Modul:fun
fun stands for "functional", but also functional programming can be fun. This library contains some typical metafunctions for functional programming, such as map, some, all, curry, as well as others.
Functions that take an array as their second argument are available as methods in the arrays created by Module:array, with the arguments reversed so that they can be called as methods.
It was started in a user sandbox (Module:User:Erutuon/functional). It is not to be confused with Lua Fun (of which there is a version at Module:User:Erutuon/luafun), even though some functions are similar.
The functions that take a table as their second argument will treat the table as an array if t[1] is not nil, and use ipairs. Otherwise, they will treat it as a hashmap, using pairs.
function map(func, iterable)- Perform a function
funcon every element initerableand return the resulting table.iterablemay be a table or a string. If a table, the function operates on every element in the array portion of the table; if a string, the function operates on every UTF-8 character in the string. The functionfunchas the following signature:func(member, i, iterable). That is, the table element or UTF-8 character is first, then the index of this element, and then the iterable value (table or string). function mapIter(func, iterator, iterable, initial_value)- Create a new array from the results of performing a function on the values returned by an iterator. Can be used in combination with
sortedPairsin Module:table.funchas the same signature described above. Not very useful withgmatch;funcwould have anilfirst argument, because the single value returned from the iterator would be supplied as the second argument tofunc. mapIter( function(parameter_value, parameter_name) return { parameter_name, parameter_value } end, sortedPairs(frame.args)) --> returns a sorted array of arrays containing parameter names and values
local export = {}
local ustring = mw.ustring
local libraryUtil = require "libraryUtil"
local checkType = libraryUtil.checkType
local checkTypeMulti = libraryUtil.checkTypeMulti
local iterableTypes = { "table", "string" }
local function _check(funcName, expectType)
if type(expectType) == "string" then
return function(argIndex, arg, nilOk)
return checkType(funcName, argIndex, arg, expectType, nilOk)
end
else
return 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
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
function export.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 export.map(func, iterable, isArray)
local check = _check 'map'
check(1, func, "function")
check(2, iterable, iterableTypes)
local array = {}
local iterator = type(iterable) == "string" and iterString
or (isArray or iterable[1] ~= nil) and ipairs or pairs
for i_or_k, val in iterator(iterable) do
array[i_or_k] = func(val, i_or_k, iterable)
end
return array
end
function export.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
function export.forEach(func, iterable, isArray)
local check = _check 'forEach'
check(1, func, "function")
check(2, iterable, iterableTypes)
local iterator = type(iterable) == "string" and iterString
or (isArray or iterable[1] ~= nil) and ipairs or pairs
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 export.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 export.some(func, t, isArray)
if isArray or 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 export.all(func, t, isArray)
if isArray or 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 export.filter(func, t, isArray)
local new_t = {}
if isArray or t[1] ~= nil then -- array
local new_i = 0
for i, v in ipairs(t) do
if func(v, i, t) then
new_i = new_i + 1
new_t[new_i] = v
end
end
else
for k, v in pairs(t) do
if func(v, k, t) then
new_t[k] = v -- or create array?
end
end
end
return new_t
end
function export.fold(func, t, accum)
for i, v in ipairs(t) do
accum = func(accum, v, i, t)
end
return accum
end
-------------------------------
-- Fancy stuff
local function capture(...)
local vals = { n = select('#', ...), ... }
return function()
return unpack(vals, 1, vals.n)
end
end
-- Log input and output of function.
-- Receives a function and returns a modified form of that function.
function export.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
export.log = export.logReturnValues
-- Convenience function to make all functions in a table log their input and output.
function export.logAll(t)
for k, v in pairs(t) do
if type(v) == "function" then
t[k] = export.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 export.memoize(func)
return setmetatable({ [func_key] = func }, mt)
end
-------------------------------
return export