#5059: Pragma to SPECIALISE on value arguments
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Reporter: batterseapower | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 7.4.1
Component: Compiler | Version: 7.0.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by simonpj):
Here's another example where I'd like to write a specialise-on-value
pragma. Consider equality on lists:
{{{
eqList [] [] = True
eqList (x:xs) [] = False
eqList [] (y:ys) = False
eqList (x:xs) (y:ys) = x==y && eqList xs ys
}}}
I'd like to specialise on the empty list
{{{
{-# SPECIALISE eqList [] xs #-}
{#- SPECIALISE eqList xs [] #-}
}}}
because in each case the result boils down to `null`, and that's great at
the call sites. This shows up in `string_of` in nofib `spectral/rewrite`.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5059#comment:8>
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