Module:15-odd-limit

Calculates approximations of intervals for a given edo and odd limit and present them in form of a table.

Do not use this module directly, use the template instead: Template:15-odd-limit.

---

Documentation transcluded from /doc

---

bit32 = require ('bit32')
utils = require ('Module:Utils')

local p = {}

local PRIME_LIST = {2, 3, 5, 7, 11, 13, 17, 19, 23}

local function is_in (v, t)
	for i = 1, #t do
		if v == t[i] then
			return true
		end
	end
	return false
end

local function table_filter (t, thres)
	for i = 1, #t do
		if t[i] > thres then
			return {unpack (t, 1, i - 1)}
		end
	end
	return t
end

local function inner_product (val, monzo)
	local result = 0
	for i = 1, #val do
		result = result + val[i]*monzo[i]
	end
	return result
end

local function monzo2ratio (monzo, subgroup)
	local num = 1
	local den = 1
	for i = 1, #subgroup do
		if monzo[i] > 0 then
			num = num*subgroup[i]^monzo[i]
		elseif monzo[i] < 0 then
			den = den*subgroup[i]^(-monzo[i])
		end
	end
	return {num = num, den = den}
end

local function ratio2monzo (ratio, subgroup)
	local monzo = {}
	for i = 1, #subgroup do
		monzo[i] = 0
		while ratio.num % subgroup[i] == 0 do
			monzo[i] = monzo[i] + 1
			ratio.num = ratio.num / subgroup[i]
		end while ratio.den % subgroup[i] == 0 do
			monzo[i] = monzo[i] - 1
			ratio.den = ratio.den / subgroup[i]
		end
	end
	return monzo
end

local function monzo2cent (monzo, subgroup)
	local jip = {}
	for i = 1, #subgroup do
		jip[i] = 1200*utils._log (subgroup[i], 2)
	end
	return inner_product (jip, monzo)
end

local function ratio_8ve_reduction (ratio)
	local oct = math.floor (utils._log (ratio.num/ratio.den, 2))
	if oct > 0 then
		ratio.den = ratio.den * 2^oct
	elseif oct < 0 then
		ratio.num = ratio.num * 2^(-oct)
	end
	return ratio
end

local function odd_limit_monzo_list_gen (limit)
	local monzo_list = {}
	local subgroup = table_filter (PRIME_LIST, limit)
	for num = 1, limit, 2 do
		for den = 1, num, 2 do
			if utils._gcd (num, den) == 1 then
				ratio = ratio_8ve_reduction ({num = num, den = den})
				table.insert (monzo_list, ratio2monzo (ratio, subgroup))
			end
		end
	end
	return monzo_list
end

local function find_error (val, subgroup, monzo_list)
	local step_size = 1200/val[1]
	local true_size
	local approx_size
	local error_list = {}
	for i = 1, #monzo_list do
		ratio = monzo2ratio (monzo_list[i], subgroup)
		comp = {2*ratio.den, ratio.num}
		true_size = monzo2cent (monzo_list[i], subgroup)
		approx_size = step_size*inner_product (val, monzo_list[i])
		error_abs = math.abs (approx_size - true_size)
		error_rel = 100*error_abs/step_size
		error_list[i] = 
		{
			ratio = ratio, 
			comp = comp, 
			error_abs = error_abs, 
			error_rel = error_rel
		}
	end
	table.sort (error_list, function (a, b) return a.error_abs < b.error_abs end)
	return error_list
end

local function approx (steps, subgroup, monzo_list, t_title)
	local t_body = {}
	local val = {}
	for i = 1, #subgroup do
		val[i] = utils._round_dec (steps*utils._log (subgroup[i], 2))
	end
	error_list = find_error (val, subgroup, monzo_list)
	for i = 1, #error_list do
		ratiocomp = string.format ("%d/%d, %d/%d", error_list[i].ratio.num, error_list[i].ratio.den, 2*error_list[i].ratio.den, error_list[i].ratio.num)
		error_abs = string.format ("%.3f", error_list[i].error_abs)
		error_rel = string.format ("%.1f", error_list[i].error_rel)
		if bit32.band (error_list[i].ratio.den, error_list[i].ratio.den - 1) == 0 and is_in (error_list[i].ratio.num, subgroup) then -- check power of 2 for den and prime for num
			ratiocomp = "'''" .. ratiocomp .. "'''"
			error_abs = "'''" .. error_abs .. "'''"
			error_rel = "'''" .. error_rel .. "'''"
		end if error_list[i].error_rel > 50 then
			ratiocomp = "''" .. ratiocomp .. "''"
			error_abs = "''" .. error_abs .. "''"
			error_rel = "''" .. error_rel .. "''"
		end
		t_body[i] = string.format ("|-\n| %s\n| %s\n| %s", ratiocomp, error_abs, error_rel)
	end

	return "{| class=\"wikitable center-all mw-collapsible mw-collapsed\"\n" ..
	"|+style=white-space:nowrap| " .. t_title .. "\n" ..
	"|-\n" ..
	"! Interval, complement\n" ..
	"! Error (abs, [[Cent|¢]])\n" ..
	"! Error (rel, [[Relative cent|%]])\n" ..
	table.concat (t_body, "\n") ..
	"\n|}"
end

-- local function prec_by_equal (steps)
-- 	return math.floor (math.log (steps*1.9)/math.log (10))
-- end

function p.odd_limit (frame)
	local steps = tonumber (frame.args['steps'])
	local limit = math.max (tonumber (frame.args['limit']), 2)
-- 	local prec = tonumber (frame.args['prec']) or prec_by_equal (steps)
	local title = frame.args['title']
	if title == nil or #title == 0 then
		title = string.format ("%d-odd-limit intervals by patent val mapping", limit)
	end
	local subgroup = table_filter (PRIME_LIST, limit)
	local monzo_list = odd_limit_monzo_list_gen (limit)

	return approx (steps, subgroup, monzo_list, title)
end

return p;