#5756: Specialize sequence into sequence_ automatically
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Reporter: EyalLotem | Owner:
Type: feature request | Status: closed
Priority: normal | Milestone:
Component: Compiler | Version: 7.2.1
Resolution: wontfix | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: | Related:
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Changes (by igloo):
* status: new => closed
* difficulty: => Unknown
* resolution: => wontfix
Comment:
Note that with `-Wall` you get a warning if you ignore a non-`()` result:
{{{
module Q where
f :: IO ()
f = do sequence [putStr "A", putStr "B"]
putStr "C"
}}}
{{{
$ ghc -c -O q.hs -fforce-recomp -Wall
q.hs:5:8: Warning:
A do-notation statement discarded a result of type [()].
Suppress this warning by saying "_ <- sequence
[putStr "A", putStr "B"]",
}}}
Thanks for the suggestion, but I'm not sure it's worth adding a special
case to the compiler to do the rewrite - especially as it's not a type-
preserving transformation.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5756#comment:1>
GHC <http://www.haskell.org/ghc/>
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