#3454: ghci freezes on failed pattern match in recursive list comprehension
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Reporter: Syzygies | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.10.4 | Severity: normal
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
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The following freezes ghci (top shows no resources consumed):
{{{
Prelude> let xs = [1..5] : [ xt | (_:xt) <- xs ] in take 7 xs
[[1,2,3,4,5],[2,3,4,5],[3,4,5],[4,5],[5],[]
}}}
This is not the same issue as
[http://hackage.haskell.org/trac/ghc/ticket/3053] (closed, invalid) as
there are no elements to filter. (This may be a well-known black hole, but
not to me; I was hoping a similar list would just terminate, trying to
avoid the Nothing case boilerplate in an unfoldl.)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3454>
GHC <http://www.haskell.org/ghc/>
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