TECS - Simple ECS implementation for Nim. TECS is aimed at speed, simplicity and convenience in operation. Also TECS is overly light and simple. It is written without using macros and has no dependencies.

Docs: https://timofffee.github.io/tecs.nim/tecs.html

Install: nimble install tecs

# Component
type PositionComponent = object
  x: int
  y: int
# Tag
type MovableTag = object
# systems
proc updatePos(world: var World) =
  var filter = withTag(world, MovableTag).withComponent(world, PositionComponent)
  for entity in filter.items:
    var position = world.getComponent(entity, PositionComponent)
    position.x += 1
proc printPos(world: var World) =
  var filter = world.withComponent(PositionComponent)
  for entity in filter.items:
    var position = world.getComponent(entity, PositionComponent)
    echo (getEntityId(entity), getEntityVersion(entity), position.x, position.y)
# init
var world = initWorld()
var entityId = world.addEntity
world.addComponent(entityId, PositionComponent(x: 10))
var entityId2 = world.addEntity
world.addComponent(entityId2, PositionComponent(x: 20))
world.addTag(entityId2, MovableTag)
proc callSystems {.inline.} =
  updatePos(world)
  printPos(world)
callSystems()
world.removeTag(entityId2, MovableTag)
callSystems()
world.freeEntity(entityId2)
callSystems()
entityId2 = world.addEntity
world.addComponent(entityId2, PositionComponent(x: 30))
world.addTag(entityId2, MovableTag)
callSystems()

I will be very happy if you help me make a convenient and simple implementation of ECS for Nim. However, try to adhere to some rules:

1. Try not to use macros. This is a very powerful thing, but it complicates the code.
2. Try to keep the code as simple and tiny as possible. The more code there is, the more difficult it is to understand it.
3. Try not to use the features of new versions of Nim. They are definitely good, but when ecs can work with a version that was released many years ago, it's even better.

• The code is not divided into submodules. This really sucks, because if there is a desire to use only a part of TECS in several files, you will have to import the entire TECS into a file every time. This is a primary task that should be solved.
• The code is not fully understood. Although this implementation is extremely tiny, however, in some places there are no necessary checks and/or the code is written too clumsily.