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Recursive ADT with three constructors (Num/Add/Mul). simp does bottom-up rewrite using algebraic identities: x + 0 -> x 0 + x -> x x * 0 -> 0 0 * x -> 0 x * 1 -> x 1 * x -> x constant folding for Num + Num and Num * Num Uses tuple pattern in nested match: 'match (simp a, simp b) with'. Add (Mul (Num 3, Num 5), Add (Num 0, Mul (Num 1, Num 7))) -> simp -> Add (Num 15, Num 7) -> eval -> 22 51 baseline programs total.
34 lines
717 B
OCaml
34 lines
717 B
OCaml
type expr =
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| Num of int
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| Add of expr * expr
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| Mul of expr * expr
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let rec simp e =
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match e with
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| Num n -> Num n
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| Add (a, b) ->
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(match (simp a, simp b) with
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| (Num 0, x) -> x
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| (x, Num 0) -> x
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| (Num n, Num m) -> Num (n + m)
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| (a', b') -> Add (a', b'))
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| Mul (a, b) ->
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(match (simp a, simp b) with
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| (Num 0, _) -> Num 0
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| (_, Num 0) -> Num 0
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| (Num 1, x) -> x
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| (x, Num 1) -> x
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| (Num n, Num m) -> Num (n * m)
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| (a', b') -> Mul (a', b'))
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let rec eval e =
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match e with
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| Num n -> n
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| Add (a, b) -> eval a + eval b
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| Mul (a, b) -> eval a * eval b
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;;
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let e = Add (Mul (Num 3, Num 5), Add (Num 0, Mul (Num 1, Num 7))) in
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eval (simp e)
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