Greetings,
I have just started to write a large amount of Perl 6 code, partly to help with testing the Pugs (and later Parrot) implementation of the language. During this process, I discovered a few details about Perl 6 that I don't yet understand, and haven't yet been able to get answers to in my reading of the Synopsis. So I'll ask about them here.
For some of these points, I just wanted clarification on something I think I already know, and for others its just a "how do I" matter:
0. As I understand it, the current state of being says that all Perl 6 code will by default "use strict" and "use warnings" (y/n), unless it's a one-liner?
1. What is the behaviour of require() in regards to what it does when a module or class was previously defined in a file that was already loaded, but that file didn't have a file name that corresponded to the module or class? Eg, say a program determines at runtime that it wants to use module Foo, and that module is defined in a file named Bar that declares both the Bar and the Foo module. If the program had already loaded file Bar sometime earlier, then will "require Foo" use the existing declaration, or try to load a file named "Foo" but fail? Or will something else happen. Essentially, I want users of my module to be able to declare a data-containing module using either method, its own file or shared in another file, and my module to just see and use it.
For reference, this is what I currently have to do in Perl 5:
no strict 'refs';
my $package_is_loaded = defined %{$template_module_name~'::'};
use strict 'refs';
unless( $package_is_loaded ) {
require $template_module_name;
}
$text = $template_module_name->get_text_by_key( $message.msg_key );I do that because Perl 5 require() always attempts to load a matching file name.
2. Related to the above, if the require() of Perl 6 will indeed try to load a file with the matching name, then what is the proper way to test if a module was already loaded? Hopefully this is elegant, rather than the Perl 5 "no strict 'refs'" cludge. ('cludge' means anything I need to un-strict to accomplish.)
3. Does my explicit new() method get a "$self:" argument that is already instantiated like other methods, or do I have to do something like a bless() on my own declared variable of the class type and explicitly return that?
4. Is it possible to create a 'class' that sub-classes a 'module' or can one only subclass a 'class'. The reason I'm declaring the parent as a module is because it doesn't have any attributes, but it does have utility functions that I wish for users of multiple sub-classes to be able to invoke off of them.
5. If I have a class property defined using "has Str %.foo;", and an object of the class is named "$bar", then is it correct syntax to refer to the property as a whole using "$bar.foo" and an element using "$bar.foo{'abc'}"?
6. I understand that sub/method arguments are passed in read-only by default. However, if (see #2) I do a "return( $bar.foo );" when will the caller getting that return value have received a reference to or a copy of the attribute?
7. Say I have 2 arrays of arrays, @foo and @bar. What is the most concise Perl 6 syntax for each of these operations in Perl 5? The Perl 5 equivalent is expressed where each is an array having array refs that are unalike in size.
@foo = @bar # a shallow copy
@foo = map { [EMAIL PROTECTED] } @bar # a deep copy8. Is it possible with a sub or method argument signiture to specify that the arguments must have defined values? Or are specced non-optional arguments only guaranteed to have the correct container passed to them?
9. What does the as() method on built-in types do on a hash that has undefined values? Does it raise a "use of undefined value in string" warning, or just substitute the empty string?
10. When using as(), can I specify that the results get sorted? Or alternately, will hashes always serialize in the same order on all platforms, unlike in Perl 5 where its pairs come out in an apparently random order? If not, I will have to continue to do manually what as() does.
Okay, that's it for my initial set of questions.
Thanks in advance for any feedback, whether they are plain answers or pointers to where *exactly* in the Perl 6 spec I should successfully find the answer.
-- Darren Duncan
