>>711
一例として
X = { 1,2,3,4,tonumber=function(self) ret=1; for i,v in ipairs(self) do ret = ret * v end; return ret end}
Y = { 1,2,3,4,tonumber=function(self) ret=0; for i,v in ipairs(self) do ret = ret + v end; return ret end}
mt = {__add=function(op1,op2) return op1:tonumber() + op2:tonumber() end}
setmetatable(X,mt); setmetatable(Y,mt)
print(X+Y); print(Y+X)