* Autorevert:: Auto Reverting non-file buffers.
* Subdir switches:: Subdirectory switches in Dired.
* Advanced Calendar/Diary Usage:: Advanced Calendar/Diary customization.
+* Emerge:: A convenient way of merging two versions of a program.
+* Picture Mode:: Editing pictures made up of characters
+ using the quarter-plane screen model.
+* Fortran:: Fortran mode and its special features.
* Index::
@end menu
If one of these functions decides that it applies to a certain date,
it returns a value that contains @var{mark}.
+@node Emerge
+@chapter Merging Files with Emerge
+@cindex Emerge
+@cindex merging files
+
+ 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. For other ways to compare files, see @ref{Comparing Files,,,
+emacs, the Emacs Manual} and @ref{Top, Ediff,, ediff, The Ediff
+Manual}.
+
+@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.
+@end menu
+
+@node Overview of Emerge
+@section Overview of Emerge
+
+ To start Emerge, run one of these four commands:
+
+@table @kbd
+@item M-x emerge-files
+@findex emerge-files
+Merge two specified files.
+
+@item M-x emerge-files-with-ancestor
+@findex emerge-files-with-ancestor
+Merge two specified files, with reference to a common ancestor.
+
+@item M-x emerge-buffers
+@findex emerge-buffers
+Merge two buffers.
+
+@item M-x emerge-buffers-with-ancestor
+@findex emerge-buffers-with-ancestor
+Merge two buffers with reference to a common ancestor in a third
+buffer.
+@end table
+
+@cindex merge buffer (Emerge)
+@cindex A and B buffers (Emerge)
+ The Emerge commands compare two files or buffers, and display the
+comparison in three buffers: one for each input text (the @dfn{A buffer}
+and the @dfn{B buffer}), and one (the @dfn{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.
+@xref{Narrowing,,, emacs, the Emacs Manual}.
+
+
+ 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
+@samp{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
+@dfn{merge commands} in the merge buffer (@pxref{Merge Commands}).
+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 @dfn{selected} difference. This
+difference is marked off in the three buffers like this:
+
+@example
+vvvvvvvvvvvvvvvvvvvv
+@var{text that differs}
+^^^^^^^^^^^^^^^^^^^^
+@end example
+
+@noindent
+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 @kbd{C-x C-w}. If you give a
+numeric argument to @code{emerge-files} or
+@code{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 @kbd{C-]}, the Emerge command does not
+save the output buffer, but you can save it yourself if you wish.
+
+@node Submodes of Emerge
+@section 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 @kbd{C-c C-c}, and the normal Emacs
+commands are also available. This allows editing the merge buffer, but
+slows down Emerge operations.
+
+ Use @kbd{e} to switch to Edit mode, and @kbd{C-c C-c f} to switch to
+Fast mode. The mode line indicates Edit and Fast modes with @samp{E}
+and @samp{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 @kbd{a} and @kbd{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 @samp{A}.
+
+ If Skip Prefers mode is in effect, the @kbd{n} and @kbd{p} commands
+skip over differences in states prefer-A and prefer-B (@pxref{State of
+Difference}). Thus you see only differences for which neither version
+is presumed ``correct.'' The mode line indicates Skip Prefers mode with
+@samp{S}.
+
+@findex emerge-auto-advance-mode
+@findex emerge-skip-prefers-mode
+ Use the command @kbd{s a} (@code{emerge-auto-advance-mode}) to set or
+clear Auto Advance mode. Use @kbd{s s}
+(@code{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.
+
+@node State of Difference
+@section State of a Difference
+
+ In the merge buffer, a difference is marked with lines of @samp{v} and
+@samp{^} characters. Each difference has one of these seven states:
+
+@table @asis
+@item A
+The difference is showing the A version. The @kbd{a} command always
+produces this state; the mode line indicates it with @samp{A}.
+
+@item B
+The difference is showing the B version. The @kbd{b} command always
+produces this state; the mode line indicates it with @samp{B}.
+
+@item default-A
+@itemx 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 @kbd{d a} chooses default-A as the default state, and @kbd{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 @kbd{d a} and @kbd{d b} between sections.
+
+@item prefer-A
+@itemx prefer-B
+The difference is showing the A or B state because it is
+@dfn{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 @samp{A*} and @samp{B*}.
+
+@item combined
+The difference is showing a combination of the A and B states, as a
+result of the @kbd{x c} or @kbd{x C} commands.
+
+Once a difference is in this state, the @kbd{a} and @kbd{b} commands
+don't do anything to it unless you give them a numeric argument.
+
+The mode line displays this state as @samp{comb}.
+@end table
+
+@node Merge Commands
+@section Merge Commands
+
+ Here are the Merge commands for Fast mode; in Edit mode, precede them
+with @kbd{C-c C-c}:
+
+@table @kbd
+@item p
+Select the previous difference.
+
+@item n
+Select the next difference.
+
+@item a
+Choose the A version of this difference.
+
+@item b
+Choose the B version of this difference.
+
+@item C-u @var{n} j
+Select difference number @var{n}.
+
+@item .
+Select the difference containing point. You can use this command in the
+merge buffer or in the A or B buffer.
+
+@item q
+Quit---finish the merge.
+
+@item C-]
+Abort---exit merging and do not save the output.
+
+@item f
+Go into Fast mode. (In Edit mode, this is actually @kbd{C-c C-c f}.)
+
+@item e
+Go into Edit mode.
+
+@item l
+Recenter (like @kbd{C-l}) all three windows.
+
+@item -
+Specify part of a prefix numeric argument.
+
+@item @var{digit}
+Also specify part of a prefix numeric argument.
+
+@item d a
+Choose the A version as the default from here down in
+the merge buffer.
+
+@item d b
+Choose the B version as the default from here down in
+the merge buffer.
+
+@item c a
+Copy the A version of this difference into the kill ring.
+
+@item c b
+Copy the B version of this difference into the kill ring.
+
+@item i a
+Insert the A version of this difference at point.
+
+@item i b
+Insert the B version of this difference at point.
+
+@item m
+Put point and mark around the difference.
+
+@item ^
+Scroll all three windows down (like @kbd{M-v}).
+
+@item v
+Scroll all three windows up (like @kbd{C-v}).
+
+@item <
+Scroll all three windows left (like @kbd{C-x <}).
+
+@item >
+Scroll all three windows right (like @kbd{C-x >}).
+
+@item |
+Reset horizontal scroll on all three windows.
+
+@item x 1
+Shrink the merge window to one line. (Use @kbd{C-u l} to restore it
+to full size.)
+
+@item x c
+Combine the two versions of this difference (@pxref{Combining in
+Emerge}).
+
+@item x f
+Show the names of the files/buffers Emerge is operating on, in a Help
+window. (Use @kbd{C-u l} to restore windows.)
+
+@item x j
+Join this difference with the following one.
+(@kbd{C-u x j} joins this difference with the previous one.)
+
+@item 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.
+
+@item x t
+Trim identical lines off the top and bottom of the difference.
+Such lines occur when the A and B versions are
+identical but differ from the ancestor version.
+@end table
+
+@node Exiting Emerge
+@section Exiting Emerge
+
+ The @kbd{q} command (@code{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.
+
+ @kbd{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 @code{t} for successful completion, or @code{nil} if you
+abort.
+
+@node Combining in Emerge
+@section Combining the Two Versions
+
+ Sometimes you want to keep @emph{both} alternatives for a particular
+difference. To do this, use @kbd{x c}, which edits the merge buffer
+like this:
+
+@example
+@group
+#ifdef NEW
+@var{version from A buffer}
+#else /* not NEW */
+@var{version from B buffer}
+#endif /* not NEW */
+@end group
+@end example
+
+@noindent
+@vindex emerge-combine-versions-template
+While this example shows C preprocessor conditionals delimiting the two
+alternative versions, you can specify the strings to use by setting
+the variable @code{emerge-combine-versions-template} to a string of your
+choice. In the string, @samp{%a} says where to put version A, and
+@samp{%b} says where to put version B. The default setting, which
+produces the results shown above, looks like this:
+
+@example
+@group
+"#ifdef NEW\n%a#else /* not NEW */\n%b#endif /* not NEW */\n"
+@end group
+@end example
+
+@node Fine Points of Emerge
+@section 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 @code{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.
