An example of using Aff to run synchronous and asynchronous effects, and how to sequentially group effects using parSequence.

AffParallelExample.purs

-- Run with `pulp run --main AffParallel`

module AffParallelExample where

import Prelude
import Control.Monad.Aff (Aff, launchAff, forkAll, later')
import Control.Monad.Console (Console, log)
import Control.Parallel (parSequence)

type Piece = String
type X = Int
type Y = Int

main = launchAff $ do

  log "Running four half-second animations synchronously (2s total time)"

  animatePieceToPosition' "s-King"   1 1
  animatePieceToPosition' "s-Queen"  1 2
  animatePieceToPosition' "s-Jack"   1 3
  animatePieceToPosition' "s-Joker"  1 4

  log "Running four half-second animations asynchronously (.5s total time)"

  forkAll
    [ animatePieceToPosition' "as-One"    2 1
    , animatePieceToPosition' "as-Two"    2 2
    , animatePieceToPosition' "as-Three"  2 3
    , animatePieceToPosition' "as-Four"   2 4 ]

  log "Running 2 sets of four-asynchronous-half-second-animations synchronously (4s total time)"

  void $ parSequence
    [ animatePieceToPosition' "Rook"   3 1
    , animatePieceToPosition' "Pawn"   3 2
    , animatePieceToPosition' "Castle" 3 3
    , animatePieceToPosition' "Horse"   3 4 ]

  void $ parSequence
    [ animatePieceToHome' "Rook"
    , animatePieceToHome' "Pawn"
    , animatePieceToHome' "Castle"
    , animatePieceToHome' "Horse" ]

  log "Done"


-- | A function that simulates an animation, e.g. moving a game piece
-- | from it's current position to point x, y
animatePieceToPosition' :: forall e. Piece -> X -> Y -> Aff (console :: CONSOLE | e) Unit
animatePieceToPosition' piece x y = do
  log $ "- Moving " <> piece <> " to " <> (showPosition x y)
  later' 1000 $ log $ "- Done moving " <> piece <> " to " <> (showPosition x y)
  where showPosition x' y' = "(" <> (show x') <> "," <> (show y') <> ")"


-- | A function that simulates an animation, e.g. moving a game piece
-- | from it's current position to it's "home" position
animatePieceToHome' :: forall e. Piece -> Aff (console :: CONSOLE | e) Unit
animatePieceToHome' piece = do
  log $ "- Moving " <> piece <> " back to 'home' position."
  later' 1000 $ log $ "- Done moving " <> piece <> " to home."

output.txt

Running four half-second animations synchronously (4s total time)
- Moving s-King to (1,1)
- Done moving s-King to (1,1)
- Moving s-Queen to (1,2)
- Done moving s-Queen to (1,2)
- Moving s-Jack to (1,3)
- Done moving s-Jack to (1,3)
- Moving s-Joker to (1,4)
- Done moving s-Joker to (1,4)
Running four one-second animations asynchronously (1s total time)
- Moving as-One to (2,1)
- Moving as-Two to (2,2)
- Moving as-Three to (2,3)
- Moving as-Four to (2,4)
Running 2 sets of four asynchronous one-second animations synchronously (2s total time)
- Moving Rook to (3,1)
- Moving Pawn to (3,2)
- Moving Castle to (3,3)
- Moving Horse to (3,4)
- Done moving as-One to (2,1)
- Done moving as-Two to (2,2)
- Done moving as-Three to (2,3)
- Done moving as-Four to (2,4)
- Done moving Rook to (3,1)
- Done moving Pawn to (3,2)
- Done moving Castle to (3,3)
- Done moving Horse to (3,4)
- Moving Rook back to 'home' position.
- Moving Pawn back to 'home' position.
- Moving Castle back to 'home' position.
- Moving Horse back to 'home' position.
- Done moving Rook to home.
- Done moving Pawn to home.
- Done moving Castle to home.
- Done moving Horse to home.
Done