From: Akim Demaille <demaille@gostai.com>
Date: Mon, 1 Sep 2008 09:39:41 +0000 (+0200)
Subject: Compute at M4 time some of the subtractions.
X-Git-Tag: v2.7.90~1049
X-Git-Url: https://git.saurik.com/bison.git/commitdiff_plain/3204049e31e71c30d0dddf7cae8738c289dbd104?ds=inline

Compute at M4 time some of the subtractions.

	* data/lalr1.cc (b4_substract): New.
	(b4_rhs_data): Use it.
---

diff --git a/ChangeLog b/ChangeLog
index 134e862d..56f39316 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2008-11-13  Akim Demaille  <demaille@gostai.com>
+
+	Compute at M4 time some of the subtractions.
+	* data/lalr1.cc (b4_substract): New.
+	(b4_rhs_data): Use it.
+
 2008-11-13  Akim Demaille  <demaille@gostai.com>
 
 	symbol::token.
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 15a42580..97ba371b 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -18,6 +18,15 @@
 
 m4_include(b4_pkgdatadir/[c++.m4])
 
+# b4_subtract(LHS, RHS)
+# ---------------------
+# Evaluate LHS - RHS if they are integer literals, otherwise expand
+# to (LHS) - (RHS).
+m4_define([b4_subtract],
+[m4_bmatch([$1$2], [^[0123456789]*$],
+           [m4_eval([$1 - $2])],
+           [($1) - ($2)])])
+
 
 # b4_args(ARG1, ...)
 # _b4_args(ARG1, ...)
@@ -107,7 +116,7 @@ m4_define([b4_lhs_location],
 # Return the data corresponding to the symbol #NUM, where the current
 # rule has RULE-LENGTH symbols on RHS.
 m4_define([b4_rhs_data],
-          [yystack_@{($1) - ($2)@}])
+          [yystack_@{b4_subtract($@)@}])
 
 
 # b4_rhs_state(RULE-LENGTH, NUM)