A constructor for constraint objects. Given a constraint expression, it denotes the associated constraint object. This means that constraints are uniquely defined by their expressions.
(<=> (The-Constraint ?Expression) (And (Constraint-Expression ?Expression) (= (Constraint.Expression ?Constraint) ?Expression)))
(=> (The-Constraint $X $Y) (Constraint-Expression $X)) (=> (= (The-Constraint ?Expression) ?Constraint) (= (Constraint.Expression ?Constraint) ?Expression)) (=> (= (The-Constraint ?Expression) ?Constraint) (Constraint-Expression ?Expression))