constraint(+Constraint,
+S0, -S)Adds a linear or integrality constraint to the linear program
corresponding to state S0. A linear constraint is of the form Left Op C,
where Left is a list of Coefficient*Variable
terms (variables in the context of linear programs can be atoms or
compound terms) and C is a non-negative numeric constant. The
list represents the sum of its elements. Op can be =, =<
or >=. The coefficient 1 can be omitted. An
integrality constraint is of the form integral(Variable)
and constrains Variable to an integral value.