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

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

[Xu Chunyang]

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

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

[Eli Zaretskii]

> From: Xu Chunyang <mail@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.

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

[Xu Chunyang]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Xu Chunyang <mail@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.

I see. I notice the term "the return value" is also used in some place
in the manual.

>> 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.

Thanks for your explanation. Feel free to close the issue.

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

[Eli Zaretskii]

> From: Xu Chunyang <mail@xuchunyang.me>
> Cc: 30816@debbugs.gnu.org
> Date: Thu, 15 Mar 2018 03:04:30 +0800
> 
> Thanks for your explanation. Feel free to close the issue.

Done.