/*
   total orderings
*/

% total ordering
X<Y, Y<Z -> X<Z.
X<X -> [].
X<Y, Y<X, X=Y.
inf=<X.
X=<undef.

% reflexive_closure

X=<X.
X<Y -> X=<Y.
X=<Y -> X=Y,X<Y.

precedence([inf,undef,=<,<]).