+
+@vindex emerge-startup-hook
+ After setting up the merge, Emerge runs the hook
+@code{emerge-startup-hook}. @xref{Hooks,,, emacs, the Emacs Manual}.
+
+@node Picture Mode
+@chapter Editing Pictures
+@cindex pictures
+@cindex making pictures out of text characters
+@findex edit-picture
+
+ To edit a picture made out of text characters (for example, a picture
+of the division of a register into fields, as a comment in a program),
+use the command @kbd{M-x edit-picture} to enter Picture mode.
+
+ In Picture mode, editing is based on the @dfn{quarter-plane} model of
+text, according to which the text characters lie studded on an area that
+stretches infinitely far to the right and downward. The concept of the end
+of a line does not exist in this model; the most you can say is where the
+last nonblank character on the line is found.
+
+ Of course, Emacs really always considers text as a sequence of
+characters, and lines really do have ends. But Picture mode replaces
+the most frequently-used commands with variants that simulate the
+quarter-plane model of text. They do this by inserting spaces or by
+converting tabs to spaces.
+
+ Most of the basic editing commands of Emacs are redefined by Picture mode
+to do essentially the same thing but in a quarter-plane way. In addition,
+Picture mode defines various keys starting with the @kbd{C-c} prefix to
+run special picture editing commands.
+
+ One of these keys, @kbd{C-c C-c}, is particularly important. Often a
+picture is part of a larger file that is usually edited in some other
+major mode. @kbd{M-x edit-picture} records the name of the previous
+major mode so you can use the @kbd{C-c C-c} command
+(@code{picture-mode-exit}) later to go back to that mode. @kbd{C-c C-c}
+also deletes spaces from the ends of lines, unless given a numeric
+argument.
+
+ The special commands of Picture mode all work in other modes (provided
+the @file{picture} library is loaded), but are not bound to keys except
+in Picture mode. The descriptions below talk of moving ``one column''
+and so on, but all the picture mode commands handle numeric arguments as
+their normal equivalents do.
+
+@vindex picture-mode-hook
+ Turning on Picture mode runs the hook @code{picture-mode-hook}.
+Additional extensions to Picture mode can be found in
+@file{artist.el}.
+
+@menu
+* Basic Picture:: Basic concepts and simple commands of Picture Mode.
+* Insert in Picture:: Controlling direction of cursor motion
+ after "self-inserting" characters.
+* Tabs in Picture:: Various features for tab stops and indentation.
+* Rectangles in Picture:: Clearing and superimposing rectangles.
+@end menu
+
+@node Basic Picture
+@section Basic Editing in Picture Mode
+
+@findex picture-forward-column
+@findex picture-backward-column
+@findex picture-move-down
+@findex picture-move-up
+@cindex editing in Picture mode
+
+ Most keys do the same thing in Picture mode that they usually do, but
+do it in a quarter-plane style. For example, @kbd{C-f} is rebound to
+run @code{picture-forward-column}, a command which moves point one
+column to the right, inserting a space if necessary so that the actual
+end of the line makes no difference. @kbd{C-b} is rebound to run
+@code{picture-backward-column}, which always moves point left one
+column, converting a tab to multiple spaces if necessary. @kbd{C-n} and
+@kbd{C-p} are rebound to run @code{picture-move-down} and
+@code{picture-move-up}, which can either insert spaces or convert tabs
+as necessary to make sure that point stays in exactly the same column.
+@kbd{C-e} runs @code{picture-end-of-line}, which moves to after the last
+nonblank character on the line. There is no need to change @kbd{C-a},
+as the choice of screen model does not affect beginnings of
+lines.
+
+@findex picture-newline
+ Insertion of text is adapted to the quarter-plane screen model
+through the use of Overwrite mode (@pxref{Minor Modes,,, emacs, the
+Emacs Manual}.) Self-inserting characters replace existing text,
+column by column, rather than pushing existing text to the right.
+@key{RET} runs @code{picture-newline}, which just moves to the
+beginning of the following line so that new text will replace that
+line.
+
+@findex picture-backward-clear-column
+@findex picture-clear-column
+@findex picture-clear-line
+ In Picture mode, the commands that normally delete or kill text,
+instead erase text (replacing it with spaces). @key{DEL}
+(@code{picture-backward-clear-column}) replaces the preceding
+character with a space rather than removing it; this moves point
+backwards. @kbd{C-d} (@code{picture-clear-column}) replaces the next
+character or characters with spaces, but does not move point. (If you
+want to clear characters to spaces and move forward over them, use
+@key{SPC}.) @kbd{C-k} (@code{picture-clear-line}) really kills the
+contents of lines, but does not delete the newlines from the buffer.
+
+@findex picture-open-line
+ To do actual insertion, you must use special commands. @kbd{C-o}
+(@code{picture-open-line}) creates a blank line after the current
+line; it never splits a line. @kbd{C-M-o} (@code{split-line}) makes
+sense in Picture mode, so it is not changed. @kbd{C-j}
+(@code{picture-duplicate-line}) inserts another line with the same
+contents below the current line.
+
+@kindex C-c C-d @r{(Picture mode)}
+ To do actual deletion in Picture mode, use @kbd{C-w}, @kbd{C-c C-d}
+(which is defined as @code{delete-char}, as @kbd{C-d} is in other
+modes), or one of the picture rectangle commands (@pxref{Rectangles in
+Picture}).
+
+@node Insert in Picture
+@section Controlling Motion after Insert
+
+@findex picture-movement-up
+@findex picture-movement-down
+@findex picture-movement-left
+@findex picture-movement-right
+@findex picture-movement-nw
+@findex picture-movement-ne
+@findex picture-movement-sw
+@findex picture-movement-se
+@kindex C-c < @r{(Picture mode)}
+@kindex C-c > @r{(Picture mode)}
+@kindex C-c ^ @r{(Picture mode)}
+@kindex C-c . @r{(Picture mode)}
+@kindex C-c ` @r{(Picture mode)}
+@kindex C-c ' @r{(Picture mode)}
+@kindex C-c / @r{(Picture mode)}
+@kindex C-c \ @r{(Picture mode)}
+ Since ``self-inserting'' characters in Picture mode overwrite and move
+point, there is no essential restriction on how point should be moved.
+Normally point moves right, but you can specify any of the eight
+orthogonal or diagonal directions for motion after a ``self-inserting''
+character. This is useful for drawing lines in the buffer.
+
+@table @kbd
+@item C-c <
+@itemx C-c @key{LEFT}
+Move left after insertion (@code{picture-movement-left}).
+@item C-c >
+@itemx C-c @key{RIGHT}
+Move right after insertion (@code{picture-movement-right}).
+@item C-c ^
+@itemx C-c @key{UP}
+Move up after insertion (@code{picture-movement-up}).
+@item C-c .
+@itemx C-c @key{DOWN}
+Move down after insertion (@code{picture-movement-down}).
+@item C-c `
+@itemx C-c @key{HOME}
+Move up and left (``northwest'') after insertion (@code{picture-movement-nw}).
+@item C-c '
+@itemx C-c @key{PAGEUP}
+Move up and right (``northeast'') after insertion
+(@code{picture-movement-ne}).
+@item C-c /
+@itemx C-c @key{END}
+Move down and left (``southwest'') after insertion
+@*(@code{picture-movement-sw}).
+@item C-c \
+@itemx C-c @key{PAGEDOWN}
+Move down and right (``southeast'') after insertion
+@*(@code{picture-movement-se}).
+@end table
+
+@kindex C-c C-f @r{(Picture mode)}
+@kindex C-c C-b @r{(Picture mode)}
+@findex picture-motion
+@findex picture-motion-reverse
+ Two motion commands move based on the current Picture insertion
+direction. The command @kbd{C-c C-f} (@code{picture-motion}) moves in the
+same direction as motion after ``insertion'' currently does, while @kbd{C-c
+C-b} (@code{picture-motion-reverse}) moves in the opposite direction.
