Exegesis 2: Damian Conway On Perl6

sumengen writes: "Damian's writing a series of articles parallel to Larry's Apocalypses. These 'Exegesis' articles will show full perl6 programs, with commentary exlaining the new features. The first Exegesis (numbered 2, to keep in sync with Larry) shows a perl6 version of a binary tree program from the Perl Cookbook. Get excited to see things like:
my int ($pre, $in, $post) are constant = (0..2);"

Comments

Re:Perl ? Mmmmm.........

[malkavian]

Urrr.. I tend to use Perl a lot.
Ya know, it's quite easy to pick up (I got up and running in an afternoon on the basics).
The prefixed identifier is pretty useful as a memory aid, so that you are ALWAYS aware of what type you're dealing with (scalar, array, hash, sub, or typeglob).
To learn what these are, you read one page in a book, and all is clear. Now, how difficult is that??
If you're having trouble extracting values out of variables, then I think you have a weird view of 'difficult'. Pulling a value out of a deep struct in C can be difficult, but using $_ being difficult? Bah.
Still, if you don't like it, fine. Your choice. But, please don't keep saying it's so difficult.
I taught my Girlfriend to use Perl in a day (at the basics), and she's never learned a programming language in her life prior to this. She's now sailing away in it happily.

Cheers,

Malk

Shades of PL/I

[geophile]

25 years ago, I spent many hours debugging a PL/I program to discover that some code I inherited relied on arcane initialization rules and got it wrong. How nice to know that untold generations of programmers will now have the same experience thanks to constructs like "my int ($pre, $in, $post) are constant = (0..2);" I was never a Perl fan and I'm even less of one now. But out of curiosity, what possible justification is there for such a construct?

I was also happy to see Basic's "dim" recycled.

Really guys, haven't we learned anything since oh, I don't know, 1965?

PERL: PERL is an Ebonics-Related Language (?)

[Jester99]

Now in Perl 6, one can have such syntax as: my int ($pre, $in, $post) is constant = (0..2);
and: $ARGS is prompts("Search? ");

With the advent of this new "is" construction and the use of passive voice in the code, I think that the following should also be added:

• A be operator,
• a being modifier, and
• the gerundative form (-ing) of any keyword should be allowed.

This would allow for such conventions as:

$*ARGS be chomping;
"LibCGI.pl" is being required;
(or if one wants to be smart:)
recognize $foo!;

Just a thought.

The language life cycle

[Animats]

There's a life cycle of languages that start out without a serious type system. It goes as follows.

• "We don't need all those declarations. We'll have nice, concise programs"
• "Without any declarations, nobody can keep their variables straight. So we'll have a few declarations, but not like those complicated languages".
• "People are writing big programs in this language, and they need types and objects. So we'll put them in".
• "Now that we have types and objects, people expect all the features that go with them. So we'll add them".
• "The declaration syntax is a mess. It's unreadable, hard to parse, and programmers have a hard time using it right. How did we get into this hole?"
• "This language is too complicated. Let's develop a simpler language."

Wash, rinse, repeat.

C went through this evolution, taking about 25 years to do so. Originally, everything in C was basically a 16-bit int. Structs were just a set of offsets. There was no type-checking; any struct field could be used with any pointer. Then came K&R C, which added a type system but made the syntax context-dependent, because the original language hadn't contemplated user-defined types. ANSI C made the type system consistent. C++ added objects. ISO C++ added templates, collections, and lots of other stuff. Now the language and its manuals are huge.

LISP also went through this cycle, again taking about 20-25 years to go from LISP 1.5 to Common LISP. So did FORTRAN and BASIC. Perl is now well along into this cycle.

If you put in the type system first, as Java, Python, Pascal, Ada, and Smalltalk did, the end result is cleaner, but the language gets an initial reputation of being complicated. Perl, though, has now grown to be more complex than any of those languages, so it's on the downslope of the cycle.

Hitchhiker's guide to Perl

[Siener]

There is a theory that if anyone ever discovers exactly what Perl is for and why it is here, it will immediately disappear and be replaced by something even more bizarrely inexplicable.

There is another theory which states that this has already happened...

There is yet a third theory which states that both the first two theories were concocted by a wily editor of the Camel Book in order to increase the universal level of uncertainty and paranoia, and so boost sales of the book.

Re:Perl ? Mmmmm.........

[Golias]

As I read down through the nested comments, and see yet another compare-and-contrast between Perl and C++, I feel compelled to point something out.

Perl is an interpreted language that lets you quickly hack big jobs with small effort.

C++ is a compiled, object-based language, designed for projects that require the advantages of the OO model and the speed of pre-compiled binary code.

A good all-purpose programmer should learn both. Asking which is better is like asking if a Mack truck is better than a Lotus Esprit Turbo... the answer depends largely on what you want to do with it.

The real strength of Perl

[Dana_D]

The real strength of Perl lay not in its technical construct, or its syntax, or even in the vast set of modules and libraries available to it. The truest strength of Perl is its culture. Larry Wall, from very early on, has tried to foster a real, positive community.

Perl6 is yet another cultural extension to Perl5. The RFC process was very messy, disorganized, and perhaps a little out-of-control. Indeed, as Larry said, he spent several months mentally thrashing as he tried to grok all of the RFC's. But that is the way he wanted it. The RFC process was a picture of a real-life war-room or think-tank.

The end result will be very exciting, I believe. The Perl6 documents, to date, have capitalized on cultural strengths of the Perl community.

Truly, Perl6 is built on the most important resource available to Larry: the huge diversity of Perl programmers all over the world. That diversity has made Perl5 a great, legendary language. I think it will make Perl6 even better. As Perl advocates, I think our best effort is in being inclusive, rather than exclusive, in our thinking.