local utils = {}

utils.sizeof = function(t)
  if not t then
    return 0
  end

  local size = 0
  for k,v in pairs(t) do
    size = size + 1
  end
  return size
end

utils.difference = function(a, b)
  local aa = {}
  for k,v in pairs(a) do aa[v]=true end
  for k,v in pairs(b) do aa[v]=nil end
  local ret = {}
  local n = 0
  for k,v in pairs(a) do
      if aa[v] then n=n+1 ret[n]=v end
  end
  return ret
end

utils.shallowClone = function(t)
  local res = {}
  for k,v in pairs(t) do
    res[k] = v
  end
  return res
end


utils.find = function(t, predicate)
  for k,v in pairs(t) do
    if predicate(v, k) then
      return v, k
    end
  end
end

return utils