/**
* Returns all facts in the model.
*
* @return the facts.
*/
public final Formula facts() {
// sig File extends Object {} { some d: Dir | this in d.entries.contents }
final Variable file = Variable.unary("this");
final Variable d = Variable.unary("d");
final Formula f0 =
file.in(d.join(entries).join(contents)).forSome(d.oneOf(Dir)).forAll(file.oneOf(File));
// sig Dir extends Object {
// entries: set DirEntry,
// parent: lone Dir
// } {
// parent = this.~@contents.~@entries
// all e1, e2 : entries | e1.name = e2.name => e1 = e2
// this !in this.^@parent
// this != Root => Root in this.^@parent
// }
final Variable dir = Variable.unary("this");
final Variable e1 = Variable.unary("e1"), e2 = Variable.unary("e2");
final Formula f1 =
(dir.join(parent)).eq(dir.join(contents.transpose()).join(entries.transpose()));
final Expression e0 = dir.join(entries);
final Formula f2 =
e1.join(name).eq(e2.join(name)).implies(e1.eq(e2)).forAll(e1.oneOf(e0).and(e2.oneOf(e0)));
final Formula f3 = dir.in(dir.join(parent.closure())).not();
final Formula f4 = dir.eq(Root).not().implies(Root.in(dir.join(parent.closure())));
final Formula f5 = f1.and(f2).and(f3).and(f4).forAll(dir.oneOf(Dir));
// one sig Root extends Dir {} { no parent }
final Formula f6 = Root.join(parent).no();
// sig DirEntry {
// name: Name,
// contents: Object
// } { one this.~entries }
final Variable entry = Variable.unary("this");
final Formula f7 = entry.join(entries.transpose()).one().forAll(entry.oneOf(DirEntry));
// fact OneParent {
// // all directories besides root xhave one parent
// all d: Dir - Root | one d.parent
// }
final Formula f8 = d.join(parent).one().forAll(d.oneOf(Dir.difference(Root)));
return f0.and(f5).and(f6).and(f7).and(f8);
}
/**
* Returns a relational encoding of the problem.
*
* @return a relational encoding of the problem.
*/
public Formula rules() {
final List<Formula> rules = new ArrayList<Formula>();
rules.add(x.function(queen, num));
rules.add(y.function(queen, num));
final Variable i = Variable.unary("n");
final Variable q1 = Variable.unary("q1"), q2 = Variable.unary("q2");
// at most one queen in each row: all i: num | lone x.i
rules.add(x.join(i).lone().forAll(i.oneOf(num)));
// at most one queen in each column: all i: num | lone y.i
rules.add(y.join(i).lone().forAll(i.oneOf(num)));
// no queen in a blocked position: all q: Queen | q.x->q.y !in blocked
rules.add(q1.join(x).product(q1.join(y)).intersection(blocked).no().forAll(q1.oneOf(queen)));
// at most one queen on each diagonal
// all q1: Queen, q2: Queen - q1 |
// let xu = prevs[q2.x] + prevs[q1.x],
// xi = prevs[q2.x] & prevs[q1.x],
// yu = prevs[q2.y] + prevs[q1.y],
// yi = prevs[q2.y] & prevs[q1.y] |
// #(xu - xi) != #(yu - yi)
final Expression ordClosure = ord.closure();
final Expression q2xPrevs = ordClosure.join(q2.join(x)), q1xPrevs = ordClosure.join(q1.join(x));
final Expression q2yPrevs = ordClosure.join(q2.join(y)), q1yPrevs = ordClosure.join(q1.join(y));
final IntExpression xDiff =
(q2xPrevs.union(q1xPrevs)).difference(q2xPrevs.intersection(q1xPrevs)).count();
final IntExpression yDiff =
(q2yPrevs.union(q1yPrevs)).difference(q2yPrevs.intersection(q1yPrevs)).count();
rules.add(xDiff.eq(yDiff).not().forAll(q1.oneOf(queen).and(q2.oneOf(queen.difference(q1)))));
return Formula.and(rules);
}
