Modul:FormatNum

local FormatNum = { suite  = "FormatNum",
                    serial = "2020-08-06",
                    item   = 15709679 };
--[[
FormatNum
 format
 minus
 padding
 roman2number
 round
 failsafe
FormatNum()
]]
local Failsafe       = FormatNum;
local DEFAULT_FORMAT = "lnwiki";
local DEFAULT_METHOD = 0;

-- Constant for round method "round half to even" (IEEE 754)
local ROUND_TO_EVEN = 0;

-- Constant for round method "round half away from zero"
-- (German: "kaufmaennisches Runden"),
-- also filters "-0" and converts it to "0".
local ROUND_AWAY_FROM_ZERO = 1;

-- Constant for U+202F
local THIN_SPACE = mw.ustring.char( 0x202F );

-- Constant for reducing code range to ANSI
local SPACER_SPAN = " ";

-- Constant for padding span element
local PADDING_SPAN = "%s%s";

-- Table storing the format options.
local FORMAT_TABLE = {
    lnwiki = {
        decimalMark = ",",
        groupMark = ".",
        groupMinLength = 4,
        groupNaturalLength = 5,
        groupOnlyIntegerPart = false
         },
    lnwikiint = {
        decimalMark = ",",
        groupMark = THIN_SPACE,
        groupMinLength = 4,
        groupNaturalLength = 5,
        groupOnlyIntegerPart = true
         },
    cd = {
        decimalMark = ",",
        groupMark = THIN_SPACE,
        groupMinLength = 4,
        groupNaturalLength = 4,
        groupOnlyIntegerPart = false
         },
    cd_currency = {
        decimalMark = ".",
        groupMark = "'",
        groupMinLength = 4,
        groupNaturalLength = 4,
        groupOnlyIntegerPart = true
         },
    ch = {
        decimalMark = ".",
        groupMark = "'",
        groupMinLength = 5,
        groupNaturalLength = 5,
        groupOnlyIntegerPart = true
         },
    ch_currency = {
        decimalMark = ".",
        groupMark = "'",
        groupMinLength = 5,
        groupNaturalLength = 5,
        groupOnlyIntegerPart = true
         },
    en = {
        decimalMark = ".",
        groupMark = ",",
        groupMinLength = 4,
        groupNaturalLength = 4,
        groupOnlyIntegerPart = true
         },
    iso31_0 = {    -- ISO 31-0 using comma as decimal mark
        decimalMark = ",",
        groupMark = THIN_SPACE,
        groupMinLength = 4,
        groupNaturalLength = 4,
        groupOnlyIntegerPart = false
         },
    iso31_0_point = {    -- ISO 31-0 using dot as decimal mark
        decimalMark = ".",
        groupMark = THIN_SPACE,
        groupMinLength = 4,
        groupNaturalLength = 4,
        groupOnlyIntegerPart = false
         },
    comma = {
        decimalMark = ",",
        groupMark = "",
        groupMinLength = 1000, -- (for performance, but also small values wouldn't matter)
        groupNaturalLength = 1000,
        groupOnlyIntegerPart = true
         },
    heights = {
        decimalMark = ",",
        groupMark = ".",
        groupMinLength = 6,
        groupNaturalLength = 6,
        groupOnlyIntegerPart = true
         },
    pc = nil   -- prevent formatting
};

-- Format table for "at" (only for convenience, same as "iso31_0").
FORMAT_TABLE.at = FORMAT_TABLE.iso31_0;

-- Constant defining digit group lengths when digit grouping is used.
local DIGIT_GROUPING_SIZE = 3;

-- Table defining roman digit values.
local ROMAN_DIGITS = { I = 1,
                       V = 5,
                       X = 10,
                       L = 50,
                       C = 100,
                       D = 500,
                       M = 1000 };

--[[
    Internally used function for rounding.

