tcfail128.hs:18:16:
    No instance for (Data.Array.Base.MArray b0 FlatVector IO)
      arising from a use of `thaw'
    The type variable `b0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there is a potential instance available:
      instance Data.Array.Base.MArray GHC.IOArray.IOArray e IO
        -- Defined in `Data.Array.Base'
    In a stmt of a 'do' block: v <- thaw tmp
    In the expression:
      do { let sL = ...
               dim = length sL
               ....;
           v <- thaw tmp;
           return () }
    In an equation for `main':
        main
          = do { let sL = ...
                     ....;
                 v <- thaw tmp;
                 return () }