On Thu, Sep 8, 2016 at 12:25 AM, Kaare Rasmussen <ka...@jasonic.dk> wrote:
> I wonder what you miss from https://docs.perl6.org/language/classtut. To > me, it explains the hows and whys very thoroughly. Now, I now people have > been hard at work improving the documentation, so if you can point to > what's missing or unclear, I'm sure it will help a lot. I forgot I looked at this before. The Task example doesn't really help a newcomer because it is combining too many new things at once: * BUILD * submethod * new * bless * named arguments syntax * slurping parameter syntax * code golfing cleverness of mapping arguments to identically named named arguments The real nail in the coffin though is that it's an example that doesn't need to use any of those features (nothing about Task really require special construction), so a quick read just makes it look like it's a very verbose syntax for doing something you normally get for free, rather than showing how it allows you to do things that you otherwise wouldn't be able to do. The rust developers talk about having a "strangeness budget", because if you introduce too many strange things at once people give up. Every object-oriented language I've used has one constructor-like method that you define. That Perl6 has two is really strange and unusual (at least coming from the background of somebody who has "only" been exposed to C++/Java/Python/Lisp/Haskell). Strange and unusual enough that it seems like there should be an example that specifically focuses on what you get out of having two, and when you should be using one versus the other. And frankly I'm not sure if it's actually two, because bless is also apparently a method (that may be you can override as well?!), even though it is supposed to be what you call to construct the object that hasn't yet been constructed... see why this might be confusing? It would be especially great if it contrasted with another language where you could demonstrate that it's awkward to do something without the feature. Here are some fairly simple things that I was left wondering how to do: * If I have a member that is read-only, when am I allowed to initialize it and after what point must already be initialized? Can I assign to it in BUILD but not new or vice versa? * If I want a constructor that takes positional arguments, do I write new or BUILD? * If I need to do some computation when the object is constructed in order to properly initialize the members, do I write new or BUILD? What if one of the members I need to initialize is read-only? * Can either new or BUILD be a multimethod? Overloading constructors is fairly common in C++ at least. >> The pair operator is explained here https://docs.perl6.org/languag e/operators#index-entry-pair_constructor and word quoting here https://docs.perl6.org/language/quoting#Word_quoting:_qw - perhaps they're more Perl 5-like, but both are very handy features. Perhaps you can expand a little as to what you'd like explained. Coming from Perl 5, I'm certainly damaged in that respect. Functions (including operators since they are just functions with a different calling syntax after all) normally just operate on their arguments without knowing anything about the context with the function was called. But the pair constructor operator **reaches back magically into the place where it was called and changes the argument it was given into a string** (because otherwise it would be an undeclared variable name). That's the kind of thing that in most languages you either can't do or you can only do by defining a macro. I've never seen anything like it. And going with the strangeness theme none of the tutorials seemed to be the least bit fazed by it, while I think somebody coming from a background without Perl will be bewildered by it.
