\ This program prints numbers in canonical signed digit (CSD)
\ representation, a binary representation with the digits, 0, 1, and T
\ (-1).  This allows creating numbers with few non-zero digits and is
\ useful for implementing multiplication by constants on machines
\ without hardware multipliers.

\ This programs was published by Rafael Deliano in Vierte Dimension
\ 1/2007, and adapted for ANS Forth (with common extensions) by Anton
\ Ertl.

\ Usage: "u CSD." prints u in CSD representation.

create SYM-TAB
'0 C, '1 C, '1 C, '0 C,
'0 C, 'T C, 'T C, '0 C,

create Y+1-TAB
0 C, 0 C, 0 C, 1 C,
0 C, 1 C, 1 C, 1 C,

: CSD.      \ ( UN1 --  )
    1 lshift    \  -- UN1' )
    <#
    begin
        DUP 7 AND DUP
        SYM-TAB + C@ hold
        Y+1-TAB + C@ SWAP 1 rshift
        -2 AND OR
    dup 0= until
    dup #> type ;