+
+@node Tabs in Picture
+@section Picture Mode Tabs
+
+@kindex M-TAB @r{(Picture mode)}
+@findex picture-tab-search
+@vindex picture-tab-chars
+ Two kinds of tab-like action are provided in Picture mode. Use
+@kbd{M-@key{TAB}} (@code{picture-tab-search}) for context-based tabbing.
+With no argument, it moves to a point underneath the next
+``interesting'' character that follows whitespace in the previous
+nonblank line. ``Next'' here means ``appearing at a horizontal position
+greater than the one point starts out at.'' With an argument, as in
+@kbd{C-u M-@key{TAB}}, this command moves to the next such interesting
+character in the current line. @kbd{M-@key{TAB}} does not change the
+text; it only moves point. ``Interesting'' characters are defined by
+the variable @code{picture-tab-chars}, which should define a set of
+characters. The syntax for this variable is like the syntax used inside
+of @samp{[@dots{}]} in a regular expression---but without the @samp{[}
+and the @samp{]}. Its default value is @code{"!-~"}.
+
+@findex picture-tab
+ @key{TAB} itself runs @code{picture-tab}, which operates based on the
+current tab stop settings; it is the Picture mode equivalent of
+@code{tab-to-tab-stop}. Normally it just moves point, but with a numeric
+argument it clears the text that it moves over.
+
+@kindex C-c TAB @r{(Picture mode)}
+@findex picture-set-tab-stops
+ The context-based and tab-stop-based forms of tabbing are brought
+together by the command @kbd{C-c @key{TAB}} (@code{picture-set-tab-stops}).
+This command sets the tab stops to the positions which @kbd{M-@key{TAB}}
+would consider significant in the current line. The use of this command,
+together with @key{TAB}, can get the effect of context-based tabbing. But
+@kbd{M-@key{TAB}} is more convenient in the cases where it is sufficient.
+
+ It may be convenient to prevent use of actual tab characters in
+pictures. For example, this prevents @kbd{C-x @key{TAB}} from messing
+up the picture. You can do this by setting the variable
+@code{indent-tabs-mode} to @code{nil}.
+
+@node Rectangles in Picture
+@section Picture Mode Rectangle Commands
+@cindex rectangles and Picture mode
+@cindex Picture mode and rectangles
+
+ Picture mode defines commands for working on rectangular pieces of
+the text in ways that fit with the quarter-plane model. The standard
+rectangle commands may also be useful. @xref{Rectangles,,, emacs, the
+Emacs Manual}.
+
+@table @kbd
+@item C-c C-k
+Clear out the region-rectangle with spaces
+(@code{picture-clear-rectangle}). With argument, delete the text.
+@item C-c C-w @var{r}
+Similar, but save rectangle contents in register @var{r} first
+(@code{picture-clear-rectangle-to-register}).
+@item C-c C-y
+Copy last killed rectangle into the buffer by overwriting, with upper
+left corner at point (@code{picture-yank-rectangle}). With argument,
+insert instead.
+@item C-c C-x @var{r}
+Similar, but use the rectangle in register @var{r}
+(@code{picture-yank-rectangle-from-register}).
+@end table
+
+@kindex C-c C-k @r{(Picture mode)}
+@kindex C-c C-w @r{(Picture mode)}
+@findex picture-clear-rectangle
+@findex picture-clear-rectangle-to-register
+ The picture rectangle commands @kbd{C-c C-k}
+(@code{picture-clear-rectangle}) and @kbd{C-c C-w}
+(@code{picture-clear-rectangle-to-register}) differ from the standard
+rectangle commands in that they normally clear the rectangle instead of
+deleting it; this is analogous with the way @kbd{C-d} is changed in Picture
+mode.
+
+ However, deletion of rectangles can be useful in Picture mode, so
+these commands delete the rectangle if given a numeric argument.
+@kbd{C-c C-k} either with or without a numeric argument saves the
+rectangle for @kbd{C-c C-y}.
+
+@kindex C-c C-y @r{(Picture mode)}
+@kindex C-c C-x @r{(Picture mode)}
+@findex picture-yank-rectangle
+@findex picture-yank-rectangle-from-register
+ The Picture mode commands for yanking rectangles differ from the
+standard ones in that they overwrite instead of inserting. This is
+the same way that Picture mode insertion of other text differs from
+other modes. @kbd{C-c C-y} (@code{picture-yank-rectangle}) inserts
+(by overwriting) the rectangle that was most recently killed, while
+@kbd{C-c C-x} (@code{picture-yank-rectangle-from-register}) does
+likewise for the rectangle found in a specified register.
+
+@node Fortran
+@chapter Fortran Mode
+@cindex Fortran mode
+@cindex mode, Fortran
+
+ 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 support for 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 @kbd{M-x fortran-mode} to switch to this major mode. This
+command runs the hook @code{fortran-mode-hook}. @xref{Hooks,,, emacs,
+the Emacs Manual}.
+
+@cindex Fortran77 and Fortran90
+@findex f90-mode
+@findex fortran-mode
+ Fortran mode is meant for editing Fortran77 ``fixed format'' (and also
+``tab format'') source code. For editing the modern Fortran90 or
+Fortran95 ``free format'' source code, use F90 mode (@code{f90-mode}).
+Emacs normally uses Fortran mode for files with extension @samp{.f},
+@samp{.F} or @samp{.for}, and F90 mode for the extension @samp{.f90} and
+@samp{.f95}. GNU Fortran supports both kinds of format.
+
+@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 support for Fortran.
+* Columns: Fortran Columns. Measuring columns for valid Fortran.
+* Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords.
+@end menu
+
+@node Fortran Motion
+@section Motion Commands
+
+ In addition to the normal commands for moving by and operating on
+``defuns'' (Fortran subprograms---functions and subroutines, as well as
+modules for F90 mode), Fortran mode provides special commands to move by
+statements and other program units.
+
+@table @kbd
+@kindex C-c C-n @r{(Fortran mode)}
+@findex fortran-next-statement
+@findex f90-next-statement
+@item C-c C-n
+Move to the beginning of the next statement
+(@code{fortran-next-statement}/@code{f90-next-statement}).
+
+@kindex C-c C-p @r{(Fortran mode)}
+@findex fortran-previous-statement
+@findex f90-previous-statement
+@item C-c C-p
+Move to the beginning of the previous statement
+(@code{fortran-previous-statement}/@code{f90-previous-statement}).
+If there is no previous statement (i.e. if called from the first
+statement in the buffer), move to the start of the buffer.
+
+@kindex C-c C-e @r{(F90 mode)}
+@findex f90-next-block
+@item C-c C-e
+Move point forward to the start of the next code block
+(@code{f90-next-block}). A code block is a subroutine,
+@code{if}--@code{endif} statement, and so forth. This command exists
+for F90 mode only, not Fortran mode. With a numeric argument, this
+moves forward that many blocks.
+
+@kindex C-c C-a @r{(F90 mode)}
+@findex f90-previous-block
+@item C-c C-a
+Move point backward to the previous code block
+(@code{f90-previous-block}). This is like @code{f90-next-block}, but
+moves backwards.
+
+@kindex C-M-n @r{(Fortran mode)}
+@findex fortran-end-of-block
+@findex f90-end-of-block
+@item C-M-n
+Move to the end of the current code block
+(@code{fortran-end-of-block}/@code{f90-end-of-block}). With a numeric
+agument, move forward that number of blocks. The mark is set before
+moving point. The F90 mode version of this command checks for
+consistency of block types and labels (if present), but it does not
+check the outermost block since that may be incomplete.
+
+@kindex C-M-p @r{(Fortran mode)}
+@findex fortran-beginning-of-block
+@findex f90-beginning-of-block
+@item C-M-p
+Move to the start of the current code block
+(@code{fortran-beginning-of-block}/@code{f90-beginning-of-block}). This
+is like @code{fortran-end-of-block}, but moves backwards.
+@end table
+
+@node Fortran Indent
+@section 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, fixed (or tab) format Fortran.
+
+@menu
+* Commands: ForIndent Commands. Commands for indenting and filling 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.
