At 2002-08-18 20:19, Jay Cox wrote:
>#ST> runST (newSTRef (3::Prelude.Int))
>#
>#Ambiguous type variable(s) `a' in the constraint `PrelShow.Show a'
>#arising from use of `PrelIO.print' at <No locn>
>#In a 'do' expression pattern binding: PrelIO.print it
I don't understand this either, actually:
$ ghci -fglasgow-exts -package lang
___ ___ _
/ _ \ /\ /\/ __(_)
/ /_\// /_/ / / | | GHC Interactive, version 5.04, for Haskell
98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.
Loading package base ... linking ... done.
Loading package haskell98 ... linking ... done.
Loading package lang ... linking ... done.
Prelude> :module ST
Prelude ST> :type runST
Inferred type is less polymorphic than expected
Quantified type variable `s' escapes
Expected type: ST s a -> t
Inferred type: (forall s1. ST s1 a) -> a
Prelude ST>
What's up with that? Can't I even look at the type? Is this the
monomorphism restriction or something?
--
Ashley Yakeley, Seattle WA
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