Update version to 1.1-1.

This removes a level of indirection and prevents passing around of entities.

.gitignore

@@ -3,3 +3,6 @@ doc/*
 index.html
 ldoc.css
 topics/*
+
+#Ignore generated rocks
+*.rock

README.md

@@ -9,9 +9,6 @@ Tiny-ecs also works well with Objected Oriented programming in lua because
 Systems and Entities do not use metatables. This means you can subclass your
 Systems and Entities, and use existing lua class frameworks with tiny-ecs, no problem.
 
-## Use It ##
-Copy paste tiny.lua into your source folder.
-
 ## Overview ##
 Tiny-ecs has four important types: Worlds, Filters, Systems, and Entities.
 Entities, however, can be any lua table, and Filters are just functions that
@@ -64,6 +61,20 @@ for i = 1, 20 do
 end
 ```
 
+## Use It ##
+Copy paste tiny.lua into your source folder. For stability and consistent API,
+please use a tagged release or use luarocks. Tagged releases will have a version
+number in `tiny._VERSION`, while other commits will just have the string 'dev'.
+
+## Luarocks ##
+Tiny-ecs is also on [Luarocks](https://luarocks.org/) and can be installed with
+`luarocks install tiny-ecs`.
+
+## Demo ##
+Check out the [demo](https://github.com/bakpakin/tiny-ecs/tree/demo-commandokibbles), a game
+originally written for Ludum Dare 32 with the theme 'An Unconventional Weapon'. The demo uses
+[LOVE](https://love2d.org/), an amazing game framework for lua.
+
 ## Testing ##
 Tiny-ecs uses [busted](http://olivinelabs.com/busted/) for testing. Install and run
 `busted` from the command line to test.
@@ -76,5 +87,5 @@ Documentation can be generated locally with [LDoc](http://stevedonovan.github.io
 
 * More testing
 * Performance testing / optimization
+* Add more System types
 * Improve Documentation
-* Add more complete examples

config.ld

@@ -2,6 +2,11 @@ file = "tiny.lua"
 project = "tiny-ecs"
 description = "Entity Component System for lua."
 backtick_references = true
-one = false
+format = 'discount'
+title = "tiny-ecs API"
+one = true
 dir = doc
-sort = true
+style = '!fixed'
+package = 'tiny-ecs'
+not_luadoc = true
+boilerplate = true

rockspecs/tiny-ecs-1.0-2.rockspec

@@ -21,4 +21,4 @@ build = {
     modules = {
         tiny = "tiny.lua"
     }
-}
+}

rockspecs/tiny-ecs-1.1-1.rockspec

@@ -0,0 +1,24 @@
+package = "tiny-ecs"
+version = "1.1-1"
+source = {
+    url = "git://github.com/bakpakin/tiny-ecs",
+    tag = "1.1-1"
+}
+description = {
+    summary = "Entity Component System for Lua.",
+    detailed = [[
+        Pure Lua implementation of an easy to use, compact, fast, and flexible
+        Entity Component System. Works well with Object Orientation.
