Re: [reactive] First draft of reactive-tetris

Just to be curious, what would be the definition of withSubs? Something like withSubs :: [a] -> Event b -> Event (b,a) withSubs xs = (fmap.fmap) head . stateE xs tail Haven't tested it, still actively learning reactive... 2008/11/18 Conal Elliott

Also, a less forgetful version of subs might be useful:

withSubs xs e :: [a] -> Event b -> Event (b,a)

and then

subs xs e = snd <$> withSubs xs e

or, if you like,

subs = (fmap.fmap.fmap) snd withSubs

Btw, you can read the three fmaps directly from the signature of withSubs (two arrows plus one Event on the way to the pair).

- Conal

On Tue, Nov 18, 2008 at 10:11 AM, Conal Elliott wrote:

...

Cool! Thanks to quicksilver for the insight on and elegant definition of subs.

How about one of the following terser variations on the randomEvent def:

randomEvent std e = subs (randoms g) e

randomEvent std = subs (randoms g)

randomEvent = subs . randoms

- Conal

2008/11/18 Creighton Hogg

...

Being a dirty schlub & replying to myself, it turns out there is a way to substitute an infinite list into an Event as we've talked about this on #haskell this morning.

subs xs e :: [a] -> Event b -> Event a subs xs e = head <$> accumE xs (tail <$ e)

so then we can very easily do

randomEvent :: (RandomGen g,Random b) => g -> Event a -> Event b randomEvent std e = let vals = randoms g in subs vals e

Cool! Now I just need to change my Tetris to do that instead of messing with a Behavior.

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