+[b4_symbol_value([(*yyvalp)], [$1])])
+
+
+# b4_rhs_data(RULE-LENGTH, NUM)
+# -----------------------------
+# Expand to the semantic stack place that contains value and location
+# of symbol number NUM in a rule of length RULE-LENGTH.
+m4_define([b4_rhs_data],
+[((yyGLRStackItem const *)yyvsp)@{YYFILL (($2) - ($1))@}.yystate])