Sync up with r21-4-11-chise-0_21-=gb2312.

[chise/xemacs-chise.git-] / lisp / subr.el

;;; subr.el --- basic lisp subroutines for XEmacs

;; Copyright (C) 1985, 1986, 1992, 1994-5, 1997 Free Software Foundation, Inc.
;; Copyright (C) 1995 Tinker Systems and INS Engineering Corp.
;; Copyright (C) 1995 Sun Microsystems.
;; Copyright (C) 2000 Ben Wing.

;; Maintainer: XEmacs Development Team
;; Keywords: extensions, dumped

;; This file is part of XEmacs.

;; XEmacs 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, or (at your option)
;; any later version.

;; XEmacs 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 XEmacs; see the file COPYING.  If not, write to the Free
;; Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
;; 02111-1307, USA.

;;; Synched up with: FSF 19.34.

;;; Commentary:

;; This file is dumped with XEmacs.

;; There's not a whole lot in common now with the FSF version,
;; be wary when applying differences.  I've left in a number of lines
;; of commentary just to give diff(1) something to synch itself with to
;; provide useful context diffs. -sb

;;; Code:

\f
;;;; Lisp language features.

(defmacro lambda (&rest cdr)
  "Return a lambda expression.
A call of the form (lambda ARGS DOCSTRING INTERACTIVE BODY) is
self-quoting; the result of evaluating the lambda expression is the
expression itself.  The lambda expression may then be treated as a
function, i.e., stored as the function value of a symbol, passed to
funcall or mapcar, etc.

ARGS should take the same form as an argument list for a `defun'.
DOCSTRING is an optional documentation string.
 If present, it should describe how to call the function.
 But documentation strings are usually not useful in nameless functions.
INTERACTIVE should be a call to the function `interactive', which see.
It may also be omitted.
BODY should be a list of lisp expressions."
  `(function (lambda ,@cdr)))

(defmacro defun-when-void (&rest args)
  "Define a function, just like `defun', unless it's already defined.
Used for compatibility among different emacs variants."
  `(if (fboundp ',(car args))
       nil
     (defun ,@args)))

(defmacro define-function-when-void (&rest args)
  "Define a function, just like `define-function', unless it's already defined.
Used for compatibility among different emacs variants."
  `(if (fboundp ,(car args))
       nil
     (define-function ,@args)))

\f
;;;; Keymap support.
;; XEmacs: removed to keymap.el

;;;; The global keymap tree.

;;; global-map, esc-map, and ctl-x-map have their values set up in
;;; keymap.c; we just give them docstrings here.

;;;; Event manipulation functions.

;; XEmacs: This stuff is done in C Code.

;;;; Obsolescent names for functions.
;; XEmacs: not used.

;; XEmacs:
(defun local-variable-if-set-p (sym buffer)
  "Return t if SYM would be local to BUFFER after it is set.
A nil value for BUFFER is *not* the same as (current-buffer), but
can be used to determine whether `make-variable-buffer-local' has been
called on SYM."
  (local-variable-p sym buffer t))

\f
;;;; Hook manipulation functions.

;; (defconst run-hooks 'run-hooks ...)

(defun make-local-hook (hook)
  "Make the hook HOOK local to the current buffer.
When a hook is local, its local and global values
work in concert: running the hook actually runs all the hook
functions listed in *either* the local value *or* the global value
of the hook variable.

This function works by making `t' a member of the buffer-local value,
which acts as a flag to run the hook functions in the default value as
well.  This works for all normal hooks, but does not work for most
non-normal hooks yet.  We will be changing the callers of non-normal
hooks so that they can handle localness; this has to be done one by
one.

This function does nothing if HOOK is already local in the current
buffer.

Do not use `make-local-variable' to make a hook variable buffer-local.

See also `add-local-hook' and `remove-local-hook'."
  (if (local-variable-p hook (current-buffer)) ; XEmacs
      nil
    (or (boundp hook) (set hook nil))
    (make-local-variable hook)
    (set hook (list t))))

(defun add-hook (hook function &optional append local)
  "Add to the value of HOOK the function FUNCTION.
FUNCTION is not added if already present.
FUNCTION is added (if necessary) at the beginning of the hook list
unless the optional argument APPEND is non-nil, in which case
FUNCTION is added at the end.

