Elephant in Cairo

An elephant in Cairo is a term used in computer programming to describe a piece of data inserted at the end of a search space, which matches the search criteria, in order to make sure the search algorithm terminates; it is a humorous example of a sentinel value. The term derives from a humorous essay circulated on the Internet and published in Byte magazine in September 1989 that described how various professions would go about hunting elephants.

When hunting elephants, the article describes programmers as following this algorithm:

This algorithm has a bug, namely a bounds checking error: if no elephants are found, the programmer will continue northwards and end up in the Mediterranean sea, causing abnormal termination by drowning.

Thus experienced programmers modify the above algorithm by placing a known elephant in Cairo to ensure that the algorithm will terminate. The modified algorithm is therefore as follows:

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