The variable in the RANGE statement, the ID variables, and the BY variables are available for the model program to examine, but their values should not be changed by the program.

Moving from object-oriented to functional programming is a paradigm shift for developers, but these key principles explain why it's worth the effort.

It is shown that the integer linear programming problem with a fixed number of variables is polynomially solvable. The proof depends on methods from geometry of numbers.