diff --git a/eval.ml b/eval.ml
index 654bd0d..185354e 100644
--- a/eval.ml
+++ b/eval.ml
@@ -20,6 +20,7 @@ and env = (string * value) list
 exception No_operation
 exception Too_many_arguments
 
+(* TODO: add proper type system *)
 module Type = struct
   type t =
     | Int
@@ -146,6 +147,7 @@ module Operator = struct
   let lt a b = Bool (compare a b < 0)
 
   (* operator table *)
+  (* TODO: refactor operator finding alg (support type vars) *)
   let operators =
     let open Type in
     let ip = Int, Int and fp = Float, Float in
@@ -248,6 +250,7 @@ let rec binop op l r =
 
 exception Unbound of string
 
+(* TODO: refactor eval, split function into parts *)
 let rec eval env ast =
   let rec aux = function
     | Nothing -> Nop
@@ -328,7 +331,7 @@ let rec eval env ast =
 
 let eval_top env_ref ast =
   let var, v = match ast with
-    | Let (var, Nfunction (arg, e)) ->
+    | Let (var, Nfunction (arg, e)) -> (* named function *)
       var, Function (Some var, arg, e, !env_ref)
     | Let (var, e) -> var, eval !env_ref e
     | ast -> "-", eval !env_ref ast