(
x1 x2 --
flag )
flag is true if and only if
x1 is bit-for-bit
the same as
x2.
Testing:
T{ 0 0 = -> <TRUE> }T
T{ 1 1 = -> <TRUE> }T
T{ -1 -1 = -> <TRUE> }T
T{ 1 0 = -> <FALSE> }T
T{ -1 0 = -> <FALSE> }T
T{ 0 1 = -> <FALSE> }T
T{ 0 -1 = -> <FALSE> }T