Add function to invert a subslide range

[eprovst]

When writing a theme, it would help to have a way to get an inverted subslide range, e.g., to have an alert function with optional subslide ranges (like Beamer):

#let alert(txt, vs: (:)) = {
   only(vs, text(txt, fill: red))
   only(invert-subslide-range(vs), txt)
}

Alternatively, alternatives-cases could stop evaluating at first match, then

#let alert(txt, vs: (:)) = alternatives-cases((vs, (:)), case => {
  set text(fill: red) if case == 0
  txt
})

would not always output the second case.

[andreasKroepelin]

Can you explain what you mean with inverted subslide range?

[eprovst]

I guess 'complementary range' would be a better description; a list of subslides where the given range is not active.

What you often want is an effect (e.g. alert) which is active on some slides and inactive on all others. From what I can tell, there is currently no (easy) way to provide such semantics, i.e. a user always has to manually provide the subslides where the effect is active and those where it is inactive.

[andreasKroepelin]

Ohh I see. How about calling it everywhere-but? You'd then have

#uncover(everywhere-but(2))[bla bla]

I'm open for other suggestions!

For your alert example, I think something like apply-only would be nice, so you could write

#apply-only("2, 4", text.with(fill: red))[bla bla]

[eprovst]

everywhere-but is definitely nicer. Alternatively, something like ("2, 4": content1, "5": content2, "otherwise": content3) as an argument to the alternatives-match function could be less confusing to end users? But that does not interact nicely with uncover, of course.

apply-only would definitely be a great tool to have!