forEach, index, repeaters, delays, every, batch, stack

[Gaetano Checinski]

I imagine schedulers and eventsystems, for now i propose the following functions:

examples:

[1,2,3]
    ::forEach( function(){ console.log(this) } ) // executes func and yields items (1,2,3,1,2)
    ::index() //counts items and yields count-1
    ::takeWhile( function(){ return this<5 } )
  //::foo(...) //and keep the stream goin...

42::toFunction()
    ::every(100) // yields every 100ms
    ::forEach( function(){ console.log(this,new Date() ) }) // console.logs bout every 100ms

[1,2,3]
    ::repeat() // repeats yield'ing 1,2,3 till infinity
    ::forEach( function(){ console.log( new Date() , this ) }) //  yields this and executes given function
    ::delay(1000) // delayed yielding
    ::forEach( function(){ console.log( new Date(), this ) }) //console.log delayed bout 5s

[1,2,3]
    ::repeat()
    ::batch(5) // yields in batches of 5

[1,2,3]
    ::repeat()
    ::stack(5) // pop and yield an element if stack is full 

[Jussi Kalliokoski]

repeat is a must have, imo - however I'd like to leave async in Trine undecided for now - it's a hard problem to tame and I'd prefer to base things on future standards such as Observables and Streams as they become more stable, rather than invent the most energy efficient fuel car when electric cars are becoming the thing, if you know what I mean. ;) Meanwhile, A General Theory of Reactivity is good reading for immediate solutions outside Trine, as well as planning for the future of Trine.

[Jussi Kalliokoski]

As for batch - how would it know which kind of a collection to yield? Or would it yield an iterator? If iterator, you could handily compose with to to get the right kind of collection:

function * batch (n) {
  let buffer = [];

  for ( const item of this ) {
    buffer.push(item);
    if ( buffer.length >= n ) {
      yield buffer[Symbol.iterator]();
      buffer = [];
    }
  }
}

[1,2,3,4]
  ::batch(2)
  ::map(to::partial(Array))
  ::to(Array)
  // returns [[1, 2], [3, 4]]

[Gaetano Checinski]

Yup, your code describes exactly what i imagined(isn't there a buffer.push(item) missing?)

I don't understand your initial question; why should batch need to know which kind of collection it has to yield? - could it get more than one kind?

EDIT: wrong button pressed... how can i remove the "closed" message?

[Jussi Kalliokoski]

EDIT: wrong button pressed... how can i remove the "closed" message?

it's ok, no need to remove it :)

isn't there a buffer.push(item) missing?

yes, nicely spotted! fixed - wonder where it went, I tried it before posting and it worked :D

I don't understand your initial question; why should batch need to know which kind of collection it has to yield? - could it get more than one kind?

IMO it shouldn't, should just be oblivious to collection types and unfold iterators only at user will instead. Just making sure I understood what you proposed. :)