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;;; case.lisp
;;;
;;; Copyright (C) 2003-2005 Peter Graves
;;; $Id$
;;;
;;; This program is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License
;;; as published by the Free Software Foundation; either version 2
;;; of the License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program; if not, write to the Free Software
;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
;;;
;;; As a special exception, the copyright holders of this library give you
;;; permission to link this library with independent modules to produce an
;;; executable, regardless of the license terms of these independent
;;; modules, and to copy and distribute the resulting executable under
;;; terms of your choice, provided that you also meet, for each linked
;;; independent module, the terms and conditions of the license of that
;;; module. An independent module is a module which is not derived from
;;; or based on this library. If you modify this library, you may extend
;;; this exception to your version of the library, but you are not
;;; obligated to do so. If you do not wish to do so, delete this
;;; exception statement from your version.
;;; Adapted from SBCL.
(in-package #:system)
;;; Is X a (possibly-improper) list of at least N elements?
(defun list-of-length-at-least-p (x n)
(or (zerop n) ; since anything can be considered an improper list of length 0
(and (consp x)
(list-of-length-at-least-p (cdr x) (1- n)))))
(defun case-body-error (name keyform keyform-value expected-type keys)
(declare (ignore name keys))
(restart-case
(error 'type-error
:datum keyform-value
:expected-type expected-type)
(store-value (value)
:report (lambda (stream)
(format stream "Supply a new value for ~S." keyform))
:interactive read-evaluated-form
value)))
;;; CASE-BODY-AUX provides the expansion once CASE-BODY has groveled
;;; all the cases. Note: it is not necessary that the resulting code
;;; signal case-failure conditions, but that's what KMP's prototype
;;; code did. We call CASE-BODY-ERROR, because of how closures are
;;; compiled. RESTART-CASE has forms with closures that the compiler
;;; causes to be generated at the top of any function using the case
;;; macros, regardless of whether they are needed.
;;;
;;; The CASE-BODY-ERROR function is defined later, when the
;;; RESTART-CASE macro has been defined.
(defun case-body-aux (name keyform keyform-value clauses keys
errorp proceedp expected-type)
(if proceedp
(let ((block (gensym))
(again (gensym)))
`(let ((,keyform-value ,keyform))
(block ,block
(tagbody
,again
(return-from
,block
(cond ,@(nreverse clauses)
(t
(setf ,keyform-value
(setf ,keyform
(case-body-error
',name ',keyform ,keyform-value
',expected-type ',keys)))
(go ,again))))))))
`(let ((,keyform-value ,keyform))
(cond
,@(nreverse clauses)
,@(if errorp
;; `((t (error 'case-failure
;; :name ',name
;; :datum ,keyform-value
;; :expected-type ',expected-type
;; :possibilities ',keys))))))))
`((t (error 'type-error
:datum ,keyform-value
:expected-type ',expected-type))))))))
;;; CASE-BODY returns code for all the standard "case" macros. NAME is
;;; the macro name, and KEYFORM is the thing to case on. MULTI-P
;;; indicates whether a branch may fire off a list of keys; otherwise,
;;; a key that is a list is interpreted in some way as a single key.
;;; When MULTI-P, TEST is applied to the value of KEYFORM and each key
;;; for a given branch; otherwise, TEST is applied to the value of
;;; KEYFORM and the entire first element, instead of each part, of the
;;; case branch. When ERRORP, no T or OTHERWISE branch is permitted,
;;; and an ERROR form is generated. When PROCEEDP, it is an error to
;;; omit ERRORP, and the ERROR form generated is executed within a
;;; RESTART-CASE allowing KEYFORM to be set and retested.
(defun case-body (name keyform cases multi-p test errorp proceedp needcasesp)
(unless (or cases (not needcasesp))
(warn "no clauses in ~S" name))
(let ((keyform-value (gensym))
(clauses ())
(keys ()))
(do* ((cases cases (cdr cases))
(case (car cases) (car cases)))
((null cases) nil)
(unless (list-of-length-at-least-p case 1)
(error "~S -- bad clause in ~S" case name))
(destructuring-bind (keyoid &rest forms) case
(cond ((and (memq keyoid '(t otherwise))
(null (cdr cases)))
(if errorp
(progn
(style-warn "~@"
keyoid name)
(push keyoid keys)
(push `((,test ,keyform-value ',keyoid) nil ,@forms)
clauses))
(push `(t nil ,@forms) clauses)))
((and multi-p (listp keyoid))
(setf keys (append keyoid keys))
(push `((or ,@(mapcar (lambda (key)
`(,test ,keyform-value ',key))
keyoid))
nil
,@forms)
clauses))
(t
(push keyoid keys)
(push `((,test ,keyform-value ',keyoid)
nil
,@forms)
clauses)))))
(case-body-aux name keyform keyform-value clauses keys errorp proceedp
`(,(if multi-p 'member 'or) ,@keys))))
(defmacro case (keyform &body cases)
"CASE Keyform {({(Key*) | Key} Form*)}*
Evaluates the Forms in the first clause with a Key EQL to the value of
Keyform. If a singleton key is T then the clause is a default clause."
(case-body 'case keyform cases t 'eql nil nil nil))
(defmacro ccase (keyform &body cases)
"CCASE Keyform {({(Key*) | Key} Form*)}*
Evaluates the Forms in the first clause with a Key EQL to the value of
Keyform. If none of the keys matches then a correctable error is
signalled."
(case-body 'ccase keyform cases t 'eql t t t))
(defmacro ecase (keyform &body cases)
"ECASE Keyform {({(Key*) | Key} Form*)}*
Evaluates the Forms in the first clause with a Key EQL to the value of
Keyform. If none of the keys matches then an error is signalled."
(case-body 'ecase keyform cases t 'eql t nil t))
(defmacro typecase (keyform &body cases)
"TYPECASE Keyform {(Type Form*)}*
Evaluates the Forms in the first clause for which TYPEP of Keyform and Type
is true."
(case-body 'typecase keyform cases nil 'typep nil nil nil))
(defmacro ctypecase (keyform &body cases)
"CTYPECASE Keyform {(Type Form*)}*
Evaluates the Forms in the first clause for which TYPEP of Keyform and Type
is true. If no form is satisfied then a correctable error is signalled."
(case-body 'ctypecase keyform cases nil 'typep t t t))
(defmacro etypecase (keyform &body cases)
"ETYPECASE Keyform {(Type Form*)}*
Evaluates the Forms in the first clause for which TYPEP of Keyform and Type
is true. If no form is satisfied then an error is signalled."
(case-body 'etypecase keyform cases nil 'typep t nil t))
