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INFO-DIR-SECTION XEmacs Editor
START-INFO-DIR-ENTRY
* XEmacs: (xemacs).             XEmacs Editor.
END-INFO-DIR-ENTRY

   This file documents the XEmacs editor.

   Copyright (C) 1985, 1986, 1988 Richard M. Stallman.  Copyright (C)
1991, 1992, 1993, 1994 Lucid, Inc.  Copyright (C) 1993, 1994 Sun
Microsystems, Inc.  Copyright (C) 1995 Amdahl Corporation.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the sections entitled "The GNU Manifesto", "Distribution" and "GNU
General Public License" are included exactly as in the original, and
provided that the entire resulting derived work is distributed under the
terms of a permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the sections entitled "The GNU Manifesto",
"Distribution" and "GNU General Public License" may be included in a
translation approved by the author instead of in the original English.

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File: xemacs.info,  Node: Matching,  Next: Comments,  Prev: Grinding,  Up: Programs

Automatic Display of Matching Parentheses
=========================================

   The Emacs parenthesis-matching feature shows you automatically how
parentheses match in the text.  Whenever a self-inserting character that
is a closing delimiter is typed, the cursor moves momentarily to the
location of the matching opening delimiter, provided that is visible on
the screen.  If it is not on the screen, some text starting with that
opening delimiter is displayed in the echo area.  Either way, you see
the grouping you are closing off.

   In Lisp, automatic matching applies only to parentheses.  In C, it
also applies to braces and brackets.  Emacs knows which characters to
regard as matching delimiters based on the syntax table set by the major
mode.  *Note Syntax::.

   If the opening delimiter and closing delimiter are mismatched--as in
`[x)'--the echo area displays a warning message.  The correct matches
are specified in the syntax table.

   Two variables control parenthesis matching displays.
`blink-matching-paren' turns the feature on or off. The default is `t'
(match display is on); `nil' turns it off.
`blink-matching-paren-distance' specifies how many characters back
Emacs searches to find a matching opening delimiter.  If the match is
not found in the specified region, scanning stops, and nothing is
displayed.  This prevents wasting lots of time scanning when there is no
match.  The default is 4000.

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File: xemacs.info,  Node: Comments,  Next: Balanced Editing,  Prev: Matching,  Up: Programs

Manipulating Comments
=====================

   The comment commands insert, kill and align comments.

`M-;'
     Insert or align comment (`indent-for-comment').

`C-x ;'
     Set comment column (`set-comment-column').

`C-u - C-x ;'
     Kill comment on current line (`kill-comment').

`M-<LFD>'
     Like <RET> followed by inserting and aligning a comment
     (`indent-new-comment-line').

   The command that creates a comment is `Meta-;'
(`indent-for-comment').  If there is no comment already on the line, a
new comment is created and aligned at a specific column called the
"comment column".  Emacs creates the comment by inserting the string at
the value of `comment-start'; see below.  Point is left after that
string.  If the text of the line extends past the comment column,
indentation is done to a suitable boundary (usually, at least one space
is inserted).  If the major mode has specified a string to terminate
comments, that string is inserted after point, to keep the syntax valid.

   You can also use `Meta-;' to align an existing comment.  If a line
already contains the string that starts comments, `M-;' just moves
point after it and re-indents it to the conventional place.  Exception:
comments starting in column 0 are not moved.

   Some major modes have special rules for indenting certain kinds of
comments in certain contexts.  For example, in Lisp code, comments which
start with two semicolons are indented as if they were lines of code,
instead of at the comment column.  Comments which start with three
semicolons are supposed to start at the left margin.  Emacs understands
these conventions by indenting a double-semicolon comment using <TAB>
and by not changing the indentation of a triple-semicolon comment at
all.

     ;; This function is just an example.
     ;;; Here either two or three semicolons are appropriate.
     (defun foo (x)
     ;;; And now, the first part of the function:
       ;; The following line adds one.
       (1+ x))           ; This line adds one.

   In C code, a comment preceded on its line by nothing but whitespace
is indented like a line of code.

   Even when an existing comment is properly aligned, `M-;' is still
useful for moving directly to the start of the comment.

   `C-u - C-x ;' (`kill-comment') kills the comment on the current
line, if there is one.  The indentation before the start of the comment
is killed as well.  If there does not appear to be a comment in the
line, nothing happens.  To reinsert the comment on another line, move
to the end of that line, type first `C-y', and then `M-;' to realign
the comment.  Note that `C-u - C-x ;' is not a distinct key; it is `C-x
;' (`set-comment-column') with a negative argument.  That command is
programmed to call `kill-comment' when called with a negative argument.
However, `kill-comment' is a valid command which you could bind
directly to a key if you wanted to.

Multiple Lines of Comments
--------------------------

   If you are typing a comment and want to continue it on another line,
use the command `Meta-<LFD>' (`indent-new-comment-line'), which
terminates the comment you are typing, creates a new blank line
afterward, and begins a new comment indented under the old one.  If
Auto Fill mode is on and you go past the fill column while typing, the
comment is continued in just this fashion.  If point is not at the end
of the line when you type `M-<LFD>', the text on the rest of the line
becomes part of the new comment line.

Options Controlling Comments
----------------------------

   The comment column is stored in the variable `comment-column'.  You
can explicitly set it to a number.  Alternatively, the command `C-x ;'
(`set-comment-column') sets the comment column to the column point is
at.  `C-u C-x ;' sets the comment column to match the last comment
before point in the buffer, and then calls `Meta-;' to align the
current line's comment under the previous one.  Note that `C-u - C-x ;'
runs the function `kill-comment' as described above.

