Module:Fun: Difference between revisions

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Revision as of 00:09, 2 July 2018

local p = {}

local ustring = mw.ustring
local libraryUtil = require "libraryUtil"
local checkType = libraryUtil.checkType
local checkTypeMulti = libraryUtil.checkTypeMulti

local iterableTypes = { "table", "string" }

local _checkCache = {}
local function _check(funcName, expectType)
	if type(expectType) == "string" then
		return function(argIndex, arg, nilOk)
			return checkType(funcName, argIndex, arg, expectType, nilOk)
		end
	else
		local checkFunc = _checkCache[funcName] -- Lua 5.1 doesn't cache functions as Lua 5.3 does.
			or function(argIndex, arg, expectType, nilOk)
				if type(expectType) == "table" then
					if not (nilOk and arg == nil) then
						return checkTypeMulti(funcName, argIndex, arg, expectType)
					end
				else
					return checkType(funcName, argIndex, arg, expectType, nilOk)
				end
			end
		_checkCache[funcName] = checkFunc
		return checkFunc
	end
end

-- Iterate over UTF-8-encoded codepoints in string.
local function iterString(str)
	local iter = string.gmatch(str, "[%z\1-\127\194-\244][\128-\191]*")
	local i = 0
	local function iterator()
		i = i + 1
		local char = iter()
		if char then
			return i, char
		end
	end
	
	return iterator
end

local function getIterator(iterable)
	return type(iterable) == "string" and iterString
		or iterable[1] ~= nil and ipairs
		or pairs
end

function p.chain(func1, func2, ...)
	return func1(func2(...))
end

--	map(function(number) return number ^ 2 end,
--		{ 1, 2, 3 })									--> { 1, 4, 9 }
--	map(function (char) return string.char(string.byte(char) - 0x20) end,
--		"abc")											--> { "A", "B", "C" }
function p.map(func, ...)
	-- If second parameter is function, redirect to mapIter.
	if type(...) == "function" then
		return p.mapIter(func, ...)
	end
	
	local iterable = ...
	local check = _check 'map'
	check(1, func, "function")
	check(2, iterable, iterableTypes)
	
	local array = {}
	local iterator = getIterator(iterable)
	for i_or_k, val in iterator(iterable) do
		array[i_or_k] = func(val, i_or_k, iterable)
	end
	return array
end

function p.mapIter(func, iter, iterable, initVal)
	local check = _check 'mapIter'
	check(1, func, "function")
	check(2, iter, "function")
	check(3, iterable, iterableTypes, true)
	
	-- initVal could be anything
	
	local array = {}
	local i = 0
	for x, y in iter, iterable, initVal do
		i = i + 1
		array[i] = func(y, x, iterable)
	end
	return array
end

local function fold(func, iterable, result, checked)
	if not checked then
		local check = _check 'fold'
		check(1, func, "function")
		check(2, iterable, iterableTypes)
		-- Result can be anything.
	end
	
	local iterator = getIterator(iterable)
	for i_or_k, val in iterator(iterable) do
		result = func(result, val, i_or_k)
	end
	
	return result
end
p.fold = fold

function p.count(func, iterable)
	local check = _check 'count'
	check(1, func, "function")
	check(2, iterable, iterableTypes)
	
	return fold(
		function (count, val)
			if func(val) then
				return count + 1
			end
			return count
		end,
		iterable,
		0,
		true)
end

function p.forEach(func, iterable)
	local check = _check 'forEach'
	check(1, func, "function")
	check(2, iterable, iterableTypes)
	
	local iterator = getIterator(iterable)
	for i_or_k, val in iterator(iterable) do
		func(val, i_or_k, iterable)
	end
	return nil
end

-------------------------------------------------
-- From [[http://lua-users.org/wiki/CurriedLua]].
-- reverse(...) : take some tuple and return a tuple of elements in reverse order
--
-- e.g. "reverse(1,2,3)" returns 3,2,1
local function reverse(...)
	-- reverse args by building a function to do it, similar to the unpack() example
	local function reverseHelper(acc, v, ...)
		if select('#', ...) == 0 then
			return v, acc()
		else
			return reverseHelper(function() return v, acc() end, ...)
		end
	end
	
	-- initial acc is the end of the list
	return reverseHelper(function() return end, ...)
end

function p.curry(func, numArgs)
	-- currying 2-argument functions seems to be the most popular application
	numArgs = numArgs or 2
	
	-- no sense currying for 1 arg or less
	if numArgs <= 1 then return func end
	
	-- helper takes an argTrace function, and number of arguments remaining to be applied
	local function curryHelper(argTrace, n)
		if n == 0 then
			-- kick off argTrace, reverse argument list, and call the original function
			return func(reverse(argTrace()))
		else
			-- "push" argument (by building a wrapper function) and decrement n
			return function(onearg)
				return curryHelper(function() return onearg, argTrace() end, n - 1)
			end
		end
	end
	
	-- push the terminal case of argTrace into the function first
	return curryHelper(function() return end, numArgs)
end

-------------------------------------------------

--	some(function(val) return val % 2 == 0 end,
--		{ 2, 3, 5, 7, 11 })						--> true
function p.some(func, t)
	if t[1] ~= nil then -- array
		for i, v in ipairs(t) do
			if func(v, i, t) then
				return true
			end
		end
	else
		for k, v in pairs(t) do
			if func(v, k, t) then
				return true
			end
		end
	end
	return false
end

--	all(function(val) return val % 2 == 0 end,
--		{ 2, 4, 8, 10, 12 })					--> true
function p.all(func, t)
	if t[1] ~= nil then -- array
		for i, v in ipairs(t) do
			if not func(v, i, t) then
				return false
			end
		end
	else
		for k, v in pairs(t) do
			if not func(v, k, t) then
				return false
			end
		end
	end
	return true
end

function p.filter(func, iterable)
	local check = _check 'filter'
	check(1, func, "function")
	check(2, iterable, iterableTypes)
	
	local new_t = {}
	local new_i = 0
	local iterator = getIterator(iterable)
	for v1, v2 in iterator(iterable) do
		if func(v2, v1, t) then
			new_i = new_i + 1
			new_t[new_i] = v
		end
	end
	
	return new_t
end

function p.range(low, high)
	low = low - 1
	return function ()
		low = low + 1
		if low <= high then
			return low
		end
	end
end


-------------------------------
-- Fancy stuff
local function capture(...)
	local vals = { ... }
	return function()
		return unpack(vals)
	end
end

-- Log input and output of function.
-- Receives a function and returns a modified form of that function.
function p.logReturnValues(func, prefix)
	return function(...)
		local inputValues = capture(...)
		local returnValues = capture(func(...))
		if prefix then
			mw.log(prefix, inputValues())
			mw.log(returnValues())
		else
			mw.log(inputValues())
			mw.log(returnValues())
		end
		return returnValues()
	end
end

p.log = p.logReturnValues

-- Convenience function to make all functions in a table log their input and output.
function p.logAll(t)
	for k, v in pairs(t) do
		if type(v) == "function" then
			t[k] = p.logReturnValues(v, tostring(k))
		end
	end
	return t
end

----- M E M O I Z A T I O N-----
-- metamethod that does the work
-- Currently supports one argument and one return value.
local func_key = {}
local function callMethod(self, x)
	local output = self[x]
	if not output then
		output = self[func_key](x)
		self[x] = output
	end
	return output
end

-- shared metatable
local mt = { __call = callMethod }

-- Create callable table.
function p.memoize(func)
	return setmetatable({ [func_key] = func }, mt)
end

-------------------------------

return p
Revision as of 00:09, 2 July 2018

Usage
