From 9d239db2d60469bb9915708c48db27813b78a2f4 Mon Sep 17 00:00:00 2001
From: David Majda <david@majda.cz>
Date: Sun, 14 Mar 2010 18:46:53 +0100
Subject: [PATCH] Simplified the example arithmetics grammar once more + addded
 comment.

---
 examples/arithmetics.pegjs | 34 ++++++++++++++--------------------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/examples/arithmetics.pegjs b/examples/arithmetics.pegjs
index 84059c5..28368a0 100644
--- a/examples/arithmetics.pegjs
+++ b/examples/arithmetics.pegjs
@@ -1,25 +1,19 @@
-start          : _ additive { return $2; }
+/*
+ * Classic example grammar, which recognizes simple arithmetic expressions like
+ * "2*(3+4)". The parser generated from this grammar then computes their value.
+ */
 
-additive       : multiplicative plus  additive { return $1 + $3; }
-               / multiplicative minus additive { return $1 - $3; }
-               / multiplicative
+start             : additive
 
-multiplicative : primary times  multiplicative { return $1 * $3; }
-               / primary divide multiplicative { return $1 / $3; }
-               / primary
+additive          : multiplicative "+" additive { return $1 + $3; }
+                  / multiplicative "-" additive { return $1 - $3; }
+                  / multiplicative
 
-primary        : integer
-               / lparen additive rparen { return $2 }
+multiplicative    : primary "*" multiplicative { return $1 * $3; }
+                  / primary "/" multiplicative { return $1 / $3; }
+                  / primary
 
-integer        "integer"
-               : [0-9]+ _ { return parseInt($1.join("")); }
+primary           : integer
+                  / "(" additive ")" { return $2; }
 
-plus           : "+" _ { return $1; }
-minus          : "-" _ { return $1; }
-times          : "*" _ { return $1; }
-divide         : "/" _ { return $1; }
-lparen         : "(" _
-rparen         : ")" _
-
-_              "whitespace"
-               : [ \t\n\r]*
+integer "integer" : [0-9]+ { return parseInt($1.join("")); }