Higher-order effects and bidirectional effects

[b-studios]

Right now we can specify interfaces as follows:

interface Proc {
  def fork { f: () => Unit }: Unit
}

we can implement them with new. However, computation is not allowed as arguments when using the try construct.

It is somewhat obvious that this can be combined with bidirectional effects, to establish a sound semantics. So, we should just implement it as:

try {
  ...
} with Proc { 
  def fork() = resume { {f} => ... f()... }
}

(this is dual to #152)

[b-studios]

Q: Are there any interesting examples we could implement with this?

[b-studios]

A first step towards this issue would be to add block parameters to operation declarations and only support them on objects (fail on handlers). Then, in a second step, we can also support handlers.

[b-studios]

For people interested in working on this issue, there is a branch containing first steps at https://github.com/effekt-lang/effekt/tree/higher-order-effects

[b-studios]

Should hopefully be fixed by #361

[jiribenes]

Fixed by #361.