global and local variables with scope

also reworked arg parsing, now has --debug flag

lib/lexer.ml

@@ -67,7 +67,7 @@ module State = struct
   let get_lexeme (state : state) (first : int) (last : int) =
     String.sub state.source first (last - first)
 
-  let advance (state : state) : char * state =
+  let next (state : state) : char * state =
     let c = state.source.[state.cur_pos] in
     let state = { state with cur_pos = state.cur_pos + 1 } in
     let state =
@@ -78,21 +78,25 @@ module State = struct
     in
     (c, state)
 
+  let advance (state : state) : state =
+    let _, state = next state in
+    state
+
   let peek (state : state) : char option =
     if not (is_at_end state) then Some state.source.[state.cur_pos] else None
 
   let advance_if (c : char) (state : state) : bool * state =
-    if peek state = Some c then (true, snd (advance state)) else (false, state)
+    if peek state = Some c then (true, snd (next state)) else (false, state)
 
   let rec advance_until (c : char) (state : state) : bool * state =
     if is_at_end state then (false, state)
     else
-      let c', state = advance state in
+      let c', state = next state in
       if c' = c then (true, state) else advance_until c state
 
   let rec advance_while (f : char -> bool) (state : state) : state =
     match peek state with
-    | Some c when f c -> advance_while f (snd (advance state))
+    | Some c when f c -> advance_while f (snd (next state))
     | _ -> state (* EOF or no match *)
 
   let append_token (pos : code_pos) (token_type : token_type) (state : state) : state =
@@ -124,16 +128,16 @@ module State = struct
     let tt = lexeme |> Hashtbl.find_opt keywords |> Option.value ~default:(Identifier lexeme) in
     append_token code_pos tt state
 
-  let rec parse_block_commend (state : state) : state =
+  let rec parse_block_comment (state : state) : state =
     (* "- 2" since we already consumed the "/*" *)
     let pos = { line = state.line; col = state.col - 2 } in
     let found, state = advance_until '*' state in
-    if not found then append_error pos "Unterminated block commend" state
+    if not found then append_error pos "Unterminated block comment" state
     else if peek state = Some '/' then
-      let state = snd @@ advance state in
+      let state = advance state in
       let lexeme = get_lexeme state (state.start_pos + 2) (state.cur_pos - 2) in
       append_token pos (Comment lexeme) state
-    else parse_block_commend state
+    else parse_block_comment state
 
   let rec tokenize_rec (state : state) : state =
     let pos = { line = state.line; col = state.col } in
@@ -142,7 +146,7 @@ module State = struct
     if is_at_end state then append_token Eof state
     else
       let state = { state with start_pos = state.cur_pos } in
-      let c, state = advance state in
+      let c, state = next state in
       let state =
         state
         |>
@@ -181,7 +185,7 @@ module State = struct
                   let _, state = advance_until '\n' state in
                   let lexeme = String.trim @@ get_lexeme state start_pos state.cur_pos in
                   append_token (Comment lexeme) state
-              | Some '*' -> parse_block_commend (snd @@ advance state)
+              | Some '*' -> parse_block_comment (advance state)
               | _ -> append_token Slash state)
         | '"' ->
             fun state ->