chocoteam/choco3 — pull request #128 by JLiangWaterloo (2013-10-20 15:23:14+00:00)
Title: Constants zero and one do not raise contradictions

For example:

```java
public static void main(String[] args) {
Solver solver = new Solver();
UndirectedGraphVar g = new UndirectedGraphVar("g", solver, 2, true);
BoolVar b0 = VF.one(solver);
BoolVar b1 = VF.zero(solver);
BoolVar b2 = VF.zero(solver);
BoolVar b3 = VF.one(solver);
g.getEnvelopGraph().addEdge(0, 1);

// Forbid the edge (0, 1)
Constraint c = new Constraint(new Variable[]{g, b0, b1, b2, b3}, solver);
c.setPropagators(new PropGraphBool(g, new BoolVar[][]{
new BoolVar[]{b0, b1},
new BoolVar[]{b2, b3}
}));
solver.post(c);

solver.set(GraphStrategyFactory.graphLexico(g));
if (solver.findSolution()) {
System.out.println("Found a solution! Entailed? " + solver.isEntailed());
} else {
System.out.println("No solution!");
}
}
```

Currently it prints: "Found a solution! Entailed? FALSE".
After the fix it prints: "No solution!"