On 27/01/2011 06:23, Ramesh Kumar wrote:
Hi Rob,
I refer to your 2 lines of code:
my $data = '<{5, 26}{20, 42, 64}{23, 48}>';
my $list = [ map { [ $_ =~ /\d+/g ] } $data =~ /(\{.*?\})/g ];
That's the type of Perl coding style I'm still trying to learn. Concise and
elegant. Beautiful!!!
Code like that can be useful as an exercise as it tests your
understanding of Perl constructs quite well. But I would never recommend
that you write like that on a regular basis as it takes a /long/ time
for someone else to comprehend if they have to maintain your code. You
would even kick yourself for being so clever if you had to come back to
some of your own code at a later date and couldn't see its structure at
a glance. That is why I wrote code that works using a loop but achieves
the same result in a similar way.
It is worth pointing out that the one-liner is also inefficient with
memory, as the list generated by $data =~ /(\{.*?\})/g is created all at
once and then mapped, whereas the loop creates and processes a single
bracketed sublist at a time. It is also likely to be slower, although I
haven't benchmarked it.
Always write something that explains what it does and so needs minimum
commenting!
I am having a tough time to crack the secret of Perl's contexts. Any
websites/books you could recommend which
covers this area in depth and clearly?
I think the section (2.7) on context in Programming Perl is clear and
helpful. And have you seen the tutorial on Perl Monks?
<http://www.perlmonks.org/?node_id=738558>
I also recommend playing with a subroutine that displays its called
context, like the program below. It lets you see the contexts that
different calls apply.
use strict;
use warnings;
sub context {
my $list_context = wantarray();
if (not defined $list_context) {
print "Void context\n";
}
elsif ($list_context) {
print "List context\n";
}
else {
print "Scalar context\n";
}
}
no warnings 'void'; # Don't warn about void calls
[ context() ];
context() & 1;
( context() );
**OUTPUT**
List context
Scalar context
Void context
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