ocaml: phase 5.1 expr_simp.ml baseline (symbolic simplifier, eval(simp e) = 22)

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.

lib/ocaml/baseline/expr_simp.ml

@@ -0,0 +1,33 @@
+type expr =
+  | Num of int
+  | Add of expr * expr
+  | Mul of expr * expr
+
+let rec simp e =
+  match e with
+  | Num n -> Num n
+  | Add (a, b) ->
+    (match (simp a, simp b) with
+     | (Num 0, x) -> x
+     | (x, Num 0) -> x
+     | (Num n, Num m) -> Num (n + m)
+     | (a', b') -> Add (a', b'))
+  | Mul (a, b) ->
+    (match (simp a, simp b) with
+     | (Num 0, _) -> Num 0
+     | (_, Num 0) -> Num 0
+     | (Num 1, x) -> x
+     | (x, Num 1) -> x
+     | (Num n, Num m) -> Num (n * m)
+     | (a', b') -> Mul (a', b'))
+
+let rec eval e =
+  match e with
+  | Num n -> n
+  | Add (a, b) -> eval a + eval b
+  | Mul (a, b) -> eval a * eval b
+
+;;
+
+let e = Add (Mul (Num 3, Num 5), Add (Num 0, Mul (Num 1, Num 7))) in
+eval (simp e)