The optional fourth argument, LOCAL, if non-nil, says to modify
the hook's buffer-local value rather than its default value.
This makes no difference if the hook is not buffer-local.
To make a hook variable buffer-local, always use
`make-local-hook', not `make-local-variable'.

HOOK should be a symbol, and FUNCTION may be any valid function.  If
HOOK is void, it is first set to nil.  If HOOK's value is a single
function, it is changed to a list of functions.

You can remove this hook yourself using `remove-hook'.

See also `add-local-hook' and `add-one-shot-hook'."
  (or (boundp hook) (set hook nil))
  (or (default-boundp hook) (set-default hook nil))
  ;; If the hook value is a single function, turn it into a list.
  (let ((old (symbol-value hook)))
    (if (or (not (listp old)) (eq (car old) 'lambda))
        (set hook (list old))))
  (if (or local
          ;; Detect the case where make-local-variable was used on a hook
          ;; and do what we used to do.
          (and (local-variable-if-set-p hook (current-buffer)) ; XEmacs
               (not (memq t (symbol-value hook)))))
      ;; Alter the local value only.
      (or (if (consp function)
              (member function (symbol-value hook))
            (memq function (symbol-value hook)))
          (set hook
               (if append
                   (append (symbol-value hook) (list function))
                 (cons function (symbol-value hook)))))
    ;; Alter the global value (which is also the only value,
    ;; if the hook doesn't have a local value).
    (or (if (consp function)
            (member function (default-value hook))
          (memq function (default-value hook)))
        (set-default hook
                     (if append
                         (append (default-value hook) (list function))
                       (cons function (default-value hook)))))))

(defun remove-hook (hook function &optional local)
  "Remove from the value of HOOK the function FUNCTION.
HOOK should be a symbol, and FUNCTION may be any valid function.  If
FUNCTION isn't the value of HOOK, or, if FUNCTION doesn't appear in the
list of hooks to run in HOOK, then nothing is done.  See `add-hook'.

The optional third argument, LOCAL, if non-nil, says to modify
the hook's buffer-local value rather than its default value.
This makes no difference if the hook is not buffer-local.
To make a hook variable buffer-local, always use
`make-local-hook', not `make-local-variable'."
  (if (or (not (boundp hook))           ;unbound symbol, or
          (not (default-boundp 'hook))
          (null (symbol-value hook))    ;value is nil, or
          (null function))              ;function is nil, then
      nil                               ;Do nothing.
    (flet ((hook-remove
            (function hook-value)
            (flet ((hook-test
                    (fn hel)
                    (or (equal fn hel)
                        (and (symbolp hel)
                             (equal fn
                                    (get hel 'one-shot-hook-fun))))))
              (if (and (consp hook-value)
                       (not (functionp hook-value)))
                  (if (member* function hook-value :test 'hook-test)
                      (setq hook-value
                            (delete* function (copy-sequence hook-value)
                                     :test 'hook-test)))
                (if (equal hook-value function)
                    (setq hook-value nil)))
              hook-value)))
      (if (or local
              ;; Detect the case where make-local-variable was used on a hook
              ;; and do what we used to do.
              (and (local-variable-p hook (current-buffer))
                   (not (memq t (symbol-value hook)))))
          (set hook (hook-remove function (symbol-value hook)))
        (set-default hook (hook-remove function (default-value hook)))))))

;; XEmacs addition
;; #### we need a coherent scheme for indicating compatibility info,
;; so that it can be programmatically retrieved.
(defun add-local-hook (hook function &optional append)
  "Add to the local value of HOOK the function FUNCTION.
This modifies only the buffer-local value for the hook (which is
automatically make buffer-local, if necessary), not its default value.
FUNCTION is not added if already present.
FUNCTION is added (if necessary) at the beginning of the hook list
unless the optional argument APPEND is non-nil, in which case
FUNCTION is added at the end.

HOOK should be a symbol, and FUNCTION may be any valid function.  If
HOOK is void, it is first set to nil.  If HOOK's value is a single
function, it is changed to a list of functions.

You can remove this hook yourself using `remove-local-hook'.