   `comment-column' is a per-buffer variable; altering the variable
affects only the current buffer.  You can also change the default value.
*Note Locals::.  Many major modes initialize this variable for the
current buffer.

   The comment commands recognize comments based on the regular
expression that is the value of the variable `comment-start-skip'.
This regexp should not match the null string.  It may match more than
the comment starting delimiter in the strictest sense of the word; for
example, in C mode the value of the variable is `"/\\*+ *"', which
matches extra stars and spaces after the `/*' itself.  (Note that `\\'
is needed in Lisp syntax to include a `\' in the string, which is needed
to deny the first star its special meaning in regexp syntax.  *Note
Regexps::.)

   When a comment command makes a new comment, it inserts the value of
`comment-start' to begin it.  The value of `comment-end' is inserted
after point and will follow the text you will insert into the comment.
In C mode, `comment-start' has the value `"/* "' and `comment-end' has
the value `" */"'.

   `comment-multi-line' controls how `M-<LFD>'
(`indent-new-comment-line') behaves when used inside a comment.  If
`comment-multi-line' is `nil', as it normally is, then `M-<LFD>'
terminates the comment on the starting line and starts a new comment on
the new following line.  If `comment-multi-line' is not `nil', then
`M-<LFD>' sets up the new following line as part of the same comment
that was found on the starting line.  This is done by not inserting a
terminator on the old line and not inserting a starter on the new line.
In languages where multi-line comments are legal, the value you choose
for this variable is a matter of taste.

   The variable `comment-indent-hook' should contain a function that is
called to compute the indentation for a newly inserted comment or for
aligning an existing comment.  Major modes set this variable
differently.  The function is called with no arguments, but with point
at the beginning of the comment, or at the end of a line if a new
comment is to be inserted.  The function should return the column in
which the comment ought to start.  For example, in Lisp mode, the
indent hook function bases its decision on the number of semicolons
that begin an existing comment and on the code in the preceding lines.

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File: xemacs.info,  Node: Balanced Editing,  Next: Lisp Completion,  Prev: Comments,  Up: Programs

Editing Without Unbalanced Parentheses
======================================

`M-('
     Put parentheses around next sexp(s) (`insert-parentheses').

`M-)'
     Move past next close parenthesis and re-indent
     (`move-over-close-and-reindent').

   The commands `M-(' (`insert-parentheses') and `M-)'
(`move-over-close-and-reindent') are designed to facilitate a style of
editing which keeps parentheses balanced at all times.  `M-(' inserts a
pair of parentheses, either together as in `()', or, if given an
argument, around the next several sexps, and leaves point after the open
parenthesis.  Instead of typing `( F O O )', you can type `M-( F O O',
which has the same effect except for leaving the cursor before the
close parenthesis.  You can then type `M-)', which moves past the close
parenthesis, deletes any indentation preceding it (in this example
there is none), and indents with <LFD> after it.

\1f
File: xemacs.info,  Node: Lisp Completion,  Next: Documentation,  Prev: Balanced Editing,  Up: Programs

Completion for Lisp Symbols
===========================

   Completion usually happens in the minibuffer.  An exception is
completion for Lisp symbol names, which is available in all buffers.

   The command `M-<TAB>' (`lisp-complete-symbol') takes the partial
Lisp symbol before point to be an abbreviation, and compares it against
all non-trivial Lisp symbols currently known to Emacs.  Any additional
characters that they all have in common are inserted at point.
Non-trivial symbols are those that have function definitions, values, or
properties.

   If there is an open-parenthesis immediately before the beginning of
the partial symbol, only symbols with function definitions are
considered as completions.

   If the partial name in the buffer has more than one possible
completion and they have no additional characters in common, a list of
all possible completions is displayed in another window.

\1f
File: xemacs.info,  Node: Documentation,  Next: Change Log,  Prev: Lisp Completion,  Up: Programs

Documentation Commands
======================

   As you edit Lisp code to be run in Emacs, you can use the commands
`C-h f' (`describe-function') and `C-h v' (`describe-variable') to
print documentation of functions and variables you want to call.  These
commands use the minibuffer to read the name of a function or variable
to document, and display the documentation in a window.

   For extra convenience, these commands provide default arguments
based on the code in the neighborhood of point.  `C-h f' sets the
default to the function called in the innermost list containing point.
`C-h v' uses the symbol name around or adjacent to point as its default.

   The `M-x manual-entry' command gives you access to documentation on
Unix commands, system calls, and libraries.  The command reads a topic
as an argument, and displays the Unix manual page for that topic.
`manual-entry' always searches all 8 sections of the manual and
concatenates all the entries it finds.  For example, the topic
`termcap' finds the description of the termcap library from section 3,
followed by the description of the termcap data base from section 5.

\1f
File: xemacs.info,  Node: Change Log,  Next: Tags,  Prev: Documentation,  Up: Programs

Change Logs
===========

   The Emacs command `M-x add-change-log-entry' helps you keep a record
of when and why you have changed a program.  It assumes that you have a
file in which you write a chronological sequence of entries describing
individual changes.  The default is to store the change entries in a
file called `ChangeLog' in the same directory as the file you are
editing.  The same `ChangeLog' file therefore records changes for all
the files in a directory.

