It's been ages since I've used a "real" functional language but wouldn't it be nice to parameterise externalities like time, and have events occur "spontaneousl

It's been ages since I've used a "real" functional language but wouldn't it be nice to parameterise externalities like time, and have events occur "spontaneously" that force application state to update? Kind of like interrupts. Or now that I think about it... it sounds a bit like React where DOM events etc force application state to update (in a pure fashion) Has this been done before? So your LED function in pseudocode looks like ToggleLeds(leds, t): for each LED LED.power = (LED.start + 1s) > t ? ON : OFF And this is invoked from main() as follows main(): ToggleLeds(this.LEDs, Events.Time) Where Events.Time is some kind of event stream which allows the runtime to reevaluate main() and any other dependent functions each time it's updated edit: And to sidestep the obvious performance issue with the function being reevaluated every few microseconds :D you would implement something like this main(): ToggleLeds(this.LEDs, Events.Time(ms=1000))