    @param a_number : Number to be rounded.
    @param a_precision : Number of significant digits of the fractional part.
                         If it is negative,
                         the according number of digits of the integer part are also rounded.
                         If it is negative but greater 1,
                         for -.1 -.2 -.3 ... -.9 only the leading digits
                         will be significant, while
    @param a_roundMethod : Numeric constant defining the round method to use.
       Supported are ROUND_TO_EVEN and ROUND_AWAY_FROM_ZERO.
    @param a_signed : Boolean, shift to typographic minus sign, or precede plus sign.

    @return String of the rounded number like returned by Lua function string.format().
]]
local function numberToString( a_number, a_precision, a_roundMethod, a_signed )
    local suitable;
    if ( a_precision < 0 ) then
        a_precision = - a_precision;
        if ( a_precision < 1 ) then
            local k = math.log10( math.abs( a_number ) );
            if ( k > 0 ) then
                a_precision = math.floor( k )
                              + 1
                              - math.floor( a_precision * 10 );
                if ( a_precision < 0 ) then
                    a_precision = 0;
                end
            else
                a_precision = 0;
            end
        else
            a_precision = math.floor( a_precision );
        end
        if (a_roundMethod == ROUND_TO_EVEN) then
            local integerPart = math.floor(math.abs(a_number) / (10 ^ a_precision));
            if (integerPart % 2 == 0) then
                -- next even number smaller than a_number / 10^precision
                a_number = a_number - 5 * (10 ^ (a_precision - 1));
                a_number = math.ceil(a_number / (10 ^ a_precision)) * (10 ^ a_precision);
            else
                -- next even number bigger than a_number / 10^precision
                a_number = a_number + 5 * (10 ^ (a_precision - 1));
                a_number = math.floor(a_number / (10 ^ a_precision)) * (10 ^ a_precision);
            end
        elseif (a_roundMethod == ROUND_AWAY_FROM_ZERO) then
            if (a_number >= 0) then
                a_number = a_number + 5 * (10 ^ (a_precision - 1));
                a_number = math.floor(a_number / (10 ^ a_precision)) * (10 ^ a_precision);
            else
                a_number = a_number - 5 * (10 ^ (a_precision - 1));
                a_number = math.ceil(a_number / (10 ^ a_precision)) * (10 ^ a_precision);
            end
        end
        -- handle it as normal integer
        a_precision = 0;
    end
    if (a_roundMethod == ROUND_AWAY_FROM_ZERO) then
        if ((a_number * (10 ^ a_precision)) - math.floor(a_number * (10 ^ a_precision)) == 0.5) then
            -- because string.format() uses round to even, we have to add (numbers >0) or
            -- subtract (numbers <0) a little bit to point into the "correct" rounding
            -- direction if a_number is exactly in the middle between two rounded numbers
            if (a_number >= 0) then
                a_number = a_number + (10 ^ -(a_precision + 1));
            else
                a_number = a_number - (10 ^ -(a_precision + 1));
            end
        else
            if (math.abs(a_number * (10 ^ a_precision)) < 0.5) then
                -- filter "-0" and convert it to 0
                a_number = math.abs(a_number);
            end
        end
    end
    suitable = string.format( "%%.%df", a_precision );
    suitable = string.format( suitable, a_number );
    if a_signed then
        if (a_number > 0) then
            suitable = "+" .. suitable;
        elseif (a_number < 0) then
            suitable = mw.ustring.char( 0x2212 ) .. suitable;
        end
    end
    return suitable;
end -- numberToString()

--[[
    Internally used for formatting.

    @param a_number : String (ASCII) of a non-negative number to be formatted.
    @param a_sign   : String with a sign char, or false
    @param a_decimalMark : String of the decimal mark to use.
    @param a_groupMark : String of the mark used for digit grouping.
    @param a_groupMinLength : Number defining the minimum length of integer part
       to use digit grouping (normally 4 or 5). However if fractional part is
       longer than DIGIT_GROUPING_SIZE (3 as default) and digit grouping of
       fractional part is not disabled via 'a_groupOnlyIntegerPart', then this
       value is ignored and set to DIGIT_GROUPING_SIZE + 1.
    @param a_groupNaturalLength : a_groupMinLength for unsigned integer; or nil
    @param a_groupOnlyIntegerPart : Boolean defining whether activating digit
       grouping only for integer part (true) or for integer and fractional part
       (false).

