func (b *BitSet) Flip(i uint) *BitSet {
	if i >= b.length {
		return b.Set(i)
	}
	b.set[i>>log2Uint64Size] ^= 1 << (i & (uint64Size - 1))
	return b
}
// Flip bit at i.
Flip bit at i.
// Flip bit at i .
func (b *BitSet) Flip(i uint) *BitSet {
	if i >= b.length {
		return b.Set(i)
	}
	b.set[i>>log2Uint64Size] ^= 1 << (i & (uint64Size - 1))
	return b
}
func ( b * BitSet ) Flip ( i uint ) * BitSet { if i >= b . length { return b . Set ( i ) } b . set [ i >> log2Uint64Size ] ^= 1 << ( i & ( uint64Size - 1 ) ) return b }
Flip bit at i.
Flip bit at i .