Class IlcConstraint

A constraint is an object in CP Optimizer. Like other CP Optimizer entities, a constraint is implemented by means of two classes: a handle class and an implementation class. In other words, an instance of the class IlcConstraint (a handle) contains a data member (the handle pointer) that points to an instance of the class IlcConstraintI (its implementation object).

Constraints as Boolean Expressions

You might also think of a constraint as a Boolean expression with a value of either IlcFalse or IlcTrue. The value of the expression depends on the satisfiability of the constraint: if the constraint cannot be violated, then the expression is fixed to IlcTrue; if the constraint cannot be satisfied, then the expression is fixed to IlcFalse. We sometimes call a constraint, a constrained Boolean expression. These expressions can be constrained themselves, and they can be combined with logical operators: or, and, and not.

Posting Constraints

When you create a constraint, CP Optimizer does not automatically take it into account. You must explicitly add the constraint to a model and extract the model.

Most member functions in this class contain assert statements. For an explanation of the macro NDEBUG (a way to turn on or turn off these assert statements), see the concept Assert and NDEBUG.

When this member function returns IlcTrue, the invoking constraint cannot be satisfied, no matter what.

For example, consider the constraint x <= y. If the domain of x is [0, 10] and the domain of y is [10, 20], then the constraint is necessarily satisfied. In contrast, if the domain of x is [11, 20] and the domain of y is [0, 10], then the constraint is necessarily violated (that is, it cannot be satisfied).

When this member function returns IlcTrue, the invoking constraint is necessarily satisfied, no matter what.