Modul:Arguments

This module provides easy processing of arguments passed from #invoke. It is a meta-module, meant for use by other modules, and should not be called from #invoke directly. Its features include:

• Easy trimming of arguments and removal of blank arguments.
• Arguments can be passed by both the current frame and by the parent frame at the same time. (More details below.)
• Arguments can be passed in directly from another Lua module or from the debug console.
• Arguments are fetched as needed, which can help avoid (some) problems with <ref>...</ref> tags.
• Most features can be customized.

Basic use

First, you need to load the module. It contains one function, named getArgs.

local getArgs = require('Module:Arguments').getArgs

In the most basic scenario, you can use getArgs inside your main function. The variable args is a table containing the arguments from #invoke. (See below for details.)

local getArgs = require('Module:Arguments').getArgs
local p = {}

function p.main(frame)
	local args = getArgs(frame)
	-- Main module code goes here.
end

return p

However, the recommended practice is to use a function just for processing arguments from #invoke. This means that if someone calls your module from another Lua module you don't have to have a frame object available, which improves performance.

local getArgs = require('Module:Arguments').getArgs
local p = {}

function p.main(frame)
	local args = getArgs(frame)
	return p._main(args)
end

function p._main(args)
	-- Main module code goes here.
end

return p

If you want multiple functions to use the arguments, and you also want them to be accessible from #invoke, you can use a wrapper function.

local getArgs = require('Module:Arguments').getArgs

local function makeInvokeFunc(funcName)
	return function (frame)
		local args = getArgs(frame)
		return p[funcName](args)
	end
end

local p = {}

p.func1 = makeInvokeFunc('_func1')

function p._func1(args)
	-- Code for the first function goes here.
end

p.func2 = makeInvokeFunc('_func2')

function p._func2(args)
	-- Code for the second function goes here.
end

return p

Options

The following options are available. They are explained in the sections below.

local args = getArgs(frame, {
	trim = false,
	removeBlanks = false,
	valueFunc = function (key, value)
		-- Code for processing one argument
	end,
	frameOnly = true,
	parentOnly = true,
	parentFirst = true,
	wrappers = {
		'Template:A wrapper template',
		'Template:Another wrapper template'
	},
	readOnly = true,
	noOverwrite = true
})

Trimming and removing blanks

Blank arguments often trip up coders new to converting MediaWiki templates to Lua. In template syntax, blank strings and strings consisting only of whitespace are considered false. However, in Lua, blank strings and strings consisting of whitespace are considered true. This means that if you don't pay attention to such arguments when you write your Lua modules, you might treat something as true that should actually be treated as false. To avoid this, by default this module removes all blank arguments.

Similarly, whitespace can cause problems when dealing with positional arguments. Although whitespace is trimmed for named arguments coming from #invoke, it is preserved for positional arguments. Most of the time this additional whitespace is not desired, so this module trims it off by default.

However, sometimes you want to use blank arguments as input, and sometimes you want to keep additional whitespace. This can be necessary to convert some templates exactly as they were written. If you want to do this, you can set the trim and removeBlanks arguments to false.

local args = getArgs(frame, {
	trim = false,
	removeBlanks = false
})

Custom formatting of arguments

Sometimes you want to remove some blank arguments but not others, or perhaps you might want to put all of the positional arguments in lower case. To do things like this you can use the valueFunc option. The input to this option must be a function that takes two parameters, key and value, and returns a single value. This value is what you will get when you access the field key in the args table.

Example 1: this function preserves whitespace for the first positional argument, but trims all other arguments and removes all other blank arguments.

local args = getArgs(frame, {
	valueFunc = function (key, value)
		if key == 1 then
			return value
		elseif value then
			value = mw.text.trim(value)
			if value ~= '' then
				return value
			end
		end
		return nil
	end
})

Example 2: this function removes blank arguments and converts all arguments to lower case, but doesn't trim whitespace from positional parameters.

local args = getArgs(frame, {
	valueFunc = function (key, value)
		if not value then
			return nil
		end
		value = mw.ustring.lower(value)
		if mw.ustring.find(value, '%S') then
			return value
		end
		return nil
	end
})

Note: the above functions will fail if passed input that is not of type string or nil. This might be the case if you use the getArgs function in the main function of your module, and that function is called by another Lua module. In this case, you will need to check the type of your input. This is not a problem if you are using a function specially for arguments from #invoke (i.e. you have p.main and p._main functions, or something similar).

Also, please note that the valueFunc function is called more or less every time an argument is requested from the args table, so if you care about performance you should make sure you aren't doing anything inefficient with your code.

