Re: Programming Question

Douglas S. Davis wrote:
> Hi,
> 
> My problem (and I am sure it must be simple to do) is that I can't 
> figure out how to compare the list of possible numbers (100 - 499) 
> with the list of already in use numbers returned by my query.  I've 
> tried various loops and while statements all to no avail.  Usually 
> what I get is that for *each* number in the result set of my query, 
> it prints out all of the numbers from 100 - 499.


Sounds like you could use a sieve, just like the famous Sieve of Eratosthenes.

> Can anyone point me in the right direction.    So in other words, 
> when I do my fetchrow() on the MySQL table, how can I take the 
> results and compare them to the 100 - 499 set of numbers.

It roughly goes like this:

# create a hash containing all numbers
     @sieve{100 .. 499} = (1)x399;

# loop over your "in use" numbers, and delete them from the hash
     while( my ($n) = $sth->fetchrow ) {
         delete $sieve{$n};
     }

# what you have left is the available numbers
     @available = sort keys %sieve;


HTH,
Rhesa

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