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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 | |
26 | (defpackage #:mdw.collect |
27 | (:use #:common-lisp #:mdw.base) |
28 | (:export #:collecting #:with-collection #:collect)) |
29 | (in-package mdw.collect) |
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 () |
35 | (let ((c (cons nil nil))) |
36 | (cons c c)))) |
37 | (defmacro collecting (vars &body body) |
38 | "Collect items into lists. The VARS are a list of collection variables -- |
39 | their values are unspecified, except that they may be passed to `collect' and |
40 | `collect-tail' If VARS is empty then *collecting-anon-list-name* is used. |
41 | VARS may be an atom instead of a singleton list. The form produces multiple |
42 | values, one for each list constructed." |
43 | (cond ((null vars) (setf vars (list *collecting-anon-list-name*))) |
44 | ((atom vars) (setf vars (list vars)))) |
45 | `(let ,(mapcar (lambda (v) `(,v (make-collector))) vars) |
46 | ,@body |
47 | (values ,@(mapcar (lambda (v) `(cdar ,v)) vars)))) |
48 | (defmacro with-collection (vars collection &body body) |
49 | "Collect items into lists VARS according to the form COLLECTION; then |
50 | evaluate BODY with VARS bound to those lists." |
51 | `(multiple-value-bind |
52 | ,(listify vars) |
53 | (collecting ,vars ,collection) |
54 | ,@body)) |
55 | (defmacro collect (x &optional (name *collecting-anon-list-name*)) |
56 | "Add item X to the `collecting' list NAME (or *collecting-anon-list-name* |
57 | by default)." |
58 | (with-gensyms tmp |
59 | `(let ((,tmp (cons ,x nil))) |
60 | (setf (cddr ,name) ,tmp) |
61 | (setf (cdr ,name) ,tmp)))) |
62 | (defmacro collect-tail (x &optional (name *collecting-anon-list-name*)) |
63 | "Make item X be the tail of `collecting' list NAME (or |
64 | *collecting-anon-list-name* by default). It is an error to continue trying |
65 | to add stuff to the list." |
66 | `(progn |
67 | (setf (cddr ,name) ,x) |
68 | (setf (cdr ,name) nil))) |
69 | |
70 | ;;;----- That's all, folks -------------------------------------------------- |