S" :" CREATE ] DOCOL
  READ-WORD CREATE
  LIT DOCOL ,
  ]
EXIT [

: ;
  LIT EXIT ,
  [ S" [" FIND >CFA , ]
  EXIT
[ IMMEDIATE

: / /MOD DROP ;
: MOD /MOD SWAP DROP ;
: NEG 0 SWAP - ;

: IF IMMEDIATE
  ' 0BRANCH ,
  HERE @
  0 ,
;

: THEN IMMEDIATE
  DUP
  HERE @ SWAP -
  SWAP !
;

: ELSE IMMEDIATE
  ' BRANCH ,
  HERE @
  0 ,
  SWAP DUP HERE @ SWAP - SWAP !
;

: BEGIN IMMEDIATE
  HERE @
;

: UNTIL IMMEDIATE
  ' 0BRANCH ,
  HERE @ - ,
;

: FIB
  0 1
  0
  BEGIN
    ROT
    DUP ROT +
    ROT ROT

    1 +
  DUP 4 PICK = UNTIL
  DROP SWAP DROP SWAP DROP
;

S" 10 FIB = " TELL
10 FIB .U
S"  (Expected: 59)" TELL NEWLINE