Nested dereferencing arrows in Perl: to omit or not to omit?
- by DVK
In Perl, when you have a nested data structure, it is permissible to omit de-referencing arrows to 2d and more level of nesting. In other words, the following two syntaxes are identical:
my $hash_ref = { 1 => [ 11, 12, 13 ], 3 => [31, 32] };
my $elem1 = $hash_ref->{1}->[1];
my $elem2 = $hash_ref->{1}[1]; # exactly the same as above
Now, my question is, is there a good reason to choose one style over the other?
It seems to be a popular bone of stylistic contention (Just on SO, I accidentally bumped into this and this in the space of 5 minutes).
So far, none of the usual suspects says anything definitive:
perldoc merely says "you are free to omit the pointer dereferencing arrow".
Conway's "Perl Best Practices" says "whenever possible, dereference with arrows", but it appears to only apply to the context of dereferencing the main reference, not optional arrows on 2d level of nested data structures.
"MAstering Perl for Bioinfirmatics" author James Tisdall doesn't give very solid preference either:
"The sharp-witted reader may have
noticed that we seem to be omitting
arrow operators between array
subscripts. (After all, these are
anonymous arrays of anonymous arrays
of anonymous arrays, etc., so
shouldn't they be written
[$array-[$i]-[$j]-[$k]?) Perl
allows this; only the arrow operator
between the variable name and the
first array subscript is required. It
make things easier on the eyes and
helps avoid carpal tunnel syndrome. On
the other hand, you may prefer to keep
the dereferencing arrows in place, to
make it clear you are dealing with
references. Your choice."
Personally, i'm on the side of "always put arrows in, since itg's more readable and obvious tiy're dealing with a reference".
