syntax for sets, powersets, bags, lists, hypermatrix

3.25: adda/dstr/literals:
. when a var is of type set,
it really means its values are a
powerset of some given enum type.
. another approach is using {a | b | c | ...}
to mean a value space,
while {,,,} means a set that involves multiple values .
. let dots do hyper-matrix structuring:
( ,,,; ,,,; . ,,,; . ...)
while in set braces, dots delimit items in a bag:
items in a bag are not ordered but duplicates are allowed;
eg, { 2 . 2 . 3 } is the bag of primes for 12 .
vs list { ;;; } which has duplicates but is ordered .