From ea9935babbe977bf5d980d06fc84f30523b3740a Mon Sep 17 00:00:00 2001
From: Devine Lu Linvega <aliceffekt@gmail.com>
Date: Fri, 12 Apr 2024 10:30:59 -0700
Subject: [PATCH] Allow for empty right-hand side rules

---
 src/modal.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/modal.c b/src/modal.c
index cf5c211..76eaab9 100644
--- a/src/modal.c
+++ b/src/modal.c
@@ -19,7 +19,7 @@ walk(char *s)
 {
 	char c;
 	int depth = 0;
-	if(s[0] == '(') {
+	if(*s == '(') {
 		while((c = *s++)) {
 			if(c == '(') depth++;
 			if(c == ')') --depth;
@@ -36,7 +36,7 @@ plode(char *s)
 	int i, depth = 0;
 	char c, *ss;
 	/* implode */
-	if(s[0] == '(') {
+	if(*s == '(') {
 		ss = walk(s);
 		while(s < ss && (c = *s++))
 			if(!spacer(c)) *outp_++ = c;
@@ -149,20 +149,22 @@ parse_frag(char *s)
 {
 	char c, *ss;
 	while((c = *s) && c <= ' ') s++;
-	ss = walk(s);
-	if(*s == '(') s++, ss--;
-	while(s < ss) *dict_++ = *s++;
+	if(*s != ')' && *s != '<' && s[1] != '>') {
+		ss = walk(s);
+		if(*s == '(') s++, ss--;
+		while(s < ss) *dict_++ = *s++;
+		s++;
+	}
 	*dict_++ = 0;
-	s++;
 	return s;
 }
 
 static char *
 create_rule(Rule *r, int id, char *s)
 {
-	char c;
 	r->id = id, s += 2;
-	r->a = dict_, s = parse_frag(s), r->b = dict_, s = parse_frag(s);
+	r->a = dict_, s = parse_frag(s);
+	r->b = dict_, s = parse_frag(s);
 	return s;
 }
 
@@ -174,13 +176,13 @@ rewrite(void)
 	while((c = *s)) {
 		if(spacer(last)) {
 			Rule *r;
-			if(s[0] == '<' && s[1] == '>') {
+			if(*s == '<' && s[1] == '>') {
 				r = rules_++;
 				s = create_rule(r, rules_ - rules - 1, s);
 				while((c = *s) && c <= ' ') s++;
 				return commit_rule(r, s, 1);
 			}
-			if(s[0] == '?' && s[1] == '(') {
+			if(*s == '?' && s[1] == '(') {
 				r = &lambda, cap = walk(s + 1);
 				create_rule(&lambda, -1, s), s = cap;
 				while((c = *s) && c <= ' ') s++;