+    ]],
+    homepage = "https://github.com/bakpakin/tiny-ecs",
+    license = "MIT"
+}
+dependencies = {
+    "lua >= 5.1"
+}
+build = {
+    type = "builtin",
+    modules = {
+        tiny = "tiny.lua"
+    }
+}

spec/tiny_spec.lua

@@ -1,24 +1,15 @@
 local tiny = require "tiny"
 
--- Taken from answer at http://stackoverflow.com/questions/640642/how-do-you-copy-a-lua-table-by-value
+local function deep_copy(x)
-local function deep_copy(o, seen)
+    if type(x) == 'table' then
-  seen = seen or {}
+        local nx = {}
-  if o == nil then return nil end
+        for k, v in next, x, nil do
-  if seen[o] then return seen[o] end
+            nx[deep_copy(k)] = deep_copy(v)
-
+        end
-  local no
+        return nx
-  if type(o) == 'table' then
+    else
-    no = {}
+        return x
-    seen[o] = no
-
-    for k, v in next, o, nil do
-      no[deep_copy(k, seen)] = deep_copy(v, seen)
     end
-    setmetatable(no, deep_copy(getmetatable(o), seen))
-  else -- number, string, boolean, etc
-    no = o
-  end
-  return no
 end
 
 local entityTemplate1 = {
@@ -97,9 +88,9 @@ describe('tiny-ecs:', function()
 
         local timePassed = 0
         local oneTimeSystem = tiny.system()
-        function oneTimeSystem:update(entities, dt)
+        function oneTimeSystem:update(dt)
             timePassed = timePassed + dt
-        end 
+        end
 
         before_each(function()
             entity1 = deep_copy(entityTemplate1)
@@ -138,15 +129,19 @@ describe('tiny-ecs:', function()
             assert.equals(0, world:getSystemCount())
         end)
 
-        it("Disable and Enable Systems", function()
+        it("Deactivate and Activate Systems", function()
-            world:deactivate(moveSystem, oneTimeSystem)
+            moveSystem.active = false
+            oneTimeSystem.active = false
             world:update(1)
+            assert.equals(world:getSystemCount(), 2)
             assert.equals(timePassed, 0)
             assert.equals(entity1.xform.x, entityTemplate1.xform.x)
-            world:activate(moveSystem, oneTimeSystem)
+            moveSystem.active = true
+            oneTimeSystem.active = true
             world:update(1)
             assert.equals(timePassed, 1)
             assert.are_not.equal(entity1.xform.x, entityTemplate1.xform.x)
+            assert.equals(world:getSystemCount(), 2)
         end)
 
         it("Clear Entities", function()

tiny.lua

@@ -1,10 +1,34 @@
+--[[
+Copyright (c) 2015 Calvin Rose
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+]]
+
 --- @module tiny-ecs
 -- @author Calvin Rose
-local tiny = { _VERSION = "1.0-2" }
+-- @license MIT
+-- @copyright 2015
+local tiny = { _VERSION = "1.1-1" }
 
 -- Local versions of standard lua functions
 local tinsert = table.insert
 local tremove = table.remove
+local tsort = table.sort
 local pairs = pairs
 local ipairs = ipairs
 local setmetatable = setmetatable
@@ -22,20 +46,49 @@ local tiny_remove
 
 --- Filter functions.
 -- A Filter is a function that selects which Entities apply to a System.
+-- Filters take two parameters, the System and the Entity, and return a boolean
+-- value indicating if the Entity should be processed by the System.
+--
+-- Filters must be added to Systems by setting the `filter` field of the System.
+-- Filter's returned by `tiny.requireAll` and `tiny.requireOne` are immutable
+-- and can be used by multiple Systems.
+--
+--    local f1 = tiny.requireAll("position", "velocity", "size")
+--    local f2 = tiny.requireOne("position", "velocity", "size")
+--
+--    local e1 = {
+--        position = {2, 3},
+--        velocity = {3, 3},
+--        size = {4, 4}
+--    }
+--
+--    local entity2 = {
+--        position = {4, 5},
+--        size = {4, 4}
+--    }
+--
+--    local e3 = {
+--        position = {2, 3},
+--        velocity = {3, 3}
+--    }
+--
+--    print(f1(nil, e1), f1(nil, e2), f1(nil, e3)) -- prints true, false, false
+--    print(f2(nil, e1), f2(nil, e2), f2(nil, e3)) -- prints true, true, true
+--
 -- @section Filter
 
---- Makes a Filter that filters Entities with specified Components.
+--- Makes a Filter that selects Entities with all specified Components and
--- An Entity must have all Components to match the filter.
+-- Filters.
--- @param ... List of Components
+-- @param ... List of required Components and other Filters.
 function tiny.requireAll(...)
     local components = {...}
     local len = #components
-    return function(_, e)
+    return function(system, e)
         local c
         for i = 1, len do
             c = components[i]
             if type(c) == 'function' then
-                if not c(_, e) then
+                if not c(system, e) then
                     return false
                 end
             elseif e[c] == nil then
@@ -46,18 +99,18 @@ function tiny.requireAll(...)
     end
 end
 
---- Makes a Filter that filters Entities with specified Components.
+--- Makes a Filter that selects Entities with at least one of the specified
--- An Entity must have at least one specified Component to match the filter.
+-- Components and Filters.
