moved unique_mapping to ferris

init.lua

@@ -33,7 +33,6 @@ local _batteries = {
 	--
 	timer = require_relative("timer"),
 	pubsub = require_relative("pubsub"),
-	unique_mapping = require_relative("unique_mapping"),
 	state_machine = require_relative("state_machine"),
 	async = require_relative("async"),
 	manual_gc = require_relative("manual_gc"),

readme.md

@@ -93,7 +93,6 @@ These modules are probably only useful to some folks in some circumstances, or a
 - [`colour`](./colour.lua) - Colour conversion routines. Alias `color`.
 - [`manual_gc`](./manual_gc.lua) - Get GC out of your update/draw calls. Useful when trying to get accurate profiling information; moves "randomness" of GC. Requires you to think a bit about your garbage budgets though.
 - [`measure`](./measure.lua) - Benchmarking helpers - measure the time or memory taken to run some code.
-- [`unique_mapping`](./unique_mapping.lua) - Generate a unique mapping from arbitrary lua values to numeric keys - essentially making up a consistent ordering for unordered data. Niche, but can be used to optimise draw batches for example, as you can't sort on textures without it.
 - [`make_pooled`](./make_pooled.lua) - add pooling/recycling capability to a class
 
 Any aliases are provided at both the `batteries` module level, and globally when exported.

unique_mapping.lua

@@ -1,62 +0,0 @@
---[[
-	unique mapping
-
-	generate a mapping from unique values to plain numbers
-	useful for arbitrarily ordering things that don't have
-	a natural ordering in lua (eg textures for batching)
-]]
-
-local unique_mapping = {}
-unique_mapping._mt = {
-	__index = unique_mapping,
-	__mode = "kv", --weak refs
-}
-
---(used as storage for non-weak data)
-local _MAP_VARS = setmetatable({}, {
-	__mode = "k" --only keys are weak
-})
-
---create a new unique mapping
-function unique_mapping:new()
-	local r =  setmetatable({}, self._mt)
-	--set up the actual vars
-	_MAP_VARS[r] = {
-		current_index = 0,
-	}
-	return r
-end
-
---private;
---get the next index for this mapping
-function unique_mapping:_increment()
-	local vars = _MAP_VARS[self]
-	vars.current_index = vars.current_index + 1
-	return vars.current_index
-end
-
---get or build a mapping for a passed value
-function unique_mapping:map(value)
-	local val = self[value]
-	if val then
-		return val
-	end
-	local i = self:_increment()
-	self[value] = i
-	return i
-end
-
---get a function representing an a < b comparision that can be used
---with table.sort and friends, like `table.sort(values, mapping:compare())`
-function unique_mapping:compare()
-	--	memoised so it doesn't generate garbage, but also doesn't
-	--	allocate until it's actually used
-	if not self._compare then
-		self._compare = function(a, b)
-			return self:map(a) < self:map(b)
-		end
-	end
-	return self._compare
-end
-
-return unique_mapping