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bug#20587: 24.1 forward-line docs inconsistent/surprising return value

From: Vivek Dasmohapatra
Subject: bug#20587: 24.1 forward-line docs inconsistent/surprising return value
Date: Sat, 16 May 2015 11:07:03 +0100 (BST)
User-agent: Alpine 2.02 (DEB 1266 2009-07-14)

Why do you think it's inconsistent?  In the first case, the command

It strikes me as inconsistent because of this:

  Precisely, if point is on line I, move to the start of line I + N
And it is precisely this which it has not been able to do.

Take the example of a case where I wish to move N lines forward
to leave a gap of N lines before I insert some text, and I use
the return value of forward-line to check how far I have moved.

On an incomplete last line with an N of 1, forward-line will return 0,
indicating that it has satisfied my request to move to the start of
line I + 1, when in fact it has not, so now I must check for end-of-buffer
explicitly to see if this case has occurred.

moved; in the second one it didn't.  So the return value looks OK to
me, and I see that the implementation goes to some length to catch the
first case and return zero.  (The doc string indeed is inaccurate.)

It did not do that. It moved to the end of line I, not the start of
line I + 1.

That's the part I find surprising.

It may be that the behaviour is so ancient that it cannot be altered without breaking things: I wouldn't push for the behaviour change in
that case. But I think the special case should be more clearly flagged
and stated.

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