+@end menu
+
+@node ForIndent Commands
+@subsection Fortran Indentation and Filling Commands
+
+@table @kbd
+@item C-M-j
+Break the current line at point and set up a continuation line
+(@code{fortran-split-line}).
+@item M-^
+Join this line to the previous line (@code{fortran-join-line}).
+@item C-M-q
+Indent all the lines of the subprogram point is in
+(@code{fortran-indent-subprogram}).
+@item M-q
+Fill a comment block or statement.
+@end table
+
+@kindex C-M-q @r{(Fortran mode)}
+@findex fortran-indent-subprogram
+ The key @kbd{C-M-q} runs @code{fortran-indent-subprogram}, a command
+to reindent all the lines of the Fortran subprogram (function or
+subroutine) containing point.
+
+@kindex C-M-j @r{(Fortran mode)}
+@findex fortran-split-line
+ The key @kbd{C-M-j} runs @code{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.
+
+@kindex M-^ @r{(Fortran mode)}
+@kindex C-c C-d @r{(Fortran mode)}
+@findex fortran-join-line
+ @kbd{M-^} or @kbd{C-c C-d} runs the command @code{fortran-join-line},
+which joins a continuation line back to the previous line, roughly as
+the inverse of @code{fortran-split-line}. The point must be on a
+continuation line when this command is invoked.
+
+@kindex M-q @r{(Fortran mode)}
+@kbd{M-q} in Fortran mode fills the comment block or statement that
+point is in. This removes any excess statement continuations.
+
+@node ForIndent Cont
+@subsection Continuation Lines
+@cindex Fortran continuation lines
+
+@vindex fortran-continuation-string
+ Most Fortran77 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 @dfn{fixed
+format}. (In GNU Emacs we always count columns from 0; but note that
+the Fortran standard counts from 1.) The variable
+@code{fortran-continuation-string} specifies what character to put in
+column 5. A line that starts with a tab character followed by any digit
+except @samp{0} is also a continuation line. We call this style of
+continuation @dfn{tab format}. (Fortran90 introduced ``free format'',
+with another style of continuation lines).
+
+@vindex indent-tabs-mode @r{(Fortran mode)}
+@vindex fortran-analyze-depth
+@vindex fortran-tab-mode-default
+ Fortran mode can use either style of continuation line. When you
+enter Fortran mode, it tries to deduce the proper continuation style
+automatically from the buffer contents. It does this by scanning up to
+@code{fortran-analyze-depth} (default 100) lines from the start of the
+buffer. The first line that begins with either a tab character or six
+spaces determines the choice. If the scan fails (for example, if the
+buffer is new and therefore empty), the value of
+@code{fortran-tab-mode-default} (@code{nil} for fixed format, and
+non-@code{nil} for tab format) is used. @samp{/t} in the mode line
+indicates tab format is selected. Fortran mode sets the value of
+@code{indent-tabs-mode} accordingly.
+
+ If the text on a line starts with the Fortran continuation marker
+@samp{$}, 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 @key{TAB}, it converts the line to the current
+continuation style. When you split a Fortran statement with
+@kbd{C-M-j}, 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.
+
+@node ForIndent Num
+@subsection 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.)
+
+@vindex fortran-line-number-indent
+ Line numbers of four digits or less are normally indented one space.
+The variable @code{fortran-line-number-indent} controls this; it
+specifies the maximum indentation a line number can have. The default
+value of the variable is 1. Fortran mode tries to prevent line number
+digits passing column 4, reducing the indentation below the specified
+maximum if necessary. If @code{fortran-line-number-indent} has the
+value 5, line numbers are right-justified to end in column 4.
+
+@vindex fortran-electric-line-number
+ 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
+@code{fortran-electric-line-number} to @code{nil}.
+
+
+@node ForIndent Conv
+@subsection 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:
+
+@itemize @bullet
+@item
+Two nested @samp{do} loops never share a @samp{continue} statement.
+
+@item
+Fortran keywords such as @samp{if}, @samp{else}, @samp{then}, @samp{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 @samp{else if} or @samp{end do}
+are acceptable, but the second word should be on the same line as the
+first and not on a continuation line.
+@end itemize
+
+@noindent
+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.
+
+@node ForIndent Vars
+@subsection Variables for Fortran Indentation
+
+@vindex fortran-do-indent
+@vindex fortran-if-indent
+@vindex fortran-structure-indent
+@vindex fortran-continuation-indent
+@vindex fortran-check-all-num@dots{}
+@vindex fortran-minimum-statement-indent@dots{}
+ Several additional variables control how Fortran indentation works:
+
+@table @code
+@item fortran-do-indent
+Extra indentation within each level of @samp{do} statement (default 3).
+
+@item fortran-if-indent
+Extra indentation within each level of @samp{if}, @samp{select case}, or
+@samp{where} statements (default 3).
+
+@item fortran-structure-indent
+Extra indentation within each level of @samp{structure}, @samp{union},
+@samp{map}, or @samp{interface} statements (default 3).
+
+@item fortran-continuation-indent
+Extra indentation for bodies of continuation lines (default 5).
+
+@item fortran-check-all-num-for-matching-do
+In Fortran77, a numbered @samp{do} statement is ended by any statement
+with a matching line number. It is common (but not compulsory) to use a
+@samp{continue} statement for this purpose. If this variable has a
+non-@code{nil} value, indenting any numbered statement must check for a
+@samp{do} that ends there. If you always end @samp{do} statements with
+a @samp{continue} line (or if you use the more modern @samp{enddo}),
+then you can speed up indentation by setting this variable to
+@code{nil}. The default is @code{nil}.
+
+@item fortran-blink-matching-if
+If this is @code{t}, indenting an @samp{endif} (or @samp{enddo}
+statement moves the cursor momentarily to the matching @samp{if} (or
+@samp{do}) statement to show where it is. The default is @code{nil}.
+
+@item 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.
+
+@item 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.
+@end table
+
+The variables controlling the indentation of comments are described in
+the following section.
+
+@node Fortran Comments
+@section Fortran Comments
+
+ The usual Emacs comment commands assume that a comment can follow a
+line of code. In Fortran77, 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.
+
+@vindex fortran-comment-line-start
+ Fortran mode can also handle the Fortran90 comment syntax where comments
+start with @samp{!} and can follow other text. Because only some Fortran77
+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
+@code{fortran-comment-line-start} to @samp{"!"}.
+
+@table @kbd
+@item M-;
+Align comment or insert new comment (@code{fortran-indent-comment}).
+
+@item C-x ;
+Applies to nonstandard @samp{!} comments only.
+
+@item C-c ;
+Turn all lines of the region into comments, or (with argument) turn them back
+into real code (@code{fortran-comment-region}).
+@end table
+
+@findex fortran-indent-comment
+ @kbd{M-;} in Fortran mode is redefined as the command
+@code{fortran-indent-comment}. Like the usual @kbd{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 @samp{!}
+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 @samp{!} 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
+@code{fortran-comment-indent-style} to one of these values:
+
+@vindex fortran-comment-indent-style
+@vindex fortran-comment-line-extra-indent
+@table @code
+@item fixed
+Align the text at a fixed column, which is the sum of
+@code{fortran-comment-line-extra-indent} and the minimum statement
+indentation. This is the default.
+
+The minimum statement indentation is
+@code{fortran-minimum-statement-indent-fixed} for fixed format
+continuation line style and @code{fortran-minimum-statement-indent-tab}
+for tab format style.
+
+@item relative
+Align the text as if it were a line of code, but with an additional
+@code{fortran-comment-line-extra-indent} columns of indentation.
+
+@item nil
+Don't move text in full-line comments automatically.
+@end table
+
+@vindex fortran-comment-indent-char
+ In addition, you can specify the character to be used to indent within
+full-line comments by setting the variable
+@code{fortran-comment-indent-char} to the single-character string you want
+to use.
+
+@vindex fortran-directive-re
+ Compiler directive lines, or preprocessor lines, have much the same
+appearance as comment lines. It is important, though, that such lines
+never be indented at all, no matter what the value of
+@code{fortran-comment-indent-style}. The variable
+@code{fortran-directive-re} is a regular expression that specifies which
+lines are directives. Matching lines are never indented, and receive
+distinctive font-locking.
