From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: xah@xahlee.org Newsgroups: gmane.emacs.help Subject: Re: Meta-Characters, Special Characters Date: 30 May 2007 18:20:17 -0700 Organization: http://groups.google.com Message-ID: <1180574417.742187.125110@x35g2000prf.googlegroups.com> References: <5c2mbdF2ung8hU1@mid.individual.net> <1180481373.651591.253210@i38g2000prf.googlegroups.com> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Trace: sea.gmane.org 1180575645 30843 80.91.229.12 (31 May 2007 01:40:45 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Thu, 31 May 2007 01:40:45 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu May 31 03:40:37 2007 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.50) id 1HtZeV-0006zp-Bb for geh-help-gnu-emacs@m.gmane.org; Thu, 31 May 2007 03:40:35 +0200 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1HtZeU-0002ff-QS for geh-help-gnu-emacs@m.gmane.org; Wed, 30 May 2007 21:40:34 -0400 Original-Path: shelby.stanford.edu!newsfeed.stanford.edu!postnews.google.com!x35g2000prf.googlegroups.com!not-for-mail Original-Newsgroups: gnu.emacs.help, comp.emacs, comp.lang.perl.misc, comp.lang.java.programmer, comp.lang.lisp Original-Lines: 192 Original-NNTP-Posting-Host: 69.236.73.43 Original-X-Trace: posting.google.com 1180574425 11070 127.0.0.1 (31 May 2007 01:20:25 GMT) Original-X-Complaints-To: groups-abuse@google.com Original-NNTP-Posting-Date: Thu, 31 May 2007 01:20:25 +0000 (UTC) In-Reply-To: <1180481373.651591.253210@i38g2000prf.googlegroups.com> User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en) AppleWebKit/419 (KHTML, like Gecko) Safari/419.3,gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: x35g2000prf.googlegroups.com; posting-host=69.236.73.43; posting-account=OIaTGwwAAABntbwd95_ohTn1wTSa5sqo Original-Xref: shelby.stanford.edu gnu.emacs.help:148967 comp.emacs:94397 comp.lang.perl.misc:609733 comp.lang.java.programmer:785406 comp.lang.lisp:221423 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:44556 Archived-At: The following is a modified and extended version of the previous article. The HTML formatted version is available at http://xahlee.org/emacs/keystroke_rep.html The Confusion of Emacs's Keystroke Representation Xah Lee, 2007-05-29 Someone wrote: =C2=AB [about the various ways to input or represent keystrokes and or non-printable characters in Emacs] As far as I can see in all those situations entering meta-characters is addressed in a different way which I find confusing, e.g.: a) _or_ C-q b) C-q C-[, C-q C-m, C-q C-j, C-q C-i c) \e, \r, \n, \t d) (define-key [(meta c) (control c) (tab c)] "This is confusing!") =C2=BB None of this complexity is intrinsic, except your item d. Your first item: =C2=ABC-q =C2=BB The C-q (or, pressing the Control key down then type q) is the keyboard shortcut to invoke the command quoted-insert. After this command is invoked, the next key press on your keyboard will force emacs to insert a character represented by that key, and withheld that key's normal function. For example, if you are doing string replacement, and you want to replace tabs by returns. When emacs prompts you to type a string to replace, you can't just press the tab key, because the normal function of a tab key in emacs will try to do a command completion. (and in other Applications, it usually switches you to the next input field) So, here you can do C-q first, then press the tab key. Similarly, you can't type the return key and expect it to insert a return character, because normally the return key will activate the OK button or =E2=80=9Cend= of input=E2=80=9D. This input mechanism usually don't exist in other text editors. In popular text editors such as Microsoft Word or Mac's Application, you usally bring up a window showing all the special characters, then press a button to insert the char you want. =C2=ABC-q C-[, C-q C-m, C-q C-j, C-q C-i=C2=BB In this, the C-q is the keyboard shortcut to invoke the command quoted- insert, which will insert a literal character of whatever character you can type on your keyboard. So, for example, C-q followed by the tab key will insert the non-printable character =E2=80=9Ctab=E2=80=9D. The C-[, C-m, C-j etc key-press combinations (Holding down Control key while pressing =E2=80=9C[=E2=80=9D, =E2=80=9Cm=E2=80=9D, =E2=80=9Cj=E2=80= =9D), are methods to input non-printable characters that may not have a corresponding key on the keyboard. For example, suppose you want to do string replacement, by replacing Carriage Return (ASCII 13) by Line Feed (ASCII 10). Depending what is your operatin system and keyboard, usually your keyboard only has a key that corresponds to just one of these characters. But now with the special method to input non-printable characters, you can now type any of the non-printable characters directly. When speaking of non-printable characters, implied in the context is some standard character set. Implicitly, we are talking about ASCII, and this applies to emacs. Now, in ASCII, there are about 30 non- printable characters. Each of these is given a standard abbreviation, and several representations for different purposes. For example, ASCII 13 is the =E2=80=9CCarriage return=E2=80=9D character, with abbr code CR, a= nd ^M as its control-key-input representation. (M being the 13th