This is Info file ../info/emacs, produced by Makeinfo-1.63 from the
input file emacs.texi.


File: emacs,  Node: Select Tags Table,  Next: Find Tag,  Prev: Create Tags Table,  Up: Tags

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

   Emacs has at any time one "selected" tags table, and all the commands
for working with tags tables use the selected one.  To select a tags
table, type `M-x visit-tags-table', which reads the tags table file
name as an argument.  The name `TAGS' in the default directory is used
as the default file name.

   All this command does is store the file name in the variable
`tags-file-name'.  Emacs does not actually read in the tags table
contents until you try to use them.  Setting this variable yourself is
just as good as using `visit-tags-table'.  The variable's initial value
is `nil'; that value tells all the commands for working with tags tables
that they must ask for a tags table file name to use.

   Using `visit-tags-table' when a tags table is already loaded gives
you a choice: you can add the new tags table to the current list of
tags tables, or start a new list.  The tags commands use all the tags
tables in the current list.  If you start a new list, the new tags table
is used *instead* of others.  If you add the new table to the current
list, it is used *as well as* the others.  When the tags commands scan
the list of tags tables, they don't always start at the beginning of
the list; they start with the first tags table (if any) that describes
the current file, proceed from there to the end of the list, and then
scan from the beginning of the list until they have covered all the
tables in the list.

   You can specify a precise list of tags tables by setting the variable
`tags-table-list' to a list of strings, like this:

     (setq tags-table-list
           '("~/emacs" "/usr/local/lib/emacs/src"))

This tells the tags commands to look at the `TAGS' files in your
`~/emacs' directory and in the `/usr/local/lib/emacs/src' directory.
The order depends on which file you are in and which tags table
mentions that file, as explained above.

   Do not set both `tags-file-name' and `tags-table-list'.


File: emacs,  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 RET'
     Find first definition of TAG (`find-tag').

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

`C-u - M-.'
     Go back to previous tag found.

`C-M-. PATTERN RET'
     Find a tag whose name matches PATTERN (`find-tag-regexp').

`C-u C-M-.'
     Find the next tag whose name matches the last pattern used.

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

`C-x 5 . TAG RET'
     Find first definition of TAG, and create a new frame to select the
     buffer (`find-tag-other-frame').

   `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, and then uses the tags table info to determine the file that the
definition is in and the approximate character position in the file of
the definition.  Then `find-tag' visits that file, moves point to the
approximate character position, and searches ever-increasing distances
away to find the tag definition.

   If an empty argument is given (just type RET), the sexp in the
buffer before or around point is used as the TAG argument.  *Note
Lists::, for info on sexps.

   You don't need to give `M-.' the full name of the tag; a part will
do.  This is because `M-.' finds tags in the table which contain TAG as
a substring.  However, it prefers an exact match to a substring match.
To find other tags that match the same substring, give `find-tag' a
numeric argument, as in `C-u M-.'; this does not read a tag name, but
continues searching the tags table's text for another tag containing
the same substring last used.  If you have a real META key, `M-0 M-.'
is an easier alternative to `C-u M-.'.

   Like most commands that can switch buffers, `find-tag' has a variant
that displays the new buffer in another window, and one that makes a
new frame for it.  The former is `C-x 4 .', which invokes the command
`find-tag-other-window'.  The latter is `C-x 5 .', which invokes
`find-tag-other-frame'.

   To move back to places you've found tags recently, use `C-u - M-.';
more generally, `M-.' with a negative numeric argument.  This command
can take you to another buffer.  `C-x 4 .' with a negative argument
finds the previous tag location in another window.

   The command `C-M-.' (`find-tag-regexp') visits the tags that match a
specified regular expression.  It is just like `M-.'  except that it
does regexp matching instead of substring matching.


File: emacs,  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.

`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::.


File: emacs,  Node: List Tags,  Prev: Tags Search,  Up: Tags

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

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

`M-x tags-apropos RET REGEXP RET'
     Display a list of all tags matching 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 file names recorded in the tags table; it is read as a
string rather than as a file name.  Therefore, completion and
defaulting are not available, and you must enter the file name the same
way it appears in the tags table.  Do not include a directory as part of
the file name unless the file name recorded in the tags table includes a
directory.

   `M-x tags-apropos' is like `apropos' for tags (*note Apropos::.).
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.