--- @param ... List of Components
+-- @param ... List of required Components and other Filters.
 function tiny.requireOne(...)
     local components = {...}
     local len = #components
-    return function(_, e)
+    return function(system, e)
         local c
         for i = 1, len do
             c = components[i]
             if type(c) == 'function' then
-                if c(_, e) then
+                if c(system, e) then
                     return true
                 end
             elseif e[c] ~= nil then
@@ -81,34 +134,44 @@ local function isSystem(table)
     return table[systemTableKey]
 end
 
---- Creates a System. Systems are tables that contain at least one field; 
+--- Creates a System. Systems are tables that contain at least one method;
--- an update function that takes parameters like so: 
+-- an update function that takes parameters like so:
--- `function system:update(entities, dt)`. `entities` is an unordered table of 
+--
--- Entities with Entities as KEYS, and `dt` is the delta time. There are also a 
+--   * `function system:update(dt)`.
--- few other optional callbacks:
+--
--- `function system:filter(entity)` - returns a boolean,
+-- There are also a few other optional callbacks:
--- `function system:onAdd(entity)` - returns nil,
+--
--- `function system:onRemove(entity)` - returns nil.
+--   * `function system:filter(entity)`
+--   * `function system:onAdd(entity)`
+--   * `function system:onRemove(entity)`
+--   * `function system:onModify(dt)`
+--
 -- For Filters, it is conveient to use `tiny.requireAll` or `tiny.requireOne`,
--- but one can write their own filters as well.
+-- but one can write their own filters as well. Set the Filter of your System
+-- like so:
+--    system.filter = tiny.requireAll("a", "b", "c")
+-- or
+--    function system:filter(entity)
+--        return entity.myRequiredComponentName ~= nil
+--    end
+--
 -- @param table A table to be used as a System, or `nil` to create a new System.
 function tiny.system(table)
-    if table == nil then
+    table = table or {}
-        table = {}
-    end
     table[systemTableKey] = true
     return table
 end
 
 -- Update function for all Processing Systems.
-local function processingSystemUpdate(system, entities, dt)
+local function processingSystemUpdate(system, dt)
+    local entities = system.entities
     local preProcess = system.preProcess
     local process = system.process
     local postProcess = system.postProcess
     local entity
 
     if preProcess then
-        preProcess(system, entities, dt)
+        preProcess(system, dt)
     end
 
     if process then
@@ -120,38 +183,83 @@ local function processingSystemUpdate(system, entities, dt)
     end
 
     if postProcess then
-        postProcess(system, entities, dt)
+        postProcess(system, dt)
     end
 end
 
---- Creates a Processing System. A Processing System iterates through its 
+--- Creates a Processing System.
--- Entities in no particluar order, and updates them individually. It has two 
+--
--- important fields, `function system:process(entity, dt)`, and `function 
+-- A Processing System iterates through its Entities in no particluar order, and
--- system:filter(entity)`. `entities` is Entities, 
+-- updates them individually. It has two important fields:
--- and `dt` is the delta time. There are also a few other 
+--
--- optional callbacks:
+--   * `function system:process(entity, dt)`
--- `function system:preProcess(entities, dt)` - returns nil,
+--   * `function system:filter(entity)`
--- `function system:postProcess(entities, dt)` - returns nil,
+--
--- `function system:onAdd(entity)` - returns nil,
+-- There are also a few other optional callbacks, including the optional
--- `function system:onRemove(entity)` - returns nil.
+-- callbacks in `tiny.system`:
--- For Filters, it is conveient to use `tiny.requireAll` or `tiny.requireOne`,
+--
--- but one can write their own filters as well.
+--   * `function system:preProcess(entities, dt)`
--- @param table A table to be used as a System, or `nil` to create a new 
+--   * `function system:postProcess(entities, dt)`
+--
+-- @param table A table to be used as a System, or `nil` to create a new
 -- Processing System.
+-- @see system
 function tiny.processingSystem(table)
-    if table == nil then
+    table = table or {}
-        table = {}
-    end
     table[systemTableKey] = true
     table.update = processingSystemUpdate
     return table
 end
 
+-- Sorts Systems by a function system.sort(entity1, entity2) on modify.
