This function returns the middle of a array sorted array
sub Return_Middle
{
    my @list = @_;
    return @list if ( scalar(@list) == 2 or
                      scalar(@list) == 1 );
    my @sorted = sort { $a <=> $b || $a cmp $b } @list;
    my @middle = drill_down(@sorted);
    return @middle;
      

   sub drill_down
   {
       my @list = @_;
       return @list if ( scalar(@list) == 2 );
       return @list if ( scalar(@list) == 1 );
       splice @list, -1, 1;
       splice @list, 0, 1;
       drill_down(@list);
   }
}

[download]
UPDATE - here is the updated code that I used along with some other subs 
my $SORTED   = \&Do_Sort;

sub Return_First
{
    return $SORTED->(@_)->[0];
}

sub Return_Last
{
    return $SORTED->(@_)->[$#{ $SORTED }];
}

sub Return_Middle
{
    return $SORTED->(@_) if @_ < 3;
    splice @_, -1, 1;
    splice @_, 0, 1;
    Return_Middle(@_);
}

sub Do_Sort
{
    sort { $a <=> $b || $a cmp $b } @_;
}

[download]

Replies are listed 'Best First'.
Re: function that returns the middle of an array
by blazar (Canon) on Jan 10, 2006 at 14:26 UTC

    How 'bout

    sub drill_down {
    my $i=@_/2;
    @_[ @_%2 ? $i : ($i-1, $i) ];
}

    [download]

    instead?

    Also, in various order:

    • No need for those scalars as == will impose scalar context anyway; to be sure 
      return @_ if @_ < 3;

      [download]
      would have sufficed in both cases;
    • you may just do: 
      drill_down(@sorted);  # as the last statement in your sub

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      instead of 
      my @middle = drill_down(@sorted);
return @middle;

      [download]
    • while it is perfectly legal to define the drill_down sub inside the Return_Middle one, they will be "global" anyway, and to do so would have some sense only if the former were a closure around some variable(s) lexically scoped to the latter, which is not the case.
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[d/l]
[select]
Re: function that returns the middle of an array
by Roy Johnson (Monsignor) on Jan 10, 2006 at 15:57 UTC
    How about this? You find the middle of the array, which will either be an integer or a half-value. Return the slice indexed from the integer portion of the midpoint through the integer portion of the midpoint + .5. If the midpoint is a half-value, those will be different (so you return the two values that straddle the middle); otherwise, they will be the same, and you return just one value. 
    sub Return_Middle {
  my $midpt = ($#_/2);
  @_[int($midpt) .. int($midpt + .5)];
}

    [download]
    Update:
    The text description in the OP suggests that the array is already sorted, so I didn't see the point of sorting it again. But my code could be a drop-in for drilldown instead of Return_Middle, or a sort step could be added to it: 
    sub Return_Middle {
  my $midpt = ($#_/2);
  (sort {$a <=> $b or $a cmp $b} @_)[int($midpt) .. int($midpt + .5)];
}

    [download]
    Caution: Contents may have been coded under pressure.
[reply]
[d/l]
[select]

      I think that your subroutine doesn't sort the array so it just returns the elements at the middle, not the median of the array.

[reply]
Re: function that returns the middle of an array
by ambrus (Abbot) on Jan 10, 2006 at 17:36 UTC
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