   You can also perform completion in the buffer on the name space of
tag names in the current tags tables.  *Note Symbol Completion::.


File: emacs,  Node: Emerge,  Next: C Mode,  Prev: Tags,  Up: Programs

Merging Files with Emerge
=========================

   It's not unusual for programmers to get their signals crossed and
modify the same program in two different directions.  To recover from
this confusion, you need to merge the two versions.  Emerge makes this
easier.  See also *Note Comparing Files::.

* Menu:

* Overview of Emerge::	    How to start Emerge.  Basic concepts.
* Submodes of Emerge::      Fast mode vs. Edit mode.
			      Skip Prefers mode and Auto Advance mode.
* State of Difference::	    You do the merge by specifying state A or B
			      for each difference.
* Merge Commands::	    Commands for selecting a difference,
			      changing states of differences, etc.
* Exiting Emerge::	    What to do when you've finished the merge.
* Combining in Emerge::	    How to keep both alternatives for a difference.
* Fine Points of Emerge::   Misc.


File: emacs,  Node: Overview of Emerge,  Next: Submodes of Emerge,  Up: Emerge

Overview of Emerge
------------------

   To start Emerge, run one of these four commands:

`M-x emerge-files'
     Merge two specified files.

`M-x emerge-files-with-ancestor'
     Merge two specified files, with reference to a common ancestor.

`M-x emerge-buffers'
     Merge two buffers.

`M-x emerge-buffers-with-ancestor'
     Merge two buffers with reference to a common ancestor in a third
     buffer.

   The Emerge commands compare two files or buffers, and display the
comparison in three buffers: one for each input text (the "A buffer"
and the "B buffer"), and one (the "merge buffer") where merging takes
place.  The merge buffer shows the full merged text, not just the
differences.  Wherever the two input texts differ, you can choose which
one of them to include in the merge buffer.

   The Emerge commands that take input from existing buffers use only
the accessible portions of those buffers, if they are narrowed (*note
Narrowing::.).

   If a common ancestor version is available, from which the two texts
to be merged were both derived, Emerge can use it to guess which
alternative is right.  Wherever one current version agrees with the
ancestor, Emerge presumes that the other current version is a deliberate
change which should be kept in the merged version.  Use the
`with-ancestor' commands if you want to specify a common ancestor text.
These commands read three file or buffer names--variant A, variant B,
and the common ancestor.

   After the comparison is done and the buffers are prepared, the
interactive merging starts.  You control the merging by typing special
"merge commands" in the merge buffer.  The merge buffer shows you a
full merged text, not just differences.  For each run of differences
between the input texts, you can choose which one of them to keep, or
edit them both together.

   The merge buffer uses a special major mode, Emerge mode, with
commands for making these choices.  But you can also edit the buffer
with ordinary Emacs commands.

   At any given time, the attention of Emerge is focused on one
particular difference, called the "selected" difference.  This
difference is marked off in the three buffers like this:

     vvvvvvvvvvvvvvvvvvvv
     TEXT THAT DIFFERS
     ^^^^^^^^^^^^^^^^^^^^

Emerge numbers all the differences sequentially and the mode line
always shows the number of the selected difference.

   Normally, the merge buffer starts out with the A version of the text.
But when the A version of a difference agrees with the common ancestor,
then the B version is initially preferred for that difference.

   Emerge leaves the merged text in the merge buffer when you exit.  At
that point, you can save it in a file with `C-x C-w'.  If you give a
numeric argument to `emerge-files' or `emerge-files-with-ancestor', it
reads the name of the output file using the minibuffer.  (This is the
last file name those commands read.) Then exiting from Emerge saves the
merged text in the output file.

   Normally, Emerge commands save the output buffer in its file when you
exit.  If you abort Emerge with `C-]', the Emerge command does not save
the output buffer, but you can save it yourself if you wish.


File: emacs,  Node: Submodes of Emerge,  Next: State of Difference,  Prev: Overview of Emerge,  Up: Emerge

Submodes of Emerge
------------------

   You can choose between two modes for giving merge commands: Fast mode
and Edit mode.  In Fast mode, basic merge commands are single
characters, but ordinary Emacs commands are disabled.  This is
convenient if you use only merge commands.  In Edit mode, all merge
commands start with the prefix key `C-c C-c', and the normal Emacs
commands are also available.  This allows editing the merge buffer, but
slows down Emerge operations.

