Examples with Formula org.logicng.formulas.Formula used on opensource projects

Example 26 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class EvaluatesToConstantPredicate method handleOr.

private Formula handleOr(final Or formula, final boolean topLevel) {
    final FormulaFactory f = formula.factory();
    final List<Formula> nops = new ArrayList<>();
    for (final Formula op : formula) {
        final Formula opResult = innerTest(op, !this.evaluatesToTrue && topLevel);
        if (isVerum(opResult)) {
            return f.verum();
        }
        if (!opResult.isConstantFormula()) {
            if (!this.evaluatesToTrue && topLevel) {
                return f.verum();
            }
            nops.add(opResult);
        }
    }
    return f.or(nops);
}

Example 27 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class NNFPredicate method test.

@Override
public boolean test(final Formula formula, final boolean cache) {
    final Tristate cached = formula.predicateCacheEntry(IS_NNF);
    if (cached != Tristate.UNDEF) {
        return cached == Tristate.TRUE;
    }
    boolean result;
    switch(formula.type()) {
        case FALSE:
        case TRUE:
        case LITERAL:
            result = true;
            break;
        case AND:
        case OR:
            result = true;
            for (final Formula op : formula) {
                if (!test(op, cache)) {
                    result = false;
                    break;
                }
            }
            break;
        case NOT:
        case IMPL:
        case EQUIV:
        case PBC:
            result = false;
            break;
        default:
            throw new IllegalArgumentException("Cannot compute NNF predicate on " + formula.type());
    }
    if (cache) {
        formula.setPredicateCacheEntry(IS_NNF, result);
    }
    return result;
}

Example 28 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class TautologyPredicate method test.

@Override
public boolean test(final Formula formula, final boolean cache) {
    final Tristate cached = formula.predicateCacheEntry(IS_TAUTOLOGY);
    if (cached != Tristate.UNDEF) {
        return cached == Tristate.TRUE;
    }
    final boolean result;
    final Formula negation = formula.negate();
    result = !negation.holds(this.satPredicate);
    if (cache) {
        formula.setPredicateCacheEntry(IS_TAUTOLOGY, result);
    }
    return result;
}

Example 29 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class PrimeCompiler method compute.

/**
 * Computes prime implicants and prime implicates for a given formula.
 * The coverage type specifies if the implicants or the implicates will
 * be complete, the other one will still be a cover of the given formula.
 * <p>
 * The prime compiler can be called with an {@link OptimizationHandler}.
 * The given handler instance will be used for every subsequent
 * {@link org.logicng.solvers.functions.OptimizationFunction} call and
 * the handler's SAT handler is used for every subsequent SAT call.
 * @param formula the formula
 * @param type    the coverage type
 * @param handler an optimization handler, can be {@code null}
 * @return the prime result or null if the computation was aborted by the handler
 */
public PrimeResult compute(final Formula formula, final PrimeResult.CoverageType type, final OptimizationHandler handler) {
    start(handler);
    final boolean completeImplicants = type == PrimeResult.CoverageType.IMPLICANTS_COMPLETE;
    final Formula formulaForComputation = completeImplicants ? formula : formula.negate();
    final Pair<List<SortedSet<Literal>>, List<SortedSet<Literal>>> result = computeGeneric(formulaForComputation, handler);
    if (result == null || aborted(handler)) {
        return null;
    }
    return new PrimeResult(completeImplicants ? result.first() : negateAll(result.second()), completeImplicants ? result.second() : negateAll(result.first()), type);
}

Example 30 with Formula

use of org.logicng.formulas.Formula in project LogicNG by logic-ng.

the class ModelCounter method simplify.

private static SimplificationResult simplify(final Collection<Formula> formulas) {
    final Assignment simpleBackbone = new Assignment();
    final SortedSet<Variable> backboneVariables = new TreeSet<>();
    for (final Formula formula : formulas) {
        if (formula.type() == FType.LITERAL) {
            final Literal lit = (Literal) formula;
            simpleBackbone.addLiteral(lit);
            backboneVariables.add(lit.variable());
        }
    }
    final List<Formula> simplified = new ArrayList<>();
    for (final Formula formula : formulas) {
        final Formula restrict = formula.restrict(simpleBackbone);
        if (restrict.type() != FType.TRUE) {
            simplified.add(restrict);
        }
    }
    return new SimplificationResult(simplified, backboneVariables);
}