Here's a hint on how to do it with floats:

Sort the array, then check the intervals (adjacent values in the array). You'll either find the value, or you'll find an interval where it *should* be, but isn't.

Note: Since many floating point values aren't representable in a binary format, you'll want to use the trick of selecting an arbitrary amount of error you'll accept when you try to determine whether two floats match. For example:

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

my $epsilon=0.000005;
my $desired=1.15;

while (<DATA>) {
        chomp;
        if (abs($desired - $_) < $epsilon) {
                print "Match found: $_\n";
        }
}
__DATA__
1.149
1.1499
1.14999
1.149999
1.1499999
1.14999999
1.149999999
[download]

$ perl 659004.pl
Match found: 1.149999
Match found: 1.1499999
Match found: 1.14999999
Match found: 1.149999999
[download]