Performs intersection (md_intersect()) and union (md_union()) on,
inter alia, messy date class objects.
For a more typical 'join' that retains all elements, even if duplicated,
please use md_multiset.
Usage
e1 %intersect% e2
# S3 method for mdate
%intersect%(e1, e2)
e1 %union% e2
# S3 method for mdate
%union%(e1, e2)
Value
A vector of the same mode for intersect,
or a common mode for union.
Arguments
e1, e2
Messy date or other class objects
Functions
%intersect% : Find intersection of sets of messy dates
%union% : Find intersection of sets of messy dates