Commit 8376d7c2 authored by Chong Yidong's avatar Chong Yidong

Updates to Documentation chapter of Lisp manual.

* doc/lispref/help.texi (Documentation, Documentation Basics, Help Functions):
Minor clarifications.
(Accessing Documentation): Clarify what documentation-property is
for.  Add xref to Keys in Documentation.

* doc/lispref/macros.texi (Defining Macros):
* doc/lispref/modes.texi (Derived Modes): Say "documentation string" instead
of docstring.

* doc/lispref/tips.texi (Documentation Tips): Don't recommend using * in
docstrings.
parent 0b19b281
......@@ -197,7 +197,7 @@ files.texi
frames.texi
functions.texi cyd
hash.texi cyd
help.texi
help.texi cyd
hooks.texi
index.texi
internals.texi
......@@ -210,7 +210,7 @@ macros.texi cyd
maps.texi
markers.texi
minibuf.texi
modes.texi
modes.texi cyd
nonascii.texi
numbers.texi cyd
objects.texi cyd
......
2012-02-19 Chong Yidong <cyd@gnu.org>
* help.texi (Documentation, Documentation Basics, Help Functions):
Minor clarifications.
(Accessing Documentation): Clarify what documentation-property is
for. Add xref to Keys in Documentation.
* tips.texi (Documentation Tips): Don't recommend using * in
docstrings.
* macros.texi (Defining Macros):
* modes.texi (Derived Modes): Say "documentation string" instead
of docstring.
2012-02-18 Chong Yidong <cyd@gnu.org>
* modes.texi (Tabulated List Mode): New node.
......
......@@ -827,8 +827,7 @@ Multiline Font Lock Constructs
Documentation
* Documentation Basics:: Good style for doc strings.
Where to put them. How Emacs stores them.
* Documentation Basics:: Where doc strings are defined and stored.
* Accessing Documentation:: How Lisp programs can access doc strings.
* Keys in Documentation:: Substituting current key bindings.
* Describing Characters:: Making printable descriptions of
......
......@@ -8,11 +8,11 @@
@chapter Documentation
@cindex documentation strings
GNU Emacs Lisp has convenient on-line help facilities, most of which
derive their information from the documentation strings associated with
functions and variables. This chapter describes how to write good
documentation strings for your Lisp programs, as well as how to write
programs to access documentation.
GNU Emacs has convenient built-in help facilities, most of which
derive their information from documentation strings associated with
functions and variables. This chapter describes how to access
documentation strings in Lisp programs. @xref{Documentation Tips},
for how to write good documentation strings.
Note that the documentation strings for Emacs are not the same thing
as the Emacs manual. Manuals have their own source files, written in
......@@ -23,12 +23,10 @@ manual is not organized in that fashion; it is organized in terms of
topics of discussion.
For commands to display documentation strings, see @ref{Help, ,
Help, emacs, The GNU Emacs Manual}. For the conventions for writing
documentation strings, see @ref{Documentation Tips}.
Help, emacs, The GNU Emacs Manual}.
@menu
* Documentation Basics:: Good style for doc strings.
Where to put them. How Emacs stores them.
* Documentation Basics:: Where doc strings are defined and stored.
* Accessing Documentation:: How Lisp programs can access doc strings.
* Keys in Documentation:: Substituting current key bindings.
* Describing Characters:: Making printable descriptions of
......@@ -52,14 +50,15 @@ string follows the argument list. In a variable definition, the
documentation string follows the initial value of the variable.
When you write a documentation string, make the first line a
complete sentence (or two complete sentences) since some commands,
such as @code{apropos}, show only the first line of a multi-line
documentation string. Also, you should not indent the second line of
a documentation string, if it has one, because that looks odd when you
complete sentence (or two complete sentences) that briefly describes
what the function or variable does. Some commands, such as
@code{apropos}, show only the first line of a multi-line documentation
string. Also, you should not indent the second line of a
documentation string, if it has one, because that looks odd when you
use @kbd{C-h f} (@code{describe-function}) or @kbd{C-h v}
(@code{describe-variable}) to view the documentation string. There
are many other conventions for doc strings; see @ref{Documentation
Tips}.
are many other conventions for documentation strings; see
@ref{Documentation Tips}.