Frames and parent frames

Arguments in the args table can be passed from the current frame or from its parent frame at the same time. To understand what this means, it is easiest to give an example. Let's say that we have a module called Module:ExampleArgs. This module prints the first two positional arguments that it is passed.

Module:ExampleArgs is then called by Template:ExampleArgs, which contains the code {{#invoke:ExampleArgs|main|firstInvokeArg}}. This produces the result "firstInvokeArg".

Now if we were to call Template:ExampleArgs, the following would happen:

Code	Result
{{ExampleArgs}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}	firstInvokeArg secondTemplateArg

There are three options you can set to change this behaviour: frameOnly, parentOnly and parentFirst. If you set frameOnly then only arguments passed from the current frame will be accepted; if you set parentOnly then only arguments passed from the parent frame will be accepted; and if you set parentFirst then arguments will be passed from both the current and parent frames, but the parent frame will have priority over the current frame. Here are the results in terms of Template:ExampleArgs:

frameOnly

Code	Result
{{ExampleArgs}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}	firstInvokeArg

parentOnly

Code	Result
{{ExampleArgs}}
{{ExampleArgs|firstTemplateArg}}	firstTemplateArg
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}	firstTemplateArg secondTemplateArg

parentFirst

Code	Result
{{ExampleArgs}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg}}	firstTemplateArg
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}	firstTemplateArg secondTemplateArg

Notes:

1. If you set both the frameOnly and parentOnly options, the module won't fetch any arguments at all from #invoke. This is probably not what you want.
2. In some situations a parent frame may not be available, e.g. if getArgs is passed the parent frame rather than the current frame. In this case, only the frame arguments will be used (unless parentOnly is set, in which case no arguments will be used) and the parentFirst and frameOnly options will have no effect.

Wrappers

The wrappers option is used to specify a limited number of templates as wrapper templates, that is, templates whose only purpose is to call a module. If the module detects that it is being called from a wrapper template, it will only check for arguments in the parent frame; otherwise it will only check for arguments in the frame passed to getArgs. This allows modules to be called by either #invoke or through a wrapper template without the loss of performance associated with having to check both the frame and the parent frame for each argument lookup.

For example, the only content of Template:Side box (excluding content in <noinclude>...</noinclude> tags) is {{#invoke:Side box|main}}. There is no point in checking the arguments passed directly to the #invoke statement for this template, as no arguments will ever be specified there. We can avoid checking arguments passed to #invoke by using the parentOnly option, but if we do this then #invoke will not work from other pages either. If this were the case, the |text=Some text in the code {{#invoke:Side box|main|text=Some text}} would be ignored completely, no matter what page it was used from. By using the wrappers option to specify 'Template:Side box' as a wrapper, we can make {{#invoke:Side box|main|text=Some text}} work from most pages, while still not requiring that the module check for arguments on the Template:Side box page itself.

Wrappers can be specified either as a string, or as an array of strings.

local args = getArgs(frame, {
	wrappers = 'Template:Wrapper template'
})

local args = getArgs(frame, {
	wrappers = {
		'Template:Wrapper 1',
		'Template:Wrapper 2',
		-- Any number of wrapper templates can be added here.
	}
})

Notes:

1. The module will automatically detect if it is being called from a wrapper template's /sandbox subpage, so there is no need to specify sandbox pages explicitly.
2. The wrappers option effectively changes the default of the frameOnly and parentOnly options. If, for example, parentOnly were explicitly set to false with wrappers set, calls via wrapper templates would result in both frame and parent arguments being loaded, though calls not via wrapper templates would result in only frame arguments being loaded.
3. If the wrappers option is set and no parent frame is available, the module will always get the arguments from the frame passed to getArgs.

Writing to the args table

Sometimes it can be useful to write new values to the args table. This is possible with the default settings of this module. (However, bear in mind that it is usually better coding style to create a new table with your new values and copy arguments from the args table as needed.)

args.foo = 'some value'

It is possible to alter this behaviour with the readOnly and noOverwrite options. If readOnly is set then it is not possible to write any values to the args table at all. If noOverwrite is set, then it is possible to add new values to the table, but it is not possible to add a value if it would overwrite any arguments that are passed from #invoke.

Ref tags

This module uses metatables to fetch arguments from #invoke. This allows access to both the frame arguments and the parent frame arguments without using the pairs() function. This can help if your module might be passed <ref>...</ref> tags as input.

