/// <summary>
/// Enforces maxvalues by disallowing values normally room for with the size of bits in an fdd
/// Value is normally expected to be the same as used in the constructor of the fdd.
/// Note: (powers of 2) -1) does not need to be constrained: 7, 255 etc.
/// </summary>
/// <param name="fdd">The fdd to constrain</param>
/// <param name="value">The values to enforce</param>
public static Bdd EnforceMaxValue(Fdd fdd, int value)
{
Bdd result;
//Always allow all bits where most significant bit isn't set
result = Kernel.Not(new Bdd(fdd.Var));
int start = (int)Math.Pow(2, Size(fdd) - 1); //lowest number with most significant bit set
for (int i = start; i <= value; i++)
{
result = Kernel.Or(result, Equal(fdd, i));
}
return(result);
}
public Bdd execute()
{
// Calls specific methods from Kernel
Bdd l = left.execute();
Bdd r = right.execute();
Bdd result = new Bdd(false);
switch (op)
{
case Kind.DIS:
result = BDD.Or(l, r);
break;
case Kind.CON:
result = BDD.And(l, r);
break;
case Kind.BIMP:
result = BDD.Equal(l, r);
break;
case Kind.NAND:
result = BDD.Nand(l, r);
break;
case Kind.XOR:
result = BDD.Xor(l, r);
break;
case Kind.NOR:
result = BDD.Nor(l, r);
break;
case Kind.NOT:
result = BDD.Not(r);
break;
}
l.Dispose(); //forced garbage collection
r.Dispose();
return(result);
}
/// <summary>
/// Creates a hard binding sort of like an fdd restrict.
/// Difference is that the binding will persist no matter
/// what changes is later added.
/// </summary>
/// <param name="fdd">the Fdd to create a binding on</param>
/// <param name="value">the constant number that is assigned to the Fdd.</param>
/// <returns></returns>
public static Bdd Equal(Fdd fdd, int value)
{
if (Log2(value) > FddDictionary[fdd.Var]) //value larger than fdd can hold.
{
return(new Bdd(false));
}
bool[] b = ToBitPattern(value, Size(fdd));
Bdd result = new Bdd(true);
for (int i = 0; i < b.Length; i++)
{
if (b[i])
{
result = Kernel.And(result, new Bdd(fdd.Var + i));
}
else
{
result = Kernel.And(result, Kernel.Not(new Bdd(fdd.Var + i)));
}
}
return(result);
}
/// <summary>
/// Not operator on Bdd
/// </summary>
/// <param name="r">Bdd</param>
/// <returns>Resulting Bdd</returns>
public static Bdd operator !(Bdd r)
{
return(Kernel.Not(r));
}
