Module documentation

This module formats a number in the local format, based on MediaWiki data. This module is used by Template:Formatnum. For usage instructions, please take a look at Template:Formatnum.

Current limitations:

  • Numbers with more than 14 decimals are not supported.
  • It still does not allow more than 20 different "KnownLanguages" (in MediaWiki's core library for Lua) on one page. This means that you can have at a maximum 20 module transclusions, where each of them is formatting a number into a different language.


Using this module from templates edit




  • lang — language code as a string (e.g. 'en', 'de', etc.). If the language is not specified (nil or empty string) or not supported, the current user's language (as reported by MediaWiki's {{int:Lang}}) will be used.
The lang named parameter is also a supported alias of the 2nd parameter.
The value "arabic-indic" is also currently supported as an alias, and replaced by a supported language code.
  • See formatNum() below for the expected values and the description of other parameter values.


This template internally uses {{#invoke:Formatnum|main}}</nowiki> to pass indirectly its parameters to the main() function of this module in the parent frame.

formatNum() edit

This function converts an value into a localized number.

Unlike "Language:formatNum()" in MediaWiki's core libraries for Lua, it correctly supports numbers using exponential notations such as 1e15 (MediaWiki's core function is currently broken and randomly forgets the exponent for some language, so that its formated numbers are incorrectly scaled and display wrong values).


formatted_string = formatnum.formatNum(value, lang, prec, compact)


  • value — as an ASCII-only number or string. If the string cannot be converted to a number with Lua's tonumber(), that string will be returned as is.
  • lang — language code as a string (e.g. 'en', 'de', etc.). If that language is not supported, localized digits and separators will not be used (except for a few languages)
  • prec — if not nil and not negative, this is the number of digits in displayed decimals (by truncating the decimals in excess or by adding zeroes). Valid range: 0 to 14.
    • when prec is not specified or nil, the decimal separator is shown only if there are 1 or more visible decimals;
    • when prec is negative or non integer it is treated like nil;
    • when prec is 0, there will never be any decimal separator or any displayed decimals;
    • when prec is positive, a decimal separator will always be present before this number of decimals, but when prec is higher than 14, it is treated like 14.
  • compact — if this option is not nil and not false, don't return any localized grouping separators (the localized decimal separator and digits are still used).


  • formatted_string = formatnum.formatNum(12345.123) — convert to user's language, using localized digits and separators
  • formatted_string = formatnum.formatNum(12345.123,'') — same thing (language code not supported)
  • formatted_string = formatnum.formatNum(12345.123,'default') — same thing (language code not supported)
  • formatted_string = formatnum.formatNum(12345.123,'en') — convert to English: "12,345.123"
  • formatted_string = formatnum.formatNum(12345.123,'fr') — convert to French: "12 345,123"
  • formatted_string = formatnum.formatNum(12345.123,'fr',2) — same thing but limit to 2 decimals: "12 345,12"
  • formatted_string = formatnum.formatNum(12345,'fr',2) — same thing (2 null decimals are padded): "12 345,00"
  • formatted_string = formatnum.formatNum(12345,'fr',2,true) — same thing but without grouping separators: "12345,00"


  • Same limit of 20 "KnownLanguages" (because it still depends on mw.Language module in order to detect localized digits and separators).
  • When specifying the "prec" parameter, decimals in excess are just truncated, and the least significant digit is not rounded.

-- This module is intended to replace the functionality of Template:Formatnum and related templates.
local p = {}

function p.main(frame)
    local args = frame:getParent().args
    local prec    = args.prec or ''
    local sep     = args.sep or ''
    local number  = args[1] or args.number or ''
    local lang    = args[2] or args.lang or ''
    -- validate the language parameter within MediaWiki's caller frame
    if lang == "arabic-indic" then -- only for back-compatibility ("arabic-indic" is not a SupportedLanguage)
        lang = "fa" -- better support than "ks"
    elseif lang == '' or not mw.language.isSupportedLanguage(lang) then
        -- Note that 'SupportedLanguages' are not necessarily 'BuiltinValidCodes', and so they are not necessarily
        -- 'KnownLanguages' (with a language name defined at least in the default localisation of the local wiki).
        -- But they all are ValidLanguageCodes (suitable as Wiki subpages or identifiers: no slash, colon, HTML tags, or entities)
        -- In addition, they do not contain any capital letter in order to be unique in page titles (restriction inexistant in BCP47),
        -- but they may violate the standard format of BCP47 language tags for specific needs in MediaWiki.
        -- Empty/unspecified and unsupported languages are treated here in Commons using the user's language,
        -- instead of the local 'ContentLanguage' of the Wiki.
        lang = frame:callParserFunction( "int", "lang" ) -- get user's chosen language
    return p.formatNum(number, lang, prec, sep ~= '')

