This gist presents 2 Lua functions for converting hash to array and vice versa. This is a common task in Redis Lua scripting.

hash2array.lua

-- $ lua hash2array.lua

-- print a table that contains numbers and strings only
local f_log_hash = function(hash, name)
  if name ~= nil then
    print(name .. ':')
  end
  for k, v in pairs(hash) do
    print(k, ' => ', v)
  end
  print()
end

-- convert a hash to an array
-- e.g. {foo='bar'} -> {'foo', 'bar'}
local f_hash_to_array = function(hash)
  local array, i = {}, 1
  for k, v in pairs(hash) do
    array[i], array[i+1], i = k, v, i+2
  end
  return array
end

-- convert an array to a hash
-- e.g. {'foo', 'bar'} -> {foo='bar'}
local f_array_to_hash = function(array)
  local hash, i = {}, nil
  for k, v in pairs(array) do
    if k % 2 == 1 then
      i = v
    else
      hash[i] = v
    end
  end
  return hash
end

-----------------------------------------
hash1 = {ten=10, foo='bar', 'hello'}
f_log_hash(hash1, 'hash1')

array = f_hash_to_array(hash1)  -- {1, 'hello', 'ten', 10, 'foo', 'bar'}
f_log_hash(array, 'array')

hash2 = f_array_to_hash(array)  -- {'hello', ten=10, foo='bar'}
f_log_hash(hash2, 'hash2')