+
+@ Catch -(2^63) as a special case since its absolute value will overflow
+@ a twos-complement 64-bit word. Return zero as though the absolute value
+@ overflowed to the bottom of the non-negative integers rather than
+@ overflowing back to the most negative integer.
+SNS | DUP
+SSTTSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSN | -(2^63)
+TSST | SUBTRACT
+NTSSSSTSSSTSSSSSSTSN | BRZ > 00010001 00000010
+
+@ Handle all the other numbers.