Working with Types in Perl - perl

Question

I worked with Fortran since years and with Types within Fortran of course.
Now, since I am employed at a new company, I have to work with Perl.
Since my main work is to operate with data within a text file and have to read through the file, I want to generate "objects" or "types" from this data.
In Fortran I would do that so the further work is much easier :)
Is it possible with Perl to generate types for a strict type schema like I can to it in Fortran?
For example ... this is what I would do in Fortran:
Type demoType
integer i
character(256) str
end Type
Then I can work with variables which are of this type. Type(demoType) demoVar e.g.
Is there any chance to work like this in Perl?
Sorry for my English ... I am native German speaking :)

Answer 1

In FORTRAN, much like C, variables mostly occupy a fixed space in memory. So a Type like your demoType describes how an item is laid out, and things like strings have to be preallocated a maximum size.
In Perl, a scalar value - mostly strings and numbers - occupies a lot more than just the space for the value itself, and so cannot be mapped in the same way.
To program in Perl you have to distance yourself from the implementation and allow the run time system to look after things for you. A string can vary in size indefinitely (subject to the memory of the computer) and the preferred way of associating sets of values is by using a hash (a type of array that is indexed by arbitrary strings instead of numbers).
For instance, a single demoType value might look like
my $demo_type = {
i => 99,
str => 'text'
}
and if you wanted to work with many such pairings then you should look at Perl objects.
If you have no experience of object-oriented software then you have a long and fascinating journey ahead of you!

Answer 2

There are some CPAN modules that can help you. This is an option: Class::Struct (which belongs to the standar perl distribution, no further installation is required). Example (taken from module documentation):
use Class::Struct;
struct( Rusage => {
ru_utime => 'Timeval', # user time used
ru_stime => 'Timeval', # system time used
});
struct( Timeval => [
tv_secs => '$', # seconds
tv_usecs => '$', # microseconds
]);
# create an object:
my $t = Rusage->new(ru_utime=>Timeval->new(), ru_stime=>Timeval->new());
# $t->ru_utime and $t->ru_stime are objects of type Timeval.
# set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
$t->ru_utime->tv_secs(100);
$t->ru_utime->tv_usecs(0);
$t->ru_stime->tv_secs(5);
$t->ru_stime->tv_usecs(0);

Answer 3

I would advise you to look at Modern Perl.
If you want to work with types, then look at Moose to work in an object-oriented way and expose methods and attributes.
The core perl is dynamically evaluation a variable to assign a type to a variable.

Answer 4

I think you may be trying to store the integer value, and the stringified value of the same number.
{
i = 123;
str = "123";
}
If that is the case, you are trying to do something that Perl does automatically for you.
my $integer = 123;
my $string = $integer;
print $string;
Another possibility is that you need to associate a number with a string. In which case you can just use:
an array.
my #data = ( 123, 'string' );
print 'integer: ', $data[0], "\n";
print 'string: ', $data[1], "\n";
an array ref.
my $data = [ 123, 'string' ];
print 'integer: ', $data->[0], "\n";
print 'string: ', $data->[1], "\n";
a hash
my %data = (
123 => 'string',
);
print $data{123}, "\n";
a hash ref
my $data = {
123 => 'string',
};
print $data->{123}, "\n";
At any rate you should really post anonymized example data, so that we can actually help you to learn Perl.
I think you should read the documentation for Perl. It is quite extensive. It is actually how I learned to program in Perl.
At the very least read perlintro and perldata. If you need to build nested data structures you should also have a look at perldsc.
You could also look at learn.perl.org.