   A change log entry starts with a header line that contains your name
and the current date.  Except for these header lines, every line in the
change log starts with a tab.  One entry can describe several changes;
each change starts with a line starting with a tab and a star.  `M-x
add-change-log-entry' visits the change log file and creates a new entry
unless the most recent entry is for today's date and your name.  In
either case, it adds a new line to start the description of another
change just after the header line of the entry.  When `M-x
add-change-log-entry' is finished, all is prepared for you to edit in
the description of what you changed and how.  You must then save the
change log file yourself.

   The change log file is always visited in Indented Text mode, which
means that <LFD> and auto-filling indent each new line like the previous
line.  This is convenient for entering the contents of an entry, which
must be indented.  *Note Text Mode::.

   Here is an example of the formatting conventions used in the change
log for Emacs:

     Wed Jun 26 19:29:32 1985  Richard M. Stallman  (rms at mit-prep)
     
             * xdisp.c (try_window_id):
             If C-k is done at end of next-to-last line,
             this fn updates window_end_vpos and cannot leave
             window_end_pos nonnegative (it is zero, in fact).
             If display is preempted before lines are output,
             this is inconsistent.  Fix by setting
             blank_end_of_window to nonzero.
     
     Tue Jun 25 05:25:33 1985  Richard M. Stallman  (rms at mit-prep)
     
             * cmds.c (Fnewline):
             Call the auto fill hook if appropriate.
     
             * xdisp.c (try_window_id):
             If point is found by compute_motion after xp, record that
             permanently.  If display_text_line sets point position wrong
             (case where line is killed, point is at eob and that line is
             not displayed), set it again in final compute_motion.

\1f
File: xemacs.info,  Node: Tags,  Next: Fortran,  Prev: Change Log,  Up: Programs

Tags Tables
===========

   A "tags table" is a description of how a multi-file program is
broken up into files.  It lists the names of the component files and the
names and positions of the functions (or other named subunits) in each
file.  Grouping the related files makes it possible to search or replace
through all the files with one command.  Recording the function names
and positions makes possible the `M-.' command which finds the
definition of a function by looking up which of the files it is in.

   Tags tables are stored in files called "tags table files".  The
conventional name for a tags table file is `TAGS'.

   Each entry in the tags table records the name of one tag, the name
of the file that the tag is defined in (implicitly), and the position
in that file of the tag's definition.

   Just what names from the described files are recorded in the tags
table depends on the programming language of the described file.  They
normally include all functions and subroutines, and may also include
global variables, data types, and anything else convenient.  Each name
recorded is called a "tag".

* Menu:

* Tag Syntax::          Tag syntax for various types of code and text files.
* Create Tags Table::   Creating a tags table with `etags'.
* Etags Regexps::       Create arbitrary tags using regular expressions.
* Select Tags Table::   How to visit a tags table.
* Find Tag::            Commands to find the definition of a specific tag.
* Tags Search::         Using a tags table for searching and replacing.
* List Tags::           Listing and finding tags defined in a file.

\1f
File: xemacs.info,  Node: Tag Syntax,  Next: Create Tags Table,  Prev: Tags,  Up: Tags

Source File Tag Syntax
----------------------

   Here is how tag syntax is defined for the most popular languages:

   * In C code, any C function or typedef is a tag, and so are
     definitions of `struct', `union' and `enum'.  You can tag function
     declarations and external variables in addition to function
     definitions by giving the `--declarations' option to `etags'.
     `#define' macro definitions and `enum' constants are also tags,
     unless you specify `--no-defines' when making the tags table.
     Similarly, global variables are tags, unless you specify
     `--no-globals'.  Use of `--no-globals' and `--no-defines' can make
     the tags table file much smaller.

   * In C++ code, in addition to all the tag constructs of C code,
     member functions are also recognized, and optionally member
     variables if you use the `--members' option.  Tags for variables
     and functions in classes are named `CLASS::VARIABLE' and
     `CLASS::FUNCTION'.  `operator' functions tags are named, for
     example `operator+'.

   * In Java code, tags include all the constructs recognized in C++,
     plus the `interface', `extends' and `implements' constructs.  Tags
     for variables and functions in classes are named `CLASS.VARIABLE'
     and `CLASS.FUNCTION'.

   * In LaTeX text, the argument of any of the commands `\chapter',
     `\section', `\subsection', `\subsubsection', `\eqno', `\label',
     `\ref', `\cite', `\bibitem', `\part', `\appendix', `\entry', or
     `\index', is a tag.

     Other commands can make tags as well, if you specify them in the
     environment variable `TEXTAGS' before invoking `etags'.  The value
     of this environment variable should be a colon-separated list of
     command names.  For example,

          TEXTAGS="def:newcommand:newenvironment"
          export TEXTAGS

     specifies (using Bourne shell syntax) that the commands `\def',
     `\newcommand' and `\newenvironment' also define tags.

   * In Lisp code, any function defined with `defun', any variable
     defined with `defvar' or `defconst', and in general the first
     argument of any expression that starts with `(def' in column zero,
     is a tag.

   * In Scheme code, tags include anything defined with `def' or with a
     construct whose name starts with `def'.  They also include
     variables set with `set!' at top level in the file.

   Several other languages are also supported:

   * In Ada code, functions, procedures, packages, tasks, and types are
     tags.  Use the `--packages-only' option to create tags for packages
     only.

   * In assembler code, labels appearing at the beginning of a line,
     followed by a colon, are tags.

   * In Bison or Yacc input files, each rule defines as a tag the
     nonterminal it constructs.  The portions of the file that contain
     C code are parsed as C code.

