Peter Verswyvelen wrote:
Derek Elkins wrote:
you can use an equivalent Reader/Environment arrow transformer.
Nice, I did not know that monad yet, thanks!
But can it be combined together with the arrows do/proc syntax? How would that look like?
Something like this? ----8<---- module Main where import Control.Arrow import Control.Arrow.Operations import Control.Arrow.Transformer.Reader -- -- Standard list/stream arrow. -- newtype SF b c = SF { runSF :: [b] -> [c] } instance Arrow SF where arr f = SF (map f) SF f >>> SF g = SF (g . f) first (SF f) = SF (uncurry zip . (f *** id) . unzip) second (SF f) = SF (uncurry zip . (id *** f) . unzip) instance ArrowLoop SF where loop (SF f) = SF $ \as -> let (bs,cs) = unzip (f (zip as (stream cs))) in bs where stream ~(x:xs) = x:stream xs instance ArrowCircuit SF where delay x = SF (init . (x:)) -- -- Some state we want to pass around without manual plumbing. -- data AudioState = AudioState { sampleRate :: Double } runAudio state graph = proc p -> (| runReader (graph -< p) |) state -- -- Some unit generators for audio. -- wrap x = x - fromIntegral (floor x) -- phasor needs the sample rate phasor phase0 = proc hz -> do sr <- pure sampleRate <<< readState -< () rec accum <- delay (wrap phase0) -< wrap (accum + hz / sr) returnA -< accum -- osc doesn't need to know about sample rate osc phase0 = proc hz -> do phase <- phasor phase0 -< hz returnA -< cos (2 * pi * phase) -- -- Test it out. -- main = print (runSF (runAudio (AudioState{sampleRate=1000}) (osc 0)) (replicate 10 100)) ----8<----
Cheers, Peter
Thanks, Claude -- http://claudiusmaximus.goto10.org