25 lines
615 B
Factor
Executable File
25 lines
615 B
Factor
Executable File
! Copyright (C) 2008 Slava Pestov.
|
|
! See http://factorcode.org/license.txt for BSD license.
|
|
USING: kernel ;
|
|
IN: boxes
|
|
|
|
TUPLE: box value full? ;
|
|
|
|
: <box> ( -- box ) box construct-empty ;
|
|
|
|
: >box ( value box -- )
|
|
dup box-full? [ "Box already has a value" throw ] when
|
|
t over set-box-full?
|
|
set-box-value ;
|
|
|
|
: box> ( box -- value )
|
|
dup box-full? [ "Box empty" throw ] unless
|
|
dup box-value f pick set-box-value
|
|
f rot set-box-full? ;
|
|
|
|
: ?box ( box -- value/f ? )
|
|
dup box-full? [ box> t ] [ drop f f ] if ;
|
|
|
|
: if-box? ( box quot -- )
|
|
>r ?box r> [ drop ] if ; inline
|