get the address of a lua object

Here's a hokey way to do it:

Pair.__tostringx = function (p)
    Pair.__tostring = nil    
    local s = "Pair " .. tostring(p)                                                                                                                                                                                                    
    Pair.__tostring = Pair.__tostringx
    return s
end
Pair.__tostring = Pair.__tostringx    

> print(p)
Pair table: 0x7fe469c1f900

You can do more string manipulation inside Pair.__tostringx to get the format you want, e.g., to remove "table".