[Haskell] I try to thaw an array of unboxed arrays to the IO monad

Simon Peyton-Jones simonpj at microsoft.com
Thu Jan 6 04:41:32 EST 2005

| The error above is telling you that there's no instance for 'MArray b
| FlatVector IO' - this is because you haven't specified the array type
| 'b' into which thaw should convert the array.  The error message is a
| bit misleading; it's really an ambiguity rather than a missing
| (I don't know whether it could be reasonably improved, though).

That is indeed horrible.  Duly improved.

    Ambiguous type variable `b' in the constraint:
      `MArray b FlatVector IO' arising from use of `thaw' at
    Probable fix: add a type signature that fixes these type variable(s)


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