23 lines
620 B
Factor
23 lines
620 B
Factor
|
! Copyright (C) 2004, 2006 Chris Double, Matthew Willis.
|
||
|
! See http://factorcode.org/license.txt for BSD license.
|
||
|
USING: arrays kernel sequences math arrays namespaces
|
||
|
|
parser effects generalizations fry words accessors ;
|
||
|
|
IN: promises
|
||
|
|
|
||
|
|
TUPLE: promise quot forced? value ;
|
||
|
|
|
||
|
|
: promise ( quot -- promise ) f f \ promise boa ;
|
||
|
|
|
||
|
|
: force ( promise -- value )
|
||
|
dup forced?>> [
|
||
|
|
dup quot>> call( -- value ) >>value
|
||
|
|
t >>forced?
|
||
|
|
] unless
|
||
|
|
value>> ;
|
||
|
|
|
||
|
|
: make-lazy-quot ( quot effect -- quot )
|
||
|
|
in>> length '[ _ _ ncurry promise ] ;
|
||
|
|
|
||
|
|
SYNTAX: LAZY:
|
||
|
|
(:) [ make-lazy-quot ] [ 2nip ] 3bi define-declared ;
|