+#undef yynerrs
+#undef yychar
+#undef yylval]b4_locations_if([
+#undef yylloc])
+
+m4_if(b4_prefix, [yy], [],
+[[/* Substitute the variable and function names. */
+#define yyparse ]b4_prefix[parse
+#define yylex ]b4_prefix[lex
+#define yyerror ]b4_prefix[error
+#define yydebug ]b4_prefix[debug
+]]b4_pure_if([], [[
+#define yylval ]b4_prefix[lval
+#define yychar ]b4_prefix[char
+#define yynerrs ]b4_prefix[nerrs]b4_locations_if([[
+#define yylloc ]b4_prefix[lloc]])]))
+
+# Hijack the epilogue to define implementations (yyerror, parser member
+# functions etc.).