Re: simple rewrite rule example

22 Jun 2010

      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

Re: simple rewrite rule example

Don Stewart