Question
2. Given below is SML code that implements a simple way to define expressions and operations on them: datatype exp = Constant of int Negate of exp | Add of exp * exp fun eval e = case e of Constant (i) => i Negate el => ~ (eval el) | Add (el, e2) => (eval el) + (eval e2) eval (Add (Constant 19, Negate (Constant 4))); (
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