Michael Lazzaro said:
>
> There has been discussion of allowing a "default" value for array cells
> -- that is, one aside from C<undef> or whatever the type-specific
> default is. Questions, in order of increased evilness:
1 and 2 seem fine to me.
> 2a) When a cell is explicitly re-undefined, does the default value take
> effect?
>
> my @a is Array( default => 'foo' ) = (1,2,3);
>
> @a[1] = undef;
> @a[1]; # undef, or 'foo'?
>
> STRAWMAN ANSWER: 'foo'.
Seems right to me. Anything else would be very confusing, I think.
> 2b) Primitive-typed arrays: Given the behavior of (2a), and the fact
> that primitive-typed arrays can't store undef, what happens here?
>
> my int @a is Array( default => 5 );
>
> @a[0] = 0;
> @a[0]; # 0, or 5?
0. Being unable to store 0 would seem to be a major limitation.
> @a[0] = undef;
> @a[0]; # 0, or 5?
An exception or 5.
Maybe undefining an element could always set it to the default value.
> 3) Can the default value be a closure, based on index location?
>
> my @a is Array( default => { $_ ** 2 });
>
> STRAWMAN ANSWER: Yes, because it's cool.
No, because it's unnecessary. You can always do
my $value = @a[$x] //= $x ** 2;
or skip the = depending on how you are trading memory / speed.
Yes, I know that just about everything is unnecessary to someone. To me,
default values as a whole seem a little unnecessary, in fact.
--
Paul Johnson - [EMAIL PROTECTED]
http://www.pjcj.net
