| 1 | ;;; -*-lisp-*- |
| 2 | ;;; |
| 3 | ;;; $Id$ |
| 4 | ;;; |
| 5 | ;;; Anaphoric extensions |
| 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 #:anaphora |
| 27 | (:use #:common-lisp) |
| 28 | (:export #:it |
| 29 | #:aif #:aif2 #:awhen #:awhen2 |
| 30 | #:aand #:awhile #:asetf #:acond)) |
| 31 | (in-package #:anaphora) |
| 32 | |
| 33 | (defmacro aif (cond then &optional else) |
| 34 | "Bind `it' to result of COND when evaluating THEN or ELSE." |
| 35 | `(let ((it ,cond)) |
| 36 | (if it ,then ,@(and else (list else))))) |
| 37 | |
| 38 | (defmacro aif2 (cond then &optional else) |
| 39 | "Bind `it' to first value of COND; switch on second." |
| 40 | (let ((tmp (gensym))) |
| 41 | `(multiple-value-bind (it ,tmp) ,cond |
| 42 | (declare (ignorable it)) |
| 43 | (if ,tmp ,then ,@(and else (list else)))))) |
| 44 | |
| 45 | (defmacro awhen (cond &body body) |
| 46 | "Bind `it' to result of COND when evaluating BODY." |
| 47 | `(let ((it ,cond)) |
| 48 | (when it ,@body))) |
| 49 | |
| 50 | (defmacro awhen2 (cond &body body) |
| 51 | "Bind `it' to first value of COND; switch on second." |
| 52 | (let ((tmp (gensym))) |
| 53 | `(multiple-value-bind (it ,tmp) ,cond |
| 54 | (declare (ignorable it)) |
| 55 | (when ,tmp ,@body)))) |
| 56 | |
| 57 | (defmacro aand (&rest things) |
| 58 | "Like `and', with `it' bound to previous value." |
| 59 | (labels ((foo (things) |
| 60 | (if (cdr things) |
| 61 | `(let ((it ,(car things))) |
| 62 | (if it ,(foo (cdr things)))) |
| 63 | (car things)))) |
| 64 | (if things |
| 65 | (foo things) |
| 66 | t))) |
| 67 | |
| 68 | (defmacro awhile (cond &body body) |
| 69 | "Like `while', with `it' bound to value of COND in BODY." |
| 70 | `(loop |
| 71 | (let ((it ,cond)) |
| 72 | (unless it (return)) |
| 73 | ,@body))) |
| 74 | |
| 75 | (defmacro asetf (&rest pairs &environment env) |
| 76 | "Set PLACE to value of FORM; in FORM, `it' is bound to current value of |
| 77 | PLACE." |
| 78 | (labels ((foo (pairs) |
| 79 | (when pairs |
| 80 | (let ((place (car pairs)) |
| 81 | (form (cadr pairs)) |
| 82 | (rest (cddr pairs))) |
| 83 | (cons (multiple-value-bind |
| 84 | (valtmps valforms newtmps setform getform) |
| 85 | (get-setf-expansion place env) |
| 86 | `(let* ,(mapcar #'list valtmps valforms) |
| 87 | (let* ((it ,getform) |
| 88 | (,(car newtmps) ,form)) |
| 89 | ,setform))) |
| 90 | (foo rest)))))) |
| 91 | (cons 'progn (foo pairs)))) |
| 92 | |
| 93 | (defmacro acond (&rest clauses) |
| 94 | "Like `cond', but in each clause the consequent has `it' bound to the value |
| 95 | of its guard." |
| 96 | (labels ((foo (clauses) |
| 97 | (when clauses |
| 98 | (let ((tmp (gensym)) |
| 99 | (clause (car clauses))) |
| 100 | `(let ((,tmp ,(car clause))) |
| 101 | (if ,tmp |
| 102 | (let ((it ,tmp)) |
| 103 | (declare (ignorable it)) |
| 104 | ,@(cdr clause)) |
| 105 | ,(foo (cdr clauses)))))))) |
| 106 | (foo clauses))) |
| 107 | |
| 108 | ;;;----- That's all, folks -------------------------------------------------- |