Re: problem of marker as position

[Kevin Rodgers <ihs_4664@yahoo.com>]

Robert J. Chassell wrote:

> I am a native English speaker and, to my embarrassment, have been
> confused.  Extra explanation is useful, since the notion of marker
> encompasses two different concepts:
> 
>   1. a position within a buffer that relocates automatically when
>      text is inserted or deleted, 
> 
>   2. a specification of which buffer the position is within.
> 
> My problem is that sometimes, I focus on concept # 2 when the person
> writing the code focuses on concept # 1 --- I should, of course, focus
> on both concepts, but forget.  A better explanation would help me
> remember.
> 
> The two concepts cannot be separated because the position must be
> within a particular buffer.

Indeed.  It would be interesting to add debugging code to marker.c
(analagous to byte_char_debug_check) that would signal an error if any
marker was being used as a position in a different buffer.  If there
aren't too many cases, it'd be simple to convert the references to the
marker M to (marker-position M).  Then the run-time check could be left
in for Lisp programmers, dependent upon a variable (analgous to
byte-debug-flag).

-- 
Kevin Rodgers