Constrains list elements to integers. This constrains the variable listed to be integers using the underlying intervals library (i.e. ic or range), and, in addition, post the constraint to the eplex instance EplexInstance, where it can later be passed onto the external solver state associated with the instance when it is invoked. The external solver will then take the integrality into account, i.e. to solve a MIP rather than a relaxed LP problem.
Note that even when problem variables have been declared as integers in other solvers (range, ria, fd, other external solver states), if the integrality constraint is not made known to this solver state, any invocation of the eplex external solver (e.g. via eplex_solve/1) will only solve a continuous relaxation.
However, when a typed_solution is retrieved (e.g. via eplex_var_get/3), this will be rounded to the nearest integer even when the integrality has only been declared with the lib(range) or lib(ic) versions of ::/2 or integers/1.