   Use `e' to switch to Edit mode, and `C-c C-c f' to switch to Fast
mode.  The mode line indicates Edit and Fast modes with `E' and `F'.

   Emerge has two additional submodes that affect how particular merge
commands work: Auto Advance mode and Skip Prefers mode.

   If Auto Advance mode is in effect, the `a' and `b' commands advance
to the next difference.  This lets you go through the merge faster as
long as you simply choose one of the alternatives from the input.  The
mode line indicates Auto Advance mode with `A'.

   If Skip Prefers mode is in effect, the `n' and `p' commands skip
over differences in states prefer-A and prefer-B (*note State of
Difference::.).  Thus you see only differences for which neither version
is presumed "correct".  The mode line indicates Skip Prefers mode with
`S'.

   Use the command `s a' (`emerge-auto-advance-mode') to set or clear
Auto Advance mode.  Use `s s' (`emerge-skip-prefers-mode') to set or
clear Skip Prefers mode.  These commands turn on the mode with a
positive argument, turns it off with a negative or zero argument, and
toggle the mode with no argument.


File: emacs,  Node: State of Difference,  Next: Merge Commands,  Prev: Submodes of Emerge,  Up: Emerge

State of a Difference
---------------------

   In the merge buffer, a difference is marked with lines of `v' and
`^' characters.  Each difference has one of these seven states:

A
     The difference is showing the A version.  The `a' command always
     produces this state; the mode line indicates it with `A'.

B
     The difference is showing the B version.  The `b' command always
     produces this state; the mode line indicates it with `B'.

default-A
default-B
     The difference is showing the A or the B state by default, because
     you haven't made a choice.  All differences start in the default-A
     state (and thus the merge buffer is a copy of the A buffer),
     except those for which one alternative is "preferred" (see below).

     When you select a difference, its state changes from default-A or
     default-B to plain A or B.  Thus, the selected difference never has
     state default-A or default-B, and these states are never displayed
     in the mode line.

     The command `d a' chooses default-A as the default state, and `d
     b' chooses default-B.  This chosen default applies to all
     differences which you haven't ever selected and for which no
     alternative is preferred.  If you are moving through the merge
     sequentially, the differences you haven't selected are those
     following the selected one.  Thus, while moving sequentially, you
     can effectively make the A version the default for some sections
     of the merge buffer and the B version the default for others by
     using `d a' and `d b' between sections.

prefer-A
prefer-B
     The difference is showing the A or B state because it is
     "preferred".  This means that you haven't made an explicit choice,
     but one alternative seems likely to be right because the other
     alternative agrees with the common ancestor.  Thus, where the A
     buffer agrees with the common ancestor, the B version is
     preferred, because chances are it is the one that was actually
     changed.

     These two states are displayed in the mode line as `A*' and `B*'.

combined
     The difference is showing a combination of the A and B states, as a
     result of the `x c' or `x C' commands.

     Once a difference is in this state, the `a' and `b' commands don't
     do anything to it unless you give them a numeric argument.

     The mode line displays this state as `comb'.


File: emacs,  Node: Merge Commands,  Next: Exiting Emerge,  Prev: State of Difference,  Up: Emerge

Merge Commands
--------------

   Here are the Merge commands for Fast mode; in Edit mode, precede them
with `C-c C-c':

`p'
     Select the previous difference.

`n'
     Select the next difference.

`a'
     Choose the A version of this difference.

`b'
     Choose the B version of this difference.

`C-u N j'
     Select difference number N.

`.'
     Select the difference containing point.  You can use this command
     in the merge buffer or in the A or B buffer.

`q'
     Quit--finish the merge.

`C-]'
     Abort--exit merging and do not save the output.

`f'
     Go into Fast mode.  (In Edit mode, this is actually `C-c C-c f'.)

`e'
     Go into Edit mode.

`l'
     Recenter (like `C-l') all three windows.

`-'
     Specify part of a prefix numeric argument.

`DIGIT'
     Also specify part of a prefix numeric argument.

`d a'
     Choose the A version as the default from here down in the merge
     buffer.

`d b'
     Choose the B version as the default from here down in the merge
     buffer.

`c a'
     Copy the A version of this difference into the kill ring.

`c b'
     Copy the B version of this difference into the kill ring.

