Re: variable type specific sigils (was Re: Sigils by example)

[Darren Duncan]

At 5:00 PM -0700 5/14/07, Darren Duncan wrote:
On the other hand, unless this steps on something, I could suggest 
dropping the @ and % anyway, so we have $array and $hash, and then 
we could instead use the @ and % sigils as a prefix to indicate in 
that case that we want them to copy by value.  For example:

  my $foo = [23, 434, 6];
  my $bar;
  $bar = $foo; # copy by reference
  @$bar = @$foo; # copy by value

Actually, I think that would be a vast improvement, as we could then 
use the @ prefix with any collection type as short-hand to say that 
= is copy by value.

As a follow-up or clarification of what I just said, here is a proposal ...

Variables of all types have $ sigils.

The semantics of $foo = $bar are unchanged; usually $foo and $bar 
point to the same container after the assignment, afaik.

Prefixing a @ or % before a variable name indicates a syntactic 
short-hand for something concerning the variable.

On declaration, saying @$foo means the same as "Array $foo", and 
saying %$foo means the same as "Hash $foo", or some such.  This works 
for my|our|has etc as well as parameter declarations.  This is 
instead of declaring @foo or %foo.

On use in an expression, @$foo = @$bar indicates we want a copy by 
value or clone or shallow copy or whatever, and $foo and $bar point 
to different containers after the assignment; the semantics are like 
the current @foo = @bar.

Similarly, use eg @@$foo rather than @@foo as appropriate.

With these changes, I see it making Perl more consistent in 
appropriate ways, and easier to use, and huffmanizing isn't worse.

Also, it means we can free up the @ and % rare ASCII symbols for 
other purposes in some situations.

I could also argue that the conception of @ meaning plural vs $ 
singular isn't really an absolute, since any value can be treated as 
either being a collection or being atomic under different 
circumstances.

-- Darren Duncan