@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2003
@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/control
Note that @code{(car foo)} is not executed if @code{(consp foo)} returns
@code{nil}, thus avoiding an error.
-@code{and} can be expressed in terms of either @code{if} or @code{cond}.
-For example:
+@code{and} expressions can also be written using either @code{if} or
+@code{cond}. Here's how:
@example
@group
@defmac dolist (var list [result]) body@dots{}
@tindex dolist
-This construct executes @var{body} once for each element of @var{list},
-using the variable @var{var} to hold the current element. Then it
-returns the value of evaluating @var{result}, or @code{nil} if
-@var{result} is omitted. For example, here is how you could use
-@code{dolist} to define the @code{reverse} function:
+This construct executes @var{body} once for each element of
+@var{list}, binding the variable @var{var} locally to hold the current
+element. Then it returns the value of evaluating @var{result}, or
+@code{nil} if @var{result} is omitted. For example, here is how you
+could use @code{dolist} to define the @code{reverse} function:
@example
(defun reverse (list)
@defmac dotimes (var count [result]) body@dots{}
@tindex dotimes
This construct executes @var{body} once for each integer from 0
-(inclusive) to @var{count} (exclusive), using the variable @var{var} to
-hold the integer for the current iteration. Then it returns the value
+(inclusive) to @var{count} (exclusive), binding the variable @var{var}
+to the integer for the current iteration. Then it returns the value
of evaluating @var{result}, or @code{nil} if @var{result} is omitted.
Here is an example of using @code{dotimes} to do something 100 times:
@subsubsection How to Signal an Error
@cindex signaling errors
- @dfn{Signalling} an error means beginning error processing. Error
+ @dfn{Signaling} an error means beginning error processing. Error
processing normally aborts all or part of the running program and
returns to a point that is set up to handle the error
(@pxref{Processing of Errors}). Here we describe how to signal an
undesirable results. Instead, use @code{(error "%s" @var{string})}.
@end defun
-@anchor{Definition of signal}
@defun signal error-symbol data
+@anchor{Definition of signal}
This function signals an error named by @var{error-symbol}. The
argument @var{data} is a list of additional Lisp objects relevant to the
circumstances of the error.
The @code{unwind-protect} construct is essential whenever you
temporarily put a data structure in an inconsistent state; it permits
-you to make the data consistent again in the event of an error or throw.
+you to make the data consistent again in the event of an error or
+throw. (Another more specific cleanup construct that is used only for
+changes in buffer contents is the atomic change group; @ref{Atomic
+Changes}.)
@defspec unwind-protect body-form cleanup-forms@dots{}
@cindex cleanup forms