As soon as <ref>...</ref> tags are accessed from Lua, they are processed by the MediaWiki software and the reference will appear in the reference list at the bottom of the article. If your module proceeds to omit the reference tag from the output, you will end up with a phantom reference - a reference that appears in the reference list, but no number that links to it. This has been a problem with modules that use pairs() to detect whether to use the arguments from the frame or the parent frame, as those modules automatically process every available argument.

This module solves this problem by allowing access to both frame and parent frame arguments, while still only fetching those arguments when it is necessary. The problem will still occur if you use pairs(args) elsewhere in your module, however.

Known limitations

The use of metatables also has its downsides. Most of the normal Lua table tools won't work properly on the args table, including the # operator, the next() function, and the functions in the table library. If using these is important for your module, you should use your own argument processing function instead of this module.

---

--[[

This module provides a number of basic mathematical operations.

]]

local yesno = require('Module:Yesno')
local getArgs = require('Module:Arguments').getArgs

local p = {} -- Holds functions to be returned from #invoke, and functions to make available to other Lua modules.
local wrap = {} -- Holds wrapper functions that process arguments from #invoke. These act as intemediary between functions meant for #invoke and functions meant for Lua.

--[[
Helper functions used to avoid redundant code.
]]

local function err(msg)
	-- Generates wikitext error messages.
	return mw.ustring.format('<strong class="error">Formatting error: %s</strong>', msg)
end

local function unpackNumberArgs(args)
	-- Returns an unpacked list of arguments specified with numerical keys.
	local ret = {}
	for k, v in pairs(args) do
		if type(k) == 'number' then
			table.insert(ret, v)
		end
	end
	return unpack(ret)
end

local function makeArgArray(...)
	-- Makes an array of arguments from a list of arguments that might include nils.
	local args = {...} -- Table of arguments. It might contain nils or non-number values, so we can't use ipairs.
	local nums = {} -- Stores the numbers of valid numerical arguments.
	local ret = {}
	for k, v in pairs(args) do
		v = p._cleanNumber(v)
		if v then
			nums[#nums + 1] = k
			args[k] = v
		end
	end
	table.sort(nums)
	for i, num in ipairs(nums) do
		ret[#ret + 1] = args[num]
	end
	return ret
end

local function applyFuncToArgs(func, ...)
	-- Use a function on all supplied arguments, and return the result. The function must accept two numbers as parameters,
	-- and must return a number as an output. This number is then supplied as input to the next function call.
	local vals = makeArgArray(...)	
	local count = #vals -- The number of valid arguments
	if count == 0 then return
		-- Exit if we have no valid args, otherwise removing the first arg would cause an error.
		nil, 0
	end 
	local ret = table.remove(vals, 1)
	for _, val in ipairs(vals) do
		ret = func(ret, val)
	end
	return ret, count
end

--[[
random

Generate a random number

Usage:
{{#invoke: Math | random }}
{{#invoke: Math | random | maximum value }}
{{#invoke: Math | random | minimum value | maximum value }}
]]

function wrap.random(args)
	local first = p._cleanNumber(args[1])
	local second = p._cleanNumber(args[2])
	return p._random(first, second)
end

function p._random(first, second)
	math.randomseed(mw.site.stats.edits + mw.site.stats.pages + os.time() + math.floor(os.clock() * 1000000000))
	-- math.random will throw an error if given an explicit nil parameter, so we need to use if statements to check the params.
	if first and second then
		if first <= second then -- math.random doesn't allow the first number to be greater than the second.
			return math.random(first, second)
		end
	elseif first then
		return math.random(first)
	else
		return math.random()
	end
end

--[[
order

Determine order of magnitude of a number

Usage:
{{#invoke: Math | order | value }}
]]

function wrap.order(args)
	local input_string = (args[1] or args.x or '0');
	local input_number = p._cleanNumber(input_string);
	if input_number == nil then
		return err('order of magnitude input appears non-numeric')
	else
		return p._order(input_number)
	end    
end

function p._order(x)
	if x == 0 then return 0 end
	return math.floor(math.log10(math.abs(x)))
end

