 M: lazy-from-by nil? ( lazy-from-by -- bool )
   drop f ;
 
-M: lazy-from-by list? ( object -- bool )
-  drop t ;
-
 TUPLE: lazy-zip list1 list2 ;
 
 C: <lazy-zip> lazy-zip

M: lazy-until nil? ( lazy-until -- bool )
   drop f ;

M: lazy-until list? ( lazy-until -- bool )
   drop t ;

TUPLE: lazy-while cons quot ;

C: <lazy-while> lazy-while

M: lazy-append nil? ( lazy-append -- bool )
   drop f ;

TUPLE: lazy-from-by n quot ;

C: lfrom-by lazy-from-by ( n quot -- list )
