From: Lukas Jiriste <ljiriste@student.42prague.com>
Date: Thu, 18 Jul 2024 11:32:26 +0000 (+0200)
Subject: Fix infinite recursion
X-Git-Url: https://git.ljiriste.work/?a=commitdiff_plain;h=d8e560f8909ddbba58f5e35eacac4b73b18aa124;p=Libft.git

Fix infinite recursion

The previous commit solved some wierd things around the add_first
function. These were created because of my misunderstanding of the
process but also (almost) prevented infinite recursion.

The infinite recurson is caused when a search for a first (nonterminal)
tokens encounteres the original token, because then it searches for it
again and is able to again find the token along the search.

The solution is to make the algorithm log what nonterminals it already
went through so that it does not try to find their first tokens during
the search for their first tokens.
---

diff --git a/ft_parse/ft_parsing_table_generate.c b/ft_parse/ft_parsing_table_generate.c
index 0396f64..acc0f80 100644
--- a/ft_parse/ft_parsing_table_generate.c
+++ b/ft_parse/ft_parsing_table_generate.c
@@ -6,7 +6,7 @@
 /*   By: ljiriste <ljiriste@student.42prague.com>   +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2024/06/27 11:16:53 by ljiriste          #+#    #+#             */
-/*   Updated: 2024/07/18 11:47:10 by ljiriste         ###   ########.fr       */
+/*   Updated: 2024/07/18 12:16:01 by ljiriste         ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -278,6 +278,7 @@ t_ft_stat	add_first(t_vec *lookahead, const t_token *token, const t_vec *rules,
 			return (success);
 		return (res);
 	}
+	append_token(lookahead, token);
 	rule.position = 0;
 	i = 1;
 	while (i < rules->size)
@@ -294,7 +295,7 @@ t_ft_stat	add_first(t_vec *lookahead, const t_token *token, const t_vec *rules,
 	return (success);
 }
 
-void	remove_empty_token(t_vec *lookahead)
+void	remove_token(t_vec *lookahead, const t_token *removed_token)
 {
 	size_t			i;
 	const t_token	*token;
@@ -304,7 +305,7 @@ void	remove_empty_token(t_vec *lookahead)
 	{
 		--i;
 		token = ft_vec_caccess(lookahead, i);
-		if (!cmp_token_type(token, &empty_token))
+		if (!cmp_token_type(token, removed_token))
 			ft_vec_erase(lookahead, i, ft_free_token);
 	}
 }
@@ -321,11 +322,14 @@ t_ft_stat	expand_lookahead(t_vec *lookahead, const t_marked_grammar_rule *rule,
 	i = rule->position;
 	while (ft_vec_contains(lookahead, &empty_token, void_cmp_token_type) && i < rule->rule->constituents.size)
 	{
-		remove_empty_token(lookahead);
+		remove_token(lookahead, &empty_token);
 		token = ft_vec_caccess(&rule->rule->constituents, i);
-		res = add_first(lookahead, token, rules, tokens);
-		if (res != success)
-			return (res);
+		if (!ft_vec_contains(lookahead, token, void_cmp_token_type))
+		{
+			res = add_first(lookahead, token, rules, tokens);
+			if (res != success)
+				return (res);
+		}
 		++i;
 	}
 	return (success);
@@ -351,6 +355,29 @@ t_ft_stat	add_to_lookahead(const t_vec *lookahead, t_vec *new_lookahead)
 	return (success);
 }
 
+void	remove_nonterminals(t_vec *lookahead, const t_vec *tokens)
+{
+	size_t			i;
+	const t_token	*token;
+
+	i = 0;
+	while (i < tokens->size)
+	{
+		token = ft_vec_caccess(tokens, i);
+		if (!cmp_token_type(token, &eof_token))
+			break ;
+		++i;
+	}
+	++i;
+	while (i < tokens->size)
+	{
+		token = ft_vec_caccess(tokens, i);
+		remove_token(lookahead, token);
+		++i;
+	}
+	return ;
+}
+
 t_ft_stat	add_lookahead(t_lr1_item *new, t_lr1_item *item, const t_vec *rules, const t_vec *tokens)
 {
 	t_ft_stat	res;
@@ -360,6 +387,7 @@ t_ft_stat	add_lookahead(t_lr1_item *new, t_lr1_item *item, const t_vec *rules, c
 		return (res);
 	++item->core.position;
 	res = expand_lookahead(&new->lookahead, &item->core, rules, tokens);
+	remove_nonterminals(&new->lookahead, tokens);
 	--item->core.position;
 	if (res != success)
 	{
@@ -368,7 +396,7 @@ t_ft_stat	add_lookahead(t_lr1_item *new, t_lr1_item *item, const t_vec *rules, c
 	}
 	if (ft_vec_contains(&new->lookahead, &empty_token, void_cmp_token_type))
 	{
-		remove_empty_token(&new->lookahead);
+		remove_token(&new->lookahead, &empty_token);
 		res = add_to_lookahead(&item->lookahead, &new->lookahead);
 	}
 	return (res);