Reader Monad

gen.js

function *f(){
  var a = yield "Arg1";
  var b = yield "Arg2";
  return a+b;
}
 
function *add(g1,g2){
  var x = yield* g1;
  var y = yield* g2;
  return x+y;
}
 
function *output(g){
  var ret = yield* g;
  console.log(ret);
}
 
function exec(g){
  var u;
  var val;
  while(u = g.next(val), !u.done){
    if(u.value == "Arg1")val = 3;
    if(u.value == "Arg2")val = 5;
  }
}
 
exec(output(add(f(),f()))); // 16