Module:Round

Documentation for this module may be created at Module:Round/doc

-- for comparing numbers but leaving trailing zeros so sorts are cleaner

local p = {}

function p.main(frame)
	local args = frame:getParent().args
	local n = args[1]
	n = string.gsub(n,',','')
	n = tonumber(n,10)
	if not n then
		return 'Value is not a number'
	end

	local round = args.round or args[2]
	-- I don't think commas matter; we're not going to allow more than 10 probably
	round = tonumber(round,10)
	if not round then
		return 'Rounding is not a number'
	end

	return p.round(n,round)
end

-- rounds a number and then adds trailing zeros
-- only after the decimal point
-- negative rounding implies numbers before the decimal point are removed
-- but that can be done with #expr
-- this is meant for padding, which #expr can't do
function p.round(n,r)
	n = tonumber(n,10)
	r = tonumber(r,10)

	if not (n and r) then
		return '--'
	end

	r = math.floor(r)
	if r < 1 then
		return math.floor(n)
	end

	-- get decimal parts
	n = tostring(n)
	n = mw.text.split(n,'%.')

	local int,dec = n[1],n[2]

	if not dec then
		dec = 0
	end

	-- round the decimal part
	dec = '0.' .. dec
	dec = tonumber(dec,10)

	local rexp = 10 ^ r

	dec = math.floor(dec * rexp + 0.5) / rexp

	dec = tostring(dec) .. string.rep('0',r)

	-- cut down to desired round
	-- start at 3 because of "0.x"
	dec = string.sub(dec,3,2+r)

	-- recombine
	n = string.format('%s.%s',int,dec)

	return n
end

return p