Remove switch operator, implement simple fallback core operator, use …

[toots]

…cross to define top-level fallback operator, define switch using it.

[smimram]

I think the best abstraction would be a select operator such that

select(f, l)

with

• f of type unit -> int
• l of type source list
  plays the f()th source.

We can implement fallback over this.

[toots]

I think the best abstraction would be a select operator such that

select(f, l)

with

• f of type unit -> int
• l of type source list
  plays the f()th source.

We can implement fallback over this.

Can you explain more in details why? I'm not sure the benefit is immediate to me.

There's a complex interaction between source.is_ready and switch predicates that makes switch implementation tricky. When starting with a fallback based on source.is_ready, the low-level implementation is pretty straight forward. Then we can build on top of that using source.available to implement the switch, still following a strict logic based on source availability..