    @return String of the formatted number according to the parameters.
]]
local function formatNumber( a_number,
                             a_sign,
                             a_decimalMark,
                             a_groupMark,
                             a_groupMinLength,
                             a_groupNaturalLength,
                             a_groupOnlyIntegerPart )
    -- find the decimal point
    local decimalPosition = a_number:find( ".", 1, true );
    local needsGrouping = false;
    if not decimalPosition then
        -- no decimal point - integer number
        local minLength = a_groupMinLength;
        if not a_sign and a_groupNaturalLength then
            minLength = a_groupNaturalLength;
        end
        decimalPosition = #a_number + 1;
        if decimalPosition > minLength then
            needsGrouping = true;
        end
    else
        -- decimal point present
        if decimalPosition > a_groupMinLength
            or (#a_number - decimalPosition > DIGIT_GROUPING_SIZE
                and  not a_groupOnlyIntegerPart) then
            needsGrouping = true;
        end
        -- replace the decimal point
        a_number = a_number:sub( 1, decimalPosition - 1 )
                   .. a_decimalMark
                   .. a_number:sub( decimalPosition + 1 );
    end
    if needsGrouping and decimalPosition > DIGIT_GROUPING_SIZE + 1 then
        -- grouping of integer part necessary
        local i = decimalPosition - DIGIT_GROUPING_SIZE;
        while (i > 1) do
            -- group the integer part
            a_number = a_number:sub( 1, i - 1 )
                       .. a_groupMark
                       .. a_number:sub( i );
            decimalPosition = decimalPosition + #a_groupMark;
            i = i - DIGIT_GROUPING_SIZE;
        end
    end
    -- skip to the end of the new decimal mark (in case it is more than one char)
    decimalPosition = decimalPosition + #a_decimalMark - 1;
    if a_groupOnlyIntegerPart then
        needsGrouping = false;
    end
    if needsGrouping  and  #a_number - decimalPosition > DIGIT_GROUPING_SIZE then
        -- grouping of fractional part necessary
        -- using negative numbers (index from the end of the string)
        local i = decimalPosition - #a_number + DIGIT_GROUPING_SIZE;
        while i < 0 do
            -- group the fractional part
            a_number = a_number:sub(1, i - 1) .. a_groupMark .. a_number:sub(i);
            i = i + DIGIT_GROUPING_SIZE;
        end
    end
    if (a_sign) then
        a_number = a_sign .. a_number;
    end
    return a_number;
end -- formatNumber()

--[[
    Formatting numbers.

    @param source : Numerical or string representation
           of an unformatted (but maybe rounded) floating point or integer number.
    @param spec : Formatting option. Currently there are
           "at", "comma", "de", "dewiki", "de_currency", "ch", "ch_currency", "en",
           "iso31_0", "iso31_0_point" and "pc" supported.
           Defaults to "dewiki".
           See the FORMAT_TABLE for details.
    @param meet : HTML padding on left or right end.
           Defaults to 'none' or 0.
           Positive figures require padding behind decimal mark,
           negative values ensure at least that absolute value
           of characters before decimal mark.

