member (FUNCTION)

Format: (member <item> <list> :test <test> :test-not <test-not> :key <key> )

Required arguments: 2

<item> : Any Lisp expression <list> : A expression which returns a list

Keyword arguments: 3

<test> /<test-not> : A function or lambda expression that can be applied to compare <item> with elements of <list> . <key> : A function or lambda expression that can be applied to elements of <list> .

The elements of <list> are compared with the <item> . If <test> is not specified, eq is used; otherwise <test> is used. If <item> is found to match an element of <list> , a list containing all the elements from <item> to the end of <list> is returned. Otherwise NIL is returned. If <test-not> is specified, member returns a list beginning with the first UNmatched element of <list> . Specifying a <key> causes member to compare <item> with the result of applying <key> to each element of <list> , rather than to the element itself.

Examples:

> (member 'riker '(picard riker worf crusher))
(RIKER WORF CRUSHER)

> (member '(lieutenant worf) 
         '((captain picard)
           (commander riker)
           (lieutenant worf)
           (ensign crusher)))
NIL

> (member '(lieutenant worf) 
         '((captain picard)
           (commander riker)
           (lieutenant worf)
           (ensign crusher))
         :test #'equal)
((LIEUTENANT WORF) (ENSIGN CRUSHER))	 

> (member 'picard '(picard riker worf crusher) :test-not #'eq)
(RIKER WORF CRUSHER)

> (member 'worf 
         '((captain picard)
           (commander riker)
           (lieutenant worf)
           (ensign crusher))
         :key #'second)
((LIEUTENANT WORF) (ENSIGN CRUSHER))