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Many languages support conditional expressions, which are similar to if statements, but return a value as a result. Thus, they are true expressions (which evaluate to a value), not statements (which may not be permitted in the context of a value). The concept of conditional expressions was first developed by John McCarthy during his research into symbolic processing and LISP in the late 1950s.

ALGOL 60 and some other members of the ALGOL family allow if–then–else as an expression. The idea of including conditional expressions was suggested by John McCarthy, though the ALGOL committee decided to use English words rather than McCarthy's mathematical syntax:

Conditional expressions have always been a fundamental part of Lisp . In pure LISP, the COND function is used. In dialects such as Scheme, Racket and Common Lisp :

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