See also `add-hook' and `make-local-hook'."
  (make-local-hook hook)
  (add-hook hook function append t))

;; XEmacs addition
(defun remove-local-hook (hook function)
  "Remove from the local value of HOOK the function FUNCTION.
This modifies only the buffer-local value for the hook, not its default
value. (Nothing happens if the hook is not buffer-local.)
HOOK should be a symbol, and FUNCTION may be any valid function.  If
FUNCTION isn't the value of HOOK, or, if FUNCTION doesn't appear in the
list of hooks to run in HOOK, then nothing is done.  See `add-hook'.

See also `add-local-hook' and `make-local-hook'."
  (if (local-variable-p hook (current-buffer))
      (remove-hook hook function t)))

(defun add-one-shot-hook (hook function &optional append local)
  "Add to the value of HOOK the one-shot function FUNCTION.
FUNCTION will automatically be removed from the hook the first time
after it runs (whether to completion or to an error).
FUNCTION is not added if already present.
FUNCTION is added (if necessary) at the beginning of the hook list
unless the optional argument APPEND is non-nil, in which case
FUNCTION is added at the end.

HOOK should be a symbol, and FUNCTION may be any valid function.  If
HOOK is void, it is first set to nil.  If HOOK's value is a single
function, it is changed to a list of functions.

You can remove this hook yourself using `remove-hook'.

See also `add-hook', `add-local-hook', and `add-local-one-shot-hook'."
  (let ((sym (gensym)))
    (fset sym `(lambda (&rest args)
                 (unwind-protect
                     (apply ',function args)
                   (remove-hook ',hook ',sym ',local))))
    (put sym 'one-shot-hook-fun function)
    (add-hook hook sym append local)))

(defun add-local-one-shot-hook (hook function &optional append)
  "Add to the local value of HOOK the one-shot function FUNCTION.
FUNCTION will automatically be removed from the hook the first time
after it runs (whether to completion or to an error).
FUNCTION is not added if already present.
FUNCTION is added (if necessary) at the beginning of the hook list
unless the optional argument APPEND is non-nil, in which case
FUNCTION is added at the end.

The optional fourth argument, LOCAL, if non-nil, says to modify
the hook's buffer-local value rather than its default value.
This makes no difference if the hook is not buffer-local.
To make a hook variable buffer-local, always use
`make-local-hook', not `make-local-variable'.

HOOK should be a symbol, and FUNCTION may be any valid function.  If
HOOK is void, it is first set to nil.  If HOOK's value is a single
function, it is changed to a list of functions.

You can remove this hook yourself using `remove-local-hook'.

See also `add-hook', `add-local-hook', and `add-local-one-shot-hook'."
  (make-local-hook hook)
  (add-one-shot-hook hook function append t))

(defun add-to-list (list-var element)
  "Add to the value of LIST-VAR the element ELEMENT if it isn't there yet.
The test for presence of ELEMENT is done with `equal'.
If you want to use `add-to-list' on a variable that is not defined
until a certain package is loaded, you should put the call to `add-to-list'
into a hook function that will be run only after loading the package.
`eval-after-load' provides one way to do this.  In some cases
other hooks, such as major mode hooks, can do the job."
  (or (member element (symbol-value list-var))
      (set list-var (cons element (symbol-value list-var)))))

;; XEmacs additions
;; called by Fkill_buffer()
(defvar kill-buffer-hook nil
  "Function or functions to be called when a buffer is killed.
The value of this variable may be buffer-local.
The buffer about to be killed is current when this hook is run.")

;; in C in FSFmacs
(defvar kill-emacs-hook nil
  "Function or functions to be called when `kill-emacs' is called,
just before emacs is actually killed.")

;; not obsolete.
;; #### These are a bad idea, because the CL RPLACA and RPLACD
;; return the cons cell, not the new CAR/CDR.         -hniksic
;; The proper definition would be:
;; (defun rplaca (conscell newcar)
;;   (setcar conscell newcar)
;;   conscell)
;; ...and analogously for RPLACD.
(define-function 'rplaca 'setcar)
(define-function 'rplacd 'setcdr)

(defun copy-symbol (symbol &optional copy-properties)
  "Return a new uninterned symbol with the same name as SYMBOL.
If COPY-PROPERTIES is non-nil, the new symbol will have a copy of
SYMBOL's value, function, and property lists."
  (let ((new (make-symbol (symbol-name symbol))))
    (when copy-properties
      ;; This will not copy SYMBOL's chain of forwarding objects, but
      ;; I think that's OK.  Callers should not expect such magic to
      ;; keep working in the copy in the first place.
      (and (boundp symbol)
           (set new (symbol-value symbol)))
      (and (fboundp symbol)
           (fset new (symbol-function symbol)))
      (setplist new (copy-list (symbol-plist symbol))))
    new))

(defun set-symbol-value-in-buffer (sym val buffer)
  "Set the value of SYM to VAL in BUFFER.  Useful with buffer-local variables.
If SYM has a buffer-local value in BUFFER, or will have one if set, this
function allows you to set the local value.