    @return String of the formatted number.
            If the argument 'spec' is invalid
            or 'source' is not a valid string representation of a number,
            'source' is returned unmodified.
]]
FormatNum.format = function ( source, spec, meet )
    local stitch = type( source );
    local r;
    if stitch == "string" then
        r = mw.text.trim( source );
        if r == "" then
            r = false;
        end
    elseif stitch == "number" then
        r = tostring( source );
    end
    if r then
        if not spec then
            spec = DEFAULT_FORMAT;
        end
        local format = FORMAT_TABLE[ spec ];
        if format then
            -- format entry found
            local sign = mw.ustring.sub( r, 1, 1 );
            local scan = mw.ustring.format( "^[%%+%%-%c]", 0x2212 );
            local last;
            if mw.ustring.match( sign, scan ) then
                -- remove sign from r, add it again later
                r = mw.ustring.sub( r, 2 );
            else
                -- was not a sign
                sign = false;
            end
            if r:sub( 1, 1 ) == "." then
                -- r begins with "." -> add a 0 to the beginning
                r = "0" .. r;
            elseif r:sub( -1 ) == "." then
                -- r ends with "." -> remove it
                r    = r:sub( 1, -2 );
                last = true;
            end
            if r == r:match( "^%d+$" )  or
               r == r:match( "^%d+%.%d+$" ) then
                -- r has valid format (only digits or digits.digits)
                r = formatNumber( r, sign,
                                  format.decimalMark,
                                  format.groupMark,
                                  format.groupMinLength,
                                  format.groupNaturalLength,
                                  format.groupOnlyIntegerPart );
                if meet then
                    local stop;
                    if not last then
                        stop = format.decimalMark;
                    end
                    r = FormatNum.padding( r, meet, stop );
                end
                --[[ Das Zeichen existiert seit 1999. Kein Bedarf an starrer Ersetzung ohne Unterschneidung
                if format.groupMark == THIN_SPACE  and
                   SPACER_SPAN  and
                   r:find( THIN_SPACE, 2, true ) then
                    r = r:gsub( THIN_SPACE, SPACER_SPAN );
                        -- gsub has two results.
                    r = tostring( mw.html.create( "span" )
                                         :css( "white-space", "nowrap" )
                                         :wikitext( r ) );
                end ]]
            else
                -- r has no valid format -> undo all modifications
                r = source;
            end
        end
    end
    return r;
end -- FormatNum.format()

FormatNum.getromanstring = function(number, style)
	local zahl = math.floor(math.abs(number)); -- erase several errors like  minus or noninteger
	zahl = zahl % 1000000; -- truncate to six decimal digits
	local lower = zahl % 1000;
	local upper = ((zahl - lower) / 1000)
	local text = ;
	local hunderttausender = (zahl - zahl % 100000 ) / 100000;
	zahl = zahl % 100000;
	local zehntausender    = (zahl - zahl % 10000 ) / 10000;
	zahl = zahl % 10000;
	local tausender        = (zahl - zahl % 1000 ) / 1000;
	zahl = zahl % 1000;
	local hunderter        = (zahl - zahl % 100 ) / 100;
	zahl = zahl % 100;
	local zehner           = (zahl - zahl % 10 ) / 10;
	local einer            = zahl % 10;
	local digit = {};
	if upper > 0 then
		if style=='over' then
			text = '';
			if hunderttausender > 0 then
				digit = {'C', 'CC', 'CCC', 'CD', 'D', 'DC', 'DCC', 'DCCC', 'CM'} ;
				text =  text .. digit[hunderttausender];
			end
			if zehntausender > 0 then
				digit = {'X', 'XX', 'XXX', 'XL', 'L', 'LX', 'LXX', 'LXXX', 'XC'} ;
				text = text .. digit[zehntausender];
			end
			if tausender > 0 then
				digit = {'I', 'II', 'III', 'IV', 'V', 'VI', 'VII', 'VIII', 'IX'} ;
				text = text .. digit[tausender];
			end
			text = text .. ''
		elseif style=='apo' then
			if hunderttausender > 0 then
				digit = {
					'ↈ',
					'ↈↈ',
					'ↈↈↈ',
					'ↈↈↈↈ',
					'ↈↈↈↈↈ',
					'ↈ ↈↈↈↈↈ',
					'ↈↈ ↈↈↈↈↈ',
					'ↈↈↈ ↈↈↈↈↈ',
					'ↈↈↈↈ ↈↈↈↈↈ'
				} ;
				text =  text .. digit[hunderttausender];
			end
			if zehntausender > 0 then
				digit = {
					'ↂ',
					'ↂↂ',
					'ↂↂↂ',
					'ↂↇ',
					'ↇ',
					'ↇↂ',
					'ↇↂↂ',
					'ↇↂↂↂ',
					'ↂↈ'
				} ;
				text = text .. digit[zehntausender];
			end
			if tausender > 0 then
				digit = {
					'ↀ',
					'ↀↀ',
					'ↀↀↀ',
					'ↀↁ',
					'ↁ',
					'ↁↀ',
					'ↁↀↀ',
					'ↁↀↀↀ',
					'ↀↂ'
				} ;
				text = text .. digit[tausender];
			end
		else
			if upper < 10 then
				text = string.rep('M',upper);
			else
				text = 'ERR!...'; -- klassische M nur bis 9999
			end
		end
	end  -- Ende  upper > 0
	if lower > 0 then
		if upper > 0 then
			text = text .. ' ';
		end
		if hunderter > 0 then
			digit = {'C', 'CC', 'CCC', 'CD', 'D', 'DC', 'DCC', 'DCCC', 'CM'} ;
			if  style=='apo' then
				digit[9] =  'Cↀ';
			end
			text = text .. digit[hunderter];
		end
		if zehner > 0 then
			digit = {'X', 'XX', 'XXX', 'XL', 'L', 'LX', 'LXX', 'LXXX', 'XC'} ;
			text = text .. digit[zehner];
		end
		if einer > 0 then
			digit = {'I', 'II', 'III', 'IV', 'V', 'VI', 'VII', 'VIII', 'IX'} ;
			text = text .. digit[einer];
		end
	end
	return text;
end

