Rob Richardson wrote:
>
> Greetings!
Hello,
> I am trying to write a Perl script for the Cuyahoga Valley Scenic
> Railroad, so that volunteers can sign up to work on trains. The
> schedule file has comma-separated lines that have the date of the
> train, the name of the train, and the names of people who will be
> working on the train (or empty entries, if nobody has signed for that
> position yet). The date is a string of the form "MM.DD.YYYY".
Why? If you store the date in a YYYYMMDD format you can sort it as is.
> There
> can be one or more trains for each date. Currently, there are never
> more than two trains on one day, but I can't assume that, especially
> since I know we're extending our route next season and another
> extension could happen in a few years. I also can't assume that the
> number of positions per train will remain constant.
>
> So, I am trying to build a data structure to hold the trains. I figure
> the best way would be to use a hash keyed by the date string. The
> values of the hash would be arrays, with one element per train. Each
> array would contain the list of positions for the train.
>
> I tried to use a data structure as described in Sam's Teach Yourself
> Perl in 21 Days. I am tripping over my own feet. Here's the code:
>
> while (<SCHEDULE>)
> {
> my ($trainsOnDate);
>
> chomp; # remove newline
> @trainData = split /,/;
> $trainDate = shift trainData;
>
> if (not exists $trainList{$trainDate})
> {
> # Create the hash element, giving it an empty anonymous array
> $trainList{$trainDate} = [];
There is no need for this test or assignment as perl will do the right
thing.
> }
>
> # Create a reference to the train data
> # $trainList{$trainDate} is a reference to the array of trains
> $trainRef = \@trainData;
> $trainsOnDate = \trainList{trainDate};
>
> push $trainsList{$trainDate}, $trainRef;
^^^^^^^^^^^^^^^^^^^^^^^
This has to be an array (something that starts with @).
> }
> close (IN);
>
> This gave me the following error:
> Type of arg 1 to push must be array (not hash element) at
> c:\INDIGO~1\HTDOCS\CREW\CALENDAR.CGI line 246, near "})"
This could be written as:
while ( <SCHEDULE> )
{
chomp; # remove newline
my ( $trainDate, @trainData ) = split /,/;
push @{$trainsList{$trainDate}}, @trainData;
}
close IN;
John
--
use Perl;
program
fulfillment
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