Cofun

A simple coroutine powered functional programming library for LuaJIT.

Why

The cofun is aimed to be simple as anyone can contribute and learn something about functional programming and maybe Lua coroutines. Also it is aimed to be simplify the implementation of functional paradigms in any LuaJIT project.

Usage

For ease of use require the library and localize its functions:

local cofun = require('cofun')
local map = cofun.map
local filter = cofun.filter
local collect = cofun.collect
-- ...

Get passed student grades

grades = iter{56, 88, 85, 44, 90}

function can_pass(grade) return grade > 60 end

filter(can_pass, grades) -- iter{88, 85, 90}

Do not process until an element contains the letter b and then take 5 uppercased elements.

function contains_b(str) return string.find(str, 'b') end

take(5, map(string.upper, dropwhile(negated(contains_b), iterator)))

Zip n iterators.

letters = iter{'a', 'b', 'c'}

for l, n in zip(letters, count()) do
  print(l, n) -- 'a', 1 | 'b', 2 | 'c', 3
end

for l, n in enumerate(letters) do
  print(l, n) -- 'a', 1 | 'b', 2 | 'c', 3
end

for l, n, f in zip(letters, count(), count(5)) do
  print(l, n, f) -- 'a', 1, 5 | 'b', 2, 6 | 'c', 3, 7
end

You can consume the values using reducing, iterating and collecting.

Iterating

Iteration is the most efficientt way of consuming because of the absence of table creation.

iterator = iter{1,7,8}
for i in iterator do
  -- Consume i
end

Collecting

Consume the iterator and collect the iterations in a table.

collect(intersperse(':', take(4, count(7))))

Produces {7, ':', 8, ':', 9, ':', 10}

Folding

Folding reduces the dimension of the iteration to single element using a binary function.

-- Concat strings
foldfirst(function(left, right) return left .. right end, iterator)
-- Find max
foldfirst(function(left, right) return left < right and right or left end, iterator)

Some reduction shortcuts are implemented too and more can be added in the future:

sum(iterator)
max(iterator)
min(iterator)

Installation

Just copy cofun.lua and you are good to go. Don't forget the licence.

TODO

Write initial code
Add docstrings
Write unit tests
Publish to luarocks

nacro90 / cofun