+
+ The normal Emacs comment command @kbd{C-x ;} has not been redefined. If
+you use @samp{!} comments, this command can be used with them. Otherwise
+it is useless in Fortran mode.
+
+@kindex C-c ; @r{(Fortran mode)}
+@findex fortran-comment-region
+@vindex fortran-comment-region
+ The command @kbd{C-c ;} (@code{fortran-comment-region}) turns all the
+lines of the region into comments by inserting the string @samp{C$$$} at
+the front of each one. With a numeric argument, it turns the region
+back into live code by deleting @samp{C$$$} from the front of each line
+in it. The string used for these comments can be controlled by setting
+the variable @code{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.
+
+@node Fortran Autofill
+@section Auto Fill in Fortran Mode
+
+ Fortran mode has specialized support for Auto Fill mode, which is a
+minor mode that automatically splits statements as you insert them
+when they become too wide. Splitting a statement involves making
+continuation lines using @code{fortran-continuation-string}
+(@pxref{ForIndent Cont}). This splitting happens when you type
+@key{SPC}, @key{RET}, or @key{TAB}, and also in the Fortran
+indentation commands. You activate Auto Fill in Fortran mode in the
+normal way. @xref{Auto Fill,,, emacs, the Emacs Manual}.
+
+@vindex fortran-break-before-delimiters
+ Auto Fill breaks lines at spaces or delimiters when the lines get
+longer than the desired width (the value of @code{fill-column}). The
+delimiters (besides whitespace) that Auto Fill can break at are
+@samp{+}, @samp{-}, @samp{/}, @samp{*}, @samp{=}, @samp{<}, @samp{>},
+and @samp{,}. The line break comes after the delimiter if the
+variable @code{fortran-break-before-delimiters} is @code{nil}.
+Otherwise (and by default), the break comes before the delimiter.
+
+ To enable Auto Fill in all Fortran buffers, add
+@code{turn-on-auto-fill} to @code{fortran-mode-hook}. @xref{Hooks,,,
+emacs, the Emacs Manual}.
+
+@node Fortran Columns
+@section Checking Columns in Fortran
+
+@table @kbd
+@item C-c C-r
+Display a ``column ruler'' momentarily above the current line
+(@code{fortran-column-ruler}).
+@item C-c C-w
+Split the current window horizontally temporarily so that it is 72
+columns wide (@code{fortran-window-create-momentarily}). This may
+help you avoid making lines longer than the 72-character limit that
+some Fortran compilers impose.
+@item C-u C-c C-w
+Split the current window horizontally so that it is 72 columns wide
+(@code{fortran-window-create}). You can then continue editing.
+@item M-x fortran-strip-sequence-nos
+Delete all text in column 72 and beyond.
+@end table
+
+@kindex C-c C-r @r{(Fortran mode)}
+@findex fortran-column-ruler
+ The command @kbd{C-c C-r} (@code{fortran-column-ruler}) shows a column
+ruler momentarily above the current line. The comment ruler is two lines
+of text that show you the locations of columns with special significance in
+Fortran programs. Square brackets show the limits of the columns for line
+numbers, and curly brackets show the limits of the columns for the
+statement body. Column numbers appear above them.
+
+ Note that the column numbers count from zero, as always in GNU Emacs.
+As a result, the numbers may be one less than those you are familiar
+with; but the positions they indicate in the line are standard for
+Fortran.
+
+@vindex fortran-column-ruler-fixed
+@vindex fortran-column-ruler-tabs
+ The text used to display the column ruler depends on the value of the
+variable @code{indent-tabs-mode}. If @code{indent-tabs-mode} is
+@code{nil}, then the value of the variable
+@code{fortran-column-ruler-fixed} is used as the column ruler.
+Otherwise, the value of the variable @code{fortran-column-ruler-tab} is
+displayed. By changing these variables, you can change the column ruler
+display.
+
+@kindex C-c C-w @r{(Fortran mode)}
+@findex fortran-window-create-momentarily
+ @kbd{C-c C-w} (@code{fortran-window-create-momentarily}) temporarily
+splits the current window horizontally, making a window 72 columns
+wide, so you can see any lines that are too long. Type a space to
+restore the normal width.
+
+@kindex C-u C-c C-w @r{(Fortran mode)}
+@findex fortran-window-create
+ You can also split the window horizontally and continue editing with
+the split in place. To do this, use @kbd{C-u C-c C-w} (@code{M-x
+fortran-window-create}). By editing in this window you can
+immediately see when you make a line too wide to be correct Fortran.
+
+@findex fortran-strip-sequence-nos
+ The command @kbd{M-x fortran-strip-sequence-nos} deletes all text in
+column 72 and beyond, on all lines in the current buffer. This is the
+easiest way to get rid of old sequence numbers.
+
+@node Fortran Abbrev
+@section Fortran Keyword Abbrevs
+
+ Fortran mode provides many built-in abbrevs for common keywords and
+declarations. These are the same sort of abbrev that you can define
+yourself. To use them, you must turn on Abbrev mode.
+@xref{Abbrevs,,, emacs, the Emacs Manual}.
+
+ The built-in abbrevs are unusual in one way: they all start with a
+semicolon. You cannot normally use semicolon in an abbrev, but Fortran
+mode makes this possible by changing the syntax of semicolon to ``word
+constituent.''
+
+ For example, one built-in Fortran abbrev is @samp{;c} for
+@samp{continue}. If you insert @samp{;c} and then insert a punctuation
+character such as a space or a newline, the @samp{;c} expands automatically
+to @samp{continue}, provided Abbrev mode is enabled.@refill
+
+ Type @samp{;?} or @samp{;C-h} to display a list of all the built-in
+Fortran abbrevs and what they stand for.
@node Index
@unnumbered Index
* Format of ChangeLog:: What the change log file looks like.
* Tags:: Go direct to any function in your program in one
command. Tags remembers which file it is in.
-* Emerge:: A convenient way of merging two versions of a program.
@end menu
@node Change Log
You can also use the collection of tag names to complete a symbol
name in the buffer. @xref{Symbol Completion}.
-@node Emerge
-@section Merging Files with Emerge
-@cindex Emerge
-@cindex merging files
-
- 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 @ref{Comparing Files}, for other ways to compare
-files, and @ref{Top, Ediff,, ediff, The Ediff Manual}.
-
-@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.
-@end menu
-
-@node Overview of Emerge
-@subsection Overview of Emerge
-
- To start Emerge, run one of these four commands:
-
-@table @kbd
-@item M-x emerge-files
-@findex emerge-files
-Merge two specified files.
-
-@item M-x emerge-files-with-ancestor
-@findex emerge-files-with-ancestor
-Merge two specified files, with reference to a common ancestor.
-
-@item M-x emerge-buffers
-@findex emerge-buffers
-Merge two buffers.
-
-@item M-x emerge-buffers-with-ancestor
-@findex emerge-buffers-with-ancestor
-Merge two buffers with reference to a common ancestor in a third
-buffer.
-@end table
-
-@cindex merge buffer (Emerge)
-@cindex A and B buffers (Emerge)
- The Emerge commands compare two files or buffers, and display the
-comparison in three buffers: one for each input text (the @dfn{A buffer}
-and the @dfn{B buffer}), and one (the @dfn{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
-(@pxref{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
-@samp{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
-@dfn{merge commands} in the merge buffer (@pxref{Merge Commands}).
-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 @dfn{selected} difference. This
-difference is marked off in the three buffers like this:
-
-@example
-vvvvvvvvvvvvvvvvvvvv
-@var{text that differs}
-^^^^^^^^^^^^^^^^^^^^
-@end example
-
-@noindent
-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 @kbd{C-x C-w}. If you give a
-numeric argument to @code{emerge-files} or
-@code{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 @kbd{C-]}, the Emerge command does not
-save the output buffer, but you can save it yourself if you wish.
