Does the opposite of ABS.

Replace the # with othing to enable it for integers.

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    function inv(number#)
   inversion# = number# * 2
   value# = number# - inversion#
endfunction value#