> In the code snippet, they define a "yield", and somehow this magically works With `with` you explicitely set the effect handler, no magic involved. > Also,

> In the code snippet, they define a "yield", and somehow this magically works With `with` you explicitely set the effect handler, no magic involved. > Also, the `fun yield( x : a ) : ()` syntax is highly unintuitive. It _takes_ an int and returns empty? So it's just a continuation? A function that does not return anything is (the poster child of) an impure function, that does nothing else but an (side) effect. That's why you need to call it as an effect and not a "normal" (pure) function. > And magically it transfers control flow to the correct place? How does it know where that is? It doesn't have to. The hidden `run` function (or whatever you want to call it) of the effect systém that actually calls the right effect handler has to know about that. The run function does something like (simplified) - see, that a effect handler with ID 'yield' is called - call the (currently registered) handler for 'yield' with the given arguments - call the continuation with the result of the handler