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New Macros

 - A function #'PARALLEL-LOOKUP that basically does assoc on two flat
   lists. Hard to describe exactly how it works -- use the source.
 - A macro PUSHEND, that pushes onto the end of a list given the list
   and a tail pointer.
 - A macro WITH-PUSH-ONTO, that does a lot of stuff and needs to be
   documented in greater detail.
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commit 83bfe1628a80d95e632311091e331a0bd64120c4 1 parent 365a4e3
@adlai authored
Showing with 33 additions and 0 deletions.
  1. +33 −0 src/utils.lisp
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33 src/utils.lisp
@@ -14,6 +14,39 @@
`(let ((it ,test))
(if it ,true ,false)))
+(defun parallel-lookup (thing key-list value-list &key (test #'eql) (key #'identity))
+ (map nil (lambda (k v)
+ (when (funcall test thing (funcall key k))
+ (return-from parallel-lookup v)))
+ key-list value-list))
+
+(defmacro pushend (new-item list list-end &environment env)
+ (multiple-value-bind (list.gvars list.vals list.gstorevars list.setter list.getter)
+ (get-setf-expansion list env)
+ (multiple-value-bind (tail.gvars tail.vals tail.gstorevars tail.setter tail.getter)
+ (get-setf-expansion list-end env)
+ (let ((gitem (gensym))
+ (list.gstorevar (first list.gstorevars))
+ (tail.gstorevar (first tail.gstorevars)))
+ `(let (,@(mapcar #'list list.gvars list.vals)
+ ,@(mapcar #'list tail.gvars tail.vals))
+ (let ((,gitem (list ,new-item)))
+ (if ,list.getter
+ (let ((,tail.gstorevar ,gitem))
+ (setf (cdr ,tail.getter) ,gitem)
+ ,tail.setter)
+ (let ((,list.gstorevar ,gitem)
+ (,tail.gstorevar ,gitem))
+ ,list.setter ,tail.setter))))))))
+
+(defmacro with-push-onto ((&rest places) &body body)
+ (let ((end-names (mapcar (fn (gensym (symbol-name _))) places)))
+ `(let (,@places ,@end-names)
+ (macrolet ((push-onto (place thing)
+ `(pushend ,thing ,place
+ ,(parallel-lookup place ',places ',end-names))))
+ ,@body))))
+
;;; This is taken from Arnesi's src/one-liners.lisp, and implements a
;;; more sophisticated version of PCL's WITH-GENSYMS.

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