`i a'
     Insert the A version of this difference at point.

`i b'
     Insert the B version of this difference at point.

`m'
     Put point and mark around the difference.

`^'
     Scroll all three windows down (like `M-v').

`v'
     Scroll all three windows up (like `C-v').

`<'
     Scroll all three windows left (like `C-x <').

`>'
     Scroll all three windows right (like `C-x >').

`|'
     Reset horizontal scroll on all three windows.

`x 1'
     Shrink the merge window to one line.  (Use `C-u l' to restore it
     to full size.)

`x c'
     Combine the two versions of this difference (*note Combining in
     Emerge::.).

`x f'
     Show the names of the files/buffers Emerge is operating on, in a
     Help window.  (Use `C-u l' to restore windows.)

`x j'
     Join this difference with the following one.  (`C-u x j' joins
     this difference with the previous one.)

`x s'
     Split this difference into two differences.  Before you use this
     command, position point in each of the three buffers at the place
     where you want to split the difference.

`x t'
     Trim identical lines off top and bottom of the difference.  Such
     lines occur when the A and B versions are identical but differ
     from the ancestor version.


File: emacs,  Node: Exiting Emerge,  Next: Combining in Emerge,  Prev: Merge Commands,  Up: Emerge

Exiting Emerge
--------------

   The `q' command (`emerge-quit') finishes the merge, storing the
results into the output file if you specified one.  It restores the A
and B buffers to their proper contents, or kills them if they were
created by Emerge and you haven't changed them.  It also disables the
Emerge commands in the merge buffer, since executing them later could
damage the contents of the various buffers.

   `C-]' aborts the merge.  This means exiting without writing the
output file.  If you didn't specify an output file, then there is no
real difference between aborting and finishing the merge.

   If the Emerge command was called from another Lisp program, then its
return value is `t' for successful completion, or `nil' if you abort.


File: emacs,  Node: Combining in Emerge,  Next: Fine Points of Emerge,  Prev: Exiting Emerge,  Up: Emerge

Combining the Two Versions
--------------------------

   Sometimes you want to keep *both* alternatives for a particular
difference.  To do this, use `x c', which edits the merge buffer like
this:

     #ifdef NEW
     VERSION FROM A BUFFER
     #else /* NEW */
     VERSION FROM B BUFFER
     #endif /* NEW */

While this example shows C preprocessor conditionals delimiting the two
alternative versions, you can specify the strings to use by setting the
variable `emerge-combine-versions-template' to a string of your choice.
In the string, `%a' says where to put version A, and `%b' says where
to put version B.  The default setting, which produces the results
shown above, looks like this:

     "#ifdef NEW\n%a#else /* NEW */\n%b#endif /* NEW */\n"


File: emacs,  Node: Fine Points of Emerge,  Prev: Combining in Emerge,  Up: Emerge

Fine Points of Emerge
---------------------

   During the merge, you mustn't try to edit the A and B buffers
yourself.  Emerge modifies them temporarily, but ultimately puts them
back the way they were.

   You can have any number of merges going at once--just don't use any
one buffer as input to more than one merge at once, since the temporary
changes made in these buffers would get in each other's way.

   Starting Emerge can take a long time because it needs to compare the
files fully.  Emacs can't do anything else until `diff' finishes.
Perhaps in the future someone will change Emerge to do the comparison in
the background when the input files are large--then you could keep on
doing other things with Emacs until Emerge is ready to accept commands.

   After setting up the merge, Emerge runs the hook
`emerge-startup-hook' (*note Hooks::.).


File: emacs,  Node: C Mode,  Next: Fortran,  Prev: Emerge,  Up: Programs

C Mode
======

   This section describes special features available in C, C++,
Objective-C and Java modes.

* Menu:

* Motion in C::
* Electric C::
* Hungry Delete::
* Other C Commands::
* Comments in C::


File: emacs,  Node: Motion in C,  Next: Electric C,  Up: C Mode

C Mode Motion Commands
----------------------

   This section commands for moving point, in C mode and related modes.

`C-c C-u'
     Move point back to the containing preprocessor conditional,
     leaving the mark behind.  A prefix argument acts as a repeat
     count.  With a negative argument, move point forward to the end of
     the containing preprocessor conditional.  When going backwards,
     `#elif' is treated like `#else' followed by `#if'.  When going
     forwards, `#elif' is ignored.

