[7][8] Unary numbers should be distinguished from repunits, which are also written as sequences of ones but have their usual decimal numerical interpretation.
Therefore, while the run-time and space requirement in unary looks better as function of the input size, it does not represent a more efficient solution.
[16] In addition to the application in tally marks, unary numbering is used as part of some data compression algorithms such as Golomb coding.
[18] A form of unary notation called Church encoding is used to represent numbers within lambda calculus.
[19] Some email spam filters tag messages with a number of asterisks in an e-mail header such as X-Spam-Bar or X-SPAM-LEVEL.
Using a unary representation instead of a decimal number lets the user search for messages with a given rating or higher.