Commit 7a095a28 authored by Attila Lendvai's avatar Attila Lendvai
Browse files

added assoc-value (written by John Fremlin)

parent 13cfae2b
......@@ -22,6 +22,45 @@ property list PLIST in the same order."
((safe-endp tail) (nreverse alist))
(push (cons (car tail) (cadr tail)) alist))))
(declaim (inline racons))
(defun racons (key value ralist)
(acons value key ralist))
(macrolet ((define-alist-get (name get-pair get-value-from-pair add doc)
(declaim (inline ,name))
(defun ,name (alist key &key (test 'eql))
(let ((pair (,get-pair key alist :test test)))
(values (,get-value-from-pair pair) pair)))
(define-setf-expander ,name (place key &key (test ''eql)
&environment env)
(multiple-value-bind (dummies vals newvals setter getter)
(get-setf-expansion place env)
(when (cdr newvals)
(error "~A cannot store multiple values in one place" ',name))
(with-unique-names (store key-val test-val alist found)
(append dummies (list key-val test-val))
(append vals (list key test))
(list store)
`(let ((,alist ,getter))
(let ((,found (,',get-pair ,key-val ,alist :test ,test-val)))
(cond (,found
(setf (,',get-value-from-pair ,found) ,store))
(let ,newvals
(setf ,(first newvals) (,',add ,key ,store ,alist))
`(,',name ,getter ,key))))))))
(define-alist-get assoc-value assoc cdr acons
"ASSOC-VALUE is an alist accessor very much like ASSOC, but it can
be used with SETF.")
(define-alist-get rassoc-value rassoc car racons
"RASSOC-VALUE is an alist accessor very much like RASSOC, but it can
be used with SETF."))
(defun malformed-plist (plist)
(error "Malformed plist: ~S" plist))
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