--[[
precision

Detemines the precision of a number using the string representation

Usage:
{{ #invoke: Math | precision | value }}
]]

function wrap.precision(args)
	local input_string = (args[1] or args.x or '0');
	local trap_fraction = args.check_fraction;
	local input_number;

	if yesno(trap_fraction, true) then -- Returns true for all input except nil, false, "no", "n", "0" and a few others. See [[Module:Yesno]].
		local pos = string.find(input_string, '/', 1, true);
		if pos ~= nil then
			if string.find(input_string, '/', pos + 1, true) == nil then
				local denominator = string.sub(input_string, pos+1, -1);
				local denom_value = tonumber(denominator);
				if denom_value ~= nil then
					return math.log10(denom_value);
				end
			end                        
		end
	end    

	input_number, input_string = p._cleanNumber(input_string);
	if input_string == nil then
		return err('precision input appears non-numeric')
	else
		return p._precision(input_string)
	end    
end

function p._precision(x)
	if type(x) == 'number' then
		x = tostring(x)
	end
	x = string.upper(x)

	local decimal = x:find('%.')
	local exponent_pos = x:find('E')
	local result = 0;

	if exponent_pos ~= nil then
		local exponent = string.sub(x, exponent_pos + 1)
		x = string.sub(x, 1, exponent_pos - 1)
		result = result - tonumber(exponent)
	end    

	if decimal ~= nil then
		result = result + string.len(x) - decimal
		return result
	end

	local pos = string.len(x);
	while x:byte(pos) == string.byte('0') do
		pos = pos - 1
		result = result - 1
		if pos <= 0 then
			return 0
		end
	end

	return result
end

--[[
max

Finds the maximum argument

Usage:
{{#invoke:Math| max | value1 | value2 | ... }}

Note, any values that do not evaluate to numbers are ignored.
]]

function wrap.max(args)
	return p._max(unpackNumberArgs(args))
end

function p._max(...)
	local function maxOfTwo(a, b)
		if a > b then
			return a
		else
			return b
		end
	end
	local max_value = applyFuncToArgs(maxOfTwo, ...)
	if max_value then
		return max_value
	end
end

--[[
min 

Finds the minimum argument

Usage:
{{#invoke:Math| min | value1 | value2 | ... }}
OR
{{#invoke:Math| min }}

When used with no arguments, it takes its input from the parent
frame.  Note, any values that do not evaluate to numbers are ignored.
]]

function wrap.min(args)
	return p._min(unpackNumberArgs(args))
end

function p._min(...)
	local function minOfTwo(a, b)
		if a < b then
			return a
		else
			return b
		end
	end
	local min_value = applyFuncToArgs(minOfTwo, ...)
	if min_value then
		return min_value
	end
end

--[[
average 

Finds the average

Usage:
{{#invoke:Math| average | value1 | value2 | ... }}
OR
{{#invoke:Math| average }}

Note, any values that do not evaluate to numbers are ignored.
]]

function wrap.average(args)
	return p._average(unpackNumberArgs(args))
end

function p._average(...)
	local function getSum(a, b)
		return a + b
	end
	local sum, count = applyFuncToArgs(getSum, ...)
	if not sum then
		return 0
	else
		return sum / count
	end
end

--[[
round

Rounds a number to specified precision

Usage:
{{#invoke:Math | round | value | precision }}

--]]

function wrap.round(args)
	local value = p._cleanNumber(args[1] or args.value or 0)
	local precision = p._cleanNumber(args[2] or args.precision or 0)
	if value == nil or precision == nil then
		return err('round input appears non-numeric')
	else
		return p._round(value, precision)
	end    
end

function p._round(value, precision)
	local rescale = math.pow(10, precision or 0);
	return math.floor(value * rescale + 0.5) / rescale;
end

--[[
mod

Implements the modulo operator

Usage:
{{#invoke:Math | mod | x | y }}

--]]

function wrap.mod(args)
	local x = p._cleanNumber(args[1])
	local y = p._cleanNumber(args[2])
	if not x then
		return err('first argument to mod appears non-numeric')
	elseif not y then
		return err('second argument to mod appears non-numeric')
	else
		return p._mod(x, y)
	end    
end

function p._mod(x, y)
	local ret = x % y
	if not (0 <= ret and ret < y) then
		ret = 0
	end
	return ret
end

--[[
gcd

Calculates the greatest common divisor of multiple numbers

Usage:
{{#invoke:Math | gcd | value 1 | value 2 | value 3 | ... }}
--]]

function wrap.gcd(args)
	return p._gcd(unpackNumberArgs(args))
end

function p._gcd(...)
	local function findGcd(a, b)
		local r = b
		local oldr = a
		while r ~= 0 do
			local quotient = math.floor(oldr / r)
			oldr, r = r, oldr - quotient * r
		end
		if oldr < 0 then
			oldr = oldr * -1
		end
		return oldr
	end
	local result, count = applyFuncToArgs(findGcd, ...)
	return result
end

--[[
precision_format

Rounds a number to the specified precision and formats according to rules 
originally used for {{template:Rnd}}.  Output is a string.