Documentation strings can contain several special substrings, which
stand for key bindings to be looked up in the current keymaps when the
......@@ -71,55 +70,67 @@ rearranges the key bindings. (@xref{Keys in Documentation}.)
Emacs Lisp mode fills documentation strings to the width
specified by @code{emacs-lisp-docstring-fill-column}.
In Emacs Lisp, a documentation string is accessible through the
function or variable that it describes:
Exactly where a documentation string is stored depends on how its
function or variable was defined or loaded into memory:
@itemize @bullet
@item
@kindex function-documentation
The documentation for a function is usually stored in the function
definition itself (@pxref{Lambda Expressions} and @pxref{Function
Documentation}). The function @code{documentation} knows how to
extract it. You can also put function documentation in the
@code{function-documentation} property of the function name. That is
useful with definitions such as keyboard macros that can't hold a
documentation string.
When you define a function (@pxref{Lambda Expressions}, and
@pxref{Function Documentation}), the documentation string is stored in
the function definition itself. You can also put function
documentation in the @code{function-documentation} property of a
function name. That is useful for function definitions which can't
hold a documentation string, such as keyboard macros.
@item
@kindex variable-documentation
The documentation for a variable is stored in the variable's property
list under the property name @code{variable-documentation}. The
function @code{documentation-property} knows how to retrieve it.
@end itemize
When you define a variable with a @code{defvar} or related form
(@pxref{Defining Variables}), the documentation is stored in the
variable's @code{variable-documentation} property.
@cindex @file{DOC-@var{version}} (documentation) file
To save space, the documentation for preloaded functions and variables
(including primitive functions and autoloaded functions) is stored in
the file @file{emacs/etc/DOC-@var{version}}---not inside Emacs. The
documentation strings for functions and variables loaded during the
Emacs session from byte-compiled files are stored in those files
(@pxref{Docs and Compilation}).
The data structure inside Emacs has an integer offset into the file, or
a list containing a file name and an integer, in place of the
documentation string. The functions @code{documentation} and
@code{documentation-property} use that information to fetch the
documentation string from the appropriate file; this is transparent to
the user.
@item
To save memory, the documentation for preloaded functions and
variables (including primitive functions and autoloaded functions) is
not kept in memory, but in the file
@file{emacs/etc/DOC-@var{version}}, where @var{version} is the Emacs
version number (@pxref{Version Info}).
@item
When a function or variable is loaded from a byte-compiled file during
the Emacs session, its documentation string is not loaded into memory.
Instead, Emacs looks it up in the byte-compiled file as needed.
@xref{Docs and Compilation}.
@end itemize
@noindent
Regardless of where the documentation string is stored, you can
retrieve it using the @code{documentation} or
@code{documentation-property} function, described in the next section.
@node Accessing Documentation
@section Access to Documentation Strings
@defun documentation-property symbol property &optional verbatim
This function returns the documentation string that is recorded in
@var{symbol}'s property list under property @var{property}. It
retrieves the text from a file if the value calls for that. If the
property value isn't @code{nil}, isn't a string, and doesn't refer to
text in a file, then it is evaluated to obtain a string.
This function returns the documentation string recorded in
@var{symbol}'s property list under property @var{property}. It is
most often used to look up the documentation strings of variables, for
which @var{property} is @code{variable-documentation}. However, it
can also be used to look up other kinds of documentation, such as for
customization groups (but for function documentation, use the
@code{documentation} command, below).
If the value recorded in the property list refers to a documentation
string stored in a @file{DOC-@var{version}} file or a byte-compiled
file, it looks up that string and returns it. If the property value
isn't @code{nil}, isn't a string, and doesn't refer to text in a file,
then it is evaluated as a Lisp expression to obtain a string.
The last thing this function does is pass the string through
@code{substitute-command-keys} to substitute actual key bindings,
unless @var{verbatim} is non-@code{nil}.
@code{substitute-command-keys} to substitute actual key bindings
(@pxref{Keys in Documentation}). However, it skips this step if
@var{verbatim} is non-@code{nil}.
