Elvis operator

In certain computer programming languages, the Elvis operator, often written ?:, is a binary operator that evaluates its first operand and returns it if its value is logically true (according to a language-dependent convention, in other words, a truthy value), and otherwise evaluates and returns its second operand. The second operand is only evaluated if it is to be returned (short-circuit evaluation). The notation of the Elvis operator was inspired by the ternary conditional operator, ? :, since the Elvis operator expression A ?: B is approximately equivalent to the ternary conditional expression A ? A : B.

The name "Elvis operator" refers to the fact that when its common notation, ?:, is viewed sideways, it resembles an emoticon of Elvis Presley with his signature hairstyle.[1]

A similar operator is the null coalescing operator, where the boolean truth(iness) check is replaced with a check for non-null instead. This is usually written ??, and can be seen in languages like C#[2] or Dart.[3]

  1. ^ Joyce Farrell (7 February 2013). Java Programming. Cengage Learning. p. 276. ISBN 978-1285081953. The new operator is called Elvis operator because it uses a question mark and a colon together (?:); if you view it sideways, it reminds you of Elvis Presley.
  2. ^ "?? Operator". C# Reference. Microsoft. Retrieved 5 December 2018.
  3. ^ "Conditional expressions". Dart Language. Google.

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