   * In Cobol code, tags are paragraph names; that is, any word
     starting in column 8 and followed by a period.

   * In Erlang code, the tags are the functions, records, and macros
     defined in the file.

   * In Fortran code, functions, subroutines and blockdata are tags.

   * In Objective C code, tags include Objective C definitions for
     classes, class categories, methods, and protocols.

   * In Pascal code, the tags are the functions and procedures defined
     in the file.

   * In Perl code, the tags are the procedures defined by the `sub',
     `my' and `local' keywords.  Use `--globals' if you want to tag
     global variables.

   * In Postscript code, the tags are the functions.

   * In Prolog code, a tag name appears at the left margin.

   * In Python code, `def' or `class' at the beginning of a line
     generate a tag.

   You can also generate tags based on regexp matching (*note Etags
Regexps::) to handle other formats and languages.

\1f
File: xemacs.info,  Node: Create Tags Table,  Next: Etags Regexps,  Prev: Tag Syntax,  Up: Tags

Creating Tags Tables
--------------------

   The `etags' program is used to create a tags table file.  It knows
the syntax of several languages, as described in *Note Tag Syntax::.
Here is how to run `etags':

     etags INPUTFILES...

The `etags' program reads the specified files, and writes a tags table
named `TAGS' in the current working directory.  You can intermix
compressed and plain text source file names.  `etags' knows about the
most common compression formats, and does the right thing.  So you can
compress all your source files and have `etags' look for compressed
versions of its file name arguments, if it does not find uncompressed
versions.  Under MS-DOS, `etags' also looks for file names like
`mycode.cgz' if it is given `mycode.c' on the command line and
`mycode.c' does not exist.

   `etags' recognizes the language used in an input file based on its
file name and contents.  You can specify the language with the
`--language=NAME' option, described below.

   If the tags table data become outdated due to changes in the files
described in the table, the way to update the tags table is the same
way it was made in the first place.  It is not necessary to do this
often.

   If the tags table fails to record a tag, or records it for the wrong
file, then Emacs cannot possibly find its definition.  However, if the
position recorded in the tags table becomes a little bit wrong (due to
some editing in the file that the tag definition is in), the only
consequence is a slight delay in finding the tag.  Even if the stored
position is very wrong, Emacs will still find the tag, but it must
search the entire file for it.

   So you should update a tags table when you define new tags that you
want to have listed, or when you move tag definitions from one file to
another, or when changes become substantial.  Normally there is no need
to update the tags table after each edit, or even every day.

   One tags table can effectively include another.  Specify the included
tags file name with the `--include=FILE' option when creating the file
that is to include it.  The latter file then acts as if it contained
all the files specified in the included file, as well as the files it
directly contains.

   If you specify the source files with relative file names when you run
`etags', the tags file will contain file names relative to the
directory where the tags file was initially written.  This way, you can
move an entire directory tree containing both the tags file and the
source files, and the tags file will still refer correctly to the source
files.

   If you specify absolute file names as arguments to `etags', then the
tags file will contain absolute file names.  This way, the tags file
will still refer to the same files even if you move it, as long as the
source files remain in the same place.  Absolute file names start with
`/', or with `DEVICE:/' on MS-DOS and MS-Windows.

   When you want to make a tags table from a great number of files, you
may have problems listing them on the command line, because some systems
have a limit on its length.  The simplest way to circumvent this limit
is to tell `etags' to read the file names from its standard input, by
typing a dash in place of the file names, like this:

     find . -name "*.[chCH]" -print | etags -

   Use the option `--language=NAME' to specify the language explicitly.
You can intermix these options with file names; each one applies to
the file names that follow it.  Specify `--language=auto' to tell
`etags' to resume guessing the language from the file names and file
contents.  Specify `--language=none' to turn off language-specific
processing entirely; then `etags' recognizes tags by regexp matching
alone (*note Etags Regexps::).

   `etags --help' prints the list of the languages `etags' knows, and
the file name rules for guessing the language. It also prints a list of
all the available `etags' options, together with a short explanation.

\1f
File: xemacs.info,  Node: Etags Regexps,  Next: Select Tags Table,  Prev: Create Tags Table,  Up: Tags

Etags Regexps
-------------

   The `--regex' option provides a general way of recognizing tags
based on regexp matching.  You can freely intermix it with file names.
Each `--regex' option adds to the preceding ones, and applies only to
the following files.  The syntax is:

     --regex=/TAGREGEXP[/NAMEREGEXP]/

where TAGREGEXP is used to match the lines to tag.  It is always
anchored, that is, it behaves as if preceded by `^'.  If you want to
account for indentation, just match any initial number of blanks by
beginning your regular expression with `[ \t]*'.  In the regular
expressions, `\' quotes the next character, and `\t' stands for the tab
character.  Note that `etags' does not handle the other C escape
sequences for special characters.

   The syntax of regular expressions in `etags' is the same as in
Emacs, augmented with the "interval operator", which works as in `grep'
and `ed'.  The syntax of an interval operator is `\{M,N\}', and its
meaning is to match the preceding expression at least M times and up to
N times.

   You should not match more characters with TAGREGEXP than that needed
to recognize what you want to tag.  If the match is such that more
characters than needed are unavoidably matched by TAGREGEXP (as will
usually be the case), you should add a NAMEREGEXP, to pick out just the
tag.  This will enable Emacs to find tags more accurately and to do
completion on tag names more reliably.  You can find some examples
below.

   The option `--ignore-case-regex' (or `-c') is like `--regex', except
that the regular expression provided will be matched without regard to
case, which is appropriate for various programming languages.

