Re: Re: Nearest Neighbour Analysis subroutine

[Elias]

I thought I had understood your comment, but there is still something I can't figure out. Why does:

my @test=qw(1 2 3 4 5 6);
(@test % 2) ? print "uneven\n" : print "even\n";
print "end\n";

Work fine, while the two versions below result in "uneven" in the first case and "even" in the second, when both should be reported as "even".

@test=qw(1 2 3 4 5 6);
testthearray1(\@test);
sub testthearray1{
(@_ % 2) ? print "uneven\n" : print "even\n";
}
testthearray2();
sub testthearray2{
(@_ % 2) ? print "uneven\n" : print "even\n";
}

The BlueCamel says "Any arguments passed to a Perl routine come in as the array @_" (pg 219), and this is clearly what you assume happens when you assign my @mat = @_ in the second line. When I include something like  print "@_" to the second line in the  sub testhearray (1 and 2), it shows up as an undefined array (or rather, ARRAY(0x9b25fd8) in the first, and nothing in the second).

I also find it strange that it is the first of the two subs that apparently requires a reference to @test instead of @_, when this is the one which includes a reference to the array when calling the subroutine.

What am I overlooking? (this humbled novice asks).

[danger]

Elias if you pass a reference to an array then @_ receives that reference -- that is, one element (no matter how big the array is). In testthearray1(\@test) you are only passing in one element. In testthearray2() you aren't passing in anything at all.

The routine I showed should just be called as:

   my @array = (1,2,3,4,5,6);
   my $ndist_sum = nneighbours(@array);

[merlyn]

@test=qw(1 2 3 4 5 6); 
testthearray1(\@test); 

sub testthearray1{ 
  (@_ % 2) ? print "uneven\n" : print "even\n"; 
}

You're passing one thing, all the time. That's always odd (and odd!). Remove the \ in front of @test.

-- Randal L. Schwartz, Perl hacker