Table3d.lua

local Table3d = {}

function Table3d.new(defaultValue)
    local self = setmetatable({},{__index = Table3d})
    
    self.defaultValue = defaultValue
    self._table = {}

    return self
end

function Table3d:get(x, y, z)
    local t = self._table
    local default = self.defaultValue

    if not t[x] then return default end
    if not t[x][y] then return default end
    return t[x][y][z] or default
end

function Table3d:set(x, y, z, value)
    local t = self._table

    t[x] = t[x] or {}
    t[x][y] = t[x][y] or {}
    
    t[x][y][z] = value
    self:prune(x,y)
end

function Table3d:prune(x,y)
    local t = self._table

    if next(t[x][y]) == nil then
        t[x][y] = nil
    end
    if next(t[x]) == nil then
        t[x] = nil
    end
end

return Table3d