Module:fun
- The following documentation is located at Module:fun/documentation. [edit]
- Useful links: subpage list • links • transclusions • testcases • sandbox
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 debug_track_module = "Module:debug/track"
local chain -- Defined below.
local chain_iter -- Defined below.
local getmetatable = getmetatable
local gmatch = string.gmatch
local ipairs = ipairs
local pairs = pairs
local pcall = pcall
local rawequal = rawequal
local rawget = rawget
local select = select
local setmetatable = setmetatable
local tostring = tostring
local type = type
local unpack = unpack
--[==[
Loaders for functions in other modules, which overwrite themselves with the target function when called. This ensures modules are only loaded when needed, retains the speed/convenience of locally-declared pre-loaded functions, and has no overhead after the first call, since the target functions are called directly in any subsequent calls.]==]
local function debug_track(...)
debug_track = require(debug_track_module)
return debug_track(...)
end
local function _iterString(iter, i)
i = i + 1
local char = iter()
if char ~= nil then
return i, char
end
end
-- Iterate over UTF-8-encoded codepoints in string.
local function iterString(str)
return _iterString, gmatch(str, ".[\128-\191]*"), 0
end
--[==[
Return {true} if the input is a function or functor (a table which can be called like a function, because it has a {__call} metamethod).
Note: if the input is a table with a protected metatable (i.e. one hidden using the `__metatable` metamethod), then this function will treat the value of `__metatable` as though it is the metatable, as that is what gets returned by `getmetatable` in such cases. If you are making use of the `__metatable` metamethod, make sure that `__metatable` is a table with a function at the `__call` key to ensure that this function returns the correct result; it does not matter if this function is the true `__call` metamethod.]==]
function export.is_callable(f)
local f_type = type(f)
if f_type == "function" then
return true
elseif f_type ~= "table" then
return false
end
-- A table is a functor if it has a `__call` metamethod. The only way to truly confirm this is by trying to call the table, but that could modify the table or other variables out of scope, so look for a `__call` metamethod instead. If the metatable is protected with `__metatable`, this may not be possible.
local mt = getmetatable(f)
if mt == nil then
return false
end
-- Check if the metatable is protected: `setmetatable` will throw an error if so.
local success = pcall(setmetatable, f, mt)
-- If it's protected, then `mt` could be anything, but use the heuristic that if a `__call` key exists then that's probably intentional.
-- This also builds in ways to ensure that this function always returns the correct result when implementing protected metatables.
if not success then
if type(mt) ~= "table" then
debug_track("fun/is_callable/protected metatable")
return false
end
local __metatable = rawget(mt, "__metatable")
-- If the value of `__metatable` is also `mt`, then `mt` must be the true metatable anyway (e.g. mw.loadData does this).
if __metatable == nil or not rawequal(mt, __metatable) then
debug_track("fun/is_callable/protected metatable")
end
end
local __call = rawget(mt, "__call")
-- `__call` metamethods have to be functions, so don't recurse to check it.
return __call ~= nil and type(__call) == "function"
end
--[==[
Takes two or more functions as arguments, and returns a new function which calls each of the input functions in turn. Any arguments given to the returned function are given to the first function, and all other functions receive the output value(s) from the previous function.]==]
function export.chain(func1, func2, ...)
local function chained_func(...)
return func2(func1(...))
end
if select("#", ...) == 0 then
return chained_func
end
return chain(chained_func, ...)
end
chain = export.chain
--[==[
Takes a generator function (i.e. a function that returns an iterator, such as {ipairs}) and one or more additional functions, and returns a new generator function. Any arguments given to the new generator (e.g. an input table) are given to the original generator, and the additional functions are called on each iteration. The first additional function takes the output from the original iterator (i.e. the function returned by the original generator), and any further functions receive the output value(s) from the previous function. This can be used to modify the values returned from an iterator.]==]
function export.chainIter(gen, new_iter, ...)
if select("#", ...) > 0 then
new_iter = chain(new_iter, ...)
end
return function(...)
local orig_iter, state, k = gen(...)
-- k has to be the first value returned by orig_iter on the last iteration, not whatever new_iter returned.
local function catch_values(...)
k = ...
if k ~= nil then
return new_iter(...)
end
end
return function()
return catch_values(orig_iter(state, k))
end, state, k
end
end
chain_iter = export.chainIter
do
local function catch_values(start, iter, state, k, ...)
if start == k or k == nil then
return k, ...
end
return catch_values(start, iter, state, iter(state, k))
end
function export.iterateFrom(start, iter, state, k)
local first = true
return function(state, k)
if first then
first = false
return catch_values(start, iter, state, iter(state, k))
end
return iter(state, k)
end, state, k
end
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 array = {}
for k, v in (type(iterable) == "string" and iterString or (isArray or iterable[1] ~= nil) and ipairs or pairs)(iterable) do
array[k] = func(v, k, iterable)
end
return array
end
function export.mapIter(func, iter, state, init)
-- init could be anything
local array, i = {}, 0
for x, y in iter, state, init do
i = i + 1
array[i] = func(y, x, state)
end
return array
end
do
local function iter_tuples(tuples)
local i = tuples.i
if i > 1 then
i = i - 1
tuples.i = i
return unpack(tuples[i])
end
end
-- Takes an iterator function, and returns a new iterator that iterates in reverse, given the same arguments.
-- Note: changes to the state during iteration are not taken into account, since all the return values are calculated in advance.
function export.reverseIter(func)
return function(...)
-- Store all returned values as a list of tuples, then iterate in reverse over that list.
local tuples, i, iter, state, val1 = {}, 0, func(...)
while true do
i = i + 1
local vals = {iter(state, val1)}
-- Terminates if the first return value is nil, even if other values are non-nil.
val1 = vals[1]
if val1 == nil then
tuples.i = i
return iter_tuples, tuples
end
tuples[i] = vals
end
end
end
end
function export.forEach(func, iterable, isArray)
for k, v in (type(iterable) == "string" and iterString or (isArray or iterable[1] ~= nil) and ipairs or pairs)(iterable) do
func(v, 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)
for k, v in ((isArray or t[1] ~= nil) and ipairs or pairs)(t) do
if func(v, k, t) then
return true
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)
for k, v in ((isArray or t[1] ~= nil) and ipairs or pairs)(t) do
if not func(v, k, t) then
return false
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
return export