| 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 #:collect |
| 27 | (:use #:common-lisp #:mdw.base) |
| 28 | (:export #:collecting #:with-collection #:collect #:collect-tail)) |
| 29 | (in-package 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 ((head (cons nil nil))) |
| 36 | (setf (car head) head)))) |
| 37 | |
| 38 | (defmacro collecting (vars &body body) |
| 39 | "Collect items into lists. The VARS are a list of collection variables -- |
| 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." |
| 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 |
| 48 | (values ,@(mapcar (lambda (v) `(the list (cdr ,v))) vars)))) |
| 49 | |
| 50 | (defmacro with-collection (vars collection &body body) |
| 51 | "Collect items into lists VARS according to the form COLLECTION; then |
| 52 | evaluate BODY with VARS bound to those lists." |
| 53 | `(multiple-value-bind |
| 54 | ,(listify vars) |
| 55 | (collecting ,vars ,collection) |
| 56 | ,@body)) |
| 57 | |
| 58 | (defmacro collect (x &optional (name *collecting-anon-list-name*)) |
| 59 | "Add item X to the `collecting' list NAME (or *collecting-anon-list-name* |
| 60 | by default)." |
| 61 | (with-gensyms new |
| 62 | `(let ((,new (cons ,x nil))) |
| 63 | (setf (cdar ,name) ,new) |
| 64 | (setf (car ,name) ,new)))) |
| 65 | |
| 66 | (defmacro collect-tail (x &optional (name *collecting-anon-list-name*)) |
| 67 | "Make item X be the tail of `collecting' list NAME (or |
| 68 | *collecting-anon-list-name* by default). It is an error to continue |
| 69 | trying to add stuff to the list." |
| 70 | `(progn |
| 71 | (setf (cdar ,name) ,x) |
| 72 | (setf (car ,name) nil))) |
| 73 | |
| 74 | ;;;----- That's all, folks -------------------------------------------------- |