Ah, thanks.
It turns out that this works:
transform t l = error "urk"
but this doesn't:
transform t l = FM $ error "urk"
So it has something to do with the newtype FMList. They are probably
already gone when rewrite rules fire?
Sjoerd
On Jun 24, 2009, at 6:32 PM, Ryan Ingram wrote:
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<[email protected]> wrote:
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
<Rules.hs>
--
Sjoerd Visscher
[email protected]
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--
Sjoerd Visscher
[email protected]
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