Others have dealt with your direct questions, id just like to point out that binary searching an array is almost never done recursively. Theres absolutely no need. Nor do I see why array slices would be useful here at all. 

use strict;
use warnings;

sub bin_search {
    my $array = shift;
    my $find  = shift;
    return unless @$array;
    my ($l,$r)=(0,$#$array);
    while ($l<=$r) {
        my $m=int(($l+$r)/2);
        if ($find<$array->[$m]) {
            $r=$m-1;
        } elsif ($find>$array->[$m]) {
            $l=$m+1;
        } else {
            return $m;
        }
    }
    return undef;
}
my @list=map { $_*2 } (1..5);
for (0..11) {
    my $pos=bin_search(\@list,$_);
    print "Search:$_ Position:",defined $pos ? $pos : "undef","\n";
}

[download]

HTH


---
demerphq

<Elian> And I do take a kind of perverse pleasure in having an OO assembly language...

In reply to Re: Binary search algorithm by demerphq
in thread Binary search algorithm by mjab

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.