@var{y} are 0 or either or both are less than zero then behavior is undefined.
@end table
+The following constants are available:
+@table @option
+@item PI
+area of the unit disc, approximatively 3.14
+@item E
+exp(1) (Euler's number), approximatively 2.718
+@item PHI
+golden ratio (1+sqrt(5))/2, approximatively 1.618
+@end table
+
Note that:
@code{*} works like AND