G'day David,
DavidB wrote:
> Hi, I can think of some reasons we use $ instead of @ for array
> indices (in Perl5):
My usual explanation goes a little like this:
In Perl, $ is pronounced 'the' or 'a' or 'this' (ie, singular):
$name # The name
$friend[0] # The first friend
$colour_of{grass} # The colour of grass
$ref->{$key} # The value $key using this reference.
On the other hand, @ means 'these' or 'those':
@friend # These friends
@friend[0..3] # These four friends
When we write an @ sign when trying to retrieve a single element, we're
really asking Perl for a list of elements. If what we really want back is
just a single element, then Perl can get confused.
I don't actually show the cases where Perl gets it wrong, instead I mention
that Perl:
(a) Will warn you if it figures out that you wanted a scalar when
you asked for a list.
(b) Will *not* warn you when it decides you actually meant a list
of one element. This means debugging your code will be a
painful experience, because Perl won't help you.
Hence the result of using @ incorrectly is almost always a warning or a
hard-to-find bug, both of which are extremely undesirable.
Cheerio,
Paul
--
Paul Fenwick <[EMAIL PROTECTED]> | http://perltraining.com.au/
Director of Training | Ph: +61 3 9354 6001
Perl Training Australia | Fax: +61 3 9354 2681
