(49G) Improved IEGCD for Integers

[Gerald H]

The programme is faster than the inbuilt command IEGCD but in contrast always returns a positive GCD in stack level Z.

eg For input

77
121

the programme returns

11
-3
2

Name: IZEGCD

Code:

::
  CK2&Dispatch
  # FFFF
  ::
    BINT0
    3UNROLL
    BEGIN
    ROT#1+UNROT
    DUPUNROT
    FPTR2 ^ZDIVext
    SWAP
    4UNROLLDUP
    Z0_
    EQUAL
    UNTIL
    DROP
    ZINT1_0_
    4ROLL
    ZERO_DO
    DUPUNROT
    5ROLL
    FPTR2 ^QMul
    FPTR2 ^QSub
    LOOP
    3PICK
    FPTR2 ^ZIsNeg?
    NOT?SEMI
    BINT3
    ZERO_DO
    ROT
    FPTR2 ^RNEGext
    LOOP
  ;
;