     { growable read-only } ;
 C: <pusher-cursor> pusher-cursor
 
-INSTANCE: pusher-cursor forward-cursor
-
-! XXX define a protocol for stream cursors that don't actually move
-M: pusher-cursor cursor-compatible? 2drop f ; inline
-M: pusher-cursor cursor-valid? drop t ; inline
-M: pusher-cursor cursor= 2drop f ; inline
-M: pusher-cursor inc-cursor ; inline
-
+INSTANCE: pusher-cursor infinite-stream-cursor
 INSTANCE: pusher-cursor output-cursor
 
 M: pusher-cursor set-cursor-value growable>> push ; inline

GENERIC: begin-cursor ( collection -- cursor )
GENERIC: end-cursor ( collection -- cursor )

: all- ( collection quot -- begin end quot )
    [ [ begin-cursor ] [ end-cursor ] bi ] dip ; inline

!
! containers

M: output-cursor set-cursor-value-unsafe set-cursor-value ; inline
M: output-cursor set-cursor-value
    dup cursor-valid? [ set-cursor-value-unsafe ] [ invalid-cursor ] if ; inline

!
! stream cursors
!

MIXIN: stream-cursor
INSTANCE: stream-cursor forward-cursor

M: stream-cursor cursor-compatible? 2drop f ; inline
M: stream-cursor cursor-valid? drop t ; inline
M: stream-cursor cursor= 2drop f ; inline

MIXIN: infinite-stream-cursor
INSTANCE: infinite-stream-cursor stream-cursor

M: infinite-stream-cursor inc-cursor ; inline

MIXIN: finite-stream-cursor
INSTANCE: finite-stream-cursor stream-cursor

SINGLETON: end-of-stream

GENERIC: cursor-stream-ended? ( cursor -- ? )

M: finite-stream-cursor inc-cursor
    dup cursor-stream-ended? [ drop end-of-stream ] when ; inline

INSTANCE: end-of-stream finite-stream-cursor

M: end-of-stream cursor-compatible? drop finite-stream-cursor? ; inline
M: end-of-stream cursor-valid? drop f ; inline
M: end-of-stream cursor= eq? ; inline
M: end-of-stream inc-cursor ; inline
M: end-of-stream cursor-stream-ended? drop t ; inline

!
! basic iterator