NOTE: At some point, this will be moved into C and will be very fast."
  (with-current-buffer buffer
    (set sym val)))

;;;; String functions.

;; XEmacs
(defun replace-in-string (str regexp newtext &optional literal)
  "Replace all matches in STR for REGEXP with NEWTEXT string,
 and returns the new string.
Optional LITERAL non-nil means do a literal replacement.
Otherwise treat `\\' in NEWTEXT as special:
  `\\&' in NEWTEXT means substitute original matched text.
  `\\N' means substitute what matched the Nth `\\(...\\)'.
       If Nth parens didn't match, substitute nothing.
  `\\\\' means insert one `\\'.
  `\\u' means upcase the next character.
  `\\l' means downcase the next character.
  `\\U' means begin upcasing all following characters.
  `\\L' means begin downcasing all following characters.
  `\\E' means terminate the effect of any `\\U' or `\\L'."
  (check-argument-type 'stringp str)
  (check-argument-type 'stringp newtext)
  (if (> (length str) 50)
      (with-temp-buffer
        (insert str)
        (goto-char 1)
          (while (re-search-forward regexp nil t)
            (replace-match newtext t literal))
          (buffer-string))
  (let ((start 0) newstr)
    (while (string-match regexp str start)
      (setq newstr (replace-match newtext t literal str)
            start (+ (match-end 0) (- (length newstr) (length str)))
            str newstr))
    str)))

(defun split-string (string &optional pattern)
  "Return a list of substrings of STRING which are separated by PATTERN.
If PATTERN is omitted, it defaults to \"[ \\f\\t\\n\\r\\v]+\"."
  (or pattern
      (setq pattern "[ \f\t\n\r\v]+"))
  (let (parts (start 0) (len (length string)))
    (if (string-match pattern string)
        (setq parts (cons (substring string 0 (match-beginning 0)) parts)
              start (match-end 0)))
    (while (and (< start len)
                (string-match pattern string (if (> start (match-beginning 0))
                                                 start
                                               (1+ start))))
      (setq parts (cons (substring string start (match-beginning 0)) parts)
            start (match-end 0)))
    (nreverse (cons (substring string start) parts))))

;; #### #### #### AAaargh!  Must be in C, because it is used insanely
;; early in the bootstrap process.
;(defun split-path (path)
;  "Explode a search path into a list of strings.
;The path components are separated with the characters specified
;with `path-separator'."
;  (while (or (not stringp path-separator)
;            (/= (length path-separator) 1))
;    (setq path-separator (signal 'error (list "\
;`path-separator' should be set to a single-character string"
;                                             path-separator))))
;  (split-string-by-char path (aref separator 0)))

(defmacro with-output-to-string (&rest forms)
  "Collect output to `standard-output' while evaluating FORMS and return
it as a string."
  ;; by "William G. Dubuque" <wgd@zurich.ai.mit.edu> w/ mods from Stig
  `(with-current-buffer (get-buffer-create
                         (generate-new-buffer-name " *string-output*"))
     (setq buffer-read-only nil)
     (buffer-disable-undo (current-buffer))
     (erase-buffer)
     (let ((standard-output (current-buffer)))
       ,@forms)
     (prog1
         (buffer-string)
       (erase-buffer))))

(defmacro with-current-buffer (buffer &rest body)
  "Temporarily make BUFFER the current buffer and execute the forms in BODY.
The value returned is the value of the last form in BODY.
See also `with-temp-buffer'."
  `(save-current-buffer
    (set-buffer ,buffer)
    ,@body))