`C-c C-p'
     Move point back over a preprocessor conditional, leaving the mark
     behind.  A prefix argument acts as a repeat count.  With a negative
     argument, move forward.

`C-c C-n'
     Move point forward across a preprocessor conditional, leaving the
     mark behind.  A prefix argument acts as a repeat count.  With a
     negative argument, move backward.

`M-a'
     Move point to the beginning of the innermost C statement.  If
     point is already at the beginning of a statement, move to the
     beginning of the preceding statement.  With prefix argument N,
     move back N - 1 statements.

     If point is within a string or comment, or next to a comment (only
     whitespace between them), this command moves by sentences instead
     of statements.

     When called from a program, this function takes two optional
     arguments: the numeric prefix argument, and a buffer position
     limit (don't move back before that place).

`M-e'
     Move point to the end of the innermost C statement.  If point is
     at the end of a statement, move to the end of the next statement.
     With prefix argument N, move forward N - 1 statements.

     If point is within a string or comment, or next to a comment (only
     whitespace between them), this command moves by sentences instead
     of statements.

     When called from a program, this function takes two optional
     arguments: the numeric prefix argument, and a buffer position
     limit (don't move past that place).

`M-x c-backward-into-nomenclature'
     Move point backward to beginning of a C++ nomenclature section or
     word.  With prefix argument N, move N times.  If N is negative,
     move forward.  C++ nomenclature means a symbol name in the style
     of NamingSymbolsWithMixedCaseAndNoUnderlines; each capital letter
     begins a section or word.

     In the GNU project, we recommend using underscores to separate
     words within an identifier in C or C++, rather than using case
     distinctions.

`M-x c-forward-into-nomenclature'
     Move point forward to end of a C++ nomenclature section or word.
     With prefix argument N, move N times.


File: emacs,  Node: Electric C,  Next: Hungry Delete,  Prev: Motion in C,  Up: C Mode

Electric C Characters
---------------------

   In C mode and related modes, certain printing characters are
"electric"--in addition to inserting themselves, they also reindent the
current line and may insert newlines.  This feature is controlled by
the variable `c-auto-newline'.  The "electric" characters are `{', `}',
`:', `#', `;', `,', `<', `>', `/' and `*'.

   Electric characters insert newlines only when the "auto-newline"
feature is enabled (indicated by `/a' in the mode line after the mode
name).  This feature is controlled by the variable `c-auto-newline'.
You can turn this feature on or off with the command `C-c C-a':

`C-c C-a'
     Toggle the auto-newline feature (`c-toggle-auto-state').  With a
     prefix argument, this command turns the auto-newline feature on if
     the argument is positive, and off if it is negative.

   The colon character is electric because that is appropriate for a
single colon.  But when you want to insert a double colon in C++, the
electric behavior of colon is inconvenient.  You can insert a double
colon with no reindentation or newlines by typing `C-c :':

`C-c :'
     Insert a double colon scope operator at point, without reindenting
     the line or adding any newlines (`c-scope-operator').

   The electric `#' key reindents the line if it appears to be the
beginning of a preprocessor directive.  This happens when the value of
`c-electric-pound-behavior' is `(alignleft)'.  You can turn this
feature off by setting `c-electric-pound-behavior' to `nil'.

   The variable `c-hanging-braces-alist' controls the insertion of
newlines before and after inserted braces.  It is an association list
with elements of the following form: `(SYNTACTIC-SYMBOL . NL-LIST)'.
Most of the syntactic symbols that appear in `c-offsets-alist' are
meaningful here as well.

   The list NL-LIST may contain either of the symbols `before' or
`after', or both; or it may be `nil'.  When a brace is inserted, the
syntactic context it defines is looked up in `c-hanging-braces-alist';
if it is found, the NL-LIST is used to determine where newlines are
inserted: either before the brace, after, or both.  If not found, the
default is to insert a newline both before and after braces.

   The variable `c-hanging-colons-alist' controls the insertion of
newlines before and after inserted colons.  It is an association list
with elements of the following form: `(SYNTACTIC-SYMBOL . NL-LIST)'.
The list NL-LIST may contain either of the symbols `before' or `after',
or both; or it may be `nil'.

