Difference between revisions of "Module:Base convert"

Latest revision as of 15:33, 7 April 2019

local p = {}

local digits = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'

function normalizeFullWidthChars(s)
	return mw.ustring.gsub(s, '[！-～]', function(s)
		return mw.ustring.char(mw.ustring.codepoint(s, 1) - 0xFEE0)
	end)
end

function p._convert(n, base, from, precision, width, default, prefix, suffix)
	n = '' .. n   -- convert to a string

	n = n:gsub(' ','') -- kill whitespace

	-- strip off any leading '0x' (unless x is a valid digit in the input base)
	from = tonumber(from)

	if not from or from < 34 then
		local c
		n, c = n:gsub('^(-?)0[Xx]', '%1')
		if c > 0 and not from then from = 16 end
	end

	-- check for a negative sign. Do this while the input is still in string form,
	-- because tonumber doesn't support negative numbers in non-10 bases.
	local sign = ''
	local c
	n, c = n:gsub('^-', '')
	if c > 0 then sign = '-' end

	-- replace any full-width Unicode characters in the string with their ASCII equivalents
	n = normalizeFullWidthChars(n)

	-- handle scientific notation with whitespace around the 'e' e.g. '5 e7'
	n = n:gsub('%s*[eE]%s*', 'e')

	from = from or 10
	local num = tonumber(n, from)
	base = tonumber(base)
	precision = tonumber(precision)
	width = tonumber(width)

	if not num or not base then return default or n end

	local i, f = math.modf(num)

	local t = {}
	repeat
		local d = (i % base) + 1
		i = math.floor(i / base)
		table.insert(t, 1, digits:sub(d, d))
	until i == 0
	while #t < (width or 0) do
		table.insert(t, 1, '0')
	end
	local intPart = table.concat(t, '')

	-- compute the fractional part
	local tf = {}
	while f > 0 and #tf < (precision or 10) do
		f = f * base
		i, f = math.modf(f)
		table.insert(tf, digits:sub(i + 1, i + 1))
	end

	-- add trailing zeros if needed
	if precision and #tf < precision then
		for i = 1, precision - #tf do
			table.insert(tf, '0')
		end
	end

	fracPart = table.concat(tf, '')

	-- remove trailing zeros if not needed
	if not precision then
		fracPart = fracPart:gsub('0*$', '')
	end

	-- add the radix point if needed
	if #fracPart > 0 then
		fracPart = '.' .. fracPart
	end

	return (prefix or '') .. sign .. intPart .. fracPart .. (suffix or '')
end

function p.convert(frame)
	-- Allow for invocation via #invoke or directly from another module
	local args
	if frame == mw.getCurrentFrame() then
		args = frame.args
	else
		args = frame
	end

	local n = args[1]
	local base = args[2]
	local from = args[3]
	return p._convert(n, base, from)
end

return p