Editing Lisp (programming language) (section)

====List-processing procedures====
Lisp provides many built-in procedures for accessing and controlling lists. Lists can be created directly with the {{Lisp2|list}} procedure, which takes any number of arguments, and returns the list of these arguments.
<syntaxhighlight lang="Lisp">
 (list 1 2 'a 3)
 ;Output: (1 2 a 3)
</syntaxhighlight>
<syntaxhighlight lang="Lisp">
 (list 1 '(2 3) 4)
 ;Output: (1 (2 3) 4)
</syntaxhighlight>
Because of the way that lists are constructed from [[cons pair]]s, the {{Lisp2|cons}} procedure can be used to add an element to the front of a list. The {{Lisp2|cons}} procedure is asymmetric in how it handles list arguments, because of how lists are constructed.
<syntaxhighlight lang="Lisp">
 (cons 1 '(2 3))
 ;Output: (1 2 3)
</syntaxhighlight>
<syntaxhighlight lang="Lisp">
 (cons '(1 2) '(3 4))
 ;Output: ((1 2) 3 4)
</syntaxhighlight>
The {{Lisp2|append}} procedure appends two (or more) lists to one another. Because Lisp lists are linked lists, appending two lists has [[Big O notation|asymptotic time complexity]] <math>O(n)</math>
<syntaxhighlight lang="Lisp">
 (append '(1 2) '(3 4))
 ;Output: (1 2 3 4)
</syntaxhighlight>
<syntaxhighlight lang="Lisp">
 (append '(1 2 3) '() '(a) '(5 6))
 ;Output: (1 2 3 a 5 6)
</syntaxhighlight>