   When a colon is inserted, the syntactic symbol it defines is looked
up in this list, and if found, the NL-LIST is used to determine where
newlines are inserted: either before the brace, after, or both.  If the
syntactic symbol is not found in this list, no newlines are inserted.

   Electric characters can also delete newlines automatically when the
auto-newline feature is enabled.  This feature makes auto-newline more
acceptable, by deleting the newlines in the most common cases where you
do not want them.  Emacs can recognize several cases in which deleting a
newline might be desirable; by setting the variable `c-cleanup-list',
you can specify *which* of these cases that should happen.  The
variable's value is a list of symbols, each describing one case for
possible deletion of a newline.  Here are the meaningful symbols, and
their meanings:

`brace-else-brace'
     Clean up `} else {' constructs by placing entire construct on a
     single line.  The clean-up occurs when you type the `{' after the
     `else', but only if there is nothing but white space between the
     braces and the `else'.

`empty-defun-braces'
     Clean up empty defun braces by placing the braces on the same
     line.  Clean-up occurs when you type the closing brace.

`defun-close-semi'
     Clean up the semicolon after a `struct' or similar type
     declaration, by placing the semicolon on the same line as the
     closing brace.  Clean-up occurs when you type the semicolon.

`list-close-comma'
     Clean up commas following braces in array and aggregate
     initializers.  Clean-up occurs when you type the comma.

`scope-operator'
     Clean up double colons which may designate a C++ scope operator, by
     placing the colons together.  Clean-up occurs when you type the
     second colon, but only when the two colons are separated by
     nothing but whitespace.


File: emacs,  Node: Hungry Delete,  Next: Other C Commands,  Prev: Electric C,  Up: C Mode

Hungry Delete Feature in C
--------------------------

   When the "hungry-delete" feature is enabled (indicated by `/h' or
`/ah' in the mode line after the mode name), a single DEL command
deletes all preceding whitespace, not just one space.  To turn this
feature on or off, use `C-c C-d':

`C-c C-d'
     Toggle the hungry-delete feature (`c-toggle-hungry-state').  With a
     prefix argument, this command turns the hungry-delete feature on
     if the argument is positive, and off if it is negative.

`C-c C-t'
     Toggle the auto-newline and hungry-delete features, both at once
     (`c-toggle-auto-hungry-state').

   The variable `c-hungry-delete-key' controls whether the
hungry-delete feature is enabled.


File: emacs,  Node: Other C Commands,  Next: Comments in C,  Prev: Hungry Delete,  Up: C Mode

Other Commands for C Mode
-------------------------

`C-M-h'
     Put mark at the end of a function definition, and put point at the
     beginning (`c-mark-function').

`M-q'
     Fill a paragraph, handling C and C++ comments (`c-fill-paragraph').
     If any part of the current line is a comment or within a comment,
     this command fills the comment or the paragraph of it that point
     is in, preserving the comment indentation and comment delimiters.

`C-c C-e'
     Run the C preprocessor on the text in the region, and show the
     result, which includes the expansion of all the macro calls
     (`c-macro-expand').  The buffer text before the region is also
     included in preprocessing, for the sake of macros defined there,
     but the output from this part isn't shown.

     When you are debugging C code that uses macros, sometimes it is
     hard to figure out precisely how the macros expand.  With this
     command, you don't have to figure it out; you can see the
     expansions.

`C-c C-\'
     Insert or align `\' characters at the ends of the lines of the
     region (`c-backslash-region').  This is useful after writing or
     editing a C macro definition.

     If a line already ends in `\', this command adjusts the amount of
     whitespace before it.  Otherwise, it inserts a new `\'.  However,
     the last line in the region is treated specially; no `\' is
     inserted on that line, and any `\' there is deleted.

`M-x cpp-highlight-buffer'
     Highlight parts of the text according to its preprocessor
     conditionals.  This command displays another buffer named `*CPP
     Edit*', which serves as a graphic menu for selecting how to
     display particular kinds of conditionals and their contents.
     After changing various settings, click on `[A]pply these settings'
     (or go to that buffer and type `a') to rehighlight the C mode
     buffer accordingly.

`C-c C-s'
     Display the syntactic information about the current source line
     (`c-show-syntactic-information').  This is the information that
     directs how the line is indented.


File: emacs,  Node: Comments in C,  Prev: Other C Commands,  Up: C Mode

Comments in C Modes
-------------------

   C mode and related modes use a number of variables for controlling
comment format.

