On Mon, Apr 23, 2001 at 01:15:13PM -0400, David Gilden wrote:
[ brought back to the list with permission ]
> my camel learning perl book has hashs with the key in quotes,
> whats going on with this?
In the early days this was necessary, otherwise the key would be
interpreted as a function and its result used as the key. I don't think
this has been necessary since perl 5.005, But, be careful if your key
actually has the same name a function. Things can get confusing. For
you if not for perl itself.
The camel's getting pretty long in the tooth now.
> And is there a short hand for the following?
>
>
> &checkPrice($in{price});
I was going to mention this before, but I forgot. Calling a sub as
&sub() is so ...... perl4. Of course it's still supported and correct,
but I find it helpful to remove superfluous punctuation. I think it
helps to make the meat of the program stand out.
> sub checkPrice{
> return ($_[0] =~ /^\$?(\d+|\d*\.\d\d)$/) ? 1 : 0;
> }
>
> # can this be rewritten as:
> sub checkPrice{
> return ( /^\$?(\d+|\d*\.\d\d)$/) ? 1 : 0;
> }
No. $_ isn't set on entry to a sub - @_ is. So you will need the first
version, but there is no need for the ?: operator.
sub checkPrice { return $_[0] =~ /^\$?(\d+|\d*\.\d\d)$/ }
Be careful when manipulating @_ though. Perl uses pass-by-reference, so
changing @_ changes the actual arguments passed to the sub. This is why
many subs start off with
my ($a1, $a2, $a3) = @_
or something similar. This takes copies of the arguments and
effectively gets you pass-by-value semantics.
Depending on how defensive you are being, you might want to check that
you are being passed one and only one parameter, possibly by using a
prototype or checking the length of @_.
Also, for a function this size I would personally also get rid of the
return keyword. All subs return the value of their last expression when
they fall off the end, and so I would use
sub checkPrice { $_[0] =~ /^\$?(\d+|\d*\.\d\d)$/ }
but I know some people are (violently) against this sort of thing. I
like using Perl's idioms, and with something this size I think it's
pretty obvious what's happening.
For another can of worms, I would also go with check_price() as the name
of the sub. See perldoc perlstyle. But this is very personal. The
convention where I work is checkPrice() and I don't like it, but I'm
learning to live with it. Almost :-)
--
Paul Johnson - [EMAIL PROTECTED]
http://www.pjcj.net
