In computer programming, ' ( or ) is a fundamental function in most dialects of the Lisp programming language. cons'"tructs" memory objects which hold two values or pointers to values. These objects are referred to as (cons) cells, conses, non-atomic s-expressions ("NATSes"), or (cons) pairs. In Lisp jargon, the expression "to cons "x" onto "y"" means to construct a new object with codice_1. The resulting pair has a left half, referred to as the CAR and CDR (the first element, or contents of the address part of register), and a right half (the second element, or contents of the decrement part of register), referred to as the CAR and CDR.