The apprentice tries to make certain he's drawing appropriate conclusions...

I was reading the various answers to this Q&A and recalled my earlier mediation with arrays. I also recalled that Camel3 noted some differences regarding delete and splice when used against arrays. So, I decided to poke at things for a bit.

Based on some experimentation, it appears the most appropriate answer the aforementioned Q&A might have been, "it depends on whether or not you want to keep that array element's slot in the array." Consider, for example, the following:

#! /usr/bin/perl -w
use strict;

my @ary = ( 1, 2, 3, 4, 5 );
my @alt = @ary;
my $ndx = getArrayIndex( 3, @ary );

# Here's how delete handles it
print "Delete - Before: ", arrayToString( @ary ), "\n";
delete $ary[ $ndx ];
print "Delete - After: ", arrayToString( @ary ), "\n";

print "\n";  # A touch of white space.

# Now, let's try splice
print "Splice - Before: ", arrayToString( @alt ), "\n";
splice( @alt, $ndx, 1 );
print "Splice - After: ", arrayToString( @alt ), "\n";

exit 1;


sub arrayToString
# --------------------------------------------------------------
# Joins an array's values without the warning for uninitized 
# elements.  Also, replaces undef values with an appropriate
# string.
# --------------------------------------------------------------
{
   my @values = @_;
   my $output = "";
   for (@values) 
   { 
      if ( defined( $_ ) )
         { $output .= $_ }
      else 
         { $output .= "undef" }

      # comment this out if you don't want trailing spaces.
      $output .= " ";  
   }
   return $output;
}

sub getArrayIndex
# --------------------------------------------------------------
# When given a scalar and an array, this either returns the 
# of the scalar in the array or -1 (not found).
# --------------------------------------------------------------
{
  my $value = shift;
  my @values = @_;
  my $result = -1;

  for ( my $index = 0; $index < @values; $index++ )
  {
    if ( $value eq $values[ $index ] )
    { 
      $result = $index;
      last;
    }
  }
    return $result;
}
[download]

If you run this, you'll note a couple of things. Deleting an array element simply undefs the value at that index, whereas splice removes it entirely. (Actually, I suspect that splice is creating a new array without that particular element.)

My questions are these:

1. Is this a fair understanding of things? Is there, perhaps, a better way?

2. I'm using arrayToString() to avoid the Use of uninitialized value in join warning that appears when you print @array; (and arrays contain undef values). Is this a reasonable (read: idiomatic) to do that?

3. Are there other issues I'm not taking into consideration?

Thanks in advance...

--f

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