C++ Reference: constraint_solver

This documentation is automatically generated.

Declaration of the core objects for the constraint solver.

The literature around constraint programming is extremely dense but one can find some basic introductions in the following links:
- http://en.wikipedia.org/wiki/Constraint_programming
- http://kti.mff.cuni.cz/~bartak/constraints/index.html

Here is a very simple Constraint Programming problem:

Knowing that we see 56 legs and 20 heads, how many pheasants and rabbits are we looking at?

Here is some simple Constraint Programming code to find out:
```   void pheasant() {
Solver s("pheasant");
IntVar* const p = s.MakeIntVar(0, 20, "pheasant"));
IntVar* const r = s.MakeIntVar(0, 20, "rabbit"));
IntExpr* const legs = s.MakeSum(s.MakeProd(p, 2), s.MakeProd(r, 4));
IntExpr* const heads = s.MakeSum(p, r);
Constraint* const ct_legs = s.MakeEquality(legs, 56);
DecisionBuilder* const db = s.MakePhase(p, r,
Solver::CHOOSE_FIRST_UNBOUND,
Solver::ASSIGN_MIN_VALUE);
s.NewSearch(db);
CHECK(s.NextSolution());
LOG(INFO) << "rabbits -> " << r->Value() << ", pheasants -> "
<< p->Value();
LOG(INFO) << s.DebugString();
s.EndSearch();
}
```
which outputs:
```   rabbits -> 8, pheasants -> 12
Solver(name = "pheasant",
state = OUTSIDE_SEARCH,
branches = 0,
fails = 0,
decisions = 0
propagation loops = 11,
demons Run = 25,
Run time = 0 ms)
```