check for object identity when subtracting zero or dividing by 1; check divide-by-zero exception
check for object identity when subtracting zero or dividing by 1; check divide-by-zero exception

BeImprovised/gambit,jasperla/gambit,thewhimer/gambit,thewhimer/gambit,thewhimer/gambit,BeImprovised/gambit,BeImprovised/gambit,jasperla/gambit,BeImprovised/gambit,acenode/gambit,acenode/gambit,jasperla/gambit,thewhimer/gambit,thewhimer/gambit,jasperla/gambit,acenode/gambit,acenode/gambit,thewhimer/gambit