DESCRIPTION:
    A set is a concept for specifying a number of classes in
    eccet. Sets are unordered collections of class numbers.
    Whereever you can specify a set, you can use the following
    notations:
    a,b	- a set combined from the two set descriptions a and b
    a-b - a set of all classes between number a and b
    ^set, ~set or !set - invert the given set.

EXAMPLES:
    1,5,7-10   - a set containing the classes 1,5,7,8,9,10
    !17,31-40  - a set containing all classes execept 17 and 31-40.

SEE ALSO:
    SET_SET, SET_ADD, SET_REMOVE, SET_SHOW
