How to get the 2-complenent of a negative number in Lua 5.2?

[Niccolo Medici <niccolomedici@...>]

Hi!

For a calculator I'm writing, that can display integers in hex/binary,
I want to display the hex (or binary) machine representation of
*negative* integers as well. The prevalent representation of negative
integers is known as "two's complement", but I don't at all care if
the Lua engine is running on a machine that uses some other
representation and that my calculator shows something other that 2's
complement in this case.

In Lua 5.1 and Lua 5.3 the solution is ridiculously simple:

    -- Lua 5.1
    > print(("%x"):format(-123456))
    fffe1dc0

    -- Lua 5.3
    > print(("%x"):format(-123456))
    fffffffffffe1dc0

This is perfect for me! (Converting this to binary is a simple and
efficient matter: by doing string replacement.) But, unfortunately, in
Lua 5.2 it fails:

    -- Lua 5.2
    > print(("%x"):format(-123456))
    stdin:1: bad argument #1 to 'format' (not a non-negative number in
proper range)

Is there a solution that works in 5.2 as well?