Seperate eval and eval_top

eval.ml

@@ -261,7 +261,7 @@ let rec binop op l r =
 
 exception Unbound of string
 
-let rec eval env ast : string * value =
+let rec eval env ast =
   let rec aux = function
     | Nint n -> Int n
     | Nfloat n -> Float n
@@ -280,7 +280,7 @@ let rec eval env ast : string * value =
     | Letin (v, e, f) ->
       let nenv = Env.make env in
       Env.set nenv v (aux e);
-      snd @@ eval nenv f
+      eval nenv f
 
     | Unary (op, t) ->
       let t = aux t in
@@ -303,12 +303,13 @@ let rec eval env ast : string * value =
           let nenv = Env.make env in
           List.combine vars args
           |> List.iter (fun (v, a) -> Env.set nenv v a);
-          snd @@ eval nenv e
+          eval nenv e
         | External f ->
           let args = List.map aux args in
           External.apply f args
         | v -> raise @@ Type.Invalid (Value.typeof v)
       end
+
     | Set_binop_pre (op, l) ->
       let l =
         match aux l with
@@ -328,10 +329,11 @@ let rec eval env ast : string * value =
        | Some a -> String (Parser.assoc_to_string a))
     | _ -> failwith "Eval.eval"
   in
+  aux ast
 
+let eval_top env ast =
   match ast with
   | Let (var, e) ->
-    let v = aux e in
-    Env.set env var v;
-    var, v
-  | ast -> "-", aux ast
+    let v = eval env e in
+    Env.set env var v; var, v
+  | ast -> "-", eval env ast

main.ml

@@ -39,7 +39,7 @@ let rep env : unit =
   if line = "quit" then raise Exit;
   let ast = line |> Lex.tokenize |> Parser.parse in
   if !debug then Ast.print ast;
-  let var, v = Eval.eval env ast in
+  let var, v = Eval.eval_top env ast in
   match v with
   | Nop -> ()
   | _ ->