info-look scheme regexp

[Kevin Ryde]

A tiny proposal,

        * info-look.el: In scheme-mode symbol regexp, disallow backquote and
        comma.

For example in a scheme-mode buffer containing

        `(("model" . ,car) ...)

        ;; model number is in `car'

with point on the "a" of each "car", this change allows C-h C-i to
give "car" as the (default) symbol to look up, instead of ",car" or
"`car".

Incidentally, excluding backquote from a symbol is not just for
comments.  Something like

        `car

is in fact a valid alternative to 'car though I don't suppose anyone
ever normally writes it like that.

*** info-look.el.~1.37.~        Sun Feb 22 10:45:23 2004
--- info-look.el        Mon Feb 23 14:54:00 2004
***************
*** 1,7 ****
  ;;; info-look.el --- major-mode-sensitive Info index lookup facility
  ;; An older version of this was known as libc.el.
  
! ;; Copyright (C) 1995,96,97,98,99,2001,2003  Free Software Foundation, Inc.
  
  ;; Author: Ralph Schleicher <address@hidden>
  ;;         (did not show signs of life (Nov 2001)  -stef)
--- 1,7 ----
  ;;; info-look.el --- major-mode-sensitive Info index lookup facility
  ;; An older version of this was known as libc.el.
  
! ;; Copyright (C) 1995,96,97,98,99,2001,2003,2004  Free Software Foundation, 
Inc.
  
  ;; Author: Ralph Schleicher <address@hidden>
  ;;         (did not show signs of life (Nov 2001)  -stef)
*************** (info-lookup-maybe-add-help
*** 808,814 ****
  
  (info-lookup-maybe-add-help
   :mode 'scheme-mode
!  :regexp "[^()'\" \t\n]+"
   :ignore-case t
   ;; Aubrey Jaffer's rendition from <URL:ftp://ftp-swiss.ai.mit.edu/pub/scm>
   :doc-spec '(("(r5rs)Index" nil
--- 808,814 ----
  
  (info-lookup-maybe-add-help
   :mode 'scheme-mode
!  :regexp "[^()`',\" \t\n]+"
   :ignore-case t
   ;; Aubrey Jaffer's rendition from <URL:ftp://ftp-swiss.ai.mit.edu/pub/scm>
   :doc-spec '(("(r5rs)Index" nil