[PATCH] Compute at M4 time some of the subtractions.

[Akim Demaille]

        * data/lalr1.cc (b4_substract): New.
        (b4_rhs_data): Use it.
---
 ChangeLog     |    6 ++++++
 data/lalr1.cc |   11 ++++++++++-
 2 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 134e862..56f3931 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2008-11-13  Akim Demaille  <address@hidden>
 
+       Compute at M4 time some of the subtractions.
+       * data/lalr1.cc (b4_substract): New.
+       (b4_rhs_data): Use it.
+
+2008-11-13  Akim Demaille  <address@hidden>
+
        symbol::token.
        This is allows the user to get the type of a token return by
        yylex.
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 15a4258..97ba371 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],
-          address@hidden($1) - ($2)@}])
+          address@hidden($@)@}])
 
 
 # b4_rhs_state(RULE-LENGTH, NUM)
-- 
1.6.0.2.588.g3102