Re: set-text-properties, remove-set-properties, add-text-properties: 1) doc string 2) return value

[Luc Teirlinck]

Richard Stallman wrote:

   I am not sure whether this is useful to document.

I do not believe that the return value is very useful (given that only
a nil return value provides any reliable info).  But since the return
value is sometimes nil and sometimes t, it might be good to document
it, just to avoid a situation where a user _believes_ that he
understands the return value and writes code relying on his mistaken
belief.

I could add:

    This function returns nil if it _knows_ that it did not replace any
    properties, non-nil otherwise.

to both the docstring and the Elisp manual, if desired.

Sincerely,

Luc.