(defmacro with-temp-file (filename &rest forms)
  "Create a new buffer, evaluate FORMS there, and write the buffer to FILENAME.
The value of the last form in FORMS is returned, like `progn'.
See also `with-temp-buffer'."
  (let ((temp-file (make-symbol "temp-file"))
        (temp-buffer (make-symbol "temp-buffer")))
    `(let ((,temp-file ,filename)
           (,temp-buffer
            (get-buffer-create (generate-new-buffer-name " *temp file*"))))
       (unwind-protect
           (prog1
               (with-current-buffer ,temp-buffer
                 ,@forms)
             (with-current-buffer ,temp-buffer
               (widen)
               (write-region (point-min) (point-max) ,temp-file nil 0)))
         (and (buffer-name ,temp-buffer)
              (kill-buffer ,temp-buffer))))))

(defmacro with-temp-buffer (&rest forms)
  "Create a temporary buffer, and evaluate FORMS there like `progn'.
See also `with-temp-file' and `with-output-to-string'."
  (let ((temp-buffer (make-symbol "temp-buffer")))
    `(let ((,temp-buffer
            (get-buffer-create (generate-new-buffer-name " *temp*"))))
       (unwind-protect
           (with-current-buffer ,temp-buffer
             ,@forms)
         (and (buffer-name ,temp-buffer)
              (kill-buffer ,temp-buffer))))))

;; Moved from mule-coding.el.
(defmacro with-string-as-buffer-contents (str &rest body)
  "With the contents of the current buffer being STR, run BODY.
Returns the new contents of the buffer, as modified by BODY.
The original current buffer is restored afterwards."
  `(with-temp-buffer
     (insert ,str)
     ,@body
     (buffer-string)))

(defun insert-face (string face)
  "Insert STRING and highlight with FACE.  Return the extent created."
  (let ((p (point)) ext)
    (insert string)
    (setq ext (make-extent p (point)))
    (set-extent-face ext face)
    ext))

;; not obsolete.
(define-function 'string= 'string-equal)
(define-function 'string< 'string-lessp)
(define-function 'int-to-string 'number-to-string)
(define-function 'string-to-int 'string-to-number)

;; These two names are a bit awkward, as they conflict with the normal
;; foo-to-bar naming scheme, but CLtL2 has them, so they stay.
(define-function 'char-int 'char-to-int)
(define-function 'int-char 'int-to-char)

\f
;; alist/plist functions
(defun plist-to-alist (plist)
  "Convert property list PLIST into the equivalent association-list form.
The alist is returned.  This converts from

\(a 1 b 2 c 3)

into

\((a . 1) (b . 2) (c . 3))

The original plist is not modified.  See also `destructive-plist-to-alist'."
  (let (alist)
    (while plist
      (setq alist (cons (cons (car plist) (cadr plist)) alist))
      (setq plist (cddr plist)))
    (nreverse alist)))

(defun destructive-plist-to-alist (plist)
  "Convert property list PLIST into the equivalent association-list form.
The alist is returned.  This converts from

\(a 1 b 2 c 3)

into

\((a . 1) (b . 2) (c . 3))

The original plist is destroyed in the process of constructing the alist.
See also `plist-to-alist'."
  (let ((head plist)
        next)
    (while plist
      ;; remember the next plist pair.
      (setq next (cddr plist))
      ;; make the cons holding the property value into the alist element.
      (setcdr (cdr plist) (cadr plist))
      (setcar (cdr plist) (car plist))
      ;; reattach into alist form.
      (setcar plist (cdr plist))
      (setcdr plist next)
      (setq plist next))
    head))

(defun alist-to-plist (alist)
  "Convert association list ALIST into the equivalent property-list form.
The plist is returned.  This converts from

\((a . 1) (b . 2) (c . 3))

into

\(a 1 b 2 c 3)

The original alist is not modified.  See also `destructive-alist-to-plist'."
  (let (plist)
    (while alist
      (let ((el (car alist)))
        (setq plist (cons (cdr el) (cons (car el) plist))))
      (setq alist (cdr alist)))
    (nreverse plist)))

;; getf, remf in cl*.el.

