Linear or logical constraints can appear as terms in numeric expressions. A linear constraint appearing as a term in a numeric expression behaves like a binary value. For example, given x and y as variables, you can write the following lines to get the truth value of x y in a binary value:

IloIntVar b(env, 0, 1);
model.add(b == (x >= y));

It is important to note here that only linear constraints can appear as arguments of logical constraints extracted by IloCplex. That is, quadratic constraints are not handled in logical constraints. Similarly, quadratic terms cannot appear as arguments of logical expressions such as IloMin, IloMax, IloAbs, and IloPiecewiseLinear.