The weired Indexing in Perl

I am learning Perl. I am doing it with a lot of a resentment, but I am slowly learning it. Normal people count from 1. Computer Scientist count from 0. Perl developers count from -1?

WTF?

oz@server ~ $ test.pl test
num of args 0 
oz@server ~ $ test.pl test test
num of args 1 
0
test
1
test
oz@server ~ $ test.pl          
num of args -1 
No arguments!
oz@server ~ $

My Code, just in case I am totally wrong about this here, :

$ cat test.pl 
#!/usr/local/bin/perl -w


print "num of args $#ARGV \n";
if ( $#ARGV > 0   ){

   for ( my $i = 0 ; $i <= $#ARGV  ; ++$i  ) {

   print "$i\n";
   print "$ARGV[$i]\n";
   }
}
if ( @ARGV > 0 )
{
  print "Number of arguments: " . scalar @ARGV . "\n";
}
else
{
print "No arguments!\n";
}

Comments

linuxpixie

Hi Amir, \ Is there is significant difference between print and say ?

Amir

Well no, counting from 0 is a common standard to which Perl adheres. It doesn't count from -1.\ \ my @array = (0, 1, 2, 3);\ print scalar @array; # 4\ print \$#array; # 3\ print \$array[0]; # 0\ \ \ Now get this:\ print \$array[-1]; # 3\ print \$array[-2]; # 2\ \ BTW, if you use at least Perl 5.10, put\ use 5.010;\ in the beginning, and use "say" instead of "print".

linuxpixie

Thanks Amir, I know it's a silly rant :-)\ But it's already weired for a lot of people to start counting from Zero (Fortran and Matlab start from 1). Now, I need to get used to counting from -1.

Amir

\$#ARGV is not the number of args. It's the last index of array @ARGV. I agree that the \$# thing is weird, but you hardly ever need to use it.\ \ scalar @ARGV is indeed the number of args.\ \ You also hardly ever have to use the C-style "for( initialization; condition; increment)" loop. It's nicer to do:\ \ my \$idx = 0;\ foreach my \$arg (@ARGV) {\ print \$idx++ . ": \$arg\n";\ }\ \ Read these pages some time:\ * http://perldoc.perl.org/perlsyn.html\ * http://perldoc.perl.org/perldata.html