randopick.lua

--[[
What if you want to pick a random option but you're not sure if that random option will be valid?
Let's do this without shufflin' , yeah?
--]]

local randopick = function(table, func)
  local indices = {}
  for i = 1, #table do
    indices[i] = i
  end
  local size = #indices -- indices is going to change size, I'm not sure what this does to "for i= 1, #indices"
  for i = 1, size do
    local ind = math.random(1,#indices) -- Grab an card, any card
    if func(table[indices[ind]]) then -- Do something with it
      break -- break if we're done
    end
    table.remove(indices, ind) -- Chuck it...
  end
end

return {randopick = randopick}

shuffle.lua

--[[
What if you want to pick a random option but you're not sure if that random option will be valid?
Instead of doing a while loop and hoping that you'll eventually land on a valid option
try shuffling the list of options and trying each one in this random order ;)

W.
--]]

local shuffle = function(table) -- standard Fisher-Yates implementation
  for i = #table, 2, -1 do
    local j = math.random(1, i)
    table[i], table[j] = table[j], table[i] -- Lua, bro... - Kev.
  end
  return t
end

local random_iter = function(table, func)
  local indices = {}
  for i = 1, #table do
    indices[i] = i
  end
  shuffle(indices)
  for i = 1, #indices do
    func(table[indices[i]])
  end
end

return { shuffle = shuffle, random_iter = random_iter }

use_case.lua

local randopick = require("randopick")

local is_valid = function(option)
  return not option.used
end

local all_options = { { "foo" }, { "bar" }, { "foobar"} }
.
local do_stuff = function(option)
  print(option[1])
  option.used = true
end

randopick.randopick(all_options, function(option)
  if(not is_valid(option)) then 
    return false
  end
  do_stuff(option)
  return true
end)