Hnum - a barbaric large number module for games.

hnum.lua

--[[
Hnum - a barbaric large number module for games.

Usage:

	local a_hundred = HNum:new(100)
	print(a_hundred:get_formatted()) -- 100


	local a_thousand = HNum:new(1000)
	print(a_thousand:get_formatted()) -- 1k

	local also_a_thousand = HNum:new(1, 1)
	print(also_a_thousand:get_formatted()) -- 1k

	a_thousand = a_thousand + 1000
	print(a_thousand:get_formatted()) -- 2k

	local a_million = HNum:new(1, 2)
	print(a_million:get_formatted()) -- 1m

	local two_billion_from_string = HNum:new("2573684736")
	print(two_billion_from_string:get_formatted()) -- 2.57b
	print(two_billion_from_string:to_string()) -- 2573684000

Note, that some precission is lost in the last example. It can be tweaked by increasing the
'precision' variable in HNum:from_string().

The methods for converting the number to and from a string are here to make storing the
value easily when saving the game. Simply store the :to_string-ed value in your save
data and pass it when creating a new instance of HNum during load.
]]--

local HNum = {}

-- Convert a number to a HNum table if needed
local function convert(num)
	if type(num) == "number" then
		num = HNum:new(num, 0)
	end
	return num
end

function HNum:new(value, thousands)
	local newObj = {
		__type = "hnum",
		value = value or 0.0,
		thousands = thousands or 0
	}
	self.__index = self
	setmetatable(newObj, self)
	if type(value) == "string" then
		newObj:from_string(value)
	end
	newObj:fix_compression()
	return newObj
end

function HNum:from_string(value)
	local precision = 2

	self.thousands = math.floor((string.len(value) - 1) / 3)
	if self.thousands == 0 then
		self.value = tonumber(value)
		self.thousands = 0
	end

	local baseValue = string.sub(value, 1, string.len(value) - (self.thousands * 3))
	self.value = tonumber(baseValue)

	precision = math.min(self.thousands, precision)
	for i = 0, precision - 1 do
		local subString = string.sub(value, string.len(baseValue) + (i * 3) + 1, string.len(baseValue) + (i * 3) + 3)
		self.value = self.value + tonumber(subString) / math.pow(1000.0, i + 1)
	end
end

function HNum:fix_compression()
	while math.abs(self.value) >= 1000.0 or self.thousands < 0 do
		self.value = self.value / 1000.0
		self.thousands = self.thousands + 1
	end

	while math.abs(self.value) < 1.0 and self.thousands > 0 do
		self.value = self.value * 1000.0
		self.thousands = self.thousands - 1
	end
end

function HNum:to_string()
	local outText = tostring(self.value)
	local charsCount = string.len(tostring(math.floor(self.value))) + (self.thousands * 3)
	local dotIdx = string.find(outText, "%.")
	if dotIdx ~= nil then
		outText = string.sub(outText, 1, dotIdx - 1) .. string.sub(outText, dotIdx + 1)
	end

	while string.len(outText) < charsCount do
		outText = outText .. "0"
	end

	return outText
end

function HNum:get_formatted()
	local outAbbrev = ""
	local abbrevs = { "", "k", "m", "b", "t" }

	if self.thousands == 0 then
		return tostring(math.floor(self.value+0.5))
	elseif self.thousands < #abbrevs then
		outAbbrev = abbrevs[self.thousands + 1]
	else
		local firstLetterCharCode = 97
		local lastLetterCharCode = 123
		local abbrevIdx = self.thousands - #abbrevs

		outAbbrev = string.char(firstLetterCharCode + abbrevIdx % (lastLetterCharCode - firstLetterCharCode))
		abbrevIdx = math.floor(abbrevIdx / (lastLetterCharCode - firstLetterCharCode))
		outAbbrev = "" .. string.char(firstLetterCharCode + abbrevIdx % (lastLetterCharCode - firstLetterCharCode)) .. outAbbrev
	end

	local truncate_mult = (10 ^ 2)
	local truncated_val = math.floor(self.value * truncate_mult) /truncate_mult
	local out = string.format("%.2f", truncated_val)
	if self.thousands > 0 then
		out = out:gsub("%.?0*$", "")
	end
	return out .. outAbbrev
end

function HNum:to_float()
	local outVal = self.value
	for i = 1, self.thousands do
		outVal = outVal * 1000
	end
	return outVal
end

function HNum:is_less_than(other)
	other = convert(other)
	return other.thousands > self.thousands or (other.thousands == self.thousands and other.value > self.value)
end

function HNum:equals(other)
	other = convert(other)
	return self.thousands == other.thousands and math.abs(self.value - other.value) < 0.00001
end

function HNum.__add(left_side, right_side)
	left_side = convert(left_side)
	right_side = convert(right_side)
	HNum.align_values(left_side, right_side)
	return HNum:new(left_side.value + right_side.value, left_side.thousands)
end

function HNum.__sub(left_side, right_side)
	left_side = convert(left_side)
	right_side = convert(right_side)
	HNum.align_values(left_side, right_side)
	return HNum:new(left_side.value - right_side.value, left_side.thousands)
end

function HNum.__mul(left_side, right_side)
	left_side = convert(left_side)
	right_side = convert(right_side)
	return HNum:new(left_side.value * right_side.value, left_side.thousands + right_side.thousands)
end

function HNum.__div(left_side, right_side)
	left_side = convert(left_side)
	right_side = convert(right_side)
	return HNum:new(left_side.value / right_side.value, left_side.thousands - right_side.thousands)
end

function HNum.__eq(left_side, right_side)
	return left_side:queals(right_side)
end

function HNum.__lt(left_side, right_side) -- less than
	return left_side.is_less_than(right_side)
end

function HNum.__le(left_side, right_side) -- less or equal
	return left_side:is_less_than(right_side) or left_side:equals(right_side)
end


function HNum.align_values(first, second)
	first = convert(first)
	second = convert(second)
	if first.thousands == second.thousands then
		return
	end

	if first.thousands > second.thousands then
		local diff = first.thousands - second.thousands
		for i = 1, diff do
			second.value = second.value / 1000.0
		end
		second.thousands = first.thousands
	else
		local diff = second.thousands - first.thousands
		for i = 1, diff do
			first.value = first.value / 1000.0
		end
		first.thousands = second.thousands
	end
end

return HNum