Removed some exceptions

eval.ml

@@ -16,6 +16,9 @@ and env = {
   parent : env option;
 }
 
+exception No_operation
+exception Too_many_arguments
+
 module Type = struct
   type t =
     | Int
@@ -25,6 +28,8 @@ module Type = struct
     | Function
     | External
 
+  exception Invalid of t
+
   let to_string = function
     | Int -> "int"
     | Float -> "float"
@@ -78,19 +83,10 @@ module Env = struct
     parent = Some parent;
   }
 
-  exception Not_found
-
-  let rec get e name =
+  let rec get_opt e name =
     match Hashtbl.find_opt e.vars name with
-    | None -> begin match e.parent with
-        | None -> raise Not_found
-        | Some p -> get p name
-      end
-    | Some value -> value
-
-  let get_opt e name =
-    try Some (get e name)
-    with Not_found -> None
+    | None -> Option.bind e.parent (fun p -> get_opt p name)
+    | Some _ as v -> v
 
   let set e name value =
     Hashtbl.replace e.vars name value
@@ -99,13 +95,6 @@ module Env = struct
     Hashtbl.add_seq e.vars seq
 end
 
-exception No_operation
-exception No_such_variable of string
-exception No_such_function of string
-exception Too_many_arguments
-
-exception Invalid_type of Type.t
-
 (* operators *)
 module Operator = struct
   type t = Ast.operator
@@ -122,12 +111,12 @@ module Operator = struct
   let vi f a b =
     match a, b with
     | Int a, Int b -> Int (f a b)
-    | _ -> raise @@ Invalid_type Int
+    | _ -> raise @@ Type.Invalid Int
 
   let vf f a b =
     match a, b with
     | Float a, Float b -> Float (f a b)
-    | _ -> raise @@ Invalid_type Float
+    | _ -> raise @@ Type.Invalid Float
 
   let operators =
     let open Type in
@@ -158,6 +147,8 @@ module Operator = struct
 end
 
 module External = struct
+  exception Invalid of string
+
   let rad r =
     r *. 180. /. Float.pi
 
@@ -166,7 +157,7 @@ module External = struct
 
   let floatfun f = function
     | Float n -> Float (f n)
-    | v -> raise @@ Invalid_type (Value.typeof v)
+    | v -> raise @@ Type.Invalid (Value.typeof v)
 
   let apply f args =
     match f, args with
@@ -175,7 +166,7 @@ module External = struct
     | "tan", [n] -> floatfun Float.tan n
     | "deg", [n] -> floatfun deg n
     | "rad", [n] -> floatfun rad n
-    | _ -> raise @@ No_such_function f
+    | _ -> raise @@ Invalid f
 end
 
 let assert_same_length vars args =
@@ -220,6 +211,8 @@ let rec binop op l r =
     end
   | Some f -> f l r
 
+exception Unbound of string
+
 let rec eval env ast : value =
   let rec aux = function
     | Nint n -> Int n
@@ -229,7 +222,7 @@ let rec eval env ast : value =
     | Nfunction (args, e) -> Function (args, e)
     | Nexternal f -> External f
     | Var v -> begin match Env.get_opt env v with
-        | None -> raise @@ No_such_variable v
+        | None -> raise @@ Unbound v
         | Some v -> v
       end
     | Unary (op, t) ->
@@ -254,13 +247,13 @@ let rec eval env ast : value =
         | External f ->
           let args = List.map aux args in
           External.apply f args
-        | v -> raise @@ Invalid_type (Value.typeof v)
+        | v -> raise @@ Type.Invalid (Value.typeof v)
       end
     | Set_binop_pre (op, l) ->
       let l =
         match aux l with
         | Int n -> n
-        | v -> raise @@ Invalid_type (Value.typeof v)
+        | v -> raise @@ Type.Invalid (Value.typeof v)
       in
       Hashtbl.replace Parser.precedence op l;
       Nop

main.ml

@@ -9,9 +9,8 @@ let error_to_string e =
   | Lex.Expected c -> sprintf "expected %c" c
   | Parser.Expected t -> sprintf "expected %s" t
   | Parser.Unexpected_token t -> sprintf "unexpected token \"%s\"" t
-  | Eval.Invalid_type t -> sprintf "invalid type %s" (Type.to_string t)
-  | Eval.No_such_variable v -> sprintf "no such variable %s" v
-  | Eval.No_such_function f -> sprintf "no such function \"%s\"" f
+  | Type.Invalid t -> sprintf "invalid type %s" (Type.to_string t)
+  | Eval.Unbound v -> sprintf "unbound value %s" v
   | Eval.Too_many_arguments -> "applied too many arguments"
   | Failure f -> sprintf "error on %s" f
   | Division_by_zero -> "cannot divide by zero"