-
-@node Submodes of Emerge
-@subsection 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 @kbd{C-c C-c}, and the normal Emacs
-commands are also available. This allows editing the merge buffer, but
-slows down Emerge operations.
-
- Use @kbd{e} to switch to Edit mode, and @kbd{C-c C-c f} to switch to
-Fast mode. The mode line indicates Edit and Fast modes with @samp{E}
-and @samp{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 @kbd{a} and @kbd{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 @samp{A}.
-
- If Skip Prefers mode is in effect, the @kbd{n} and @kbd{p} commands
-skip over differences in states prefer-A and prefer-B (@pxref{State of
-Difference}). Thus you see only differences for which neither version
-is presumed ``correct.'' The mode line indicates Skip Prefers mode with
-@samp{S}.
-
-@findex emerge-auto-advance-mode
-@findex emerge-skip-prefers-mode
- Use the command @kbd{s a} (@code{emerge-auto-advance-mode}) to set or
-clear Auto Advance mode. Use @kbd{s s}
-(@code{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.
-
-@node State of Difference
-@subsection State of a Difference
-
- In the merge buffer, a difference is marked with lines of @samp{v} and
-@samp{^} characters. Each difference has one of these seven states:
-
-@table @asis
-@item A
-The difference is showing the A version. The @kbd{a} command always
-produces this state; the mode line indicates it with @samp{A}.
-
-@item B
-The difference is showing the B version. The @kbd{b} command always
-produces this state; the mode line indicates it with @samp{B}.
-
-@item default-A
-@itemx 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 @kbd{d a} chooses default-A as the default state, and @kbd{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 @kbd{d a} and @kbd{d b} between sections.
-
-@item prefer-A
-@itemx prefer-B
-The difference is showing the A or B state because it is
-@dfn{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 @samp{A*} and @samp{B*}.
-
-@item combined
-The difference is showing a combination of the A and B states, as a
-result of the @kbd{x c} or @kbd{x C} commands.
-
-Once a difference is in this state, the @kbd{a} and @kbd{b} commands
-don't do anything to it unless you give them a numeric argument.
-
-The mode line displays this state as @samp{comb}.
-@end table
-
-@node Merge Commands
-@subsection Merge Commands
-
- Here are the Merge commands for Fast mode; in Edit mode, precede them
-with @kbd{C-c C-c}:
-
-@table @kbd
-@item p
-Select the previous difference.
-
-@item n
-Select the next difference.
-
-@item a
-Choose the A version of this difference.
-
-@item b
-Choose the B version of this difference.
-
-@item C-u @var{n} j
-Select difference number @var{n}.
-
-@item .
-Select the difference containing point. You can use this command in the
-merge buffer or in the A or B buffer.
-
-@item q
-Quit---finish the merge.
-
-@item C-]
-Abort---exit merging and do not save the output.
-
-@item f
-Go into Fast mode. (In Edit mode, this is actually @kbd{C-c C-c f}.)
-
-@item e
-Go into Edit mode.
-
-@item l
-Recenter (like @kbd{C-l}) all three windows.
-
-@item -
-Specify part of a prefix numeric argument.
-
-@item @var{digit}
-Also specify part of a prefix numeric argument.
-
-@item d a
-Choose the A version as the default from here down in
-the merge buffer.
-
-@item d b
-Choose the B version as the default from here down in
-the merge buffer.
-
-@item c a
-Copy the A version of this difference into the kill ring.
-
-@item c b
-Copy the B version of this difference into the kill ring.
-
-@item i a
-Insert the A version of this difference at point.
-
-@item i b
-Insert the B version of this difference at point.
-
-@item m
-Put point and mark around the difference.
-
-@item ^
-Scroll all three windows down (like @kbd{M-v}).
-
-@item v
-Scroll all three windows up (like @kbd{C-v}).
-
-@item <
-Scroll all three windows left (like @kbd{C-x <}).
-
-@item >
-Scroll all three windows right (like @kbd{C-x >}).
-
-@item |
-Reset horizontal scroll on all three windows.
-
-@item x 1
-Shrink the merge window to one line. (Use @kbd{C-u l} to restore it
-to full size.)
-
-@item x c
-Combine the two versions of this difference (@pxref{Combining in
-Emerge}).
-
-@item x f
-Show the names of the files/buffers Emerge is operating on, in a Help
-window. (Use @kbd{C-u l} to restore windows.)
-
-@item x j
-Join this difference with the following one.
-(@kbd{C-u x j} joins this difference with the previous one.)
-
-@item 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.
-
-@item x t
-Trim identical lines off the top and bottom of the difference.
-Such lines occur when the A and B versions are
-identical but differ from the ancestor version.
-@end table
-
-@node Exiting Emerge
-@subsection Exiting Emerge
-
- The @kbd{q} command (@code{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.
-
- @kbd{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 @code{t} for successful completion, or @code{nil} if you
-abort.
-
-@node Combining in Emerge
-@subsection Combining the Two Versions
-
- Sometimes you want to keep @emph{both} alternatives for a particular
-difference. To do this, use @kbd{x c}, which edits the merge buffer
-like this:
-
-@example
-@group
-#ifdef NEW
-@var{version from A buffer}
-#else /* not NEW */
-@var{version from B buffer}
-#endif /* not NEW */
-@end group
-@end example
-
-@noindent
-@vindex emerge-combine-versions-template
-While this example shows C preprocessor conditionals delimiting the two
-alternative versions, you can specify the strings to use by setting
-the variable @code{emerge-combine-versions-template} to a string of your
-choice. In the string, @samp{%a} says where to put version A, and
-@samp{%b} says where to put version B. The default setting, which
-produces the results shown above, looks like this:
-
-@example
-@group
-"#ifdef NEW\n%a#else /* not NEW */\n%b#endif /* not NEW */\n"
-@end group
-@end example
-
-@node Fine Points of Emerge
-@subsection 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 @code{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.
-
-@vindex emerge-startup-hook
- After setting up the merge, Emerge runs the hook
-@code{emerge-startup-hook} (@pxref{Hooks}).
-
@ignore
arch-tag: b9d83dfb-82ea-4ff6-bab5-05a3617091fb
@end ignore
* Misc for Programs:: Other Emacs features useful for editing programs.
* C Modes:: Special commands of C, C++, Objective-C,
Java, and Pike modes.
-* Fortran:: Fortran mode and its special features.
* Asm Mode:: Asm mode and its special features.
@end menu
Separate manuals are available for the modes for Ada (@pxref{Top, , Ada
Mode, ada-mode, Ada Mode}), C/C++/Objective C/Java/Corba IDL/Pike/AWK
(@pxref{Top, , CC Mode, ccmode, CC Mode}) and the IDLWAVE modes
-(@pxref{Top, , IDLWAVE, idlwave, IDLWAVE User Manual}).
+(@pxref{Top, , IDLWAVE, idlwave, IDLWAVE User Manual}). For Fortran
+mode, @inforef{Fortran,, emacs-xtra}.
@cindex mode hook
@vindex c-mode-hook
names.
@end table
-@node Fortran
-@section Fortran Mode
-@cindex Fortran mode
-@cindex mode, Fortran
-
- 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 support for 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 @kbd{M-x fortran-mode} to switch to this major mode. This command
-runs the hook @code{fortran-mode-hook} (@pxref{Hooks}).
-
-@cindex Fortran77 and Fortran90
-@findex f90-mode
-@findex fortran-mode
- Fortran mode is meant for editing Fortran77 ``fixed format'' (and also
-``tab format'') source code. For editing the modern Fortran90 or
-Fortran95 ``free format'' source code, use F90 mode (@code{f90-mode}).
-Emacs normally uses Fortran mode for files with extension @samp{.f},
-@samp{.F} or @samp{.for}, and F90 mode for the extension @samp{.f90} and
-@samp{.f95}. GNU Fortran supports both kinds of format.
-
-@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 support for Fortran.
-* Columns: Fortran Columns. Measuring columns for valid Fortran.
-* Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords.
-@end menu
-
-@node Fortran Motion
-@subsection Motion Commands
-
- In addition to the normal commands for moving by and operating on
-``defuns'' (Fortran subprograms---functions and subroutines, as well as
-modules for F90 mode), Fortran mode provides special commands to move by
-statements and other program units.
