Class Module

---------
--CLASS--
---------
local class_list = {}
local class_membercopy = function(v)
    return type(v)=="table" and table.copy(v) or v
end
local class_extends = setmetatable({},{
    __index = function(t,k) return{1, class_list[k] or error("base class not found: '"..tostring(k).."'")} end
})
local class_operator = function(op)
    return function(f) return {2,{op,f}} end
end
local class_mt = {
    __newindex = function(t,name,cls)
        local constructor = cls[name] or function() end
        local funcs,members = {},{}
        local extends,meta = {},{__index = funcs}
        local function fillextends(t)
            if table.find(extends,t) then error("class '"..name.."' can only inherit '"..t.name.."' once") end
            extends[#extends+1] = t
            for i=1,#t[4] do
                fillextends(t[4][i])
            end
        end
        if type(name)~="string" then error("class name must be a string") end
        if type(constructor)~="function" then error("member with same name as class must be constructor function") end
        for k,v in pairs(cls) do
            if type(k) == "string" then
                local x = type(v) == "function" and funcs or members
                x[k] = class_membercopy(v)
            elseif type(k) == "number" then
                assert(type(v)=="table","anonymous members are not allowed")
                if v[1] == 1 then
                    fillextends(v[2])
                elseif v[1] == 2 then
                    local op = v[2][1]
                    local f = v[2][2]
                    local t ={
                        ["+"] = "__add", ["*"] = "__mult", ["-"] = "__sub", ["/"] = "__div", ["%"] = "__mod",
                        ["^"] = "__pow", ["--"] = "__unm", [".."] = "__concat", ["#"] = "__len",
                        ["()"] = "__call", ["~"] = "__gc"
                    }
                    meta[t[op] or op] = f
                end
            end
        end
        for i=1,#extends do
            for k,v in pairs(extends[i][3]) do members[k] = members[k] or v end
        end
        local constr = function(t, ...)
            for i=1,#extends do extends[i][1](t) end
            constructor(t,...)
        end
        class_list[name] = {constr,funcs,members,extends,meta,name=name}
        funcs["type"] = function(t) return class_list[name] end
        setmetatable(funcs,{
            __index = function(t,k)
                for i=1,#extends do
                    if extends[i][2][k] then    return extends[i][2][k] end
                end
            end
        })
    end,
    __index = function(t,name)
        if name == "extends" then return class_extends
        elseif name == "operator" then return class_operator end
        local cls = class_list[name]
        if not cls then
            return function(x) t[name] = x end
        end
        local r = {}
        for k,v in pairs(cls[3]) do
            r[k] = class_membercopy(v)
        end
        return function(...)
            setmetatable(r,cls[5])
            cls[1](r,...)
            return r
        end
    end
}
class = setmetatable({},class_mt)