Info [was Re: re-search beginning of line or whitespace]

[Tim Johnson <tim@johnsons-web.com>]

* Neon Absentius <absent@sdf.lonestar.org> [051103 11:45]:
> On Wed, Nov 02, 2005 at 08:19:14AM -0900, thus spake Tim Johnson:
> It is explained nicely in the elisp manual:
> 
> ,----[ (info "(elisp) Regexp Special") ]
> | `\'
> |      has two functions: it quotes the special characters (including
> |      `\'), and it introduces additional special constructs.
> | 
> |      Because `\' quotes special characters, `\$' is a regular
> |      expression that matches only `$', and `\[' is a regular expression
> |      that matches only `[', and so on.
> | 
> |      Note that `\' also has special meaning in the read syntax of Lisp
> |      strings (*note String Type::), and must be quoted with `\'.  For
> |      example, the regular expression that matches the `\' character is
> |      `\\'.  To write a Lisp string that contains the characters `\\',
> |      Lisp syntax requires you to quote each `\' with another `\'.
> |      Therefore, the read syntax for a regular expression matching `\'
> |      is `"\\\\"'.
> `----
> 
> You see, for the regular expression parser of emacs certain
> characters have to be escaped for example "|" when one uses it to
> indicate disjunction, so you write it "\|".  However when you write
> a Lisp program the regexp is entered as a string, and since "\" is
> an elisp escape character a sting that contains "\|" is interpreted
> as "|".  You don't want that, you want the string to pass to the
> "regexp machine" as is, you want the regexp to have "\|"; therefore
> you have to escape the slash thus "\\|".  
> 
> I hope this makes some sense.
 
   Indeed. Thank you very much Neon.
   FYI: I use both Xemacs and GNU emacs. I note that from emacs and
        in invoking 'info' from the bash shell that I can not find
        a Menu item for emacs or elisp. It looks as if those
        components are not installed.

        In Xemacs, info provides "Lispref: (lispref)" as a menu
        item, which leads me to the regex topic.

  For GNU emacs, how may I install these missing items?

  cheers
  tim

-- 
Tim Johnson <tim@johnsons-web.com>
      http://www.alaska-internet-solutions.com