#4978: Continuation passing style loop doesn't compile into a loop
---------------------------------+------------------------------------------
Reporter: tibbe | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 7.4.1
Component: Compiler | Version: 7.0.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by batterseapower):
Simon's example gets the "correct" arity of 2 if you replace the go_pap
case in exprIsCheap' with (all (exprIsCheap' good_app) args). Although the
comment there explicitly warns against doing this, I feel that is the
right thing to do: why should f get arity 2 here:
{{{
f = \a -> let x = map g
y = map h
in \b -> .. y .. f ..
}}}
But not here:
{{{
f = \a -> let y = map (map g)
in \b -> .. y .. f ..
}}}
There is no substantiative difference between the terms, but the current
analysis treats them differently because it is sensitive to whether
something is let-bound or occurs as an argument.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4978#comment:12>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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