sharkdp
commented
8 years ago I hope this is the right venue to ask this kind of question.
Sure!
As you pointed out, the issue is that runFlareDrawing expects a UI Drawing, i.e. some interface that produces a pure value (a Drawing). As you have to run an effectful computation to generate that Drawing, you cannot use runFlareDrawing.
You can solve this by using runFlareWith instead (in your case, a = Int):
runFlareWith :: forall e. ElementId
-> (a -> Eff (dom :: DOM, channel :: CHANNEL | e) Unit)
-> UI e a
-> Eff (dom :: DOM, channel :: CHANNEL | e) UnitAs the second argument, this expects a custom function that can run any effectful computation (for you, eff includes RANDOM and Canvas). You can provide your own rendering function, something like:
drawRandomPoints :: forall eff. Context2D
-> Int
-> Eff (random :: RANDOM, canvas :: Canvas | eff) Unit
drawRandomPoints ctx n = do
clearRect ctx { x: 0.0, y: 0.0, w: width, h: height }
drawing <- randomPoints n
render ctx drawingFinally, in your main function, you would call runFlareWith instead:
main = do
Just canvas <- getCanvasElementById "canvas"
ctx <- getContext2D canvas
let ui = intRange "numPoints" 1 100 10
runFlareWith "controls" (drawRandomPoints ctx) uiYou can try it out here: http://sharkdp.github.io/try-flare/?gist=bdb4548abb6103be3e2a
oblitum
Say I would like a slider to choose a number
nand then plotnrandom points.I can do this easily if the points are deterministic, but once they're random I need to generate them in an
Eff (random :: RANDOM | e)context, and it's not obvious to me how to sequence that with the UI applicative. (I tried a number of things, but none of them worked.)See example (and non-example): https://gist.github.com/joelgrus/b27c12fc159367ea2440
I hope this is the right venue to ask this kind of question. Thanks!