Use single chars for set operators

Using letters for operators may prove to be a silly choice but I tried
to use those that look somewhat like the correct symbols.

diff --git a/grammar b/grammar
index b395a8950fcfbcf2be486da79fe98acbe288d89d..dbb99e72b17b94f00820e6044ae75ad27f1fb543 100644 (file)
--- a/grammar
+++ b/grammar
@@ -51,11 +51,16 @@ set -> set_name
 set -> LEFT_CURLY set_definition RIGHT_CURLY
 set -> LEFT_BRACKET set set_op set RIGHT_BRACKET
 set -> transform set
-set_op -> UNION
-set_op -> INTERSECTION
-set_op -> DIFFERENCE
-set_op -> CARTESIAN_PRODUCT
-set_op -> MINKOWSKI_SUM
+set_op -> union
+set_op -> intersection
+set_op -> difference
+set_op -> cartesian_product
+set_op -> minkowski_sum
+union -> U
+intersection -> N
+difference -> BACKSLASH
+cartesian_product -> X
+minkowski_sum -> PLUS
 transform -> rotation
 transform -> translate
 transform -> mirror