Emanuel Berg writes:

> In one of my w3m extensions [1] I have
>
>     (defun empty-string-p (str)
>       (string= str "") )
>
> which obviously has nothing to do with w3m. Well, it's
> been known to happen. I can live with having it there.
>
> However, the next time I want to use it in some other
> file the byte-compiler tells me
>
>     In end of data: wrap-search.el:98:1:Warning: the
>     function `empty-string-p' is not known to
>     be defined.
>
> OK, I get that away with
>
>     (require 'w3m-unisearch) ; get empty-string-p
>
> But now I have a mention of w3m, in a file that has
> nothing to do with w3m, to get empty-string-p, which
> has nothing to do with w3m!

Hi!

You can use `string-empty-p' from subr-x.el or `seq-empty-p' from
seq.el (which works on all sequence data types).

seq.el will be included in Emacs 25.1, but in the meantime you can
install it from GNU Elpa.

Cheers,
Nico
-- 
Nicolas Petton
http://nicolas-petton.fr