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861345b4 | 1 | ;;; -*-lisp-*- |
2 | ;;; | |
3 | ;;; $Id$ | |
4 | ;;; | |
5 | ;;; Collecting things into lists | |
6 | ;;; | |
7 | ;;; (c) 2005 Straylight/Edgeware | |
8 | ;;; | |
9 | ||
10 | ;;;----- Licensing notice --------------------------------------------------- | |
11 | ;;; | |
12 | ;;; This program is free software; you can redistribute it and/or modify | |
13 | ;;; it under the terms of the GNU General Public License as published by | |
14 | ;;; the Free Software Foundation; either version 2 of the License, or | |
15 | ;;; (at your option) any later version. | |
16 | ;;; | |
17 | ;;; This program is distributed in the hope that it will be useful, | |
18 | ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | ;;; GNU General Public License for more details. | |
21 | ;;; | |
22 | ;;; You should have received a copy of the GNU General Public License | |
23 | ;;; along with this program; if not, write to the Free Software Foundation, | |
24 | ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | ||
bf0a8c39 | 26 | (defpackage #:collect |
861345b4 | 27 | (:use #:common-lisp #:mdw.base) |
512c44e0 | 28 | (:export #:collecting #:with-collection #:collect #:collect-tail)) |
bf0a8c39 | 29 | (in-package collect) |
861345b4 | 30 | |
31 | (eval-when (:compile-toplevel :load-toplevel) | |
32 | (defvar *collecting-anon-list-name* (gensym) | |
33 | "The default name for anonymous `collecting' lists.") | |
34 | (defun make-collector () | |
a721f2f2 MW |
35 | (let ((head (cons nil nil))) |
36 | (setf (car head) head)))) | |
288343df | 37 | |
861345b4 | 38 | (defmacro collecting (vars &body body) |
39 | "Collect items into lists. The VARS are a list of collection variables -- | |
0ff9df03 MW |
40 | their values are unspecified, except that they may be passed to `collect' |
41 | and `collect-tail' If VARS is empty then *collecting-anon-list-name* is | |
42 | used. VARS may be an atom instead of a singleton list. The form produces | |
43 | multiple values, one for each list constructed." | |
861345b4 | 44 | (cond ((null vars) (setf vars (list *collecting-anon-list-name*))) |
45 | ((atom vars) (setf vars (list vars)))) | |
46 | `(let ,(mapcar (lambda (v) `(,v (make-collector))) vars) | |
47 | ,@body | |
447aca39 | 48 | (values ,@(mapcar (lambda (v) `(the list (cdr ,v))) vars)))) |
288343df | 49 | |
861345b4 | 50 | (defmacro with-collection (vars collection &body body) |
51 | "Collect items into lists VARS according to the form COLLECTION; then | |
0ff9df03 | 52 | evaluate BODY with VARS bound to those lists." |
861345b4 | 53 | `(multiple-value-bind |
0ff9df03 | 54 | ,(listify vars) |
861345b4 | 55 | (collecting ,vars ,collection) |
56 | ,@body)) | |
288343df | 57 | |
861345b4 | 58 | (defmacro collect (x &optional (name *collecting-anon-list-name*)) |
59 | "Add item X to the `collecting' list NAME (or *collecting-anon-list-name* | |
0ff9df03 | 60 | by default)." |
a721f2f2 MW |
61 | (with-gensyms new |
62 | `(let ((,new (cons ,x nil))) | |
63 | (setf (cdar ,name) ,new) | |
64 | (setf (car ,name) ,new)))) | |
288343df | 65 | |
861345b4 | 66 | (defmacro collect-tail (x &optional (name *collecting-anon-list-name*)) |
67 | "Make item X be the tail of `collecting' list NAME (or | |
0ff9df03 MW |
68 | *collecting-anon-list-name* by default). It is an error to continue |
69 | trying to add stuff to the list." | |
861345b4 | 70 | `(progn |
a721f2f2 MW |
71 | (setf (cdar ,name) ,x) |
72 | (setf (car ,name) nil))) | |
861345b4 | 73 | |
74 | ;;;----- That's all, folks -------------------------------------------------- |