internal override BooleanExpression ToDNF_Helper()
{
var newOperands = this.operands.Select(x => x.ToDNF_Helper());
// flatten a conjunction over the operands to get operands without superfluous operator levels,
// i.e. when one of the operands was a disjunction, but becomes a conjunction due to distributing
// when putting it into DNF, we need to flatten in order to get all conjunction operands into the same layer
var newOperandsList = ((Conjunction) new Conjunction(newOperands).Flatten()).GetOperands().ToList();
var disjunctions = newOperands.Where(op => op is Disjunction).Cast <Disjunction>();
if (!disjunctions.Any())
{ // no operand is a disjunction, so we can't distribute anything.
return(new Conjunction(newOperands));
}
else
{
Disjunction disj = disjunctions.First();
// disjunction will be distributed, so remove it
newOperandsList.Remove(disj);
var distributedOperandLists = new List <List <BooleanExpression> >();
foreach (BooleanExpression op in disj.GetOperands())
{
distributedOperandLists.Add(newOperandsList.Append(op).ToList());
}
BooleanExpression resultDisj = new Disjunction(distributedOperandLists.Select(ops => new Conjunction(ops).ToDNF_Helper()));
resultDisj = resultDisj.Flatten().Simplify().ToDNF_Helper().Simplify();
return(resultDisj);
}
}
public override BooleanExpression Flatten()
{
var flattenedOperands = this.GetOperands().Select(op => op.Flatten());
var resultOperands = new List <BooleanExpression>();
foreach (BooleanExpression expr in flattenedOperands)
{
if (expr is Disjunction disj)
{
foreach (BooleanExpression op in disj.GetOperands())
{
resultOperands.Add(op);
}
}
else
{
resultOperands.Add(expr);
}
}
var result = new Disjunction(resultOperands);
return(result);
}