(defmacro putf (plist property value)
  "Add property PROPERTY to plist PLIST with value VALUE.
Analogous to (setq PLIST (plist-put PLIST PROPERTY VALUE))."
  `(setq ,plist (plist-put ,plist ,property ,value)))

(defmacro laxputf (lax-plist property value)
  "Add property PROPERTY to lax plist LAX-PLIST with value VALUE.
Analogous to (setq LAX-PLIST (lax-plist-put LAX-PLIST PROPERTY VALUE))."
  `(setq ,lax-plist (lax-plist-put ,lax-plist ,property ,value)))

(defmacro laxremf (lax-plist property)
  "Remove property PROPERTY from lax plist LAX-PLIST.
Analogous to (setq LAX-PLIST (lax-plist-remprop LAX-PLIST PROPERTY))."
  `(setq ,lax-plist (lax-plist-remprop ,lax-plist ,property)))
\f
;;; Error functions

(defun error (datum &rest args)
  "Signal a non-continuable error.
DATUM should normally be an error symbol, i.e. a symbol defined using
`define-error'.  ARGS will be made into a list, and DATUM and ARGS passed
as the two arguments to `signal', the most basic error handling function.

This error is not continuable: you cannot continue execution after the
error using the debugger `r' command.  See also `cerror'.

The correct semantics of ARGS varies from error to error, but for most
errors that need to be generated in Lisp code, the first argument
should be a string describing the *context* of the error (i.e. the
exact operation being performed and what went wrong), and the remaining
arguments or \"frobs\" (most often, there is one) specify the
offending object(s) and/or provide additional details such as the exact
error when a file error occurred, e.g.:

-- the buffer in which an editing error occurred.
-- an invalid value that was encountered. (In such cases, the string
   should describe the purpose or \"semantics\" of the value [e.g. if the
   value is an argument to a function, the name of the argument; if the value
   is the value corresponding to a keyword, the name of the keyword; if the
   value is supposed to be a list length, say this and say what the purpose
   of the list is; etc.] as well as specifying why the value is invalid, if
   that's not self-evident.)
-- the file in which an error occurred. (In such cases, there should be a
   second frob, probably a string, specifying the exact error that occurred.
   This does not occur in the string that precedes the first frob, because
   that frob describes the exact operation that was happening.

For historical compatibility, DATUM can also be a string.  In this case,
DATUM and ARGS are passed together as the arguments to `format', and then
an error is signalled using the error symbol `error' and formatted string.
Although this usage of `error' is very common, it is deprecated because it
totally defeats the purpose of having structured errors.  There is now
a rich set of defined errors you can use:

error
  syntax-error
    invalid-read-syntax
    list-formation-error
      malformed-list
        malformed-property-list
      circular-list
        circular-property-list

  invalid-argument
    wrong-type-argument
    args-out-of-range
    wrong-number-of-arguments
    invalid-function
    no-catch

  invalid-state
    void-function
    cyclic-function-indirection
    void-variable
    cyclic-variable-indirection

  invalid-operation
    invalid-change
      setting-constant
    editing-error
      beginning-of-buffer
      end-of-buffer
      buffer-read-only
    io-error
      end-of-file
    arith-error
      range-error
      domain-error
      singularity-error
      overflow-error
      underflow-error

The five most common errors you will probably use or base your new
errors off of are `syntax-error', `invalid-argument', `invalid-state',
`invalid-operation', and `invalid-change'.  Note the semantic differences:

-- `syntax-error' is for errors in complex structures: parsed strings, lists,
   and the like.
-- `invalid-argument' is for errors in a simple value.  Typically, the entire
   value, not just one part of it, is wrong.
-- `invalid-state' means that some settings have been changed in such a way
   that their current state is unallowable.  More and more, code is being
   written more carefully, and catches the error when the settings are being
   changed, rather than afterwards.  This leads us to the next error:
-- `invalid-change' means that an attempt is being made to change some settings
   into an invalid state.  `invalid-change' is a type of `invalid-operation'.
-- `invalid-operation' refers to all cases where code is trying to do something
   that's disallowed.  This includes file errors, buffer errors (e.g. running
   off the end of a buffer), `invalid-change' as just mentioned, and
   arithmetic errors.

