rules maybe like this (full code below)
; example
gui: make object! [
a: rule-var "a0"
b: rule-var "b0"
c: rule-var "c0"
rule [ a b ] func [][ trace-state "one of [a b] changed" c/set
'c-by-rule-ab ]
rule[ c ] func[][ trace-state "c changed" ]
trace-state: func[id][print ["rule[" id "]" a/get b/get c/get]] ;
tool
]
I prefer the browser-like approach of Rebol/View:
one page per action, create a new page after each action. No hidden
Recursion, no bugs.
In einer eMail vom 17.02.00 04:39:17 (MEZ) Mitteleurop�ische Zeit schreibt
[EMAIL PROTECTED]:
> Those interested in new and unusual programming constructs, take a look at
> R++ from AT&T, where Bjarne Stroustrup, the inventor of C++, works. Here's
> the link:
> http://www.research.att.com/sw/tools/r++/
>
> <Quote>
> R++ extends the C++ language with a single new programming construct -- the
> rule. In addition to data-members and member functions, R++ adds a new kind
> of member to C++ classes namely "member rules". A rule is a statement
> composed of a condition and an action that specifies what to do when the
> condition becomes true. Whenever some program data changes, rules whose
> conditions involve that data are examined, and if a rule's condition
> evaluates to true, its action is executed. The action may of course modify
> data and therefore trigger other rules. Currently R++ is implemented as a
> pre-processor. It translates R++ rules into C++ code.
> </Quote>
>
> What would this look like in REBOL?
>
> Andrew Martin
> ICQ: 26227169
> http://members.xoom.com/AndrewMartin/
>
[REBOL[]
;
; tools: rule-var rule
;
rule-var: func [ init-value ][
make object! [
value: init-value
listeners: copy []
set: func [ new-value ] [
value: new-value
foreach here listeners [ here ]
]
get: func[][value]
listen: func[ listener ][ append listeners :listener ]
]
]
rule: function[vars method][sum vals][
foreach here vars [
val: get here
val/listen get 'method
]
]
;
; example
;
gui: make object! [
a: rule-var "a0"
b: rule-var "b0"
c: rule-var "c0"
rule [ a b ] func [][ trace-state "one of [a b] changed" c/set
'c-by-rule-ab ]
rule[ c ] func[][ trace-state "c changed" ]
trace-state: func[id][print ["rule[" id "]" a/get b/get c/get]] ;
tool
]
print "set a"
gui/a/set 'a1
print "set b"
gui/b/set 'b1
print "set c"
gui/c/set 'c1
print "done"
]
Gruss Volker
