Your FMLists are defaulting to Integer, so the rule (which
specifically mentions Int) doesn't apply. Simon's code doesn't have
this problem because of the explicit signature on "upto"; you could do
the same by limiting "singleton" to Int.
-- ryan
On Wed, Jun 24, 2009 at 12:44 AM, Sjoerd Visscher
Thanks for looking into this.
Your code does give me 2 firings. But not when I replace [] with FMList. See the attached code.
Sjoerd
On Jun 23, 2009, at 5:59 PM, Simon Peyton-Jones wrote:
| I have a rewrite rule as follows: | | {-# RULES | "transform/transform" forall (f::forall m. Monoid m => (a -> m) -> (b - | > m)) | (g::forall m. Monoid m => (b -> m) -> (c | -> m)) | (l::FMList c). transform f (transform g | l) = transform (g.f) l | #-} | | It fires on this code: | | print $ transform (. (*2)) (transform (. (+1)) (upto 10)) | | But it doesn't fire on this code: | | print $ map (*2) (map (+1) (upto 10)))
That's odd. It works for me.
Specifically, I compiled the attached code with GHC 6.10, and I get two firings of transform/transform.
Does that not happen for you?
Simon
-- Sjoerd Visscher sjoerd@w3future.com
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