A.54.4.1 Example 1
This is the "radiation therapy" example, taken from Introduction to Operations Research by Hillier and Lieberman.
Prolog DCG notation is used to implicitly thread the state through posting the constraints:
:- use_module(library(simplex)). radiation(S) :- gen_state(S0), post_constraints(S0, S1), minimize([0.4*x1, 0.5*x2], S1, S). post_constraints --> constraint([0.3*x1, 0.1*x2] =< 2.7), constraint([0.5*x1, 0.5*x2] = 6), constraint([0.6*x1, 0.4*x2] >= 6), constraint([x1] >= 0), constraint([x2] >= 0).
An example query:
?- radiation(S), variable_value(S, x1, Val1), variable_value(S, x2, Val2). Val1 = 15 rdiv 2, Val2 = 9 rdiv 2.