Module:Roman
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This module implements the {{Roman}} template. For behavioral documentation, please see the template page. For test cases, please see Template:Roman/testcases.
- Module supports 0 as a Roman numeral, displays as 'N'.
- Prior to 25 April 2016, used to display 69105 as LXVMMMMCV. With the addition of IX and IV being 9000 and 4000 respectively, we now display 69105 as LXIXCV.
- Module handles decimal, fractional, and arithmetic expressions to a precision of 1/1728. Template:Green
Handling tricky cases (like 0.00001 and 99.99999)
- Find the Roman numerals for the integer part of the number.
- If the number is not an integer:
- Add half of the smallest unit (1/1728) to simulate rounding instead of truncation.
- Ensure this new result is between 1/1728 and 1727/1728. (actually 1.1/1728 and 1727.1/1728 due to floating point rounding issues)
- Hence, 0.00001 is guaranteed to have at least the smallest unit symbol (instead of being blank or 0), and 99.99999 does not display as 100 or 99 and 2 halves.
Validation
- Template:Roman/testcases
- Module:Roman/testcases - does not contain fractional/decimal tests
- The template supports subst: and safesubst:.
-- This module implements {{Roman}}. local p = {} -- This function implements the {{overline}} template. local function overline(s) return mw.ustring.format( '<span style="text-decoration:overline;">%s</span>', s ) end -- Gets the Roman numerals for a given numeral table. Returns both the string of -- numerals and the value of the number after it is finished being processed. local function getLetters(num, t) local ret = {} for _, v in ipairs(t) do local val, letter = unpack(v) while num >= val do num = num - val table.insert(ret, letter) end end return table.concat(ret), num end -- The main control flow of the module. local function _main(args) -- Get input and exit displaying nothing if the input is empty. if args[1] == nil then return end local num = tonumber(args[1]) if not num or num < 0 or num == math.huge then error('Invalid number ' .. args[1], 2) elseif num == 0 then return 'N' end -- Return a message for numbers too big to be expressed in Roman numerals. if num >= 5000000 then return args[2] or 'N/A' end local ret = '' -- Find the Roman numerals for the large part of numbers. -- 23 April 2016 - tweaked to >= 4000 to accept big Roman 'IV' -- The if statement is not strictly necessary, but makes the algorithm -- more efficient for smaller numbers. if num >= 4000 then local bigRomans = { { 1000000, 'M' }, { 900000, 'CM' }, { 500000, 'D' }, { 400000, 'CD' }, { 100000, 'C' }, { 90000, 'XC' }, { 50000, 'L' }, { 40000, 'XL' }, { 10000, 'X' }, { 9000, 'IX' }, { 5000, 'V' }, { 4000, 'IV' }, } local bigLetters bigLetters, num = getLetters(num, bigRomans) ret = overline(bigLetters) end -- Find the Roman numerals for numbers less than the big Roman threshold. local smallRomans = { { 1000, 'M' }, { 900, 'CM' }, { 500, 'D' }, { 400, 'CD' }, { 100, 'C' }, { 90, 'XC' }, { 50, 'L' }, { 40, 'XL' }, { 10, 'X' }, { 9, 'IX' }, { 5, 'V' }, { 4, 'IV' }, { 1, 'I' } } local smallLetters = getLetters( num, smallRomans ) ret = ret .. smallLetters if args.fraction == 'yes' then -- Find the Roman numerals for the fractional parts of numbers. -- If num is not a whole number, add half of 1/1728 (the smallest unit) to equate to rounding. -- Ensure we're not less than the smallest unit or larger than 1 - smallest unit -- to avoid getting two "half" symbols or no symbols at all num = num - math.floor(num) if num ~= 0 then num = math.max(1.1/1728, math.min(1727.1/1728, num + 1/3456)) end local fractionalRomans = { { 1/2, 'S' }, { 5/12, "''':'''•''':'''" }, { 1/3, "'''::'''" }, { 1/4, "''':'''•" }, { 1/6, "''':'''" }, { 1/12, '•' }, { 1/24, 'Є' }, { 1/36, 'ƧƧ' }, { 1/48, 'Ɔ' }, { 1/72, 'Ƨ' }, { 1/144, '<s>Ƨ</s>' }, { 1/288, '℈' }, { 1/1728, '»' }, } local fractionalLetters = getLetters(num, fractionalRomans) ret = ret .. fractionalLetters end return ret end function p.main(frame) -- If called via #invoke, use the args passed into the invoking -- template, or the args passed to #invoke if any exist. Otherwise -- assume args are being passed directly in from the debug console -- or from another Lua module. local origArgs if frame == mw.getCurrentFrame() then origArgs = frame:getParent().args for k, v in pairs(frame.args) do origArgs = frame.args break end else origArgs = frame end -- Trim whitespace and remove blank arguments. local args = {} for k, v in pairs(origArgs) do if type( v ) == 'string' then v = mw.text.trim(v) end if v ~= '' then args[k] = v end end -- exit if not given anything if args == nil or args == {} then return end -- Given mathematical expression, simplify to a number if type(args[1]) == 'string' then args[1] = mw.ext.ParserFunctions.expr(args[1]) end return _main(args) end return p