Indices in Info.

[Luc Teirlinck <teirllm@dms.auburn.edu>]

Both Emacs Info and stand-alone Info have some trouble with various
index entries.  In many cases, the conclusion might be that we should
just "outlaw" such entries.

Problem 1: both Emacs and stand-alone, or maybe just texinfo.txi

g (texinfo)Concept Index

Click on:

* $Id::                                  GNU Sample Texts.

Result:

byte-code: No such anchor in tag table or node in tag table or file: $Id
(Emacs)

$Id: No such file or directory (stand-alone).

Proposed solution:  Just institute a convention that an index entry
should never end in a colon.  Those two colons in an index entry look
weird anyway, even if they would not produce a bug.  Of course, also
follow that convention.

Problem 2: Emacs, or maybe texinfo.txi

g (texinfo)Command and Variable Index

Click on:

* (newline):                             Multiple Spaces.

Result:

Info-find-node: Info file newline does not exist

Reason: Index entry starting with a parenthetical remark.

The stand-alone Info correctly visits Multiple Spaces.

What is the conclusion here: "Emacs should be able to handle this
correctly" or "starting an index entry with a parenthetical remark
makes no sense"?  In this particular instance, it definitely would
seem more logical to have entries named "newline", "space" and "tab",
rather than "(newline)", "(space)" and "(tab)".  (I guess these were
just typos, or not?)

Problem 3: No real problem but maybe worth mentioning. Also, should be
compared with problem 4.

I produced the following index for experimentation purposes:

Index
*****

* Menu:

* Aha: oho:                              Top.
* Oho:ihi:                               Top.


Both Emacs and stand-alone fail to visit "Top" in the first entry. Of
course, no bug, but it might be worth emphasizing in 
(texinfo)Index Entries that an index entry should *never* contain a
colon followed by a space or tab.

Problem 4:

Emacs visits Top in the _second_ entry above, stand-alone Info does not.

>From info.el:

;;  - a menu item MAY contain colons but not colon-space ": "
;;  - a menu item ending with ": " (but not ":: ") is an index entry
;;  - a node name MAY NOT contain a colon
;; This distinction is to support indexing of computer programming
;; language terms that may contain ":" but not ": ".


If it is worth while for Emacs Info to support those computer
programming language terms, it might also be worth while for the
stand-alone version to do so.  People constructing index entries do so
for both versions, so one should be consistent.

All conventions we decide on for index entries could be described in
(texinfo)Index Entries.

Sincerely,

Luc.