On 11/30/2011 03:06 PM, Jeswin wrote:
I've been trying to figure out how to print 2 arrays into 2 columns. I
came across this code and it works but gives me a problem in the
output.
sub transpose {
map { my $i = $_; [ map $_->[ $i ], @_ ] } 0 .. $#{ $_[0] }
}
print "@$_\n" for transpose \( @unknown_abs, @unknown_conc );
Those nested maps are making me think too hard, and I'm still not sure I
understand what they're doing. I'd rather debug the KISS version:
$ cat print-arrays-side-by-side.pl
#!/usr/bin/perl
use strict;
use warnings;
my @array1 = ("Fred", "Barney", "Wilma", "Betty");
my @array2 = ("Flintstone", "Rubble", "Flintstone"); ### Oops!
print "C style:\n";
for (my $i = 0; $i < @array1; $i++) {
print join " ", "\t", $array1[$i], $array2[$i], "\n";
}
print "More Perlish:\n";
print join " ", "\t", $array1[$_], $array2[$_], "\n" for 0 .. $#array1;
$ perl print-arrays-side-by-side.pl
C style:
Fred Flintstone
Barney Rubble
Wilma Flintstone
Use of uninitialized value in join or string at
print-arrays-side-by-side.pl line 8.
Betty
More Perlish:
Fred Flintstone
Barney Rubble
Wilma Flintstone
Use of uninitialized value in join or string at
print-arrays-side-by-side.pl line 11.
Betty
Note that the code doesn't check for equal length arrays (or undefined
elements, or reference elements, or ...). @array1 has one more element
than @array2, thus the warning:
Use of uninitialized value in join or string at
print-arrays-side-by-side.pl line 11.
Try inserting "undef" as an element and see what happens. What about a
reference, such as "\0"?
If you're going to deal with Perl, "Learning Perl" is the place to start:
http://shop.oreilly.com/product/0636920018452.do
HTH,
David
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