-let level1_pattern_lexer = mk_lexer level1_pattern_token
-let level2_ast_lexer = mk_lexer level2_ast_token
-let level2_meta_lexer = mk_lexer level2_meta_token
-
-let lookup_ligatures lexeme =
- try
- if lexeme.[0] = '\\'
- then [ Utf8Macro.expand (String.sub lexeme 1 (String.length lexeme - 1)) ]
- else List.rev (Hashtbl.find_all ligatures lexeme)
- with Invalid_argument _ | Utf8Macro.Macro_not_found _ -> []
+let initial_level1_pattern_lexer () = mk_lexer level1_pattern_token
+let initial_level2_ast_lexer () = mk_lexer level2_ast_token
+let initial_level2_meta_lexer () = mk_lexer level2_meta_token
+
+
+let level1_pattern_lexer_ref = ref (initial_level1_pattern_lexer ())
+let level2_ast_lexer_ref = ref (initial_level2_ast_lexer ())
+let level2_meta_lexer_ref = ref (initial_level2_meta_lexer ())
+
+let level1_pattern_lexer () = !level1_pattern_lexer_ref
+let level2_ast_lexer () = !level2_ast_lexer_ref
+let level2_meta_lexer () = !level2_meta_lexer_ref
+
+let history = ref [];;
+
+let push () =
+ history :=
+ (!level2_ast_keywords,!level1_pattern_lexer_ref,
+ !level2_ast_lexer_ref,!level2_meta_lexer_ref) :: !history;
+ level2_ast_keywords := initial_level2_ast_keywords ();
+ initialize_keywords ();
+ level1_pattern_lexer_ref := initial_level1_pattern_lexer ();
+ level2_ast_lexer_ref := initial_level2_ast_lexer ();
+ level2_meta_lexer_ref := initial_level2_meta_lexer ();
+;;
+
+let pop () =
+ match !history with
+ | [] -> assert false
+ | (kwd,pl,al,ml) :: tl ->
+ level2_ast_keywords := kwd;
+ level1_pattern_lexer_ref := pl;
+ level2_ast_lexer_ref := al;
+ level2_meta_lexer_ref := ml;
+ history := tl
+;;