   The `-R' option deletes all the regexps defined with `--regex'
options.  It applies to the file names following it, as you can see
from the following example:

     etags --regex=/REG1/ voo.doo --regex=/REG2/ \
         bar.ber -R --lang=lisp los.er

Here `etags' chooses the parsing language for `voo.doo' and `bar.ber'
according to their contents.  `etags' also uses REG1 to recognize
additional tags in `voo.doo', and both REG1 and REG2 to recognize
additional tags in `bar.ber'.  `etags' uses the Lisp tags rules, and no
regexp matching, to recognize tags in `los.er'.

   A regular expression can be bound to a given language, by prepending
it with `{lang}'.  When you do this, `etags' will use the regular
expression only for files of that language.  `etags --help' prints the
list of languages recognised by `etags'.  The following example tags
the `DEFVAR' macros in the Emacs source files.  `etags' applies this
regular expression to C files only:

     --regex='{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/'

This feature is particularly useful when storing a list of regular
expressions in a file.  The following option syntax instructs `etags'
to read two files of regular expressions.  The regular expressions
contained in the second file are matched without regard to case.

     --regex=@first-file --ignore-case-regex=@second-file

A regex file contains one regular expressions per line.  Empty lines,
and lines beginning with space or tab are ignored.  When the first
character in a line is `@', `etags' assumes that the rest of the line
is the name of a file of regular expressions.  This means that such
files can be nested.  All the other lines are taken to be regular
expressions.  For example, one can create a file called `emacs.tags'
with the following contents (the first line in the file is a comment):

             -- This is for GNU Emacs source files
     {c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/

and then use it like this:

     etags --regex=@emacs.tags *.[ch] */*.[ch]

   Here are some more examples.  The regexps are quoted to protect them
from shell interpretation.

   * Tag Octave files:

          etags --language=none \
                --regex='/[ \t]*function.*=[ \t]*\([^ \t]*\)[ \t]*(/\1/' \
                --regex='/###key \(.*\)/\1/' \
                --regex='/[ \t]*global[ \t].*/' \
                *.m

     Note that tags are not generated for scripts so that you have to
     add a line by yourself of the form `###key <script-name>' if you
     want to jump to it.

   * Tag Tcl files:

          etags --language=none --regex='/proc[ \t]+\([^ \t]+\)/\1/' *.tcl

   * Tag VHDL files:

          --language=none \
          --regex='/[ \t]*\(ARCHITECTURE\|CONFIGURATION\) +[^ ]* +OF/' \
          --regex='/[ \t]*\(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\
          \( BODY\)?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/'

\1f
File: xemacs.info,  Node: Select Tags Table,  Next: Find Tag,  Prev: Etags Regexps,  Up: Tags

Selecting a Tags Table
----------------------

   At any time Emacs has one "selected" tags table, and all the commands
for working with tags tables use the selected one.  To select a tags
table, use the variable `tag-table-alist'.

   The value of `tag-table-alist' is a list that determines which
`TAGS' files should be active for a given buffer.  This is not really
an association list, in that all elements are checked.  The car of each
element of this list is a pattern against which the buffers file name
is compared; if it matches, then the cdr of the list should be the name
of the tags table to use.  If more than one element of this list
matches the buffers file name, all of the associated tags tables are
used.  Earlier ones are searched first.

   If the car of elements of this list are strings, they are treated as
regular-expressions against which the file is compared (like the
`auto-mode-alist').  If they are not strings, they are evaluated.  If
they evaluate to non-`nil', the current buffer is considered to match.

   If the cdr of the elements of this list are strings, they are
assumed to name a tags file.  If they name a directory, the string
`tags' is appended to them to get the file name.  If they are not
strings, they are evaluated and must return an appropriate string.

   For example:

       (setq tag-table-alist
             '(("/usr/src/public/perl/" . "/usr/src/public/perl/perl-3.0/")
               ("\\.el$" . "/usr/local/emacs/src/")
               ("/jbw/gnu/" . "/usr15/degree/stud/jbw/gnu/")
               ("" . "/usr/local/emacs/src/")
               ))

   The example defines the tags table alist in the following way:

   * Anything in the directory `/usr/src/public/perl/' should use the
     `TAGS' file `/usr/src/public/perl/perl-3.0/TAGS'.

   * Files ending in `.el' should use the `TAGS' file
     `/usr/local/emacs/src/TAGS'.

   * Anything in or below the directory `/jbw/gnu/' should use the
     `TAGS' file `/usr15/degree/stud/jbw/gnu/TAGS'.

   If you had a file called `/usr/jbw/foo.el', it would use both `TAGS'
files,
`/usr/local/emacs/src/TAGS' and `/usr15/degree/stud/jbw/gnu/TAGS' (in
that order), because it matches both patterns.

   If the buffer-local variable `buffer-tag-table' is set, it names a
tags table that is searched before all others when `find-tag' is
executed from this buffer.

   If there is a file called `TAGS' in the same directory as the file
in question, then that tags file will always be used as well (after the
`buffer-tag-table' but before the tables specified by this list).

   If the variable `tags-file-name' is set, the `TAGS' file it names
will apply to all buffers (for backwards compatibility.)  It is searched
first.

   If the value of the variable `tags-always-build-completion-table' is
`t', the tags file will always be added to the completion table without
asking first, regardless of the size of the tags file.

