A type is LessThanComparable if it is ordered: it must be
possible to compare two objects of that type using operator<,
and operator< must be a strict weak ordering relation. |X||A
type that is a model of LessThanComparable| |x, y, z||Object of
type X| Consider the relation !(x < y) && !(y < x). If this
relation is transitive (that is, if !(x < y) && !(y < x) && !(y
< z) && !(z < y) implies !(x < z) && !(z < x)), then it
satisfies the mathematical definition of an equivalence
relation. In this case, operator< is a strict weak ordering. If
operator< is a strict weak ordering, and if each equivalence
class has only a single element, then operator< is a total
ordering. |Name||Expression||Type requirements||Return type|
|Less||x < y||Convertible to bool| |Less||x < y||x and y are in
the domain of <| |Irreflexivity||x < x must be false.|
|Antisymmetry||x < y implies !(y < x) | |Transitivity||x < y and
y < z implies x < z |  Only operator< is fundamental; the other
inequality operators are essentially syntactic sug