`c-block-comments-indent-p'
     This variable specifies how to reindent block comments.  The C
     modes support five styles of block comments:

           style 1:    style 2 (GNU):   style 3:    style 4:    style 5:
           /*          /* Blah          /*          /*          /*
              blah        blah.  */      * blah     ** blah     blah
              blah                       * blah     ** blah     blah
              */                         */         */          */

     For the styles 1 through 4, `c-block-comments-indent-p' should be
     `nil' (the default).  If you want to use style 5, set
     `c-block-comments-indent-p' to `t'.

     This variable has no effect on the indentation of the comment-start
     itself or on insertion of asterisks when auto-filling C comments.
     It does not affect `M-q' either.

`c-comment-only-line-offset'
     Extra offset for line which contains only the start of a comment.
     It can be either an integer or a cons cell of the form
     `(NON-ANCHORED-OFFSET . ANCHORED-OFFSET)', where
     NON-ANCHORED-OFFSET is the amount of offset given to
     non-column-zero anchored comment-only lines, and ANCHORED-OFFSET
     is the amount of offset to give column-zero anchored comment-only
     lines.  Just an integer as value is equivalent to `(VAL . 0)'.

`c-comment-start-regexp'
     This buffer-local variable specifies how to recognize the start of
     a comment.

`c-hanging-comment-ender-p'
     If this variable is `nil', `c-fill-paragraph' leaves the comment
     terminator of a block comment on a line by itself.  The default
     value is `t', which always puts the comment-end delimiter `*/' at
     the end of the last line of the comment text.


File: emacs,  Node: Fortran,  Next: Asm Mode,  Prev: C Mode,  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.
Fortran mode has its own Auto Fill mode that breaks long lines into
proper Fortran continuation lines.

   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.  This command
runs the hook `fortran-mode-hook' (*note Hooks::.).

* Menu:

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


File: emacs,  Node: Fortran Motion,  Next: Fortran Indent,  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, 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').


File: emacs,  Node: Fortran Indent,  Next: Fortran Comments,  Prev: Fortran Motion,  Up: Fortran

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

   Special commands and features are needed for indenting Fortran code
in order to 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.
* Contline: ForIndent Cont.      How continuation lines indent.
* 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.


File: emacs,  Node: ForIndent Commands,  Next: ForIndent Cont,  Up: Fortran Indent

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

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

`LFD'
     Indent the current and start a new indented line
     (`fortran-indent-new-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').

   Fortran mode redefines TAB to reindent the current line for Fortran
(`fortran-indent-line').  This command indents Line numbers and
continuation markers to their required columns, and independently
indents the body of the statement based on its nesting in the program.

   The key `LFD' runs the command `fortran-indent-new-line', which
reindents the current line then makes and indents a new line.  This
command is useful to reindent the closing statement of `do' loops and
other blocks before starting a new line.

   The key `C-M-q' runs `fortran-indent-subprogram', a command to
reindent all the lines of the Fortran subprogram (function or
subroutine) containing point.

   The key `M-LFD' runs `fortran-split-line', which splits 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.


File: emacs,  Node: ForIndent Cont,  Next: ForIndent Num,  Prev: ForIndent Commands,  Up: Fortran Indent

Continuation Lines
..................

   Most modern Fortran compilers allow two ways of writing continuation
lines.  If the first non-space character on a line is in column 5, then
that line is a continuation of the previous line.  We call this "fixed
format".  (In GNU Emacs we always count columns from 0.)  The variable
`fortran-continuation-string' specifies what character to put on column
5.  A line that starts with a tab character followed by any digit
except `0' is also a continuation line.  We call this style of
continuation "tab format".

   Fortran mode can make either style of continuation line, but you
must specify which one you prefer.  The value of the variable
`indent-tabs-mode' controls the choice: `nil' for fixed format, and
non-`nil' for tab format.  You can tell which style is presently in
effect by the presence or absence of the string `Tab' in the mode line.

   If the text on a line starts with the conventional Fortran
continuation marker `$', or if it begins with any non-whitespace
character in column 5, Fortran mode treats it as a continuation line.
When you indent a continuation line with TAB, it converts the line to
the current continuation style.  When you split a Fortran statement
with `M-LFD', the continuation marker on the newline is created
according to the continuation style.

