From b6e00cd862d80fef042d927d6ce05463e7cd7522 Mon Sep 17 00:00:00 2001
From: Hyeonung Baek <wiserlix@gmail.com>
Date: Fri, 18 Feb 2022 16:49:20 +0900
Subject: [PATCH] Fix recursive function

---
 eval.ml | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/eval.ml b/eval.ml
index ad2f098..654bd0d 100644
--- a/eval.ml
+++ b/eval.ml
@@ -7,7 +7,8 @@ type value =
   | Bool of bool
   | String of string
   | Symbol of string
-  | Function of string * expr * env
+  (* (name), arg, expression, name *)
+  | Function of string option * string * expr * env
   | External of string
   | Nop (* return of system operations (will be deprecated) *)
 
@@ -255,7 +256,7 @@ let rec eval env ast =
     | Nbool b -> Bool b
     | Nstring s -> String s
     | Nsymbol s -> Symbol s
-    | Nfunction (arg, e) -> Function (arg, e, env)
+    | Nfunction (arg, e) -> Function (None, arg, e, env)
     | Nexternal f -> External f
 
     | Var v -> begin match Env.get_opt env v with
@@ -282,11 +283,10 @@ let rec eval env ast =
 
     | Apply (v, args) ->
       begin match aux v with
-        | Function (var, e, env) as f ->
+        | Function (itself, var, e, env) as f ->
           begin match args with
             | [] -> f
             | a::args ->
-              let itself = match v with Var v -> Some v | _ -> None in
               let env =
                 (* binding itself into env for recursion *)
                 Option.fold
@@ -327,9 +327,11 @@ let rec eval env ast =
   aux ast
 
 let eval_top env_ref ast =
-  match ast with
-  | Let (var, e) ->
-    let v = eval !env_ref e in
-    env_ref := Env.bind (var, v) !env_ref;
-    var, v
-  | ast -> "-", eval !env_ref ast
+  let var, v = match ast with
+    | Let (var, Nfunction (arg, e)) ->
+      var, Function (Some var, arg, e, !env_ref)
+    | Let (var, e) -> var, eval !env_ref e
+    | ast -> "-", eval !env_ref ast
+  in
+  if var <> "-" then env_ref := Env.bind (var, v) !env_ref;
+  var, v