local digit = { -- substitution of decimal digits for languages not supported by mw.language:formatNum() in core Lua libraries for MediaWiki
    ["ml-old"] = { '൦', '൧', '൨', '൩', '൪', '൫', '൬', '൭', '൮', '൯' },
    ["mn"]     = { '᠐', '᠑', '᠒', '᠓', '᠔', '᠕', '᠖', '᠗', '᠘', '᠙'},
    ["ta"]     = { '௦', '௧', '௨', '௩', '௪', '௫', '௬', '௭', '௮', '௯'},
    ["te"]     = { '౦', '౧', '౨', '౩', '౪', '౫', '౬', '౭', '౮', '౯'},
    ["th"]     = { '๐', '๑', '๒', '๓', '๔', '๕', '๖', '๗', '๘', '๙'}

function p.formatNum(number, lang, prec, compact)

    -- Do not alter the specified value when it is not a valid number, return it as is
    local value = tonumber(number)
    if value == nil then
        return number
    -- Basic ASCII-only formatting (without paddings)
    number = tostring(value)

    -- Check the presence of an exponent (incorrectly managed in mw.language:FormatNum() and even forgotten due to an internal bug, e.g. in Hindi)
    local exponent
    local pos = string.find(number, '[Ee]')
    if pos ~= nil then
        exponent = string.sub(number, pos + 1, string.len(number))
        number = string.sub(number, 1, pos - 1)
        exponent = ''

    -- Check the minimum precision requested
    prec = tonumber(prec) -- nil if not specified as a true number
    if prec ~= nil then
        prec = math.floor(prec)
        if prec < 0 then
            prec = nil -- discard an incorrect precision (not a positive integer)
        elseif prec > 14 then
            prec = 14 -- maximum precision supported by tostring(number)

    -- Preprocess the minimum precision in the ASCII string
    local dot
    if (prec or 0) > 0 then
        pos = string.find(number, '.', 1, true) -- plain search, no regexp
        if pos ~= nil then
            prec = pos + prec - string.len(number) -- effective number of trailing decimals to add or remove
            dot = '' -- already present
            dot = mw.ustring.sub (, 2, 2) -- must be added
        dot = '' -- don't add dot
        prec = 0 -- don't alter the precision

    if lang ~= nil and mw.language.isKnownLanguageTag(lang) == true then
        -- Convert number to localized digits, decimal separator, and group separators
        local language = mw.getLanguage(lang)
        if compact then
            number = language:formatNum(tonumber(number), { noCommafy = 'y' }) -- caveat: can load localized resources for up to 20 languages
            number = language:formatNum(tonumber(number)) -- caveat: can load localized resources for up to 20 languages
        -- Postprocessing the precision
        if prec > 0 then
            local zero = language:formatNum(0)
            number = number .. dot .. mw.ustring.rep(zero, prec)
        elseif prec < 0 then
            -- TODO: rounding of last decimal; here only truncate decimals in excess
            number = mw.ustring.sub(number, 1, mw.ustring.len(number) + prec)

        -- Append the localized base-10 exponent without grouping separators (there's no reliable way to detect a localized leading symbol 'E')
        if exponent ~= '' then
            number = number .. 'E' .. language:formatNum(tonumber(exponent),{noCommafy=true})
    else -- not localized, ASCII only
        -- Postprocessing the precision
        if prec > 0 then
            number = number .. dot .. mw.string.rep('0', prec)
        elseif prec < 0 then
            -- TODO: rounding of last decimal; here only truncate decimals in excess
            number = mw.string.sub(number, 1, mw.string.len(number) + prec)

        -- Append the base-10 exponent
        if exponent ~= '' then
            number = number .. 'E' .. exponent

    -- Special cases for substitution of ASCII digits (missing support in Lua core libraries for some languages)
    if digit[lang] then
        for i, v in ipairs(digit[lang]) do
            number = mw.ustring.gsub(number, tostring(i - 1), v)

    return number

return p