+local function sortedSystemOnModify(system, dt)
+    local entities = system.entities
+    local entityIndices = system.entityIndices
+    local sortDelegate = system.sortDelegate
+    if not sortDelegate then
+        local compare = system.compare
+        sortDelegate = function(e1, e2)
+            compare(system, e1, e2)
+        end
+        system.sortDelegate = sortDelegate
+    end
+    tsort(entities, sortDelegate)
+    for i = 1, #entities do
+        local entity = entities[i]
+        entityIndices[entity] = i
+    end
+end
+
+--- Creates a Sorted Processing System. A Sorted System iterates through its
+-- Entities in a specific order, and updates them individually. It has three
+-- important methods:
+--
+--   * `function system:process(entity, dt)`
+--   * `function system:compare(entity1, entity2)`
+--   * `function system:filter(entity)`
+--
+-- Sorted Systems have the same optitonal callbacks as ProcessingSystems.
+-- @param table A table to be used as a System, or `nil` to create a new
+-- Sorted System.
+-- @see system
+-- @see processingSystem
+function tiny.sortedSystem(table)
+    table = table or {}
+    table[systemTableKey] = true
+    table.update = processingSystemUpdate
+    table.onModify = sortedSystemOnModify
+    table.sort = sortedSystemOnModify
+    return table
+end
+
 --- World functions.
--- A World is a container that manages Entities and Systems. The tiny-ecs module
+-- A World is a container that manages Entities and Systems. Typically, a
--- is set to be the `__index` of all World tables, so the often clearer syntax of
+-- program uses one World at a time.
--- World:method can be used for any function in the library. For example,
+--
--- `tiny.add(world, e1, e2, e3)` is the same as `world:add(e1, e2, e3).`
+-- The tiny-ecs module is set to be the `__index` of all World tables, so the
+-- often clearer syntax of `world:method()` can be used for any function in the
+-- library. For example, `tiny.add(world, e1, e2, e3)` is the same as
+-- `world:add(e1, e2, e3).`
 -- @section World
 
 local worldMetaTable = { __index = tiny }
@@ -176,7 +284,7 @@ function tiny.world(...)
         -- List of Entities to remove
         systemsToRemove = {},
 
-        -- Set of Entities 
+        -- Set of Entities
         entities = {},
 
         -- Number of Entities in World.
@@ -199,9 +307,8 @@ function tiny.world(...)
 end
 
 --- Adds an Entity to the world.
--- The new Entity will enter the world next time World:update is called.
+-- Also call this on Entities that have changed Components such that they
--- Also call this on Entities that have changed Components such that it 
+-- match different Filters.
--- matches different systems.
 -- @param world
 -- @param entity
 function tiny.addEntity(world, entity)
@@ -214,7 +321,6 @@ end
 tiny_addEntity = tiny.addEntity
 
 --- Adds a System to the world.
--- The new System will enter the world next time World:update is called.
 -- @param world
 -- @param system
 function tiny.addSystem(world, system)
@@ -224,11 +330,10 @@ end
 tiny_addSystem = tiny.addSystem
 
 --- Shortcut for adding multiple Entities and Systems to the World.
--- New objects will enter the World the next time World:update(dt) is called.
--- Also call this method when an Entity has had its Components changed, such
--- that it matches different Filters.
 -- @param world
 -- @param ... Systems and Entities
+-- @see addEntity
+-- @see addSystem
 function tiny.add(world, ...)
     local args = {...}
     for _, obj in ipairs(args) do
@@ -242,9 +347,6 @@ end
 tiny_add = tiny.add
 
 --- Removes an Entity to the World.
--- The Entity will exit the World next time World:update is called.
--- Also call this on Entities that have changed Components such that it 
--- matches different systems.
 -- @param world
 -- @param entity
 function tiny.removeEntity(world, entity)
@@ -254,7 +356,6 @@ end
 tiny_removeEntity = tiny.removeEntity
 
 --- Removes a System from the world.
--- The System will exit the World next time World:update is called.
 -- @param world
 -- @param system
 function tiny.removeSystem(world, system)
@@ -263,10 +364,11 @@ function tiny.removeSystem(world, system)
 end
 tiny_removeSystem = tiny.removeSystem
 
---- Shortcut for removing multiple Entities and Systems from the World. 
+--- Shortcut for removing multiple Entities and Systems from the World.
