public static IEnumerable <uint> Permutations(uint value, int numBits)
{
uint baseTerm = Bit.GetFirst(value, numBits);
uint mask = Bit.GetRange(value, numBits, numBits);
uint variant = 0;
int variantLength = Bit.OnesCount(mask);
if (variantLength == 0)
{
yield return(baseTerm);
yield break;
}
uint maxVariant = Bit.MaxNum(variantLength);
for (; variant <= maxVariant; variant++)
{
uint variantOne = 1;
uint lastVariantOne = 1u << variantLength;
uint maskOne = 1;
uint permutation = baseTerm;
do
{
if ((mask & maskOne) != 0)
{
if ((variant & variantOne) == 0)
{
permutation &= ~maskOne;
}
else
{
permutation |= maskOne;
}
variantOne <<= 1;
}
maskOne <<= 1;
} while (variantOne < lastVariantOne);
yield return(permutation);
}
}