apecs

apecs is an Entity Component System (ECS) framework inspired by specs and Entitas. ECS presents a data-driven approach to game development, that elegantly tackles many of the unique issues of game programming. apecs aims to be

• Fast - apecs is designed for high-performance applications. Its performance is competitive with Rust ECS libraries.
• Simple - Game logic is expressed using a small number of combinators, and minimal boilerplate.
• Safe - The cmap/cfold-DSL hides all the dangers of the low-level API.
• Extensible - apecs can be used with anything that implements the low-level API. See apecs-physics or apecs-stm for examples.

Links

• manual (see #19)
• tutorial
• documentation
• apecs-physics

Performance

ecs-bench shows that apecs is competitive with the fastest Rust ECS frameworks.

Example

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

import Apecs
import Control.Monad
import Apecs.Util
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