Major Section: ACL2-BUILT-INS
General Forms: (member x lst) (member x lst :test 'eql) ; same as above (eql as equality test) (member x lst :test 'eq) ; same, but eq is equality test (member x lst :test 'equal) ; same, but equal is equality test
(Member x lst) equals the longest tail of the list lst that begins
with x, or else nil if no such tail exists. The optional keyword,
:TEST, has no effect logically, but provides the test (default eql)
used for comparing x with successive elements of lst.
The guard for a call of member depends on the test. In all cases,
the second argument must satisfy true-listp. If the test is eql,
then either the first argument must be suitable for eql (see eqlablep)
or the second argument must satisfy eqlable-listp. If the test is
eq, then either the first argument must be a symbol or the second
argument must satisfy symbol-listp.
See equality-variants for a discussion of the relation between member and
its variants:
(member-eq x lst)is equivalent to(member x lst :test 'eq);
(member-equal x lst)is equivalent to(member x lst :test 'equal).
In particular, reasoning about any of these primitives reduces to reasoning
about the function member-equal.
Member is defined by Common Lisp. See any Common Lisp documentation for
more information.
