bitmasking basic readings

So lately I've been exposed to using bitmasking for several tasks, and it's a cool and niche enough topic so that I delved a bit into it.

Appart from datastructures that depend on bit indexing like persistent datastructures, bit trees, bloom/cuckoo filters or others,  there's the concept of "plain" bit masking to optimize bookkeeping of a set of numbers (they can be indices of an array) in one big number.

Here are some examples of them:

• http://www.catonmat.net/blog/low-level-bit-hacks-you-absolutely-must-know/
• https://www.hackerearth.com/practice/algorithms/dynamic-programming/bit-masking/tutorial/
• ratpoison's rudeness feature
• dwm's tags feature