A Proxy can be described as two coroutines bound together.
From a position inside of a function, one coroutine represents the interface to the incoming function parameter, the other represents the interface of the return value.
enum ProxySum<A,B,X,Y,R,E>{
Await(a:A,arw:Unary<B,Proxy<A,B,X,Y,R,E>>);
Yield(y:Y,arw:Unary<X,Proxy<A,B,X,Y,R,E>>);
Defer(ft:Belay<A,B,X,Y,R,E>);
Ended(res:Chunk<R,E>);
}Yield and Await are reflections of each other,
Defer is the abstraction of the runtime necessary to work in a polyglot environment.
Currently I'm working on ProcessServer and ProcessClient in stx_asys on a bunch of combinators that will allow composition of behaviours over console programs.