Re: point-min and 1

[martin rudalics <rudalics@gmx.at>]

 > goto-char is an interactive built-in function in `C source code'.
 >
 > It is bound to <menu-bar> <edit> <goto> <go-to-pos>.
 >
 > (goto-char POSITION)
 >
 > Set point to POSITION, a number or marker.
 > Beginning of buffer is position (point-min), end is (point-max).
 >
 > The return value is POSITION.
 >
 > [back]
 >
 > Can you guess from that what is done and returned when the buffer is
 > narrowed and you call (cons (goto-char 1) (point))?

No.  The doc-string is incomplete in this regard.  But a similar thing
happens when I want to go to a marker and that marker's position is not
within the accessible portion of the buffer.  (And no, I see no need to
enhance the doc-string.  It's all in the Elisp manual.)

 >>From the DOC string, you could get an error thrown, or point is put
 > outside of the narrowed region and a number of different things.  It is
 > not at all clear that you get no error, and something like (1 . 90) is
 > returned.
 >
 > In order to find that out, you have not only to read the doc string, but
 > the actual source code.
 >
 > Whether or not the actual result turns out what it is, it is a lousy
 > idea to have to dig through the source code and all intricacies before
 > being able to tell what some code does.
 >
 > The less information and detail you need to access before figuring out
 > the function of some code, the better.
 >
 > Not least of all because you don't have dozens of accidental
 > dependencies if at one point of time some of the incidental semantics
 > are chosen to change.

I hope you don't expect me to dispute anything you say here ;-)

But all these arguments apply as well when you call (goto-char 1) in a
widened buffer.  One case against I could come up with is, that in a
narrowed buffer referential transparency is lost because

(goto-char (+ 1 1))

is not equivalent to

(goto-char (+ (point-min) 1))

but I've been told once that referential transparency does not have very
high priority within the development of Emacs.

martin