hf" is not preserving semantics so I can see if the rule is
applied by executing the result.

I would be thankful for any hint on how to get the rule applied as
well as how to get jhc to report which rules it has applied during


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