On Sun, Apr 13, 2008 at 3:10 PM, John W. Krahn <[EMAIL PROTECTED]> wrote:
(cut)
> > my $c = &$cmpf($arr->[$mid], $value);
> >
>
> That is usually written as:
>
>
> my $c = $cmpf->($arr->[$mid], $value);
Thanks Chas. and John for your feedback. I think I'm happy with this version:
#!/usr/bin/perl -w
use strict;
# By sefault it works on strings
sub binary_search {
my $arr = shift;
my $value = shift;
my $cmpf = shift || sub {$_[0] cmp $_[1]};
my $left = 0;
my $right = $#$arr;
while ($left <= $right) {
my $mid = ($right + $left) >> 1;
my $c = $cmpf->($arr->[$mid], $value);
return 1
if ($c == 0);
if ($c > 0) {
$right = $mid - 1
} else {
$left = $mid + 1
}
}
return 0
}
my @arr = qw(1 2 3 11); # the array must be sorted
print "searching in @arr\n";
print "Let's use a string comparison function first\n";
for (0, 2, 3, 11, 12)
{
print "is $_ there? => " . binary_search([EMAIL PROTECTED], $_) . "\n"
}
print "\nNow let's use a numerical comparison function\n";
for (1, 11)
{
print "is $_ there? => " . binary_search([EMAIL PROTECTED], $_, sub {$_[0] <=>
$_[1]}) . "\n"
}
Thanks,
Nelson.-
--
http://arhuaco.org
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
http://learn.perl.org/