--[[
    Convert possible Unicode minus U+2212 into ASCII hyphen-minus.

    @param source : String representation of a number.
    @param larger : nil/false = Unicode -> ASCII.

    @return String with one Unicode minus replaced by ASCII hyphen-minus.
]]
FormatNum.minus = function ( source, larger )
    local r = mw.ustring.char( 0x2212 );
    if larger then
        r = source:gsub( "-", r, 1 );
    else
        r = mw.ustring.gsub( source, r, "-", 1 );
    end
    -- gsub has two results.
    return r;
end -- FormatNum.minus()

--[[
    HTML padding of number strings.

    @param number : string with floating point or integer number
    @param meet :  Positive figures require padding behind decimal mark,
           negative values ensure at least that absolute value
           of characters before decimal mark.
           Defaults to 'none' or 0.
    @param stop : string with decimal mark; if false: number is integer.

    @return String of the formatted number.
]]
FormatNum.padding = function ( number, meet, stop )
    local r = number;
    if type( number ) == "string"    and
       type( meet ) == "number"    and
       ( not stop   or
         ( type( stop ) == "string"  and
           stop:match( "^%p$" ) ) ) then
        local m = math.floor( meet );
        if m ~= 0 then
            local i, s;
            r = mw.text.trim( r );
            if stop then
                i = r:find( stop, 1, true );
                s = "";
            else
                i = mw.ustring.len( r );
                s = ".";
            end
            if i then
                local left = ( m < 0 );
                local n    = m + i;
                if left then
                    n = 1 - n;
                else
                    n = n - mw.ustring.len( r );
                end
                if n > 0 then
                    s = string.format( PADDING_SPAN,
                                       s,
                                       string.rep( "0", n ) );
                    if left then
                        r = s .. r;
                    else
                        r = r .. s;
                    end
                end
            end
        end
    end
    return r;
end -- FormatNum.padding()

--[[
    Convert string of roman digits into number.
    @param roman :  string with roman number, case-insensitive,
                    and possibly trailing suffix.
    @param suffix : nil, or string with pattern for permitted suffix.
    @return
        1. Read number, or false if error.
        2. nil, or string with detected trailing suffix.
]]
FormatNum.roman2number = function ( roman, suffix )
    local d  = mw.text.split( roman, "" );
    local n  = #d;
    local r  = 0;
    local r2 = false;
    local k;
    for i = 1, n do
        k = ROMAN_DIGITS[ d[ i ]:upper() ];
        if k then
            d[ i ] = k;
        else
            r2 = table.concat( d, "", i );
            if suffix   and   mw.ustring.match( r2, "^" .. suffix ) then
                n = i - 1;
            else
                r = false;
            end
            break;    -- for i
        end
    end    -- for i
    if r then
        local j = 0;
        local l = true;
        for i = n, 1, -1 do
            k = d[ i ];
            if k > j then
                r = r + k;
                l = true;
            elseif k < j then
                r = r - k;
                l = false;
            elseif l then
                r = r + k;
            else
                r = r - k;
            end
            j = k;
        end    -- for i
    end
    return r, r2;
end -- FormatNum.roman2number()

--[[
    Rounding numbers.

