From: Dan Zwell <dzwell@...>
Date: 2007-08-18T01:44:31+09:00
Subject: Re: wishing of reactive programming in ruby

ashishwave wrote:
> i just was wondering that whether the heavy developers/users of
> reactive languages like kanaputs or reactive-C etc will ever get
> reactive features in ruby.
> 
> in kanaputs, If the variable 'c' is defined as  c = a + b; and if the
> reactivity of 'c' is set (c.reactive = true;), then each time the
> value of 'a' or 'b' changes then the value of 'c' is updated as the
> result of the addition
> 
> 
> bye :-)
> Ashish
> ashishwave@yahoo.com.
> 

I haven't used reactive languages, but can't this be emulated by using 
methods and instance variables?
To emulate:
c = a+b; c.reactive = true
use:
def c; @a+@b; end

Then you could pretend c was a variable. To reset the value, just 
redefine c(). It would be simpler if all variables were methods, not 
instance variables. If you wanted, you could write a wrapper for that, 
so that set_reactive("c", "a + b") or set_reactive("c=a+b") would wrab a 
call to class_eval or instance_eval that defined the method as "def c; 
a() + b(); end". If you did this, however, you could never set a, b, or 
c by simple assignment.

A big problem might be parsing the input. I could elaborate on some 
suggestions. (I wrote code that converts standard arithmatic notation to 
reverse polish notation, which is very easy to evaluate. You could also 
do a simpler scheme like not allowing more than one operation.) Let me 
know if you are interested. And let me know if I'm not grasping reactive 
programming correctly--I've never used it.

Dan