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

Example 16 with Formula

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

the class VariablesFunction method apply.

@Override
public SortedSet<Variable> apply(final Formula formula, final boolean cache) {
    final Object cached = formula.functionCacheEntry(VARIABLES);
    if (cached != null) {
        return (SortedSet<Variable>) cached;
    }
    SortedSet<Variable> result = new TreeSet<>();
    switch(formula.type()) {
        case FALSE:
        case TRUE:
            result = new TreeSet<>();
            break;
        case LITERAL:
            final Literal lit = (Literal) formula;
            result.add(lit.variable());
            break;
        case NOT:
            final Not not = (Not) formula;
            result = apply(not.operand(), cache);
            break;
        case IMPL:
        case EQUIV:
            final BinaryOperator binary = (BinaryOperator) formula;
            result.addAll(apply(binary.left(), cache));
            result.addAll(apply(binary.right(), cache));
            break;
        case OR:
        case AND:
            final NAryOperator nary = (NAryOperator) formula;
            for (final Formula op : nary) {
                result.addAll(apply(op, cache));
            }
            break;
        case PBC:
            final PBConstraint pbc = (PBConstraint) formula;
            result = FormulaHelper.variables(pbc.literals());
            break;
        default:
            throw new IllegalStateException("Unknown formula type " + formula.type());
    }
    result = Collections.unmodifiableSortedSet(result);
    if (cache) {
        formula.setFunctionCacheEntry(VARIABLES, result);
    }
    return result;
}

Example 17 with Formula

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

the class DnnfCompiler method conjoin.

protected Formula conjoin(final Formula implied, final DTreeNode tree, final int currentShannons) throws TimeoutException {
    final Formula left;
    final Formula right;
    if (implied == this.f.falsum() || (left = cnfAux(tree.left(), currentShannons)) == this.f.falsum() || (right = cnfAux(tree.right(), currentShannons)) == this.f.falsum()) {
        return this.f.falsum();
    } else {
        return this.f.and(implied, left, right);
    }
}

Example 18 with Formula

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

the class DnnfCompiler method cnf2Ddnnf.

protected Formula cnf2Ddnnf(final DTree tree, final int currentShannons) throws TimeoutException {
    final BitSet separator = tree.dynamicSeparator();
    final Formula implied = this.newlyImpliedLiterals(tree.staticVarSet());
    if (separator.isEmpty()) {
        if (tree instanceof DTreeLeaf) {
            return this.f.and(implied, leaf2Ddnnf((DTreeLeaf) tree));
        } else {
            return conjoin(implied, (DTreeNode) tree, currentShannons);
        }
    } else {
        final int var = chooseShannonVariable(tree, separator, currentShannons);
        if (this.handler != null && !this.handler.shannonExpansion()) {
            throw new TimeoutException();
        }
        /* Positive branch */
        Formula positiveDnnf = this.f.falsum();
        if (this.solver.decide(var, true)) {
            positiveDnnf = cnf2Ddnnf(tree, currentShannons + 1);
        }
        this.solver.undoDecide(var);
        if (positiveDnnf == this.f.falsum()) {
            if (this.solver.atAssertionLevel() && this.solver.assertCdLiteral()) {
                return cnf2Ddnnf(tree);
            } else {
                return this.f.falsum();
            }
        }
        /* Negative branch */
        Formula negativeDnnf = this.f.falsum();
        if (this.solver.decide(var, false)) {
            negativeDnnf = cnf2Ddnnf(tree, currentShannons + 1);
        }
        this.solver.undoDecide(var);
        if (negativeDnnf == this.f.falsum()) {
            if (this.solver.atAssertionLevel() && this.solver.assertCdLiteral()) {
                return cnf2Ddnnf(tree);
            } else {
                return this.f.falsum();
            }
        }
        final Literal lit = this.solver.litForIdx(var);
        final Formula positiveBranch = this.f.and(lit, positiveDnnf);
        final Formula negativeBranch = this.f.and(lit.negate(), negativeDnnf);
        return this.f.and(implied, this.f.or(positiveBranch, negativeBranch));
    }
}

Example 19 with Formula

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

the class DnnfCompiler method compile.

protected Formula compile(final DTree dTree, final DnnfCompilationHandler handler) {
    if (this.nonUnitClauses.isAtomicFormula()) {
        return this.cnf;
    }
    if (!this.solver.start()) {
        return this.f.falsum();
    }
    initializeCaches(dTree);
    this.handler = handler;
    start(handler);
    Formula result;
    try {
        result = cnf2Ddnnf(dTree);
    } catch (final TimeoutException e) {
        result = null;
    }
    this.handler = null;
    return result == null ? null : this.f.and(this.unitClauses, result);
}

Example 20 with Formula

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

the class DnnfFactory method compile.

/**
 * Compiles the given formula to a DNNF instance.
 * @param formula the formula
 * @return the compiled DNNF
 */
public Dnnf compile(final Formula formula) {
    final SortedSet<Variable> originalVariables = new TreeSet<>(formula.variables());
    final Formula cnf = formula.cnf();
    originalVariables.addAll(cnf.variables());
    final Formula simplifedFormula = simplifyFormula(cnf);
    final DnnfCompiler compiler = new DnnfCompiler(simplifedFormula);
    final Formula dnnf = compiler.compile(new MinFillDTreeGenerator());
    return new Dnnf(originalVariables, dnnf);
}