   The function `M-x visit-tags-table', is largely made obsolete by the
variable `tag-table-alist', tells tags commands to use the tags table
file FILE first.  The FILE should be the name of a file created with
the `etags' program.  A directory name is also acceptable; it means the
file `TAGS' in that directory.  The function only stores the file name
you provide in the variable `tags-file-name'.  Emacs does not actually
read in the tags table contents until you try to use them.  You can set
the variable explicitly instead of using `visit-tags-table'.  The value
of the variable `tags-file-name' is the name of the tags table used by
all buffers.  This is for backward compatibility, and is largely
supplanted by the variable `tag-table-alist'.

\1f
File: xemacs.info,  Node: Find Tag,  Next: Tags Search,  Prev: Select Tags Table,  Up: Tags

Finding a Tag
-------------

   The most important thing that a tags table enables you to do is to
find the definition of a specific tag.

`M-. TAG &OPTIONAL OTHER-WINDOW'
     Find first definition of TAG (`find-tag').

`C-u M-.'
     Find next alternate definition of last tag specified.

`C-x 4 . TAG'
     Find first definition of TAG, but display it in another window
     (`find-tag-other-window').

   `M-.' (`find-tag') is the command to find the definition of a
specified tag.  It searches through the tags table for that tag, as a
string, then uses the tags table information to determine the file in
which the definition is used and the approximate character position of
the definition in the file.  Then `find-tag' visits the file, moves
point to the approximate character position, and starts searching
ever-increasing distances away for the text that should appear at the
beginning of the definition.

   If an empty argument is given (by typing <RET>), the sexp in the
buffer before or around point is used as the name of the tag to find.
*Note Lists::, for information on sexps.

   The argument to `find-tag' need not be the whole tag name; it can be
a substring of a tag name.  However, there can be many tag names
containing the substring you specify.  Since `find-tag' works by
searching the text of the tags table, it finds the first tag in the
table that the specified substring appears in.  To find other tags that
match the substring, give `find-tag' a numeric argument, as in `C-u
M-.'.  This does not read a tag name, but continues searching the tag
table's text for another tag containing the same substring last used.
If your keyboard has a real <META> key, `M-0 M-.' is an easier
alternative to `C-u M-.'.

   If the optional second argument OTHER-WINDOW is non-`nil', it uses
another window to display the tag.  Multiple active tags tables and
completion are supported.

   Variables of note include the following:

`tag-table-alist'
     Controls which tables apply to which buffers.

`tags-file-name'
     Stores a default tags table.

`tags-build-completion-table'
     Controls completion behavior.

`buffer-tag-table'
     Specifies a buffer-local table.

`make-tags-files-invisible'
     Sets whether tags tables should be very hidden.

`tag-mark-stack-max'
     Specifies how many tags-based hops to remember.

   Like most commands that can switch buffers, `find-tag' has another
similar command that displays the new buffer in another window.  `C-x 4
.' invokes the function `find-tag-other-window'.  (This key sequence
ends with a period.)

   Emacs comes with a tags table file `TAGS' (in the directory
containing Lisp libraries) that includes all the Lisp libraries and all
the C sources of Emacs.  By specifying this file with `visit-tags-table'
and then using `M-.' you can quickly look at the source of any Emacs
function.

\1f
File: xemacs.info,  Node: Tags Search,  Next: List Tags,  Prev: Find Tag,  Up: Tags

Searching and Replacing with Tags Tables
----------------------------------------

   The commands in this section visit and search all the files listed
in the selected tags table, one by one.  For these commands, the tags
table serves only to specify a sequence of files to search.  A related
command is `M-x grep' (*note Compilation::).

`M-x tags-search <RET> REGEXP <RET>'
     Search for REGEXP through the files in the selected tags table.

`M-x tags-query-replace <RET> REGEXP <RET> REPLACEMENT <RET>'
     Perform a `query-replace-regexp' on each file in the selected tags
     table.

`M-,'
     Restart one of the commands above, from the current location of
     point (`tags-loop-continue').

   `M-x tags-search' reads a regexp using the minibuffer, then searches
for matches in all the files in the selected tags table, one file at a
time.  It displays the name of the file being searched so you can
follow its progress.  As soon as it finds an occurrence, `tags-search'
returns.

   Having found one match, you probably want to find all the rest.  To
find one more match, type `M-,' (`tags-loop-continue') to resume the
`tags-search'.  This searches the rest of the current buffer, followed
by the remaining files of the tags table.

   `M-x tags-query-replace' performs a single `query-replace-regexp'
through all the files in the tags table.  It reads a regexp to search
for and a string to replace with, just like ordinary `M-x
query-replace-regexp'.  It searches much like `M-x tags-search', but
repeatedly, processing matches according to your input.  *Note
Replace::, for more information on query replace.

   It is possible to get through all the files in the tags table with a
single invocation of `M-x tags-query-replace'.  But often it is useful
to exit temporarily, which you can do with any input event that has no
special query replace meaning.  You can resume the query replace
subsequently by typing `M-,'; this command resumes the last tags search
or replace command that you did.

   The commands in this section carry out much broader searches than the
`find-tag' family.  The `find-tag' commands search only for definitions
of tags that match your substring or regexp.  The commands
`tags-search' and `tags-query-replace' find every occurrence of the
regexp, as ordinary search commands and replace commands do in the
current buffer.

   These commands create buffers only temporarily for the files that
they have to search (those which are not already visited in Emacs
buffers).  Buffers in which no match is found are quickly killed; the
others continue to exist.

