feat: add 'directly head/tail recursion' optimized syntax '+'

grammars/f1_g4_translate.py

@@ -75,11 +75,30 @@ def esc_token(self, t):
         t = t.replace('\t', '\\t')
         return t
 
-    def rule_to_s(self, rule, grammar):
-        return ' '.join(["'%s'" % self.esc_token(t)
+    def rule_to_s(self, key, rule, grammar):
+        # feat: add 'directly head/tail recursion' optimized syntax '+'
+        if len(rule) == 0:
+            return ''
+
+        # head recursion
+        recursion = False
+        if rule[0] == key:
+            rule = rule[1:]
+            recursion = True
+        # tail recursion
+        if rule[-1] == key:
+            rule = rule[:-1]
+            recursion = True
+
+        # append rules
+        data = ' '.join(["'%s'" % self.esc_token(t)
                          if t not in grammar else self.to_key(t)
                          for t in rule])
 
+        if recursion:
+            data = "(%s)+" % data
+        return data
+
     def translate(self):
         lines = ['grammar Grammar;']
         entries = '\n    | '.join([self.to_key(entry_k) + ' EOF' for entry_k in self.entry_keys])
@@ -89,7 +108,7 @@ def translate(self):
     ;''' % entries)
         for k in self.grammar_keys:
             rules = self.grammar[k]
-            v = '\n    | '.join([self.rule_to_s(rule, self.grammar)
+            v = '\n    | '.join([self.rule_to_s(key, rule, self.grammar)
                                  for rule in rules])
             lines.append('''\
 %s