From: Mark Hubbart <discord@...>
Date: 2004-05-01T08:18:50+09:00
Subject: Re: def [](v) xx; return yy; end # returned value is ignored !?


On Apr 30, 2004, at 1:54 PM, Jean-Hugues ROBERT wrote:

> That makes sense. Yet, I am missing the xxx= where I do control the 
> value assigned to the lvalue.
> I am not alone. At this point there are multiple known cases where it 
> would be needed for transparency:
>   - Reference, a reference is an indirect mean of access to a lvalue's 
> value that is dereferenced when the value is needed and that also 
> makes it possible to assign a value to the lvalue at any time.
>   - Lazy, a Lazy is a value that is computed when it is needed, not 
> before.
>   - Future, a Future is the returned value of an asynchronous method 
> call that is waited for when it is needed, not before.
>   - LogicVariable, a LogicVariable is a variable that can be free in 
> addition to being bound to some value as regular variables are.

I'm not sure what the problem is... What sort of circumstance will this 
cause a problem? Perhaps you are thinking that assignment should do 
something more than it was intended to.

Using your Pointer example, you could do this:

   p = Pointer.new()
   x = p[] = "hello"
   (p[] = "hello").inspect

In line 2, would you expect something other than a simple "hello" 
string to be assigned to x?
In line 3, would you expect #inspect to be called on p, rather than on 
the assigned value?

You say that these are 'known cases', quite possibly I am ignorant 
about this, but I don't see how you couldn't have an object that 
computes it's value only when requested, and how assignement would be 
at fault. Maybe a short example of a problem-causing situation would 
help.

--Mark