Module:Interval table

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This module should not be invoked directly; use its corresponding template instead: Template:Interval table.

This module automatically generates a table of intervals for an equal-step tuning, showing which just intervals are approximated relatively accurately.

Introspection summary for Module:Interval table
Functions provided (1) Line Function Params 39 interval_table (invokable) (frame)	Lua modules required (5) Variable Module Functions used ET Module:ET parse approximate cents iv Module:Interval _to_cents rat Module:Rational eq ud Module:Ups and downs notation get_note_names_table u Module:Utils gcd _round

No function descriptions were provided. The Lua code may have further information.

---

local p = {}
local u = require('Module:Utils')
local iv = require('Module:Interval')
local rat = require('Module:Rational')
local ud = require('Module:Ups and downs notation')
local ET = require('Module:ET')

-- Generates list of ratios up to a max numerator & denominator, and max ratio size 
local function get_ratios_list(max_nd, max_size)
	local ratios = {}
	for i=1,max_nd do
		for j=1,max_nd do
			if (i/j) >= 1 and (i/j) <= max_size then
				ratios[#ratios + 1] = {i/u.gcd(i,j),j/u.gcd(i,j)}
			end
		end
	end
	
	-- Remove duplicates
	local res = {}
	local hash = {}
	for _,v in ipairs(ratios) do
	   if (not hash[ratios]) then
	       res[#res+1] = v 
	       hash[v] = true
	   end
	end
	
	return res
end

-- Utility fuunction to get specific note name with ud.get_note_names_table
-- (this is essentially what "Template:Ups and downs note name" does)

local function ud_note(et, fifth, step)
	return table.concat(ud.get_note_names_table(et, fifth)[step], ", "):sub(0, -1)	
end

function p.interval_table(frame)
	local tuning = frame.args['tuning']
	local et = ET.parse(tuning) or ET.parse('12edo')
	local wikitext = '{|class="wikitable"\n'
	local octave = ET.approximate(et, 2)
	local fifth = ET.approximate(et, 3/2)
	local fifth_error = ET.cents(et, fifth) - iv._to_cents(3/2)
	local dual_fifth = math.abs(fifth_error) > (400 / et.size)
	local dual_flat_fifth = ET.approximate(et, 3/2, -1)
	local dual_sharp_fifth = ET.approximate(et, 3/2, 1)
	local ratios_list = get_ratios_list(40, 6)

	wikitext = wikitext .. '!Steps\n'
	wikitext = wikitext .. '!Cents\n'
	if rat.eq(et.equave, 2) then
		if dual_fifth then
			wikitext = wikitext .. '![[Ups and downs notation]]<br>(dual flat fifth ' .. dual_flat_fifth  .. '\\' .. et.size .. ')\n'
			wikitext = wikitext .. '![[Ups and downs notation]]<br>(dual sharp fifth ' .. dual_sharp_fifth .. '\\' .. et.size .. ')\n'
		else
			wikitext = wikitext .. '![[Ups and downs notation]]\n'
			wikitext = wikitext .. '![[Ups and downs notation]]\n'
		end
	end
	
	wikitext = wikitext .. '!Approximate ratios\n'
	
	for i=0,et.size do
		wikitext = wikitext .. '|-\n'
		wikitext = wikitext .. '|' .. i .. '\n'
		wikitext = wikitext .. '|' .. u._round(ET.cents(et, i), 6) .. '\n'
		if rat.eq(et.equave, 2) then
			if dual_fifth then
				wikitext = wikitext .. '|' .. ud_note(et, dual_flat_fifth, i) .. '\n'
				wikitext = wikitext .. '|' .. ud_note(et, dual_sharp_fifth, i) .. '\n'
			else
				wikitext = wikitext .. '|' .. ud_note(et, fifth, i) .. '\n'
			end
		end
		wikitext = wikitext .. '|'
		for j=1,#ratios_list do
			local n = ratios_list[j][1]
			local d = ratios_list[j][2]
			-- In approximate ratios column, show all ratios in the list that are within 1/3 of ET size (33.3 relative cents)
			if math.abs(ET.cents(et, i) - (math.log(n/d)/math.log(2)) * 1200) <= (400 / et.size) then
				wikitext = wikitext .. '[[' .. n .. '/' .. d .. ']]' .. ' '
			end
		end
		wikitext = wikitext .. '\n'
	end
	
	
	
	wikitext = wikitext .. '|}'

	return wikitext
end

return p