See also `cerror', `signal', and `signal-error'."
  (while t (apply
            'cerror datum args)))

(defun cerror (datum &rest args)
  "Like `error' but signals a continuable error."
  (cond ((stringp datum)
         (signal 'error (list (apply 'format datum args))))
        ((defined-error-p datum)
         (signal datum args))
        (t
         (error 'invalid-argument "datum not string or error symbol" datum))))

(defmacro check-argument-type (predicate argument)
  "Check that ARGUMENT satisfies PREDICATE.
This is a macro, and ARGUMENT is not evaluated.  If ARGUMENT is an lvalue,
this function signals a continuable `wrong-type-argument' error until the
returned value satisfies PREDICATE, and assigns the returned value
to ARGUMENT.  Otherwise, this function signals a non-continuable
`wrong-type-argument' error if the returned value does not satisfy PREDICATE."
  (if (symbolp argument)
      `(if (not (,(eval predicate) ,argument))
           (setq ,argument
                 (wrong-type-argument ,predicate ,argument)))
    `(if (not (,(eval predicate) ,argument))
         (signal-error 'wrong-type-argument (list ,predicate ,argument)))))

(defun signal-error (error-symbol data)
  "Signal a non-continuable error.  Args are ERROR-SYMBOL, and associated DATA.
An error symbol is a symbol defined using `define-error'.
DATA should be a list.  Its elements are printed as part of the error message.
If the signal is handled, DATA is made available to the handler.
See also `signal', and the functions to handle errors: `condition-case'
and `call-with-condition-handler'."
  (while t
    (signal error-symbol data)))

(defun define-error (error-sym doc-string &optional inherits-from)
  "Define a new error, denoted by ERROR-SYM.
DOC-STRING is an informative message explaining the error, and will be
printed out when an unhandled error occurs.
ERROR-SYM is a sub-error of INHERITS-FROM (which defaults to `error').

\[`define-error' internally works by putting on ERROR-SYM an `error-message'
property whose value is DOC-STRING, and an `error-conditions' property
that is a list of ERROR-SYM followed by each of its super-errors, up
to and including `error'.  You will sometimes see code that sets this up
directly rather than calling `define-error', but you should *not* do this
yourself.]"
  (check-argument-type 'symbolp error-sym)
  (check-argument-type 'stringp doc-string)
  (put error-sym 'error-message doc-string)
  (or inherits-from (setq inherits-from 'error))
  (let ((conds (get inherits-from 'error-conditions)))
    (or conds (signal-error 'error (list "Not an error symbol" error-sym)))
    (put error-sym 'error-conditions (cons error-sym conds))))

(defun defined-error-p (sym)
  "Returns non-nil if SYM names a currently-defined error."
  (and (symbolp sym) (not (null (get sym 'error-conditions)))))

;;;; Miscellanea.

;; This is now in C.
;(defun buffer-substring-no-properties (start end)
;  "Return the text from START to END, without text properties, as a string."
;  (let ((string (buffer-substring start end)))
;    (set-text-properties 0 (length string) nil string)
;    string))

(defun get-buffer-window-list (&optional buffer minibuf frame)
  "Return windows currently displaying BUFFER, or nil if none.
BUFFER defaults to the current buffer.
See `walk-windows' for the meaning of MINIBUF and FRAME."
  (cond ((null buffer)
         (setq buffer (current-buffer)))
        ((not (bufferp buffer))
         (setq buffer (get-buffer buffer))))
  (let (windows)
    (walk-windows (lambda (window)
                    (if (eq (window-buffer window) buffer)
                        (push window windows)))
                  minibuf frame)
    windows))

(defun ignore (&rest ignore)
  "Do nothing and return nil.
This function accepts any number of arguments, but ignores them."
  (interactive)
  nil)

(define-function 'eval-in-buffer 'with-current-buffer)
(make-obsolete 'eval-in-buffer 'with-current-buffer)

;;; The real defn is in abbrev.el but some early callers
;;;  (eg lisp-mode-abbrev-table) want this before abbrev.el is loaded...

(if (not (fboundp 'define-abbrev-table))
    (progn
      (setq abbrev-table-name-list '())
      (fset 'define-abbrev-table (function (lambda (name defs)
                                   ;; These are fixed-up when abbrev.el loads.
                                   (setq abbrev-table-name-list
                                         (cons (cons name defs)
                                               abbrev-table-name-list)))))))

;;; `functionp' has been moved into C.