-
-@table @kbd
-@kindex C-c C-n @r{(Fortran mode)}
-@findex fortran-next-statement
-@findex f90-next-statement
-@item C-c C-n
-Move to the beginning of the next statement
-(@code{fortran-next-statement}/@code{f90-next-statement}).
-
-@kindex C-c C-p @r{(Fortran mode)}
-@findex fortran-previous-statement
-@findex f90-previous-statement
-@item C-c C-p
-Move to the beginning of the previous statement
-(@code{fortran-previous-statement}/@code{f90-previous-statement}).
-If there is no previous statement (i.e. if called from the first
-statement in the buffer), move to the start of the buffer.
-
-@kindex C-c C-e @r{(F90 mode)}
-@findex f90-next-block
-@item C-c C-e
-Move point forward to the start of the next code block
-(@code{f90-next-block}). A code block is a subroutine,
-@code{if}--@code{endif} statement, and so forth. This command exists
-for F90 mode only, not Fortran mode. With a numeric argument, this
-moves forward that many blocks.
-
-@kindex C-c C-a @r{(F90 mode)}
-@findex f90-previous-block
-@item C-c C-a
-Move point backward to the previous code block
-(@code{f90-previous-block}). This is like @code{f90-next-block}, but
-moves backwards.
-
-@kindex C-M-n @r{(Fortran mode)}
-@findex fortran-end-of-block
-@findex f90-end-of-block
-@item C-M-n
-Move to the end of the current code block
-(@code{fortran-end-of-block}/@code{f90-end-of-block}). With a numeric
-agument, move forward that number of blocks. The mark is set before
-moving point. The F90 mode version of this command checks for
-consistency of block types and labels (if present), but it does not
-check the outermost block since that may be incomplete.
-
-@kindex C-M-p @r{(Fortran mode)}
-@findex fortran-beginning-of-block
-@findex f90-beginning-of-block
-@item C-M-p
-Move to the start of the current code block
-(@code{fortran-beginning-of-block}/@code{f90-beginning-of-block}). This
-is like @code{fortran-end-of-block}, but moves backwards.
-@end table
-
-@node Fortran Indent
-@subsection 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, fixed (or tab) format Fortran.
-
-@menu
-* Commands: ForIndent Commands. Commands for indenting and filling 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.
-@end menu
-
-@node ForIndent Commands
-@subsubsection Fortran Indentation and Filling Commands
-
-@table @kbd
-@item C-M-j
-Break the current line at point and set up a continuation line
-(@code{fortran-split-line}).
-@item M-^
-Join this line to the previous line (@code{fortran-join-line}).
-@item C-M-q
-Indent all the lines of the subprogram point is in
-(@code{fortran-indent-subprogram}).
-@item M-q
-Fill a comment block or statement.
-@end table
-
-@kindex C-M-q @r{(Fortran mode)}
-@findex fortran-indent-subprogram
- The key @kbd{C-M-q} runs @code{fortran-indent-subprogram}, a command
-to reindent all the lines of the Fortran subprogram (function or
-subroutine) containing point.
-
-@kindex C-M-j @r{(Fortran mode)}
-@findex fortran-split-line
- The key @kbd{C-M-j} runs @code{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.
-
-@kindex M-^ @r{(Fortran mode)}
-@kindex C-c C-d @r{(Fortran mode)}
-@findex fortran-join-line
- @kbd{M-^} or @kbd{C-c C-d} runs the command @code{fortran-join-line},
-which joins a continuation line back to the previous line, roughly as
-the inverse of @code{fortran-split-line}. The point must be on a
-continuation line when this command is invoked.
-
-@kindex M-q @r{(Fortran mode)}
-@kbd{M-q} in Fortran mode fills the comment block or statement that
-point is in. This removes any excess statement continuations.
-
-@node ForIndent Cont
-@subsubsection Continuation Lines
-@cindex Fortran continuation lines
-
-@vindex fortran-continuation-string
- Most Fortran77 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 @dfn{fixed
-format}. (In GNU Emacs we always count columns from 0; but note that
-the Fortran standard counts from 1.) The variable
-@code{fortran-continuation-string} specifies what character to put in
-column 5. A line that starts with a tab character followed by any digit
-except @samp{0} is also a continuation line. We call this style of
-continuation @dfn{tab format}. (Fortran90 introduced ``free format'',
-with another style of continuation lines).
-
-@vindex indent-tabs-mode @r{(Fortran mode)}
-@vindex fortran-analyze-depth
-@vindex fortran-tab-mode-default
- Fortran mode can use either style of continuation line. When you
-enter Fortran mode, it tries to deduce the proper continuation style
-automatically from the buffer contents. It does this by scanning up to
-@code{fortran-analyze-depth} (default 100) lines from the start of the
-buffer. The first line that begins with either a tab character or six
-spaces determines the choice. If the scan fails (for example, if the
-buffer is new and therefore empty), the value of
-@code{fortran-tab-mode-default} (@code{nil} for fixed format, and
-non-@code{nil} for tab format) is used. @samp{/t} in the mode line
-indicates tab format is selected. Fortran mode sets the value of
-@code{indent-tabs-mode} accordingly (@pxref{Just Spaces}).
-
- If the text on a line starts with the Fortran continuation marker
-@samp{$}, 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 @key{TAB}, it converts the line to the current
-continuation style. When you split a Fortran statement with
-@kbd{C-M-j}, 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.
-
-@node ForIndent Num
-@subsubsection 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.)
-
-@vindex fortran-line-number-indent
- Line numbers of four digits or less are normally indented one space.
-The variable @code{fortran-line-number-indent} controls this; it
-specifies the maximum indentation a line number can have. The default
-value of the variable is 1. Fortran mode tries to prevent line number
-digits passing column 4, reducing the indentation below the specified
-maximum if necessary. If @code{fortran-line-number-indent} has the
-value 5, line numbers are right-justified to end in column 4.
-
-@vindex fortran-electric-line-number
- 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
-@code{fortran-electric-line-number} to @code{nil}.
-
-
-@node ForIndent Conv
-@subsubsection 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:
-
-@itemize @bullet
-@item
-Two nested @samp{do} loops never share a @samp{continue} statement.
-
-@item
-Fortran keywords such as @samp{if}, @samp{else}, @samp{then}, @samp{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 @samp{else if} or @samp{end do}
-are acceptable, but the second word should be on the same line as the
-first and not on a continuation line.
-@end itemize
-
-@noindent
-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.
-
-@node ForIndent Vars
-@subsubsection Variables for Fortran Indentation
-
-@vindex fortran-do-indent
-@vindex fortran-if-indent
-@vindex fortran-structure-indent
-@vindex fortran-continuation-indent
-@vindex fortran-check-all-num@dots{}
-@vindex fortran-minimum-statement-indent@dots{}
- Several additional variables control how Fortran indentation works:
-
-@table @code
-@item fortran-do-indent
-Extra indentation within each level of @samp{do} statement (default 3).
-
-@item fortran-if-indent
-Extra indentation within each level of @samp{if}, @samp{select case}, or
-@samp{where} statements (default 3).
-
-@item fortran-structure-indent
-Extra indentation within each level of @samp{structure}, @samp{union},
-@samp{map}, or @samp{interface} statements (default 3).
-
-@item fortran-continuation-indent
-Extra indentation for bodies of continuation lines (default 5).
-
-@item fortran-check-all-num-for-matching-do
-In Fortran77, a numbered @samp{do} statement is ended by any statement
-with a matching line number. It is common (but not compulsory) to use a
-@samp{continue} statement for this purpose. If this variable has a
-non-@code{nil} value, indenting any numbered statement must check for a
-@samp{do} that ends there. If you always end @samp{do} statements with
-a @samp{continue} line (or if you use the more modern @samp{enddo}),
-then you can speed up indentation by setting this variable to
-@code{nil}. The default is @code{nil}.
-
-@item fortran-blink-matching-if
-If this is @code{t}, indenting an @samp{endif} (or @samp{enddo}
-statement moves the cursor momentarily to the matching @samp{if} (or
-@samp{do}) statement to show where it is. The default is @code{nil}.
