The next data structure that we'll look at is a set. A set is similar to a list, except it does not have a specific order and each element may only appear once. Both the data structures are very useful because while in a list is fast to access the elements near the top or the bottom, and the order of the elements is preserved, in a set is very fast to test for membership, that is, to immediately know if a given element was added or not. Moreover in a set a given element can exist only in a single copy.
Some of the important commands in working with sets are SADD, SREM, SISMEMBER, SMEMBERS and SUNION.
SADD adds the given member to the set, again this command is also variadic.
SADD superpowers "flight" SADD superpowers "x-ray vision" "reflexes"
SREM removes the given member from the set, returning 1 or 0 to signal if the member was actually there or not.
SREM superpowers "reflexes" => 1 SREM superpowers "making pizza" => 0