// Negates this simple expression
private SimpleExpression negate() {
SimpleExpression ret = null;
if (sop == NEG) ret = getChild(0);
else if (sop == LIT) ret = (equals(szero)) ? sone : szero;
else if (sop >= EQ && sop <= GT) {
ret = (SimpleExpression) clone();
ret.sop = negateOp(sop);
} else if (sop == AND || sop == OR) {
ret = new SimpleExpression((sop == AND) ? OR : AND);
for (SimpleExpression child : children) ret.add(child.negate());
} else {
ret = new SimpleExpression(NEG);
ret.add(this);
}
return ret;
}
// Normalizes an AND|OR operation
private SimpleExpression normalizeLogic() {
if (!allow(LOGIC)) return this;
TreeSet<SimpleExpression> set = new TreeSet<SimpleExpression>(children);
TreeSet<SimpleExpression> neg = new TreeSet<SimpleExpression>();
SimpleExpression ret = new SimpleExpression(sop);
for (SimpleExpression child : set) {
if (sop == AND) {
if (child.equals(szero) || neg.contains(child)) return szero;
else if (child.sop != LIT) // ==LIT means non-zero literal.
ret.add(child);
} else // sop == OR
{
if ((child.sop == LIT && !child.equals(szero)) || neg.contains(child)) return sone;
else if (child.sop != LIT) // ==LIT means zero literal.
ret.add(child);
}
neg.add(child.negate());
}
if (ret.children.size() == 0) // skipped literals.
ret = (ret.sop == AND) ? sone : szero;
else if (ret.children.size() == 1) ret = ret.getChild(0);
// Tools.printlnStatus("[LOGIC] "+this+" --> "+ret, 1);
return ret;
}