-
-@item 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.
-
-@item 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.
-@end table
-
-The variables controlling the indentation of comments are described in
-the following section.
-
-@node Fortran Comments
-@subsection Fortran Comments
-
- The usual Emacs comment commands assume that a comment can follow a
-line of code. In Fortran77, 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.
-
-@vindex fortran-comment-line-start
- Fortran mode can also handle the Fortran90 comment syntax where comments
-start with @samp{!} and can follow other text. Because only some Fortran77
-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
-@code{fortran-comment-line-start} to @samp{"!"}.
-
-@table @kbd
-@item M-;
-Align comment or insert new comment (@code{fortran-indent-comment}).
-
-@item C-x ;
-Applies to nonstandard @samp{!} comments only.
-
-@item C-c ;
-Turn all lines of the region into comments, or (with argument) turn them back
-into real code (@code{fortran-comment-region}).
-@end table
-
-@findex fortran-indent-comment
- @kbd{M-;} in Fortran mode is redefined as the command
-@code{fortran-indent-comment}. Like the usual @kbd{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 @samp{!}
-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 @samp{!} 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
-@code{fortran-comment-indent-style} to one of these values:
-
-@vindex fortran-comment-indent-style
-@vindex fortran-comment-line-extra-indent
-@table @code
-@item fixed
-Align the text at a fixed column, which is the sum of
-@code{fortran-comment-line-extra-indent} and the minimum statement
-indentation. This is the default.
-
-The minimum statement indentation is
-@code{fortran-minimum-statement-indent-fixed} for fixed format
-continuation line style and @code{fortran-minimum-statement-indent-tab}
-for tab format style.
-
-@item relative
-Align the text as if it were a line of code, but with an additional
-@code{fortran-comment-line-extra-indent} columns of indentation.
-
-@item nil
-Don't move text in full-line comments automatically.
-@end table
-
-@vindex fortran-comment-indent-char
- In addition, you can specify the character to be used to indent within
-full-line comments by setting the variable
-@code{fortran-comment-indent-char} to the single-character string you want
-to use.
-
-@vindex fortran-directive-re
- Compiler directive lines, or preprocessor lines, have much the same
-appearance as comment lines. It is important, though, that such lines
-never be indented at all, no matter what the value of
-@code{fortran-comment-indent-style}. The variable
-@code{fortran-directive-re} is a regular expression that specifies which
-lines are directives. Matching lines are never indented, and receive
-distinctive font-locking.
-
- The normal Emacs comment command @kbd{C-x ;} has not been redefined. If
-you use @samp{!} comments, this command can be used with them. Otherwise
-it is useless in Fortran mode.
-
-@kindex C-c ; @r{(Fortran mode)}
-@findex fortran-comment-region
-@vindex fortran-comment-region
- The command @kbd{C-c ;} (@code{fortran-comment-region}) turns all the
-lines of the region into comments by inserting the string @samp{C$$$} at
-the front of each one. With a numeric argument, it turns the region
-back into live code by deleting @samp{C$$$} from the front of each line
-in it. The string used for these comments can be controlled by setting
-the variable @code{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.
-
-@node Fortran Autofill
-@subsection Auto Fill in Fortran Mode
-
- Fortran mode has specialized support for Auto Fill mode, which is a
-minor mode that automatically splits statements as you insert them when
-they become too wide. Splitting a statement involves making
-continuation lines using @code{fortran-continuation-string}
-(@pxref{ForIndent Cont}). This splitting happens when you type
-@key{SPC}, @key{RET}, or @key{TAB}, and also in the Fortran indentation
-commands. You activate Auto Fill in Fortran mode in the normal way
-(@pxref{Auto Fill}).
-
-@vindex fortran-break-before-delimiters
- Auto Fill breaks lines at spaces or delimiters when the lines get
-longer than the desired width (the value of @code{fill-column}). The
-delimiters (besides whitespace) that Auto Fill can break at are
-@samp{+}, @samp{-}, @samp{/}, @samp{*}, @samp{=}, @samp{<}, @samp{>},
-and @samp{,}. The line break comes after the delimiter if the
-variable @code{fortran-break-before-delimiters} is @code{nil}.
-Otherwise (and by default), the break comes before the delimiter.
-
- To enable Auto Fill in all Fortran buffers, add
-@code{turn-on-auto-fill} to @code{fortran-mode-hook}. @xref{Hooks}.
-
-@node Fortran Columns
-@subsection Checking Columns in Fortran
-
-@table @kbd
-@item C-c C-r
-Display a ``column ruler'' momentarily above the current line
-(@code{fortran-column-ruler}).
-@item C-c C-w
-Split the current window horizontally temporarily so that it is 72
-columns wide (@code{fortran-window-create-momentarily}). This may
-help you avoid making lines longer than the 72-character limit that
-some Fortran compilers impose.
-@item C-u C-c C-w
-Split the current window horizontally so that it is 72 columns wide
-(@code{fortran-window-create}). You can then continue editing.
-@item M-x fortran-strip-sequence-nos
-Delete all text in column 72 and beyond.
-@end table
-
-@kindex C-c C-r @r{(Fortran mode)}
-@findex fortran-column-ruler
- The command @kbd{C-c C-r} (@code{fortran-column-ruler}) shows a column
-ruler momentarily above the current line. The comment ruler is two lines
-of text that show you the locations of columns with special significance in
-Fortran programs. Square brackets show the limits of the columns for line
-numbers, and curly brackets show the limits of the columns for the
-statement body. Column numbers appear above them.
-
- Note that the column numbers count from zero, as always in GNU Emacs.
-As a result, the numbers may be one less than those you are familiar
-with; but the positions they indicate in the line are standard for
-Fortran.
-
-@vindex fortran-column-ruler-fixed
-@vindex fortran-column-ruler-tabs
- The text used to display the column ruler depends on the value of the
-variable @code{indent-tabs-mode}. If @code{indent-tabs-mode} is
-@code{nil}, then the value of the variable
-@code{fortran-column-ruler-fixed} is used as the column ruler.
-Otherwise, the value of the variable @code{fortran-column-ruler-tab} is
-displayed. By changing these variables, you can change the column ruler
-display.
-
-@kindex C-c C-w @r{(Fortran mode)}
-@findex fortran-window-create-momentarily
- @kbd{C-c C-w} (@code{fortran-window-create-momentarily}) temporarily
-splits the current window horizontally, making a window 72 columns
-wide, so you can see any lines that are too long. Type a space to
-restore the normal width.
-
-@kindex C-u C-c C-w @r{(Fortran mode)}
-@findex fortran-window-create
- You can also split the window horizontally and continue editing with
-the split in place. To do this, use @kbd{C-u C-c C-w} (@code{M-x
-fortran-window-create}). By editing in this window you can
-immediately see when you make a line too wide to be correct Fortran.
-
-@findex fortran-strip-sequence-nos
- The command @kbd{M-x fortran-strip-sequence-nos} deletes all text in
-column 72 and beyond, on all lines in the current buffer. This is the
-easiest way to get rid of old sequence numbers.
-
-@node Fortran Abbrev
-@subsection Fortran Keyword Abbrevs
-
- Fortran mode provides many built-in abbrevs for common keywords and
-declarations. These are the same sort of abbrev that you can define
-yourself. To use them, you must turn on Abbrev mode. @xref{Abbrevs}.
-
- The built-in abbrevs are unusual in one way: they all start with a
-semicolon. You cannot normally use semicolon in an abbrev, but Fortran
-mode makes this possible by changing the syntax of semicolon to ``word
-constituent.''
-
- For example, one built-in Fortran abbrev is @samp{;c} for
-@samp{continue}. If you insert @samp{;c} and then insert a punctuation
-character such as a space or a newline, the @samp{;c} expands automatically
-to @samp{continue}, provided Abbrev mode is enabled.@refill
-
- Type @samp{;?} or @samp{;C-h} to display a list of all the built-in
-Fortran abbrevs and what they stand for.
-
@node Asm Mode
@section Asm Mode