Re: Very slow array searching

[George P.]

On Tue, 29 Jul 2003, Rafaqat Ali Chaudhary wrote:

> Dear all,
>
> I've a function which searches a given number from an array and returns
> the result.
>
> Function:
>
> 1.    sub checkNumber($)
> 2.    {
> 3.            my ($l_number) =  @_;
> 4.            my $l_status;
> 5.            my @matches= grep { /$l_number/ } @numbers;

The grep function will look through all elements in @numbers
and return all elements that match the pattern.

Since you are only looking for the first match, a foreach loop
will do just fine.

Also, using the regular expression /$l_number/ will search
for the number as a string in @numbers.
That means that you will get TRUE, if @numbers contains ('101')
and the number you are searching for is 1.

One way of doing it is,

$l_status = 'FALSE';
foreach (@numbers)
    {
    if ($_ == $l_number)
        {
        $l_status = 'TRUE';
        last;
        }
    }

Or, for the memory conscious,
(since foreach involves loading all elements into memory)

$l_status = 'FALSE';
for (my $i=0; $i < @numbers; $i++)
    {
    if ($numbers[$i] == $l_number)
        {
        $l_status = 'TRUE';
        last;
        }
    }


Bye,
George P.

> 6.            if  (@matches) {
> 7.                    $l_status="TRUE";
> 8.            }
> 9.            else {
> 10.                   $l_status="FALSE";
> 11.           }
> 12.           return $l_status;
> 13.   }


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