Associative operators with an identity are extremely common in programming, inverses are much less common. Most ways to turn a lot of data into a little data ha

Associative operators with an identity are extremely common in programming, inverses are much less common. Most ways to turn a lot of data into a little data have a monoid hidden in them with the identity serving as a default value in the case of missing data. There is nothing you can comcatenate to a list to get the empty list, nothing you can OR with True to get False, and nothing you can union with a set to get the empty set.