Usage:
{{#invoke: Math | precision_format | number | precision }}
]]

function wrap.precision_format(args)
	local value_string = args[1] or 0
	local precision = args[2] or 0
	return p._precision_format(value_string, precision)
end

function p._precision_format(value_string, precision)
	-- For access to Mediawiki built-in formatter.
	local lang = mw.getContentLanguage();

	local value
	value, value_string = p._cleanNumber(value_string)
	precision = p._cleanNumber(precision)

	-- Check for non-numeric input
	if value == nil or precision == nil then
		return err('invalid input when rounding')
	end

	local current_precision = p._precision(value)
	local order = p._order(value)

	-- Due to round-off effects it is neccesary to limit the returned precision under
	-- some circumstances because the terminal digits will be inaccurately reported.
	if order + precision >= 14 then
		orig_precision = p._precision(value_string)
		if order + orig_precision >= 14 then
			precision = 13 - order;        
		end        
	end

	-- If rounding off, truncate extra digits
	if precision < current_precision then
		value = p._round(value, precision)
		current_precision = p._precision(value)
	end    

	local formatted_num = lang:formatNum(math.abs(value))
	local sign

	-- Use proper unary minus sign rather than ASCII default
	if value < 0 then
		sign = '−'
	else
		sign = ''
	end    

	-- Handle cases requiring scientific notation
	if string.find(formatted_num, 'E', 1, true) ~= nil or math.abs(order) >= 9 then
		value = value * math.pow(10, -order)
		current_precision = current_precision + order
		precision = precision + order
		formatted_num = lang:formatNum(math.abs(value))
	else
		order = 0;        
	end
	formatted_num = sign .. formatted_num

	-- Pad with zeros, if needed    
	if current_precision < precision then
		local padding
		if current_precision <= 0 then
			if precision > 0 then
				local zero_sep = lang:formatNum(1.1)
				formatted_num = formatted_num .. zero_sep:sub(2,2)

				padding = precision
				if padding > 20 then
					padding = 20
				end

				formatted_num = formatted_num .. string.rep('0', padding)
			end            
		else                   
			padding = precision - current_precision
			if padding > 20 then
				padding = 20
			end
			formatted_num = formatted_num .. string.rep('0', padding)
		end
	end

	-- Add exponential notation, if necessary.
	if order ~= 0 then
		-- Use proper unary minus sign rather than ASCII default
		if order < 0 then
			order = '−' .. lang:formatNum(math.abs(order))
		else
			order = lang:formatNum(order)
		end    

		formatted_num = formatted_num .. '<span style="margin:0 .15em 0 .25em">×</span>10<sup>' .. order .. '</sup>'
	end

	return formatted_num
end

--[[
Helper function that interprets the input numerically.  If the 
input does not appear to be a number, attempts evaluating it as
a parser functions expression.
]]

function p._cleanNumber(number_string)
	if type(number_string) == 'number' then
		-- We were passed a number, so we don't need to do any processing.
		return number_string, tostring(number_string)
	elseif type(number_string) ~= 'string' or not number_string:find('%S') then
		-- We were passed a non-string or a blank string, so exit.
		return nil, nil;
	end

	-- Attempt basic conversion
	local number = tonumber(number_string)

	-- If failed, attempt to evaluate input as an expression
	if number == nil then
		local frame = mw.getCurrentFrame()
		local attempt = frame:preprocess('{{#expr: ' .. number_string .. '}}')
		attempt = tonumber(attempt)
		if attempt ~= nil then
			number = attempt
			number_string = tostring(number)
		else
			number = nil
			number_string = nil
		end
	else
		number_string = number_string:match("^%s*(.-)%s*$") -- String is valid but may contain padding, clean it.
		number_string = number_string:match("^%+(.*)$") or number_string -- Trim any leading + signs.
		if number_string:find('^%-?0[xX]') then
			-- Number is using 0xnnn notation to indicate base 16; use the number that Lua detected instead.
			number_string = tostring(number)
		end
	end

	return number, number_string
end

--[[
Wrapper function that does basic argument processing. This ensures that all functions from #invoke can use either the current
frame or the parent frame, and it also trims whitespace for all arguments and removes blank arguments.
]]

local function makeWrapper(funcName)
	return function (frame)
		local args = getArgs(frame) -- Argument processing is left to Module:Arguments. Whitespace is trimmed and blank arguments are removed.
		return wrap[funcName](args)
	end
end

for funcName in pairs(wrap) do
	p[funcName] = makeWrapper(funcName)
end

return p