   It may have struck you that `tags-search' is a lot like `grep'.  You
can also run `grep' itself as an inferior of Emacs and have Emacs show
you the matching lines one by one.  This works much like running a
compilation; finding the source locations of the `grep' matches works
like finding the compilation errors.  *Note Compilation::.

   If you wish to process all the files in a selected tags table, but
`M-x tags-search' and `M-x tags-query-replace' are not giving you the
desired result, you can use `M-x next-file'.

`C-u M-x next-file'
     With a numeric argument, regardless of its value, visit the first
     file in the tags table and prepare to advance sequentially by
     files.

`M-x next-file'
     Visit the next file in the selected tags table.

\1f
File: xemacs.info,  Node: List Tags,  Prev: Tags Search,  Up: Tags

Tags Table Inquiries
--------------------

`M-x list-tags'
     Display a list of the tags defined in a specific program file.

`M-x tags-apropos'
     Display a list of all tags matching a specified regexp.

   `M-x list-tags' reads the name of one of the files described by the
selected tags table, and displays a list of all the tags defined in that
file.  The "file name" argument is really just a string to compare
against the names recorded in the tags table; it is read as a string
rather than a file name.  Therefore, completion and defaulting are not
available, and you must enter the string the same way it appears in the
tag table.  Do not include a directory as part of the file name unless
the file name recorded in the tags table contains that directory.

   `M-x tags-apropos' is like `apropos' for tags.  It reads a regexp,
then finds all the tags in the selected tags table whose entries match
that regexp, and displays the tag names found.

\1f
File: xemacs.info,  Node: Fortran,  Next: Asm Mode,  Prev: Tags,  Up: Programs

Fortran Mode
============

   Fortran mode provides special motion commands for Fortran statements
and subprograms, and indentation commands that understand Fortran
conventions of nesting, line numbers, and continuation statements.

   Special commands for comments are provided because Fortran comments
are unlike those of other languages.

   Built-in abbrevs optionally save typing when you insert Fortran
keywords.

   Use `M-x fortran-mode' to switch to this major mode.  Doing so calls
the value of `fortran-mode-hook' as a function of no arguments if that
variable has a non-`nil' value.

* Menu:

* Motion: Fortran Motion.     Moving point by statements or subprograms.
* Indent: Fortran Indent.     Indentation commands for Fortran.
* Comments: Fortran Comments. Inserting and aligning comments.
* Columns: Fortran Columns.   Measuring columns for valid Fortran.
* Abbrev: Fortran Abbrev.     Built-in abbrevs for Fortran keywords.

   Fortran mode was contributed by Michael Prange.

\1f
File: xemacs.info,  Node: Fortran Motion,  Next: Fortran Indent,  Prev: Fortran,  Up: Fortran

Motion Commands
---------------

   Fortran mode provides special commands to move by subprograms
(functions and subroutines) and by statements.  There is also a command
to put the region around one subprogram, which is convenient for
killing it or moving it.

`C-M-a'
     Move to beginning of subprogram
     (`beginning-of-fortran-subprogram').

`C-M-e'
     Move to end of subprogram (`end-of-fortran-subprogram').

`C-M-h'
     Put point at beginning of subprogram and mark at end
     (`mark-fortran-subprogram').

`C-c C-n'
     Move to beginning of current or next statement (`fortran-next-
     statement').

`C-c C-p'
     Move to beginning of current or previous statement (`fortran-
     previous-statement').

\1f
File: xemacs.info,  Node: Fortran Indent,  Next: Fortran Comments,  Prev: Fortran Motion,  Up: Fortran

Fortran Indentation
-------------------

   Special commands and features are available for indenting Fortran
code.  They make sure various syntactic entities (line numbers, comment
line indicators, and continuation line flags) appear in the columns
that are required for standard Fortran.

* Menu:

* Commands: ForIndent Commands. Commands for indenting Fortran.
* Numbers:  ForIndent Num.      How line numbers auto-indent.
* Conv:     ForIndent Conv.     Conventions you must obey to avoid trouble.
* Vars:     ForIndent Vars.     Variables controlling Fortran indent style.

\1f
File: xemacs.info,  Node: ForIndent Commands,  Next: ForIndent Num,  Prev: Fortran Indent,  Up: Fortran Indent

Fortran Indentation Commands
............................

`<TAB>'
     Indent the current line (`fortran-indent-line').

`M-<LFD>'
     Break the current line and set up a continuation line.

`C-M-q'
     Indent all the lines of the subprogram point is in
     (`fortran-indent-subprogram').

   <TAB> is redefined by Fortran mode to reindent the current line for
Fortran (`fortran-indent-line').  Line numbers and continuation markers
are indented to their required columns, and the body of the statement
is independently indented, based on its nesting in the program.

   The key `C-M-q' is redefined as `fortran-indent-subprogram', a
command that reindents all the lines of the Fortran subprogram
(function or subroutine) containing point.

   The key `M-<LFD>' is redefined as `fortran-split-line', a command to
split a line in the appropriate fashion for Fortran.  In a non-comment
line, the second half becomes a continuation line and is indented
accordingly.  In a comment line, both halves become separate comment
lines.

\1f
File: xemacs.info,  Node: ForIndent Num,  Next: ForIndent Conv,  Prev: ForIndent Commands,  Up: Fortran Indent

Line Numbers and Continuation
.............................

   If a number is the first non-whitespace in the line, it is assumed
to be a line number and is moved to columns 0 through 4.  (Columns are
always counted from 0 in XEmacs.)  If the text on the line starts with
the conventional Fortran continuation marker `$', it is moved to column
5.  If the text begins with any non whitespace character in column 5,
it is assumed to be an unconventional continuation marker and remains
in column 5.