--- Objects will exit the World the next time World:update(dt) is called.
 -- @param world
 -- @param ... Systems and Entities
+-- @see removeEntity
+-- @see removeSystem
 function tiny.remove(world, ...)
     local args = {...}
     for _, obj in ipairs(args) do
@@ -279,19 +381,8 @@ function tiny.remove(world, ...)
 end
 tiny_remove = tiny.remove
 
---- Updates a System.
+-- Adds and removes Systems that have been marked from the World.
--- @param world
+function tiny_manageSystems(world)
--- @param system A System in the World to update
--- @param dt Delta time
-function tiny.updateSystem(world, system, dt)
-    local es = world.systemEntities[system]
-    system:update(es, dt)
-end
-
---- Adds and removes Systems that have been marked from the World.
--- The user of this library should seldom if ever call this.
--- @param world
-function tiny.manageSystems(world)
 
         local s2a, s2r = world.systemsToAdd, world.systemsToRemove
 
@@ -303,18 +394,17 @@ function tiny.manageSystems(world)
         local systemIndices = world.systemIndices
         local entities = world.entities
         local systems = world.systems
-
+        local system, index, filter
-        local system, systemData, index, filter, entityList, entityIndices, entityIndex, onRemove, onAdd
+        local entityList, entityIndices, entityIndex, onRemove, onAdd
 
         -- Remove Systems
         for i = 1, #s2r do
             system = s2r[i]
             index = systemIndices[system]
             if index then
-                systemData = systems[index]
                 onRemove = system.onRemove
                 if onRemove then
-                    entityList = systemData.entities
+                    entityList = system.entities
                     for j = 1, #entityList do
                         onRemove(system, entityList[j])
                     end
@@ -322,7 +412,7 @@ function tiny.manageSystems(world)
                 systemIndices[system] = nil
                 tremove(systems, index)
                 for j = index, #systems do
-                    systemIndices[systems[j].system] = j
+                    systemIndices[systems[j]] = j
                 end
             end
             s2r[i] = nil
@@ -334,10 +424,13 @@ function tiny.manageSystems(world)
             if not systemIndices[system] then
                 entityList = {}
                 entityIndices = {}
-                systemData = { system = system, entities = entityList, indices = entityIndices, active = true }
+                system.entities = entityList
+                system.indices = entityIndices
+                system.active = true
+                system.modified = true
                 index = #systems + 1
                 systemIndices[system] = index
-                systems[index] = systemData
+                systems[index] = system
 
                 -- Try to add Entities
                 onAdd = system.onAdd
@@ -359,12 +452,9 @@ function tiny.manageSystems(world)
         end
 
 end
-tiny_manageSystems = tiny.manageSystems
 
---- Adds and removes Entities that have been marked.
+-- Adds and removes Entities that have been marked.
--- The user of this library should seldom if ever call this.
+function tiny_manageEntities(world)
--- @param world
-function tiny.manageEntities(world)
 
     local e2a, e2r = world.entitiesToAdd, world.entitiesToRemove
 
@@ -376,7 +466,8 @@ function tiny.manageEntities(world)
     local entities = world.entities
     local systems = world.systems
     local entityCount = world.entityCount
-    local entity, system, systemData, index, onRemove, onAdd, ses, seis, filter, tmpEntity
+    local entity, system, index
+    local onRemove, onAdd, ses, seis, filter, tmpEntity
 
     -- Remove Entities
     for i = 1, #e2r do
@@ -385,13 +476,13 @@ function tiny.manageEntities(world)
             entities[entity] = nil
 
             for j = 1, #systems do
-                systemData = systems[j]
+                system = systems[j]
-                system = systemData.system
+                ses = system.entities
-                ses = systemData.entities
+                seis = system.indices
-                seis = systemData.indices
                 index = seis[entity]
 
                 if index then
+                    system.modified = true
                     tmpEntity = ses[#ses]
                     ses[index] = tmpEntity
                     seis[tmpEntity] = index
@@ -418,12 +509,12 @@ function tiny.manageEntities(world)
             entities[entity] = true
 
             for j = 1, #systems do
-                systemData = systems[j]
+                system = systems[j]
-                system = systemData.system
+                ses = system.entities
-                ses = systemData.entities
+                seis = system.indices
-                seis = systemData.indices
                 filter = system.filter
                 if filter and filter(system, entity) then
+                    system.modified = true
                     index = #ses + 1
                     ses[index] = entity
                     seis[entity] = index
@@ -444,11 +535,9 @@ function tiny.manageEntities(world)
     world.entityCount = entityCount
 
 end
-tiny_manageEntities = tiny.manageEntities
 
 --- Updates the World.
