jac:

Hi,

I'd like to learn how to use ghc rewrite rules. I simply want to replace a function called f by a function called g. I do not unterstand why the rule f->g does not fire.

Cheers, Jan

module Main where

{-# RULES "f->g" forall x. f x = g x #-}

main :: IO () main = print (f 1)

{-# NOINLINE f #-} f :: a -> Bool f _ = False

g :: a -> Bool g _ = True

Did you enable rewrite rules? $ ghc -fenable-rewrite-rules A.hs --make $ time ./A True ./A 0.01s user 0.00s system 88% cpu 0.011 total Using ghc-core: 1 RuleFired 1 f->g -- Don