factor/extra/promises/promises.factor

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Factor
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! Copyright (C) 2004 Chris Double.
! See http://factorcode.org/license.txt for BSD license.
!
! Updated by Matthew Willis, July 2006
! Updated by Chris Double, September 2006
USING: arrays kernel sequences math vectors arrays namespaces
quotations parser effects inference words ;
IN: promises
TUPLE: promise quot forced? value ;
: promise ( quot -- promise )
f f \ promise boa ;
: promise-with ( value quot -- promise )
curry promise ;
: promise-with2 ( value1 value2 quot -- promise )
2curry promise ;
: force ( promise -- value )
#! Force the given promise leaving the value of calling the
#! promises quotation on the stack. Re-forcing the promise
#! will return the same value and not recall the quotation.
dup promise-forced? [
dup promise-quot call over set-promise-value
t over set-promise-forced?
] unless
promise-value ;
: stack-effect-in ( quot word -- n )
stack-effect [ ] [ infer ] ?if effect-in length ;
: make-lazy-quot ( word quot -- quot )
[
dup ,
swap stack-effect-in \ curry <repetition> %
\ promise ,
] [ ] make ;
: LAZY:
CREATE-WORD
dup parse-definition
make-lazy-quot define ; parsing