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### Re: Re: Finding missing elements in a sequence (code)

by runrig (Abbot)
 on Nov 06, 2001 at 21:37 UTC ( #123631=note: print w/replies, xml ) Need Help??

Are all the numbers zero padded to the same length?? Then see my answer below but use the default sort instead of the numeric sort in both places. The first numeric sort is 'numerifying' the strings and stripping the leading zeroes which messes up the rest of the routine.

Update: Ok, its not necessarily the first sort stripping the zeroes (in my test case, I was doing a numeric sort before I called the sub, so that's what I was seeing), but it does cause the subsequent statements to treat the list as numbers instead of character strings. So you should treat them as either numbers or characters throughout the sub (like using the +0 trick to begin with), but not both.

• Comment on Re: Re: Finding missing elements in a sequence (code)

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Re: Re: Re: Finding missing elements in a sequence (code)
by clemburg (Curate) on Nov 06, 2001 at 22:13 UTC

The first numeric sort is 'numerifying' the strings and stripping the leading zeroes which messes up the rest of the routine.

I am not if that is right, at least not in the simple sense of what you say. See:

```sub find_holes {
my @list = @{ shift() };
@list = sort { \$a <=> \$b } @list;
my \$low = \$list[0];
my \$high = \$list[-1];
my %isthere = map { \$_ => 0 } (\$low..\$high);
print "@{[sort keys %isthere]}\n\n";
print "@list\n\n";
\$isthere{\$_} = "yes" for map {\$_+0} @list;
my @vacancies = grep { not \$isthere{\$_} } sort keys %isthere;
return \@vacancies;
}

my @issues = @{ [
'00001',
'00002',
'00003',
'00004',
#          '00005',
'00006',
'00007',
'00008',
'00009',
#...
] };

print join("\n", @{ find_holes( \@issues ) });

Prints:

```d:\tmp\try>perl try.pl
perl try.pl
1 2 3 4 5 6 7 8 9

00001 00002 00003 00004 00006 00007 00008 00009

5

What the sort probably does is to fill the number entry in the glob of the entries of @list. But why does the ".." operator use the number slot, while the hash access code and print use the string slot?

Christian Lemburg
Brainbench MVP for Perl
http://www.brainbench.com

Re: Runrig and Finding missing elements in a sequence (code)
by demerphq (Chancellor) on Nov 06, 2001 at 22:10 UTC
My gut feeling is that depending on having the input file correctly padded is a bad call, especially if there are humans involved in the process. Better to pad the output as is appropriate.

OTOH if the data is _guaranteed_ to be padded correctly then your point is good and I would utilize it. Anything that minimizes the amount of code required is a Good Thing in my book.

Just my \$0.02 :-)

Yves / DeMerphq
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