    @param number : string with unformatted floating point or integer number, or number.
    @param precision : number of significant fractional part digits.
           If precision is negative, the integer part is rounded as well.
    @param method : number defining the rounding method to use.
           Currently are supported only
              0 for 'IEEE 754' rounding (default) and
              1 for 'round half away from zero'.
           If another number is supplied, the result is undefined.
    @param lone : boolean or nil; omit decimal separator
           on floating point numbers without trailing digits.

    @return String of the rounded number as returned by Lua function string.format().
]]
FormatNum.round = function ( source, precision, method, lone )
    local n = math.floor( precision );
    local r;
    if n then
        local stitch = type( source );
        local lower;
        if stitch == "string" then
            r = mw.text.trim( source );
            if r == "" then
                r = false;
            elseif n > 0 then
                local s = r:match( "^-?%d+%.(%d+)$" );
                if not s  or  #s < n then
                    n = false;
                end
            else
                lower = r:find( ".", 1, true )  and  not lone;
            end
            if r and n then
                r = tonumber( r );
            end
        elseif stitch == "number" then
            r = source;
        end
        if r and n then
            local m;
            if type( method ) == "number" then
                m = math.floor( method );
            else
                m = DEFAULT_METHOD;
            end
            r = numberToString( r, n, m );
            if lower then
                r = r .. ".";
            end
        end
    end
    return r or source;
end -- FormatNum.round()

--[[
    Retrieve versioning and check for compliance.

    @param atleast : string with with required version
                    or "wikidata" or "~" or "@", or false.

    @return String with with queried version, also if problem,
                   or false if appropriate
]]
Failsafe.failsafe = function ( atleast )
    -- Retrieve versioning and check for compliance
    -- Precondition:
    --     atleast  -- string, with required version
    --                         or "wikidata" or "~" or "@" or false
    -- Postcondition:
    --     Returns  string  -- with queried version/item, also if problem
    --              false   -- if appropriate
    -- 2020-08-01
    local last  = ( atleast == "~" )
    local link  = ( atleast == "@" )
    local since = atleast
    local r
    if last  or  link  or  since == "wikidata" then
        local item = Failsafe.item
        since = false
        if type( item ) == "number"  and  item > 0 then
            local suited = string.format( "Q%d", item )
            local entity = mw.wikibase.getEntity( suited )
            if type( entity ) == "table" then
                local seek = Failsafe.serialProperty or "P348"
                local vsn  = entity:formatPropertyValues( seek )
                if type( vsn ) == "table"  and
                   type( vsn.value ) == "string"  and
                   vsn.value ~= "" then
                    if last  and  vsn.value == Failsafe.serial then
                        r = false
                    elseif link then
                        if mw.title.getCurrentTitle().prefixedText  ==
                           mw.wikibase.getSitelink( suited ) then
                            r = false
                        else
                            r = suited
                        end
                    else
                        r = vsn.value
                    end
                end
            end
        end
    end
    if type( r ) == "nil" then
        if not since  or  since <= Failsafe.serial then
            r = Failsafe.serial
        else
            r = false
        end
    end
    return r
end -- Failsafe.failsafe()

local p = { };

p.format = function ( frame )
    -- @param 1 : unformatted (but maybe rounded) floating point or integer number.
    -- @param 2 : Formatting option. Currently there are supported:
    --                 "at", "comma", "de", "dewiki", "de_currency", "ch",
    --                 "ch_currency", "en", "iso31_0", "iso31_0_point" and "pc".
    local source = frame.args[ 1 ];
    local spec   = frame.args[ 2 ];
    if spec then
        spec = mw.text.trim( spec );
        if spec == "" then
            spec = false;
        end
    end
    return FormatNum.format( source, spec )  or  "";
end -- .format()

