3.7.83. Difference between pairs of variables

A constraint that allows expressing that a set of pairs of variables are different. Two pairs of variables (X 1 ,Y 1 ) and (X 2 ,Y 2 ) are different if and only if X 1 X 2 or Y 1 Y 2 . Constraint 𝚕𝚎𝚡_𝚊𝚕𝚕𝚍𝚒𝚏𝚏𝚎𝚛𝚎𝚗𝚝_𝚎𝚡𝚌𝚎𝚙𝚝_0 ignores pairs for which both components are assigned value 0.