GNU bug report logs - #30816
27.0.50; Info documentation of previous-property-change is not very clear

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Xu Chunyang <mail <at> xuchunyang.me>
Cc: 30816 <at> debbugs.gnu.org
Subject: bug#30816: 27.0.50; Info documentation of previous-property-change is not very clear
Date: Wed, 14 Mar 2018 18:26:46 +0200

> From: Xu Chunyang <mail <at> xuchunyang.me>
> Date: Wed, 14 Mar 2018 17:58:32 +0800
> 
> 
> (info "(elisp) Property Search") has the following:
> 
>      -- Function: previous-property-change pos &optional object limit
>          This is like ‘next-property-change’, but scans back from POS
>          instead of forward.  If the value is non-‘nil’, it is a position
>                                  ^^^^^^^^^
>          less than or equal to POS; it equals POS only if LIMIT equals POS.
>                                     ^^
> 
> I don't understand the second sentence. What "the value" stands for?

When we say "value" in the context of describing a function, we mean
the value the function returns.  In this case, the value returned by
previous-property-change.

> If it stands for LIMIT, what "it" stands for?

"It" stands for the value returned by the function.  the text says
that the function returns the position of the previous change of the
property, and that position could only be the same as the starting
position POS if LIMIT is equal to POS, i.e. if LIMIT forces the
function to stop at its starting position.

I hope this clarifies the issue.

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