Simple Login Screen using StoryBoard

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Asynchronous download using Coroutine - Lua

require("socket")

function download()
    local host, file, port = "www.w3.org", "/TR/REC-html32.html", 80
    local connection = assert(socket.connect(host, port))
    local count = 0    -- counts number of bytes read

    connection:send("GET " .. file .. " HTTP/1.0\r\n\r\n")

    while true do
        local response, status = receive(connection)

        if(response ~= nill) then count = count + string.len(response) end
        --print(response)
        if status == "closed" then break end
    end

    connection:close()

    print(file, count)
end

--[[function receive(connection)
    connection:settimeout(0)
    return connection:receive(2^10)
end]]--

function receive(connection)
    connection:settimeout(0)   -- do not block

    local response, status = connection:receive(2^10)

    if status == "timeout" then
        coroutine.yield(connection)
    end

    return response, status
end

threads = {}    -- list of all live threads

function get ()
  -- create coroutine
  local co = coroutine.create(function ()    download()  end)
  -- insert it in the list
  table.insert(threads, co)
end

function dispatcher()
    while true do
        local count = table.getn(threads)

        if(count <= 0) then break end

        for i = 1, count do
            local status, ret = coroutine.resume(threads[i])

            if not ret then table.remove(threads, i) break end
        end
    end
end

get()
get()
get()
get()
get()

dispatcher()

Permutations using Coroutines in Lua

First let's look at the algorithm for Permutations using recursion

algorithm Permutation(array, count)
              if array index is 0, display the array

              for each item in array until count
                     swap last and first item                    
                     Permutation(array, count -1)
                     swap last and first item                    
              end
end

now the code

function permuterate (a, n)
      if n == 0 then
        --printResult(a)
        coroutine.yield(a)
      else
        for i=1,n do

        --print("iteration=", i, "n=", n, "last=", a[n], "i th=",a[i])
          -- put i-th element as the last one
          a[n], a[i] = a[i], a[n]

          -- generate all permutations of the other elements
          permuterate(a, n - 1)

          --print("i=", i, "n=", n, "last=", a[n], "i th=",a[i])
          -- restore i-th element
          a[n], a[i] = a[i], a[n]

        end
      end
end

function printResult (a)
    for i,v in ipairs(a) do
        io.write(v, " ")
    end
    io.write("\n")
end

function createPermuterate(list)
    local pick = table.getn(list)
    local co = coroutine.create(function () permuterate(list, pick) end)

    return function()
                local _, value = coroutine.resume(co)

                return value
            end
end

function createPermuterate1(list)
    local pick = table.getn(list)
    return coroutine.wrap(function () permuterate(list, pick) end)
end

for p in createPermuterate{"1","2","3";n=3} do
    printResult(p)
end

for p in createPermuterate1{1,2,3;n=3} do
    printResult(p)
end

Coroutine in Lua - Consumer driven Producer-Consumer implementation

function send(task)
    coroutine.yield(task)
end

function receive()
    return coroutine.resume(co)
end

function consumer()
    while true do
        local _, task = receive()

        if(task == nil) then break end

        print("Processed item", task)
    end
end

co = coroutine.create(function ()
    local file = io.open("io.txt", "r")

    while true do
        local task = file:read("*line")

        if(task ~= nil) then
            send(task)
            print("waiting for consumer to signal")
        else
            break
        end
    end
end)

consumer()