Hi John,
thanks for your E-mail. See below for my response.
On Sunday 17 Apr 2011 04:17:32 John W. Krahn wrote:
> Shlomi Fish wrote:
> > On Saturday 16 Apr 2011 09:06:02 Gurunath Katagi wrote:
> >> hi .. i am new to perl ..
> >> i have a input file something pasted as below ..
> >>
> >> 16 50
> >> 16 30
> >> 16 23
> >> 17 88
> >> 17 99
> >> 18 89
> >> 18 1
> >> ..
> >> --
> >>
> >> and i want the output something like this :
> >> 16 50 30 23
> >> 17 88 99
> >> 18 99 1
> >>
> >> i.e for each values in the first column, i want the elements in the
> >> second column to be a one row ..
> >>
> >> can be anybody give me psuedocode , to how to go about this ..
> >> thank you
> >
> > This should work (tested):
> >
> > Regards,
> >
> > Shlomi Fish
> >
> > ----------------------------- SNIP ------------------------
> >
> > #!/usr/bin/perl
> >
> > use strict;
> > use warnings;
> >
> > my $filename = shift(@ARGV);
> >
> > open my $in_fh, '<', $filename
> >
> > or die "Cannot open '$filename' for reading";
>
> You should include the $! or $^E variable in the error message so you
> know why it failed.
Correct - it was not oversight on my part.
>
> > my $last_key = undef;
>
> ICK!
>
Well, I'm trying to specify that I initialise it to a value where it needs to
be set.
> > my @values;
> >
> > sub print_line
> > {
>
> You are using a subroutine for this??? Really?
>
Yes, because it is duplicate code.
> Why are you using global variables instead of lexically scoped
> variables? You should know better.
>
Well, «my @values;» is a lexically scoped variable - it's just part of the
global scope of the program. You cannot access it from a different module.
Regarding global variables - I could have created an object and a module out
of it, but that's overengineering for such a silly script, which is all the
author has asked for. See:
http://en.wikipedia.org/wiki/You_ain%27t_gonna_need_it
> > print $last_key, ' ', join(' ', @values), "\n";
>
> Or:
>
> print join( ' ', $last_key, @values ), "\n";
>
> Or even:
>
> print "$last_key @values\n";
>
> Is there really a good reason to make it more complicated than it needs
> to be?
>
Well, I dislike interpolating arrays, and I was trying to be explicit. But
«print "$last_key @values\n";» will also work nicely.
> > return;
> >
> > }
> >
> > while (my $line =<$in_fh>)
> > {
> >
> > chomp($line);
> >
> > my ($new_key, $new_value) = split(/\s+/, $line);
>
> What if there is leading whitespace?
What if there's an earthquake? It wasn't in the SPEC.
>
> You do realize that split(/\s+/) removes ALL (trailing) whitespace so
> using chomp() is redundant.
I realise it now. But using chomp on a line explicitly, in case you are not
interested in keeping the newline is a good habit which should be followed
religiously.
Regards,
Shlomi Fish
--
-----------------------------------------------------------------
Shlomi Fish http://www.shlomifish.org/
The Case for File Swapping - http://shlom.in/file-swap
Every successful open-source project will eventually spawn a sub-project.
Please reply to list if it's a mailing list post - http://shlom.in/reply .
--
To unsubscribe, e-mail: beginners-unsubscr...@perl.org
For additional commands, e-mail: beginners-h...@perl.org
http://learn.perl.org/
