other.emacses

windows版本的emacs

\| specifies an alternative.  Two regular expressions A and B with \| in
between form an expression that matches anything that either A or B will
match.  Thus, "foo\|bar" matches either "foo" or "bar" but no other
string.

\| applies to the larges possible surrounding expressions.  Only a
surrounding \( ... \) grouping can limit the grouping power of \|.

Full backtracking capability exists when multiple \|'s are used.

****		-- \( ... \) --

\( ... \) are a grouping construct that serves three purposes:

1.  To enclose a set of \| alternatives for other operations.
    Thus, "\(foo\|bar\)x" matches either "foox" or "barx".
2.  To enclose a complicated expression for * to operate on.
    Thus, "ba\(na\)*" matches "bananana", etc., with any number
    of na's (zero or more).
3.  To mark a matched substring for future reference.

Application 3 is not a consequence of the idea of a parenthetical
grouping; it is a separate feature which happens to be assigned as a
second meaning to the same \( ... \) construct because there is no
conflict in practice between the two meanings.  Here is an explanation
of this feature.

		-- \digit --

After the end of a \( ... \) construct, the matcher remembers the
beginning and end of the text matched by that construct.  Then, later on
in the regular expression, you can use \ followed by a digit to mean,
``match the same text matched this time by the \( ... \) construct.''
The first nine \( ... \) constructs that appear in a regular expression
are assigned numbers 1 through 9 in order of their beginnings.  \1
through \9 can be used to refer to the text matched by the corresponding
\( ... \) construct.

For example, "\(.*\)\1" matches any string that is composed of two
identical halves.  The "\(.*\)" matches the first half, which can be
anything, but the \1 that follows must match the same exact text.

****		-- \` --

Matches the empty string, but only if it is at the beginning of the buffer.

****		-- \' --

Matches the empty string, but only if it is at the end of the buffer.

****		-- \b --

Matches the empty string, but only if it is at the beginning or end of
a word.  Thus, "\bfoo\b" matches any occurrence of "foo" as a separate word.
"\bball\(s\|\)\b" matches "ball" or "balls" as a separate word.

****		-- \B --

Matches the empty string, provided it is NOT at the beginning or end of
a word.

****		-- \< --

Matches the empty string, provided it is at the beginning of a word.

****		-- \> --

Matches the empty string, provided it is at the end of a word.

****		-- \w --

Matches any word-constituent character.  The editor syntax table determines
which characters these are.

****		-- \W --

Matches any character that is not a word-constituent.

****		-- \s<code> --

Matches any character whose syntax is <code>.  <code> is a letter that
represents a syntax code: thus, "w" for word constituent, "-" for
whitespace, "(" for open-parenthesis, etc.  Thus, "\s(" matches any
character with open-parenthesis syntax.

****		-- \S<code> --

Matches any character whose syntax is not <code>.

* How is this Emacs different from Gosling Emacs?

** Advantages of Gosling Emacs:

1. The program itself is much smaller.
GNU Emacs uses about 250k more pure storage.
As a result, Gosling Emacs can run on machines
that cannot run GNU Emacs.  There is not much difference
in the amount of impure storage in the two programs.

2. In some versions there is support for other forks to
establish communications channels to Emacs (using sockets?).

3. There is a direct interface to dbm (data bases).

** Advantages of GNU Emacs:

*** True Lisp, not Mocklisp.

GNU Emacs's extension language has real symbols, lists
and vectors.  Many extensions are much simpler, and some
become possible that were nearly impossible in Gosling Emacs.
Many primitives can have cleaner interfaces, and some features
need not be put in as special primitives because you can do
them easily yourself.

*** But Mocklisp still works.

An automatic conversion package plus a run-time library
allows you to convert a Mocklisp library into a Lisp library.

*** Commands are better crafted.

For example, nearly every editing function for which a
numeric argument would make sense as a repeat count does
accept a repeat count, and does handle a negative argument
in the way you would expect.

*** The manual is clearer.

Everyone tells me it is a very good manual.

*** Better on-line documentation.

Both functions and variables have documentation strings that
describe exactly how to use them.

*** C mode is smart.

It really knows how to indent each line correctly,
for most popular indentation styles.  (Some variables
control which style is used; popular named styles are also supported.)

*** Compatible with PDP-10 Emacs, Multics Emacs and Zmacs.

The commands in GNU Emacs are nearly the same as in the
original Emacs and the other Emacses which imitated it.
(A few have been changed to fit the Unix environment better.)

*** Support for Gosling's Emacs commands.

M-x set-gosmacs-bindings rebinds many editing commands for
compatibility with Gosling's Emacs.
M-x set-gnu-bindings reverses the change.

*** Side-by-side windows.

You can split a GNU Emacs window either horizontally or
vertically.

*** Redisplay is faster.

GNU Emacs sends about the same stuff to the terminal that
Gosling's does, but GNU Emacs uses much less CPU time to
decide what to do.

*** Entirely termcap-driven.

GNU Emacs has nearly no special code for any terminal type.  Various
new termcap strings make it possible to handle all terminals nearly as
fast as they could be handled by special-case code.

*** Display-hiding features.

For example, Outline Mode makes it possible for you to edit
an outline, making entire sub-branches of the outline visible
or invisible when you wish.

*** You can interrupt with Control-G.

Even a looping Lisp program can be stopped this way.
And even a loop in C code does not stop you from killing
Emacs and getting back to your shell.

*** Per-buffer Undo.

You can undo the last several changes, in each buffer
independently.

*** The editor code itself is clean.

Many people have remarked on how much they enjoy reading
the code for GNU Emacs.

One other note: The program etc/cvtmail that comes with GNU Emacs can
be used to convert a mail directory for Gosling Emacs's Rmail into a
Unix mail file that you could read into GNU Emacs's Rmail.