   The setting of continuation style affects several other aspects of
editing in Fortran mode.  In fixed format mode, the minimum column
number for the body of a statement is 6.  Lines inside of Fortran
blocks that are indented to larger column numbers always use only the
space character for whitespace.  In tab format mode, the minimum column
number for the statement body is 8, and the whitespace before column 8
must always consist of one tab character.

   When you enter Fortran mode for an existing file, it tries to deduce
the proper continuation style automatically from the file contents.
The first line that begins with either a tab character or six spaces
determines the choice.  The variable `fortran-analyze-depth' specifies
how many lines to consider (at the beginning of the file); if none of
those lines indicates a style, then the variable
`fortran-tab-mode-default' specifies the style.  If it is `nil', that
specifies fixed format, and non-`nil' specifies tab format.


File: emacs,  Node: ForIndent Num,  Next: ForIndent Conv,  Prev: ForIndent Cont,  Up: Fortran Indent

Line Numbers
............

   If a number is the first non-whitespace in the line, Fortran
indentation assumes it is a line number and moves it to columns 0
through 4.  (Columns always count from 0 in GNU Emacs.)

   Line numbers of four digits or less are normally indented one space.
The variable `fortran-line-number-indent' controls this; it specifies
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 this 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.


File: emacs,  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.

   * Fortran keywords such as `if', `else', `then', `do' and others are
     written without embedded whitespace or line breaks.

     Fortran compilers generally ignore whitespace outside of string
     constants, but Fortran mode does not recognize these keywords if
     they are not contiguous.  Constructs such as `else if' or `end do'
     are acceptable, but the second word should be on the same line as
     the first and not on a continuation line.

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


File: emacs,  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 (default 3).

`fortran-if-indent'
     Extra indentation within each level of `if' statement (default 3).
     This value is also used for extra indentation within each level of
     the Fortran 90 `where' statement.

`fortran-structure-indent'
     Extra indentation within each level of `structure', `union', or
     `map' statements (default 3).

`fortran-continuation-indent'
     Extra indentation for bodies of continuation lines (default 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-blink-matching-if'
     If this is `t', indenting an `endif' statement moves the cursor
     momentarily to the matching `if' statement to show where it is.
     The default is `nil'.

`fortran-minimum-statement-indent-fixed'
     Minimum indentation for fortran statements when using fixed format
     continuation line style.  Statement bodies are never indented less
     than this much.  The default is 6.

`fortran-minimum-statement-indent-tab'
     Minimum indentation for fortran statements for tab format
     continuation line style.  Statement bodies are never indented less
     than this much.  The default is 8.


File: emacs,  Node: Fortran Comments,  Next: Fortran Autofill,  Prev: Fortran Indent,  Up: Fortran

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 nonstandard 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 said in advance to do so.  To do this, set 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 argument)
     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, this
recognizes any kind of existing comment and aligns its text
appropriately; if there is no existing comment, a comment is inserted
and aligned.  But inserting and aligning comments are not the same in
Fortran mode as in other modes.

   When a new comment must be inserted, if the current line is blank, a
full-line comment is inserted.  On a non-blank line, a nonstandard `!'
comment is inserted if you have said you want to use them.  Otherwise a
full-line comment is inserted on a new line before the current line.

   Nonstandard `!' comments are aligned like comments in other
languages, but full-line comments are different.  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'
     Align the text at a fixed column, which is the sum of
     `fortran-comment-line-extra-indent' and the minimum statement
     indentation.  This is the default.

     The minimum statement indentation is
     `fortran-minimum-statement-indent-fixed' for fixed format
     continuation line style and `fortran-minimum-statement-indent-tab'
     for tab format style.

`relative'
     Align the text as if it were a line of code, but with an additional
     `fortran-comment-line-extra-indent' columns of indentation.

`nil'
     Don't move text in full-line columns automatically at all.

   In addition, you can specify the character to be used to indent
within full-line comments by setting the variable
`fortran-comment-indent-char' to the single-character string you want
to use.

   Fortran mode introduces two variables `comment-line-start' and
`comment-line-start-skip' which play for full-line comments the same
roles played by `comment-start' and `comment-start-skip' 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.  If
you use `!' comments, this command can be used with them.  Otherwise it
is useless in Fortran mode.

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

