apecs

apecs is an Entity Component System (ECS) library for game development.

apecs aims to be

• Fast - Performance is competitive with Rust ECS libraries (see benchmark results below)
• Safe - Completely hides the dangers of the low-level machinery
• Concise - Game logic is expressed using a small number of powerful combinators
• Flexible - Easily add new modules or backends
• Cool

Links

• documentation on hackage
• tutorial and other examples
• community chat at #apecs on the haskell gamedev discord or #haskell-game:matrix.org

Games/articles

• Notakto, and associated blog post/apecs tutorial by @Ashe
• mallRL - a grocery shopping roguelike by @nmaehlmann
• An implementation of the Unity tutorial project using apecs by @mewhhaha
• SpaceMar by @dpwiz
• Achtung die haskell by @mewhhaha
• (Your game here)

Packages

• apecs

  

• apecs-physics - 2D physics using the Chipmunk2D engine

  

• apecs-gloss - Simple frontend for gloss-based rendering

  

• apecs-stm - STM-based stores for easy concurrency

  

• examples

  

Example

{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables   #-}
{-# LANGUAGE TemplateHaskell       #-}
{-# LANGUAGE TypeFamilies          #-}

import Apecs
import Linear (V2 (..))

newtype Position = Position (V2 Double) deriving Show
newtype Velocity = Velocity (V2 Double) deriving Show
data Flying = Flying

makeWorldAndComponents "World" [''Position, ''Velocity, ''Flying]

game :: System World ()
game = do
  newEntity (Position 0, Velocity 1)
  newEntity (Position 2, Velocity 1)
  newEntity (Position 1, Velocity 2, Flying)

  -- 1. Add velocity to position
  -- 2. Apply gravity to non-flying entities
  -- 3. Print a list of entities and their positions
  cmap $ \(Position p, Velocity v) -> Position (v+p)
  cmap $ \(Velocity v, _ :: Not Flying) -> Velocity (v - V2 0 1)
  cmapM_ $ \(Position p, Entity e) -> liftIO . print $ (e, p)

main :: IO ()
main = initWorld >>= runSystem game