[NumericPrelude] Bug in Numeric Prelude or GHC?
lemming at henning-thielemann.de
Mon Jun 20 19:59:16 BST 2011
On Mon, 20 Jun 2011, Grigory Sarnitskiy wrote:
> a = Var "a"
> in ghci :
> *Main> -a :: Expression Float
> No instance for (GHC.Num.Num (Expression Float))
> arising from a use of syntactic negation
> Possible fix:
> add an instance declaration for (GHC.Num.Num (Expression Float))
> In the expression: - a :: Expression Float
> In an equation for `it': it = - a :: Expression Float
Is this a difference between GHCi and GHC? I know there is some syntactic
sugar that does not work in GHCi, but works in GHC. I even think it was
already reported somewhere, but I cannot find a GHC trac ticket.
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