Sometimes you might use bits in an integer to encode data, e.g.; - A bitset index - Bitflags (e.g. to represent logging levels) - Feature flags `bit_count`

Sometimes you might use bits in an integer to encode data, e.g.; - A bitset index - Bitflags (e.g. to represent logging levels) - Feature flags `bit_count` (aka `popcount`) gives you an efficient way to figure out how many bits within those structures are set and not set.