--- Frees Entities that have been marked for freeing, adds
+-- Put this in your main loop.
--- entities that have been marked for adding, etc.
 -- @param world
 -- @param dt Delta time
 function tiny.update(world, dt)
@@ -457,20 +546,31 @@ function tiny.update(world, dt)
     tiny_manageEntities(world)
 
     local systems = world.systems
-    local systemData
+    local system, update, onModify, entities
 
     --  Iterate through Systems IN ORDER
     for i = 1, #systems do
-        systemData = systems[i]
+        system = systems[i]
-        if systemData.active then
+        if system.active then
-            systemData.system:update(systemData.entities, dt)
+
+            -- Call the modify callback on Systems that have been modified.
+            onModify = system.onModify
+            if onModify and system.modified then
+                onModify(system, dt)
+            end
+
+            --Update Systems that have an update method (most Systems)
+            update = system.update
+            if update then
+                update(system, dt)
+            end
+
+            system.modified = false
         end
     end
 end
 
 --- Removes all Entities from the World.
--- When World:update(dt) is next called,
--- all Entities will be removed.
 -- @param world
 function tiny.clearEntities(world)
     for e in pairs(world.entities) do
@@ -479,13 +579,11 @@ function tiny.clearEntities(world)
 end
 
 --- Removes all Systems from the World.
--- When World:update(dt) is next called,
--- all Systems will be removed.
 -- @param world
 function tiny.clearSystems(world)
     local systems = world.systems
     for i = #systems, 1, -1 do
-        tiny_removeSystem(world, systems[i].system)
+        tiny_removeSystem(world, systems[i])
     end
 end
 
@@ -501,7 +599,7 @@ function tiny.getSystemCount(world)
     return #(world.systems)
 end
 
---- Gets the index of a System in the world. Lower indexed Systems are processed
+--- Gets the index of a System in the World. Lower indexed Systems are processed
 -- before higher indexed systems.
 -- @param world
 -- @param system
@@ -509,8 +607,8 @@ function tiny.getSystemIndex(world, system)
     return world.systemIndices[system]
 end
 
---- Sets the index of a System in the world. Changes the order in
+--- Sets the index of a System in the World. Changes the order in
--- which they Systems processed, because lower indexed Systems are processed 
+-- which they Systems processed, because lower indexed Systems are processed
 -- first.
 -- @param world
 -- @param system
@@ -519,39 +617,13 @@ function tiny.setSystemIndex(world, system, index)
     local systemIndices = world.systemIndices
     local oldIndex = systemIndices[system]
     local systems = world.systems
-    local systemData = systems[oldIndex]
+    local system = systems[oldIndex]
 
     tremove(systems, oldIndex)
-    tinsert(systems, index, systemData)
+    tinsert(systems, index, system)
 
     for i = oldIndex, index, index >= oldIndex and 1 or -1 do
-        systemIndices[systems[i].system] = i
+        systemIndices[systems[i]] = i
-    end
-end
-
---- Activates Systems in the World.
--- Activated Systems will be update whenever tiny.update(world, dt) is called.
--- @param world
--- @param ... Systems to activate. The Systems must already be added to the
--- World.
-function tiny.activate(world, ...)
-    local args = {...}
-    for _, system in ipairs(args) do
-        world.systems[world.systemIndices[system]].active = true
-    end
-end
-
---- Deactivates Systems in the World.
--- Deactivated Systems must be update manually, and will not update when the
--- rest of World updates. They will, however, process new Entities added while
--- the System is deactivated.
--- @param world
--- @param ... Systems to deactivate. The Systems must already be added to the
--- World.
-function tiny.deactivate(world, ...)
-    local args = {...}
-    for _, system in ipairs(args) do
-        world.systems[world.systemIndices[system]].active = false
     end
 end