   Line numbers of four digits or less are normally indented one space.
This amount is controlled by the variable `fortran-line-number-indent',
which is the maximum indentation a line number can have.  Line numbers
are indented to right-justify them to end in column 4 unless that would
require more than the maximum indentation.  The default value of the
variable is 1.

   Simply inserting a line number is enough to indent it according to
these rules.  As each digit is inserted, the indentation is recomputed.
To turn off this feature, set the variable
`fortran-electric-line-number' to `nil'.  Then inserting line numbers
is like inserting anything else.

\1f
File: xemacs.info,  Node: ForIndent Conv,  Next: ForIndent Vars,  Prev: ForIndent Num,  Up: Fortran Indent

Syntactic Conventions
.....................

   Fortran mode assumes that you follow certain conventions that
simplify the task of understanding a Fortran program well enough to
indent it properly:

   * Two nested `do' loops never share a `continue' statement.

   * The same character appears in column 5 of all continuation lines.
     It is the value of the variable `fortran-continuation-char'.  By
     default, this character is `$'.

If you fail to follow these conventions, the indentation commands may
indent some lines unaesthetically.  However, a correct Fortran program
will retain its meaning when reindented even if the conventions are not
followed.

\1f
File: xemacs.info,  Node: ForIndent Vars,  Prev: ForIndent Conv,  Up: Fortran Indent

Variables for Fortran Indentation
.................................

   Several additional variables control how Fortran indentation works.

`fortran-do-indent'
     Extra indentation within each level of `do' statement (the default
     is 3).

`fortran-if-indent'
     Extra indentation within each level of `if' statement (the default
     is 3).

`fortran-continuation-indent'
     Extra indentation for bodies of continuation lines (the default is
     5).

`fortran-check-all-num-for-matching-do'
     If this is `nil', indentation assumes that each `do' statement
     ends on a `continue' statement.  Therefore, when computing
     indentation for a statement other than `continue', it can save
     time by not checking for a `do' statement ending there.  If this
     is non-`nil', indenting any numbered statement must check for a
     `do' that ends there.  The default is `nil'.

`fortran-minimum-statement-indent'
     Minimum indentation for Fortran statements.  For standard Fortran,
     this is 6.  Statement bodies are always indented at least this
     much.

\1f
File: xemacs.info,  Node: Fortran Comments,  Next: Fortran Columns,  Prev: Fortran Indent,  Up: Fortran

Comments
--------

   The usual Emacs comment commands assume that a comment can follow a
line of code.  In Fortran, the standard comment syntax requires an
entire line to be just a comment.  Therefore, Fortran mode replaces the
standard Emacs comment commands and defines some new variables.

   Fortran mode can also handle a non-standard comment syntax where
comments start with `!' and can follow other text.  Because only some
Fortran compilers accept this syntax, Fortran mode will not insert such
comments unless you have specified to do so in advance by setting the
variable `comment-start' to `"!"' (*note Variables::).

`M-;'
     Align comment or insert new comment (`fortran-comment-indent').

`C-x ;'
     Applies to nonstandard `!' comments only.

`C-c ;'
     Turn all lines of the region into comments, or (with arg) turn
     them back into real code (`fortran-comment-region').

   `M-;' in Fortran mode is redefined as the command
`fortran-comment-indent'.  Like the usual `M-;' command, it recognizes
an existing comment and aligns its text appropriately.  If there is no
existing comment, a comment is inserted and aligned.

   Inserting and aligning comments is not the same in Fortran mode as in
other modes.  When a new comment must be inserted, a full-line comment
is inserted if the current line is blank.  On a non-blank line, a
non-standard `!' comment is inserted if you previously specified you
wanted to use them.  Otherwise a full-line comment is inserted on a new
line before the current line.

   Non-standard `!' comments are aligned like comments in other
languages, but full-line comments are aligned differently.  In a
standard full-line comment, the comment delimiter itself must always
appear in column zero.  What can be aligned is the text within the
comment.  You can choose from three styles of alignment by setting the
variable `fortran-comment-indent-style' to one of these values:

`fixed'
     The text is aligned at a fixed column, which is the value of
     `fortran-comment-line-column'.  This is the default.

`relative'
     The text is aligned as if it were a line of code, but with an
     additional `fortran-comment-line-column' columns of indentation.

`nil'
     Text in full-line columns is not moved automatically.

   You can also specify the character to be used to indent within
full-line comments by setting the variable `fortran-comment-indent-char'
to the character you want to use.

   Fortran mode introduces two variables `comment-line-start' and
`comment-line-start-skip', which do for full-line comments what
`comment-start' and `comment-start-skip' do for ordinary text-following
comments.  Normally these are set properly by Fortran mode, so you do
not need to change them.

   The normal Emacs comment command `C-x ;' has not been redefined.  It
can therefore be used if you use `!' comments, but is useless in
Fortran mode otherwise.

   The command `C-c ;' (`fortran-comment-region') turns all the lines
of the region into comments by inserting the string `C$$$' at the front
of each one.  With a numeric arg, the region is turned back into live
code by deleting `C$$$' from the front of each line.  You can control
the string used for the comments by setting the variable
`fortran-comment-region'.  Note that here we have an example of a
command and a variable with the same name; the two uses of the name
never conflict because in Lisp and in Emacs it is always clear from the
context which one is referred to.