From: intc_ctor@... (Phil Tomson)
Date: 2004-02-09T06:39:18+09:00
Subject: Re: flip flop operator proposal (from condition to condition do )

Joel VanderWerf <vjoel@PATH.Berkeley.EDU> wrote in message news:<401FFA2D.40608@path.berkeley.edu>...
> Phil Tomson wrote:
> > Jamis Buck <jgb3@email.byu.edu> wrote in message news:<401F1E82.1080008@email.byu.edu>...
> > 
 
> > Another idea would be to have a 'from (condition) to (condition)'
> > statement that looks looks like:
> >   from l=~/BEGIN/ to l=~/END/ do
> >     #do something in this range
> >   end
> > 
> > Then we just need some way to determine if the range is inclusive or
> > exclusive...
> >   from l=~/BEGIN/ to l=~/END/ inclusive do
> >     puts l
> >   end
> > 
> > #prints:
> > BEGIN
> >   foo
> >    bar
> > END
> > 
> >   from l=~/BEGIN/ to l=~/END/ exclusive do
> >     puts l
> >   end
> 
> Very readable! It may be an improvement that the flipflop isn't being 
> used with if, but with a special keyword. The hidden state bothers me 
> less that way. Of course you lose the possibility of a condition with 
> more complex logic.

Couldn't you just use the returned FlipFlop object for those purposes?

  ff = from l=~/BEGIN/ to l=~/END/ #no block passed in

then you could do things with ff:
  if ff.set?
    #do something
  else
    #do something else
  end

The from (condition) to (condition) would just be syntactic sugar for
the creation of a FlipFlop object.  (kind of like [] is for Array and
{} is for Hash, or lamda is for Proc).  Come to think of it, couldn't
ff be a functional object, kind of like a closure (Proc)?  Actually,
it's probably more like a set of conditions that a Proc must evaluate
when it (the block being passed in to the from .. to .. ) is called.

....just thinking out loud.  Should probably try to prototype something
that doesn't require any syntax changes.

Phil