Le 21/12/2021 à 22:29, David Kastrup a écrit :
Jean Abou Samra <j...@abou-samra.fr> writes:
[Valentin]
Hello Jean, hello David, hello Kieren,
you should even be able to write (if sten (ly:stencil-extent sten)),
as the stencil should always be a stencil or #f.
The two universally accepted values for any property
regardless of the predicate are #f and '(), so it
may still be '(), which is why checking with specific
predicates like this is often used in LilyPond's
source.
'() is a bit of an ugly cookie since it for some reason has been chosen
to be the default for unset properties (seems like a Lisp rather than
Scheme idea to me) but shouldn't be used by users for stuff not formally
fitting the predicate.
In my handwavy impression of trying to sort-of guess unwritten coding
conventions.
Hm. Reminds me of
\version "2.22.1"
{
\once \override NoteHead.X-extent = #'()
a'1
\once \override NoteHead.X-extent = ##f
a'1
}
Which happens because of
Grob::Grob (SCM basicprops)
{
// [...]
if (scm_is_null (get_property_data (this, "X-extent")))
set_property (this, "X-extent", Grob::stencil_width_proc);
if (scm_is_null (get_property_data (this, "Y-extent")))
set_property (this, "Y-extent",
Unpure_pure_container::make_smob
(Grob::stencil_height_proc,
Grob::pure_stencil_height_proc));
if (scm_is_null (get_property_data (this, "vertical-skylines")))
set_property (this, "vertical-skylines",
Unpure_pure_container::make_smob
(Grob::simple_vertical_skylines_from_extents_proc,
Grob::pure_simple_vertical_skylines_from_extents_proc));
if (scm_is_null (get_property_data (this, "horizontal-skylines")))
set_property (this, "horizontal-skylines",
Unpure_pure_container::make_smob
(Grob::simple_horizontal_skylines_from_extents_proc,
Grob::pure_simple_horizontal_skylines_from_extents_proc));
}
So I admit that my practice of setting properties
to #'() is not in line with the expectations of
part of the code base and I should take the habit
of writing ##f instead. Thanks for the notice.
But I wonder if we should update the comment in
bool
type_check_assignment (SCM sym, SCM val, SCM type_symbol)
{
// [...]
/*
[...]
TODO: should remove #f from allowed vals?
*/
if (scm_is_null (val) || scm_is_false (val))
return true;
// [...]
}
Best,
Jean