p.minus = function ( frame )
    -- @param 1 : number, with possible Unicode minus or vice versa.
    -- @param 2 : boolean, turning ASCII hyphen into Unicode minus.
    local larger = frame.args[ 2 ];
    if larger then
        larger = mw.text.trim( larger );
        if larger == "" or larger == "0" then
            larger = false;
        end
    end
    return FormatNum.minus( frame.args[ 1 ], larger );
end -- .minus()

p.padding = function ( frame )
    -- @param 1 : number to be padded
    -- @param 2 : number of trailing or leading figures for alignment
    -- @param 3 : string with decimal mark
    local r    = frame.args[ 1 ];
    local meet = tonumber( frame.args[ 2 ] );
    local stop = frame.args[ 3 ];
    if r and meet and stop then
        stop = mw.text.trim( stop );
        r = FormatNum.padding( r, meet, stop );
    else
        r = r or "";
    end
    return r;
end -- .padding()

p.roman =  function ( frame )
    -- @param 1 : an Integer less than 1 000 000
    -- @param 2 : formatting code: 'over' for overline style, 'apo' for apostrophus, any other for 'M' only up to 9999
    local para1 =  tonumber(frame.args[1] or ) or 0 ;
    local para2 =  string.lower(frame.args[2] or '');
	return FormatNum.getromanstring(para1,para2)  or  "";
end

p.roman2number = function ( frame )
    -- @param 1 : roman number, possibly with trailing suffix
    -- @param 2 : pattern for permitted suffix, or not
    local r = frame.args[ 1 ];
    if r then
        local suffix = frame.args[ 2 ];
        r = mw.text.trim( r );
        if #r > 0 then
            if suffix then
                suffix = mw.text.trim( suffix );
                if #suffix == 0 then
                    suffix = false;
                end
            end
            r = FormatNum.roman2number( r, suffix )
        end
    end
    return r or "";
end -- .roman2number()

p.round = function ( frame )
    -- @param 1 : unformatted floating point or integer number.
    -- @param 2 : precision; number of significant fractional part digits.
    --            If precision is negative, the integer part is rounded as well.
    -- @param method : number defining the rounding method to be used.
    --                 Currently are supported only
    --                    0 for 'IEEE 754' rounding (default) and
    --                    1 for 'round half away from zero'.
    --                 If another number is supplied, the result is undefined.
    -- @param format : trigger formatting, if set to a formatting option.
    -- @param padding : trigger formatting and padding, if set to a number.
    local r         = frame.args[ 1 ];
    local precision = tonumber( frame.args[ 2 ] );
    if r and precision then
        local suitable = frame.args.format;
        local meet     = tonumber( frame.args.padding );
        local method   = tonumber( frame.args.method );
        local int      = frame.args[ 2 ]:find( "-0", 1, true );
        r = FormatNum.round( r, precision, method, int );
        if suitable then
            suitable = mw.text.trim( suitable );
            if #suitable == 0 then
                suitable = false;
            end
        end
        if suitable or meet then
            r = FormatNum.format( r, suitable, meet );
        end
    else
        r = r or "";
    end
    return r;
end -- .round()

p.failsafe = function ( frame )
    -- Retrieve versioning and check for compliance.
    -- @param 1 : string with with required version, or empty.
    -- @return String with appropriate version, or false.
    local s = type( frame );
    local since;
    if s == "table" then
        since = frame.args[ 1 ];
    elseif s == "string" then
        since = frame;
    end
    if since then
        since = mw.text.trim( since );
        if #since == 0 then
            since = false;
        end
    end
    return Failsafe.failsafe( since )  or  "";
end

-- Export access for Lua modules
p.FormatNum = function ()
    return FormatNum;
end -- .FormatNum()

return p;