Help with Numbers..Please

[spacey]

Hello All,
Could somebody please suggest a solution to what I hope is a simple problem.

I have some code that increments a number using $number++.
My only problem is that I need the number to increment in full.
What I mean by this is :-
My number is ‘000001’ obviously when I auto increment this using ++ it drops the existing zeros.

Can I overcome this? Or do I have to run a regular
expression on it after incrementing it adding the zeros back in?

Any help on this would be more then appreciated.
Regards,
Gareth

[broquaint]

Just make sure your number variable is a string e.g

my $n = "0001";
print "$n\n" and $n++
  for 1 .. 5;

__output__

0001
0002
0003
0004
0005


HTH

_________
broquaint

[dakkar]

The docs say that the "string magic increment" works with variables that

has been used in only string contexts since it was set, and has a value that is not the empty string and matches the pattern "/^[a-zA-Z]*[0-9]*\z/"

-- 
        dakkar - Mobilis in mobile

Most of my code is tested...

Perl is strongly typed, it just has very few types (Dan)

[Reverend Phil]

Thanks for the warning. I have used the magical mystery increment quite often, and didn't realize that it could be problematic depending on previously used context for the variable. I'll have to look over some code to make sure (if I can find it), though I haven't had a problem with it yet.

[ph0enix]

Numerical value of your number is 1 so the 'droping zeros' is correct behaviour. Try printf or sprintf for formating your outputs.

my $number = 1;
printf '%06d', $number;

or get it back into $number variable

$number = sprintf('%06d', $number);

[Anonymous Monk]

$number = sprintf("%06d", $number++);

[bart]

Close, but no cigar. This will increment the number after the returned value is used. Either of the next will do, as the modified value isn't being retained:

$number = sprintf("%06d", ++$number);

$number = sprintf("%06d", $number+1);

[Improv]

If you want something for the general case, try the code below..
Read more... (804 Bytes)

[spacey]

Hello Again,

Thank you All for what must be the fastest reply i have ever had.

All your information has been most helpful
regards
Gareth

[perlguy]

Update: Abigail-II's point is well taken on posting incorrect code. Strike this one and don't bother. I found the problem case after I had already posted. Appologies.

Update 2: This following regex should work better, and won't fail in the test cases. The same number of digits will be in the output, unless all 9s are in the string, in which case it will just add 1 digit to the front of the string to accomodate. Again, just an exercise.

$number =~ s/([^9]?9*)$/$1+1/e;

Back to the original post:

Here is a regular expression way to do it:

my $number = '0001999';
$number =~ s/([^9]9+|\d)$/$1+1/e;
print "$number\n";

It has a flaw: if all the numbers are 9, it will drop the last nine and add a 10, so probably not something you would want to use in production code. But the other test cases that I worked with were fine. It was more of an exercise than anything.

[Abigail-II]

Uhm, if you already know it's flawed, by bother posting? How useful is incorrect code?

Anyway, here's a regexp solution that is much simpler, and doesn't fail on "9":

    s/(\d+)/$1+1/e;

Abigail

[perlguy]

It won't fail on '9', but your proposed alternative regular expression won't work on '009' for example, as '10' would be the output instead of the requested '010'. Just an observation.

[Anonymous Monk]

Hi Gareth, Use regular numbers to do your calculation and sprintf back into the value that you need. See code below. #!/usr/bin/perl for (0..10) { my $value = sprintf("%.5d",$_); print $value,"\n"; }

[dopey]

Can't you just auto increment and then add the zeros on the next line?

[Anonymous Monk]

Hi, If you want the zeros, you should pad these on when they are needed for display. When using the number, it will be simply a number. I have a requirement to do this on my project. I use this function that I wrote:

sub zeroPad () {

  my $number     = $_[0];
  my $charLength = $_[1];

  if ($charLength > 10000) { return; }  # Sanity Check

  my $tmp;

  # Front pad with zeros
  $tmp = $number;
  while ( length ($tmp) < $charLength ) {
       $tmp = "0" . $tmp;
  }
  return $tmp;

} # end zeroPad