;;(defun functionp (object)
;;  "Non-nil if OBJECT can be called as a function."
;;  (or (and (symbolp object) (fboundp object))
;;      (subrp object)
;;      (compiled-function-p object)
;;      (eq (car-safe object) 'lambda)))



(defun function-interactive (function)
  "Return the interactive specification of FUNCTION.
FUNCTION can be any funcallable object.
The specification will be returned as the list of the symbol `interactive'
 and the specs.
If FUNCTION is not interactive, nil will be returned."
  (setq function (indirect-function function))
  (cond ((compiled-function-p function)
         (compiled-function-interactive function))
        ((subrp function)
         (subr-interactive function))
        ((eq (car-safe function) 'lambda)
         (let ((spec (if (stringp (nth 2 function))
                         (nth 3 function)
                       (nth 2 function))))
           (and (eq (car-safe spec) 'interactive)
                spec)))
        (t
         (error "Non-funcallable object: %s" function))))

(defun function-allows-args (function n)
  "Return whether FUNCTION can be called with N arguments."
  (and (<= (function-min-args function) n)
       (or (null (function-max-args function))
           (<= n (function-max-args function)))))

;; This function used to be an alias to `buffer-substring', except
;; that FSF Emacs 20.4 added a BUFFER argument in an incompatible way.
;; The new FSF's semantics makes more sense, but we try to support
;; both for backward compatibility.
(defun buffer-string (&optional buffer old-end old-buffer)
  "Return the contents of the current buffer as a string.
If narrowing is in effect, this function returns only the visible part
of the buffer.

If BUFFER is specified, the contents of that buffer are returned.

The arguments OLD-END and OLD-BUFFER are supported for backward
compatibility with pre-21.2 XEmacsen times when arguments to this
function were (buffer-string &optional START END BUFFER)."
  (cond
   ((or (stringp buffer) (bufferp buffer))
    ;; Most definitely the new way.
    (buffer-substring nil nil buffer))
   ((or (stringp old-buffer) (bufferp old-buffer)
        (natnump buffer) (natnump old-end))
    ;; Definitely the old way.
    (buffer-substring buffer old-end old-buffer))
   (t
    ;; Probably the old way.
    (buffer-substring buffer old-end old-buffer))))

;; This was not present before.  I think Jamie had some objections
;; to this, so I'm leaving this undefined for now. --ben

;;; The objection is this: there is more than one way to load the same file.
;;; "foo", "foo.elc", "foo.el", and "/some/path/foo.elc" are all different
;;; ways to load the exact same code.  `eval-after-load' is too stupid to
;;; deal with this sort of thing.  If this sort of feature is desired, then
;;; it should work off of a hook on `provide'.  Features are unique and
;;; the arguments to (load) are not.  --Stig

;; We provide this for FSFmacs compatibility, at least until we devise
;; something better.

;;;; Specifying things to do after certain files are loaded.

(defun eval-after-load (file form)
  "Arrange that, if FILE is ever loaded, FORM will be run at that time.
This makes or adds to an entry on `after-load-alist'.
If FILE is already loaded, evaluate FORM right now.
It does nothing if FORM is already on the list for FILE.
FILE should be the name of a library, with no directory name."
  ;; Make sure there is an element for FILE.
  (or (assoc file after-load-alist)
      (setq after-load-alist (cons (list file) after-load-alist)))
  ;; Add FORM to the element if it isn't there.
  (let ((elt (assoc file after-load-alist)))
    (or (member form (cdr elt))
        (progn
          (nconc elt (list form))
          ;; If the file has been loaded already, run FORM right away.
          (and (assoc file load-history)
               (eval form)))))
  form)
(make-compatible 'eval-after-load "")

(defun eval-next-after-load (file)
  "Read the following input sexp, and run it whenever FILE is loaded.
This makes or adds to an entry on `after-load-alist'.
FILE should be the name of a library, with no directory name."
  (eval-after-load file (read)))
(make-compatible 'eval-next-after-load "")

; alternate names (not obsolete)
(if (not (fboundp 'mod)) (define-function 'mod '%))
(define-function 'move-marker 'set-marker)
(define-function 'beep 'ding)  ; preserve lingual purity
(define-function 'indent-to-column 'indent-to)
(define-function 'backward-delete-char 'delete-backward-char)
(define-function 'search-forward-regexp (symbol-function 're-search-forward))
(define-function 'search-backward-regexp (symbol-function 're-search-backward))
(define-function 'remove-directory 'delete-directory)
(define-function 'set-match-data 'store-match-data)
(define-function 'send-string-to-terminal 'external-debugging-output)

;;; subr.el ends here