scalaz-stream-metaphor.txt

process, absent anything else, is strictly pull

you should think of run like a giant wheel that is spinning and pulling in some rope, which is the process

the other end of that rope MAY be attached to a queue

you're pulling from that queue

and there may be an observer sitting on the rope which pushes into another queue

but ultimately, you still need the wheel, even when you're observing into the queue

(remember that "to" is just "observe" in disguise)

wye is a bit like having bizarre contraption that takes two ropes and produces a single one

but instead of doing the natural thing by winding the two ropes together

it slices the ropes laterally and restitches them

so it needs to wheels that are running to pull each rope individually

and it just fashions a new rope out of thin air

in the hopes that someone at the other end of that new rope is pulling on it

if that hypothetical someone doesn't pull fast enough, it stops its incoming wheels

so that it doesn't just build a gigantic pile of rope