(
xd --
flag )
flag is true if and only if
xd is equal to zero.
Testing:
T{ 1. D0= -> <FALSE> }T
T{ MIN-INT 0 D0= -> <FALSE> }T
T{ MAX-2INT D0= -> <FALSE> }T
T{ -1 MAX-INT D0= -> <FALSE> }T
T{ 0. D0= -> <TRUE> }T
T{ -1. D0= -> <FALSE> }T
T{ 0 MIN-INT D0= -> <FALSE> }T