* How is this Emacs different from CCA Emacs?

** GNU Emacs Lisp vs CCA Elisp.

GNU Emacs Lisp does not have a distinction between Lisp functions
and Emacs functions, or between Lisp variables and Emacs variables.
The Lisp and the editor are integrated.  A Lisp function defined
with defun is callable as an editor command if you put an
interactive calling spec in it; for example, 
  (defun forward-character (n)
    (interactive "p")
    (goto-char (+ (point) n)))
defines a function of one argument that moves point forward by
a specified number of characters.  Programs could call this function,
as in (forward-character 6), or it could be assigned to a key,
in which case the "p" says to pass the prefix numeric arg as
the function's argument.  As a result of this feature, you often
need not have two different functions, one to be called by programs
and another to read arguments from the user conveniently; the same
function can do both.

CCA Elisp tries to be a subset of Common Lisp and tries to
have as many Common Lisp functions as possible (though it is still
only a small fraction of full Common Lisp).  GNU Emacs Lisp
is somewhat similar to Common Lisp just because of my Maclisp
and Lisp Machine background, but it has several distinct incompatibilities
in both syntax and semantics.  Also, I have not attempted to
provide many Common Lisp functions that you could write in Lisp,
or others that provide no new capability in the circumstances.

GNU Emacs Lisp does not have packages, readtables, or character objects
(it uses integers to represent characters).

On the other hand, windows, buffers, relocatable markers and processes
are first class objects in GNU Emacs Lisp.  You can get information about them
and do things to them in a Lispy fashion.  Not so in CCA Emacs.

In GNU Emacs Lisp, you cannot open a file and read or write characters
or Lisp objects from it.  This feature is painful to support, and
is not fundamentally necessary in an Emacs, because instead you
can read the file into a buffer, read or write characters or
Lisp objects in the buffer, and then write the buffer into the file.

On the other hand, GNU Emacs Lisp does allow you to rename, delete, add
names to, and copy files; also to find out whether a file is a
directory, whether it is a symbolic link and to what name, whether
you can read it or write it, find out its directory component,
expand a relative pathname, find completions of a file name, etc.,
which you cannot do in CCA Elisp.

GNU Emacs Lisp uses dynamic scope exclusively.  This enables you to
bind variables which affect the execution of the editor, such as
indent-tabs-mode.

GNU Emacs Lisp code is normally compiled into byte code.  Most of the
standard editing commands are written in Lisp, and many are
dumped, pure, in the Emacs that users normally run.

GNU Emacs allows you to interrupt a runaway Lisp program with
Control-g.

** GNU Emacs Editing Advantages

GNU Emacs is faster for many things, especially insertion of text
and file I/O.

GNU Emacs allows you to undo more than just the last command
with the undo command (C-x u, or C-_).  You can undo quite a ways back.
Undo information is separate for each buffer; changes in one buffer
do not affect your ability to undo in another buffer.

GNU Emacs commands that want to display some output do so by putting
it in a buffer and displaying that buffer in a window.  This
technique comes from Gosling Emacs.  It has both advantages and
disadvantages when compared with the technique, copied by CCA Emacs
from my original Emacs which inherited it from TECO, of having "type
out" which appears on top of the text in the current window but
disappears automatically at the next input character.

GNU Emacs does not use the concept of "subsystems".  Instead, it uses
highly specialized major modes.  For example, dired in GNU Emacs has
the same commands as dired does in other versions of Emacs, give or
take a few, but it is a major mode, not a subsystem.  The advantage
of this is that you do not have to "exit" from dired and lose the
state of dired in order to edit files again.  You can simply switch
to another buffer, and switch back to the dired buffer later.  You
can also have several dired buffers, looking at different directories.

It is still possible to write a subsystem--your own command loop--
in GNU Emacs, but it is not recommended, since writing a major mode
for a special buffer is better.

Recursive edits are also rarely used, for the same reason: it is better
to make a new buffer and put it in a special major mode.  Sending
mail is done this way.

GNU Emacs expects everyone to use find-file (C-x C-f) for reading
in files; its C-x C-v command kills the current buffer and then finds
the specified file.

As a result, users do not need to think about the complexities
of subsystems, recursive edits, and various ways to read in files
or what to do if a buffer contains changes to some other file.

GNU Emacs uses its own format of tag table, made by the "etags"
program.  This format makes finding a tag much faster.

Dissociated Press is supported.


** GNU Emacs Editing Disadvantages.

GNU Emacs does not display the location of the mark.

GNU Emacs does not have a concept of numbers of buffers,
or a permanent ordering of buffers, or searching through multiple
buffers.  The tags-search command provides a way to search
through several buffers automatically.

GNU Emacs does not provide commands to visit files without
setting the buffer's default directory.  Users can write such
commands in Lisp by copying the code of the standard file
visiting commands and modifying them.

GNU Emacs does not support "plus options" in the command
arguments or in buffer-selection commands, except for line numbers.

GNU Emacs does not support encryption.  Down with security!

GNU Emacs does not support replaying keystroke files,
and does not normally write keystroke files.


** Neutral Differences

GNU Emacs uses TAB, not ESC, to complete file names, buffer names,
command names, etc.

GNU Emacs uses LFD to terminate searches, instead of
the C-d uses by CCA Emacs.  (Actually, this character is controlled
by a parameter in GNU Emacs.)  C-M-s in GNU Emacs is an interactive
regular expression search, but you can get to a noninteractive
one by typing ESC right after the C-M-s.

In GNU Emacs, C-x s asks, for each modified file buffer, whether
to save it.

GNU Emacs indicates line continuation with "\" and line
truncation (at either margin) with "$".

The command to resume a tags-search or tags-query-replace in
GNU Emacs is Meta-Comma.