True story :
Many years ago I was given a couple of his books as a
Newtonsday presnet. Once contained a chapter on base -2 arithmeatic. I
spent the next day or so designing a base -2 full-adder circuit and
soldering it up. Never found any practical use for it, but...
You could always
solder up a computer around it. :-)
I was always planning to....
Base -2 has some interesting features. Obviously you can represent all
+ve and -ve numbers in it. Since -1(10) = 11(-2), a 'negate' operation is
performed by shifting the number left one bit and adding it (using a base
-2 adder) to the original number. The full adder has 4 inputs (all of the
same 'weight') and 3 outputs (sum, carry to tyhe next bit, carry to the
next-but-1 bit). It's a positional notation so shift-and-add multiply
(and prsumably shift-and-subtract division) work in the obvious way.
-tony