Major Section: ACL2-BUILT-INS
General Forms: (rassoc x alist) (rassoc x alist :test 'eql) ; same as above (eql as equality test) (rassoc x alist :test 'eq) ; same, but eq is equality test (rassoc x alist :test 'equal) ; same, but equal is equality test
(Rassoc x alist) is the first member of alist whose cdr is
x, or nil if no such member exists. (rassoc x alist) is thus
similar to (assoc x alist), the difference being that it looks for the
first pair in the given alist whose cdr, rather than car, is
eql to x. See assoc. The optional keyword, :TEST, has no
effect logically, but provides the test (default eql) used for
comparing x with the cdrs of successive elements of lst.
The guard for a call of rassoc depends on the test. In all cases,
the second argument must satisfy alistp. If the test is eql,
then either the first argument must be suitable for eql (see eqlablep)
or the second argument must satisfy r-eqlable-alistp. If the test is
eq, then either the first argument must be a symbol or the second
argument must satisfy r-symbol-alistp.
See equality-variants for a discussion of the relation between rassoc and
its variants:
(rassoc-eq x lst)is equivalent to(rassoc x lst :test 'eq);
(rassoc-equal x lst)is equivalent to(rassoc x lst :test 'equal).
In particular, reasoning about any of these primitives reduces to reasoning
about the function rassoc-equal.
Rassoc is defined by Common Lisp. See any Common Lisp documentation for
more information.
