Re: RFC 171 (v1) my Dog $spot should call a constructor implicitly

[Hildo Biersma]

Matt Youell wrote:
> 
> So perhaps sometimes in Perl we could say:
> 
>     my Dog $spot = undef;    # Automagically knows to be a Dog ref instead
> of a Dog object because of the undef.
>     if ($age > 12) {
>          $spot = new Doberman();
>      } else {
>          $spot = new Corgi();
>      }

Right now, the default behavior of perl is that un-initialized variables
are automatically undef.  It would be weird to have to do explicit
assignment of an variable to say so.

I feel this discussion confuses multiple things:
- Is a scalar an object or a reference to an object?
- Must references to objects always be initialized at definition time?

If feel that a scalar, even a typed one, is a reference to an object,
not an object itself.  undef is a reasonable initial value for a
reference.  In fact, supporting undefined references is necessary to
build any complex data structure. 

Hence, I feel automatic initialization is the wrong thing to do.  If we
want a quick and easy way to initalize object references with a
default-constructed object, we should have separate syntax to do so.  

What is the problem with:
  my Dog $spot;                 # Not initialized
  my Dog $spot = Corgi->new();  # Explicit construction and assignment
  my Dog $spot : default;       # Call default constructor
(and feel free to replace the attribute 'default' with any other you'd
like)

Hildo