@smallexample
@group
......@@ -270,13 +281,13 @@ When the `track-eol' feature is doing its job, the value is 9999.
@end group
@end smallexample
@defun Snarf-documentation filename
@anchor{Definition of Snarf-documentation}
This function is used only during Emacs initialization, just before
the runnable Emacs is dumped. It finds the file offsets of the
documentation strings stored in the file @var{filename}, and records
them in the in-core function definitions and variable property lists in
place of the actual strings. @xref{Building Emacs}.
@defun Snarf-documentation filename
This function is used when building Emacs, just before the runnable
Emacs is dumped. It finds the positions of the documentation strings
stored in the file @var{filename}, and records those positions into
memory in the function definitions and variable property lists.
@xref{Building Emacs}.
Emacs reads the file @var{filename} from the @file{emacs/etc} directory.
When the dumped Emacs is later executed, the same file will be looked
......@@ -515,13 +526,14 @@ definition as a function, variable, or face, or has properties.
The function returns a list of elements that look like this:
@example
(@var{symbol} @var{score} @var{fn-doc} @var{var-doc}
(@var{symbol} @var{score} @var{functionn-doc} @var{variable-doc}
@var{plist-doc} @var{widget-doc} @var{face-doc} @var{group-doc})
@end example
Here, @var{score} is an integer measure of how important the symbol
seems to be as a match, and the remaining elements are documentation
strings for @var{symbol}'s various roles (or @code{nil}).
seems to be as a match. Each of the remaining elements is a
documentation string, or @code{nil}, for @var{symbol} as a function,
variable, etc.
It also displays the symbols in a buffer named @samp{*Apropos*}, each
with a one-line description taken from the beginning of its
......
......@@ -258,7 +258,8 @@ Specify how to indent calls to this macro. @xref{Indenting Macros},
for more details.
@item (doc-string @var{number})
Specify which element of the macro is the doc string, if any.
Specify which element of the macro is the documentation string, if
any.
@end table
A @code{declare} form only has its special effect in the body of a
......
......@@ -800,10 +800,10 @@ You can also specify @code{nil} for @var{parent}. This gives the new
mode no parent. Then @code{define-derived-mode} behaves as described
above, but, of course, omits all actions connected with @var{parent}.
The argument @var{docstring} specifies the documentation string for
the new mode. @code{define-derived-mode} adds some general
information about the mode's hook, followed by the mode's keymap, at
the end of this docstring. If you omit @var{docstring},
The argument @var{docstring} specifies the documentation string for the
new mode. @code{define-derived-mode} adds some general information
about the mode's hook, followed by the mode's keymap, at the end of this
documentation string. If you omit @var{docstring},
@code{define-derived-mode} generates a documentation string.
The @var{keyword-args} are pairs of keywords and values. The values
......
......@@ -826,9 +826,7 @@ In Dired, visit the file or directory named on this line.
@item
When you define a variable that users ought to set interactively, you
normally should use @code{defcustom}. However, if for some reason you
use @code{defvar} instead, start the doc string with a @samp{*}.
@xref{Defining Variables}.
should use @code{defcustom}. @xref{Defining Variables}.
@item
The documentation string for a variable that is a yes-or-no flag should
......
......@@ -848,8 +848,7 @@ Multiline Font Lock Constructs
Documentation
* Documentation Basics:: Good style for doc strings.
Where to put them. How Emacs stores them.
* Documentation Basics:: Where doc strings are defined and stored.
* Accessing Documentation:: How Lisp programs can access doc strings.
* Keys in Documentation:: Substituting current key bindings.
* Describing Characters:: Making printable descriptions of
......
......@@ -847,8 +847,7 @@ Multiline Font Lock Constructs
Documentation
* Documentation Basics:: Good style for doc strings.
Where to put them. How Emacs stores them.
* Documentation Basics:: Where doc strings are defined and stored.
* Accessing Documentation:: How Lisp programs can access doc strings.
* Keys in Documentation:: Substituting current key bindings.
* Describing Characters:: Making printable descriptions of
......
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