First commit

lib/miniImp.ml

@@ -0,0 +1,104 @@
+type variable = string
+
+type p_exp =
+    Main of variable * variable * c_exp (* def main with input x output y as c *)
+and c_exp =
+    Skip
+  | Assignment of variable * a_exp      (* x := a *)
+  | Sequence of c_exp * c_exp           (* c; c *)
+  | If of b_exp * c_exp * c_exp         (* if b then c else c *)
+  | While of b_exp * c_exp              (* while b do c *)
+and b_exp =
+    Boolean of bool                     (* v *)
+  | BAnd of b_exp * b_exp               (* b and b *)
+  | BNot of b_exp                       (* not b *)
+  | BCmpLess of a_exp * a_exp           (* a < a *)
+and a_exp =
+    Variable of variable                (* x *)
+  | Integer of int                      (* n *)
+  | Plus of a_exp * a_exp               (* a + a *)
+  | Minus of a_exp * a_exp              (* a - a *)
+  | Times of a_exp * a_exp              (* a * a *)
+
+
+
+module VariableMap = Map.Make(String)
+
+type memory = {
+  assignments: int VariableMap.t
+}
+
+
+exception AbsentAssignment of string
+
+let rec evaluate (mem: memory) (command: c_exp) =
+  match command with
+    Skip -> mem
+  | Assignment (v, exp_a) -> {assignments = VariableMap.add v (evaluate_a mem exp_a) mem.assignments}
+  | Sequence (exp_c1, exp_c2) -> (
+      let mem2 = evaluate mem exp_c1 in
+      evaluate mem2 exp_c2
+    )
+  | If (exp_b, exp_c1, exp_c2) -> (
+      if evaluate_b mem exp_b then
+        evaluate mem exp_c1
+      else
+        evaluate mem exp_c2
+    )
+  | While (exp_b, exp_c) -> (
+      if evaluate_b mem exp_b then
+        let mem2 = evaluate mem exp_c in
+        evaluate mem2 command
+      else
+        mem
+    )
+
+and evaluate_a (mem: memory) (exp_a: a_exp) =
+  match exp_a with
+    Variable v -> (
+      match VariableMap.find_opt v mem.assignments with
+        None -> raise (AbsentAssignment ("The variable " ^ v ^ " is not defined."))
+      | Some a -> a
+    )
+  | Integer n -> n
+  | Plus (exp_a1, exp_a2) -> (
+      let exp_a1val = evaluate_a mem exp_a1 in
+      let exp_a2val = evaluate_a mem exp_a2 in
+      exp_a1val + exp_a2val
+    )
+  | Minus (exp_a1, exp_a2) -> (
+      let exp_a1val = evaluate_a mem exp_a1 in
+      let exp_a2val = evaluate_a mem exp_a2 in
+      exp_a1val - exp_a2val
+    )
+  | Times (exp_a1, exp_a2) -> (
+      let exp_a1val = evaluate_a mem exp_a1 in
+      let exp_a2val = evaluate_a mem exp_a2 in
+      exp_a1val * exp_a2val
+    )
+and evaluate_b (mem: memory) (exp_b: b_exp) =
+  match exp_b with
+    Boolean b -> b
+  | BAnd (exp_b1, exp_b2) -> (
+      let exp_b1val = evaluate_b mem exp_b1 in
+      let exp_b2val = evaluate_b mem exp_b2 in
+      exp_b1val && exp_b2val
+    )
+  | BNot (exp_b) -> (
+      not (evaluate_b mem exp_b)
+    )
+  | BCmpLess (exp_a1, exp_a2) -> (
+      let exp_a1val = evaluate_a mem exp_a1 in
+      let exp_a2val = evaluate_a mem exp_a2 in
+      exp_a1val < exp_a2val
+    )
+
+
+let reduce (iin : int) (program: p_exp) =
+  match program with
+    Main (vin, vout, expression) -> (
+      let mem : memory = {assignments = (VariableMap.empty |> VariableMap.add vin iin)} in
+      match VariableMap.find_opt vout (evaluate mem expression).assignments with
+        None -> raise (AbsentAssignment ("The output variable is not defined (" ^ vout ^ ")"))
+      | Some a -> a
+    )