☰
ordered
🌌ordered
ordered -- feature for immutable values that have an infix <= function
predicate that defines a total order
features inheriting from ordered define a total order of their values
NYI: the compiler should check that features inheriting from this are
actually immutable.
three-way comparison between this and other.
result is < 0 if this < other
result is > 0 if this > other
result is = 0 if this = other