On Thu, 23 Oct 2003 12:20 pm, Pratik Bhadra wrote:
>
> data Expr = Lit1 Int | Lit2 Bool | Var String | BinOp Op Expr Expr
>
> My evaluate code is as follows...
>
> evaluate :: Expr -> Store -> Expr
>
> evaluate ( Lit1 n ) st = n
> evaluate ( Lit2 n ) st = n
A function must match its type signature and the type signature
must be consistent irrespective of the function arguments.
The first line of the evaluation has the type,
Expr -> Store -> Int
The second line has the type,
Expr -> Store -> Bool
Tom
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