- Syntax:
-
rassoc
item alist &key key test test-not
entry
rassoc-if
predicate alist &key key
entry
rassoc-if-not
predicate alist &key key
entry
- Arguments and Values:
-
item - an object.
alist - an association list.
predicate - a designator for
a function of one argument
that returns a generalized boolean.
test - a designator for a function of two arguments
that returns a generalized boolean.
test-not - a designator for
a function of two arguments
that returns a generalized boolean.
key - a designator for a function of one argument,
or nil.
entry - a cons that is an element of the alist,
or nil.
- Description:
-
rassoc, rassoc-if, and rassoc-if-not
return the first cons whose cdr
satisfies the test.
If no such cons is found, nil is returned.
If nil appears in alist in place of a pair, it is ignored.
- Examples:
-
(setq alist '((1 . "one") (2 . "two") (3 . 3)))
((1 . "one") (2 . "two") (3 . 3))
(rassoc 3 alist) (3 . 3)
(rassoc "two" alist) NIL
(rassoc "two" alist :test 'equal) (2 . "two")
(rassoc 1 alist :key #'(lambda (x) (if (numberp x) (/ x 3)))) (3 . 3)
(rassoc 'a '((a . b) (b . c) (c . a) (z . a))) (C . A)
(rassoc-if #'stringp alist) (1 . "one")
(rassoc-if-not #'vectorp alist) (3 . 3)
- See Also:
-
assoc,
Section 3.6 Traversal Rules and Side Effects
- Notes:
-
The :test-not parameter is deprecated.
The function rassoc-if-not is deprecated.
It is possible to rplaca the result of rassoc,
provided that it is not nil, in order to "update" alist.
The expressions
(rassoc item list :test fn)
and
(find item list :test fn :key #'cdr)
are equivalent in meaning, except when the item is nil and nil appears in place of a pair in the alist.
See the function assoc.
- Allegro CL Implementation Details:
-
None.
14 Conses