of the English alphabet), and Control-m is the conventional means to input the character, and the conventional method to indicate a control key combination is by using the caret =E2=80=9C^=E2=80=9D followed by the chara= cter. For the full detail, look at the table in the wikipedia article: ASCII=E2=86=97. In general, the practical issues involved for a non-printable character, in the context of a programing language for text editing, are: its display representation, its input method, and the display representation for the character's input method. (Note: Emacs also has a general way to input non-printable and or non- typable characters of the unicode standard. See Emacs and Unicode Tips ) =C2=AB\e, \r, \n, \t =C2=BB This is a ad-hoc set of input and display representation for a few non- printable characters. This set is started by the motherfucking unix tech geeking morons, and by its free and speedy nature as cigarette given to children, today has spread to many languages (Perl, Java, C+ +, C#, Python, JavaScript ...) and is a de facto standard. The damage is to such a degree that the general concept of unprintable characters, their representation, and their method of input, all treated in one systematic, simple way, are not in the consciousness of average industrial programers. I do not know the history of these display representations. It is my guess, that part of the reason for these, is that the unix text editor vi, doesn't have a general way to input and or represent non-printable chars. Other reasons are that these particular non-printable chars are vastly far more frequently needed in text/string manipulation among programing languages, and the blackslash representation are somewhat more intuitive, and processing blackslahsed characters as a =E2=80=9Cstring escape=E2=80=9D mechanism works better as a representation inside strings f= or programing languages, than the representations of prefixing a caret =E2=80=9C^=E2=80=9D. =C2=AB (global-set-key (kbd "M-a") 'func-name) ; meta a (global-set-key (kbd "C-a") 'func-name) ; control a (global-set-key [f2] 'func-name) ; F2 key (global-set-key [kp-2] 'func-name) ; the 2 key on the number keypad (global-set-key [M-f2] 'func-name) ; meta f2 (global-set-key [(meta shift a)] 'func-name) ; Meta shift a (capital A) (global-set-key [?\C-x ?a] 'func-name) ; control x, followed by a (global-set-key [?\C-x f2] 'func-name) ; control x, followed by f2 [This is confusing!] =C2=BB These are elisp code to define a keyboard shortcuts. This is the only part of complexity in our context that we can blame emacs's design. Emacs today has several rather confusing ways for keystroke representation, out of mostly historical reasons. For example, the need to keep compatibility between Emacs and Xemacs=E2=86=97. Another examp= le of a reason, is that elisp the language uses integer to represent printable characters. So, for example, the number 97 in lisp's keystroke code also means the keystroke =E2=80=9Ca=E2=80=9D. These mostly h= istorical reasons, are exacerbated by the influence of unix mentality =E2=80=9CWhy Change when it ain't broken=E2=80=9D. Note here, that keystroke combination and sequence, is not the same and cannot be mapped to character's input/representation in a character set such as ASCII. For example, the F1 key in vast majority of keyboards, isn't a character. The Alt modifier key, isn't a character nor is it a function in one of ASCII's non-printable character. The keys on the number keypad, need a different representation than the ones on the main keyboard section. So, this means, when you have a editor with a language such as emacs, that allows users to define arbitrary key stroke combination and sequences, you necessarily have to come up with a system to represent keystrokes. So, this complexity is a intrinsic complexity. (Side note: A easy way to understand what's intrinsic vs extraneous complexity is to think: =E2=80=9CMy god, why is math so complex? God must h= ave fucked up in its design.=E2=80=9D. The gist is that, certain things, are inherently complex by nature, while others, are extraneous complexity that are artificially created by lousy design or historical baggage. As a concrete example in computing, languages like Lisp, is in general very well designed. Due to its simplicity and almost no artificial complexity, programers are immediately exposed to many of the intrinsic complexity of computing. While languages like C and its litters such as C++, Java, C#, Perl etc and in general software in unix, created by the unix motherfuckers, are filled to the brim with artificial complexity due to mostly laziness/hack, ignorance, and lies.) For various ways to represent keystrokes in emacs, see How to Define Keyboard Shortcuts in Emacs. For the unix mentality =E2=80=9CWhy Change when it ain't broken=E2=80=9D, s= ee Why Change when it ain't broken. We, as software creators, must not have unix's =E2=80=9Cwhy change when it ain't broken=E2=80=9D attitude. Emacs itself, although far more well thought out than the majority of software, nevertheless acquired many baggage in its 30 or so years of old age. I would recommend that we start a effort to eliminate some of these outdated baggage. Please see: The Modernization of Emacs. Xah xah@xahlee.org =E2=88=91 http://xahlee.org/