Thank you :)
So I wasn't too far out with the (de)referencing...that's a relief!
Would it be correct that @$self->{'column'} is trying to dereference $self first and then access the column key of the dereferenced value?
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Would it be correct that @$self->{'column'} is trying to dereference
$self first ...
My narrative would be that @$self->{'column'} is trying to
dereference $self first as an array reference (it's
not; it's a blessed hash reference).
... and then access the column key of the dereferenced value?
Once the attempt to dereference a hash ref. as an array fails,
that's it: parsing cannot continue. If parsing went on, it would
have to deal with an expression equivalent to
@some_array->{'column'}
that makes no Perlish sense. Looked at another way, even if the
proper hash reference dereferencing operator (the %
sigil) were used, the expression would still make no sense
(update: now; see Update below):
%$self->{'column'}
is equivalent to
%some_hash->{'column'}
Update: Well, actually... It dawned on me that a long time
ago, in a Perliverse far, far away, this sort of expression
did, briefly, enjoy some validity:
Win8 Strawberry 5.8.9.5 (32) Mon 03/29/2021 3:40:28
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings -l
my %hash = qw(column vertical fence horizontal);
print %hash->{'column'};
Using a hash as a reference is deprecated at - line 3.
my @array = qw(column fence);
print @array->[1];
Using an array as a reference is deprecated at - line 6.
my $ar = \@array;
print @$ar->[0];
Using an array as a reference is deprecated at - line 9.
^Z
vertical
fence
column
(Update: Changed 5.8 example to include array
reference; hash reference assumed to work similarly.)
As it was told to me, the history of this syntax is that it began
as a bug and was elevated by use into a "feature." As you see, it
persisted as late as Perl version 5.8, although even by then
it was deprecated.
By version 5.30, it was entirely extirpated:
Win8 Strawberry 5.30.3.1 (64) Mon 03/29/2021 2:54:54
C:\@Work\Perl\monks
>perl
my %hash = qw(column vertical fence horizontal);
print %hash->{'column'};
Can't use a hash as a reference at - line 3.
Win8 Strawberry 5.30.3.1 (64) Mon 03/29/2021 2:55:26
C:\@Work\Perl\monks
>perl
my @array = qw(column fence);
print @array->[1];
Can't use an array as a reference at - line 3.
Of course, something like @$hash_reference has always been verboten.
Give a man a fish: <%-{-{-{-<
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A simple test is to try {@$self}->{'column'} and see if that gives the same result (it does).
I tend to be explicit always in this sort of dereferencing context because I'm never quite sure without thinking about it and I assume most other people working with the code will do the same thing.
Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond
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