apecs: A fast ECS for game engine programming

[ bsd3, control, data, game, library ] [ Propose Tags ]

A fast ECS for game engine programming

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Versions [faq],,,,,,,,,,,,,,,,,,,,,,,,,,,,, 0.7.0, 0.7.1, 0.7.2, 0.7.3, 0.8.0, 0.8.1, 0.8.2, 0.8.3, 0.9.0, 0.9.1, 0.9.2
Dependencies async, base (>=4.9 && <4.11), containers, mtl, template-haskell, vector [details]
License BSD-3-Clause
Author Jonas Carpay
Maintainer jonascarpay@gmail.com
Revised Revision 1 made by HerbertValerioRiedel at 2019-02-03T20:01:37Z
Category Game, Control, Data
Home page https://github.com/jonascarpay/apecs#readme
Source repo head: git clone git://github.com/jonascarpay/apecs.git
Uploaded by jonascarpay at 2017-09-28T19:58:09Z
Distributions LTSHaskell:0.7.3, NixOS:0.9.2, Stackage:0.7.3
Downloads 19549 total (180 in the last 30 days)
Rating 2.0 (votes: 1) [estimated by Bayesian average]
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Status Hackage Matrix CI
Docs available [build log]
Last success reported on 2017-09-28 [all 1 reports]




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hackage | documentation | tutorials

apecs is an Entity Component System inspired by specs and Entitas. It exposes a DSL that translates to fast storage operations, resulting in expressivity without sacrificing performance or safety.

There is an example below, and a tutorial can be found here. For a general introduction to ECS, see this talk or here.


Performance is good. Running the ecs-bench pos_vel benchmark shows that we can keep up with specs, which was written in Rust:

| | specs | apecs | | ------ | ------ | ------ | | build | 699 us | 285 us | | update | 34 us | 46 us |

There is a performance guide here.


import Apecs
import Apecs.TH (makeWorld)
import Apecs.Stores (Cache)
import Linear

newtype Position = Position (V2 Double) deriving Show
-- Turn Position into a component by specifiying the type of its Storage
instance Component Position where
  -- The simplest store is a Map
  type Storage Position = Map Position

newtype Velocity = Velocity (V2 Double)
instance Component Velocity where
  -- We can add a Cache for faster access
  type Storage Velocity = Cache 100 (Map Velocity)

data Player = Player -- A single constructor component for tagging the player
instance Component Player where
  -- Unique contains at most one component. See the Stores module.
  type Storage Player = Unique Player

-- Generate a world type and instances
makeWorld "World" [''Position, ''Velocity, ''Player]

game :: System World ()
game = do
  -- Create new entities
  ety <- newEntity (Position 0)
  -- Components can be composed using tuples
  newEntity (Position 0, Velocity 1)
  newEntity (Position 1, Velocity 1, Player)

  -- set (over)writes components
  set ety (Velocity 2)

  let stepVelocity (Position p, Velocity v) = Position (v+p)

  -- Side effects
  liftIO$ putStrLn "Stepping velocities"
  -- rmap maps a pure function over all entities in its domain
  rmap stepVelocity
  -- prmap n does the same, but in parallel
  prmap 2 stepVelocity

  -- Print all positions
  cmapM_ $ \(Position p) -> liftIO (print p)

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