Projekt Sauron: kod zadania map-reduce: merge-sort.

mergesort.lua

-- =====================================================================================================================
-- MOCK INTERFEJSU DOSTĘPNEGO NA APPCE
-- Dzięki temu można "ot tak" wrzucić kod w interpreter i będzie działać
-- ---------------------------------------------------------------------------------------------------------------------
local android = {}
function android.send(self, x)
    print("ANDROID:SEND:", x)
end
function android.sleep(self, t)
    print("ANDROID:SLEEP:", t)
    local os = require "os"
    os.execute("sleep "..tonumber(t))
end
function android.getLatitude(self)
    local res = 20.019
    print("ANDROID:GETLATITUDE >>", res)
    return res
end
function android.getLongitude(self)
    local res = 50.0655
    print("ANDROID:GETLLONGITUDE >>", res)
    return res
end
function android.getTime(self)
    local res = os.time()
    print("ANDROID:GETLLONGITUDE >>", res)
    return res
end


-- ===== DOKLEJANA ZAWARTOŚĆ ===========================================================================================
-- zadanie wysyłane do urządzenia
-- --- JAK TESTOWAĆ? ---------------------------------------------------------------------------------------------------
-- Odkomentować jedną z sekcji MAP, REDUCE albo CHUNKS tuż poniżej

-- ----- MAP ------------------
-- local val1 = {2, 0, 4, 6, 2}
-- ----- REDUCE ---------------
-- local val1 = {0, 2, 2, 4, 6}
-- local val2 = {0, 1, 2, 3, 4}
-- ----- CHUNKS ---------------
local val2 = {3,1,4,1,5,9,2,6,5}

-- tak naprawdę to jedno z tych powyżej powinno być doklejane do appki


-- ===== CHUNKIFY-MAP-REDUCE ===========================================================================================
function domap(xs)
    table.sort(xs)
    return xs
end
function reduce(xs, ys)
    local res = {}
    while next(xs) ~= nil and next(ys) ~= nil do
        if xs[1] <= ys[1]
        then table.insert(res, table.remove(xs, 1))
        else table.insert(res, table.remove(ys, 1)) end
    end
    if next(xs) == nil then
        for k,v in pairs(ys) do table.insert(res,v) end
    elseif next(ys) == nil then 
        for k,v in pairs(xs) do table.insert(res,v) end
    end
    return res
end
function chunks(xs)
    local chunklen = 3
    local res = {}
    while next(xs) ~= nil do
        local tmp = {}
        while #tmp < chunklen and next(xs) ~= nil do
            table.insert(tmp, table.remove(xs, 1))
        end
        table.insert(res, tmp)
    end
    return res
end


-- ===== helpers =======================================================================================================
function table2json(xs)
    return "[" .. table.concat(xs, ',') .. "]"
end
function map(func, array)
  local new_array = {}
  for i,v in ipairs(array) do
    new_array[i] = func(v)
  end
  return new_array
end

-- ===== dispatcher ====================================================================================================
if val1 ~= nil and val2 ~= nil then -- REDUCE
    android:send(table2json(reduce(val1, val2)))
elseif val1 ~= nil then             -- DOMAP
    android:send(table2json(domap(val1)))
elseif val2 ~= nil then             -- CHUNKIFY
    val2 = "[" .. table.concat((map(table2json, chunks(val2))), ", ") .. "]"
    android:send(val2)
else                                -- dunno... ;_;
end

Jeśli:

-- ----- MAP ------------------
local val1 = {2, 0, 4, 6, 2}

Wynik:

❯ luajit mergesort.lua
ANDROID:SEND:   [0,2,2,4,6]