Slashdot Mirror
Exegesis 6 (Perl 6 Subroutines) Released
chromatic writes "Perl.com has just published Damian Conway's Exegesis 6 which gives practical examples demonstrating how to use the new subroutine and method semantics in Perl 6. This is the companion to Larry Wall's Apocalypse 6 which discussed the changes planned for subroutines in Perl 6."
- Everyone in the world had a chance to submit RFCs
- Larry is taking each section of the 3rd edition Programming Perl and turning it into a white-paper on the way Perl 6 will work, using the RFCs that touch on that section of Perl as a sort of shopping list, and accepting, modifying or rejecting them as needed. These are called the Apocalypses.
- After an Apocolypse is out, Damian starts working on some real-world examples to make it all more concrete. These are called the Exegeses. Sometimes these also have examples of syntax and semantics that have been worked out via the mailing lists
- Eventually, this will lead to the Design Documents
Hope that helps clear this up for those who aren't sure what's going on when they see a new Apocolypse or Exegesis come forth.sub Fahrenheit_to_Kelvin (Num $temp is rw) {
... ; :-)
Verbosity in coding, yeah that will go over well with people who are used to
int lbn, rax,
Don't get me wrong I'm a big fan of Perl, but not for its completeness as a language but for the ability to quickly write small utils to parse text.
But I suppose whatever floats peoples boats.
Tom
Someday, I'll have a real sig.
You don't have to! You could just as well use:
Perl will allow either. It's your choice. You can do the quick one-off-hack-it-up-at-3am-after-two-large-pots-of- coffee, and you can have a large programming project that must be maintained for years to come.
You have the choice. Pick whichever method fits the task at hand.
20 mil and I will! Learn Esperanto with 20M others.
Read the last page of Exegesis 6 to see the Perl 5 version of the code. It's astonishingly simpler and clearer in Perl 6.
See the Inline modules on the CPAN.
See Perl Design Paterns, an article on Perl.com.
See the CPAN.
I've read the Perl parser. You're right about this one.
how to invest, a novice's guide
I've never seen a language with so much syntax. Perl 5 had more than enough, now they've more than doubled it.
:= and ::=, ~=, ~~, .... = does assignment, := does binding and ::= works at compile time and is normally used to define types and such, ~= is pattern matching, and I have no idea what ~~ does.
...
You have { } for blocks, and for automatically parameterized blocks (ie. anonymous functions).
You have =,
You have the new <== and ==> pipeline operators. They are dataflow operators. Like so:
$foo ==> my_func ==> $bar;
is the same as
$bar <== my_func <== $foo
is the same as
$bar = my_func($foo);
is the same as
You already had the $,@,%,& to prefix variables with.
You have more uses for * now, as in slurpy arrays and splicing. As in, the * can make an array parameter slurp up all the remaining arguments, or it can make an argument flatten into a list of arguments.
They've added some wierd << foo >> syntax that I didn't even bother to read about as I was in syntax shock.
They've added ^ which indicates that a variable in a block is actually a parameter and therefore the blocks is actually a parameterized blocks (ie. anonymous function). So, now you can't tell if something surrounded by { }'s is just a block of code or whether it's an anonymous function. Although, I don't think this is a problem as it's usually obvious from the context.
And I didn't even read to the end of the paper!
Makes me want to go write some Lisp, which is perhaps the antithesis of Perl. Lisp has the maximum possibile flexibility through having the minimum possible syntax. Perl originally had little flexibility, now they are trying to add more by adding more syntax. The problem is, if they want to get anywhere near Lisp-level flexibility with this method they'll need to move to Unicode for the syntax!
Justin Dubs
Shortly after I started reading Exegesis 6 I was somewhat frightened by how complex Perl had become since I stopped keeping track of updates. Of course scripting languages have always been known for borrowing the best from other programming languages, so I kept reading in the hopes that I'd recognise something. I saw some features like the is constant declaration and started worrying that maybe they'd decided to borrow some features from the very popular but insanely evil Visual Basic. But then I saw this:
and realised that, just as Python is (alleged to be?) adding Lisp-like features, Perl is adding ML-like features! That line above is (minus the '::' and ';') straight out of a Haskell program. Then I started to notice more Haskell-like syntax:
feed (Cat c) =
feed (Lion l) =
And I'm sure a more thorough reading would turn up even more. (For example, the smart-match operator reminds me of the type inferences done in a Hindley-Milner type system.) So it appears that any sufficiently advanced language contains an implementation of a purely functional language, not specifically Scheme. :) Has Damian (who certainly has Haskell exposure) or Larry ever mentioned any of these influences?
Perhaps the Perl motto should be changed from TMTOWTDI to TAMODVPCWDSSAAMSTWDI:
"There's a multitude of different visually pleasing constructions with deceptively subtle syntax and auto-magical semantics that will do it."
Okay, I love Perl 5... Perl 6 looks really cool but overwhelming. I'm glad they're adding the options for stricter type-checking and such, but remembering the syntactic shortcuts is gonna be even harder. I don't even want to know what the parser code looks like...
My bicyles
It's not just you, but about 80% of the syntax stays the same. Much of the rest requires a few parser rule overrides. See ... And Now For Something Completely Similar, also by Damian.
Backwards compatibility is a huge concern. That's why Ponie exists and why Dan's so careful about supporting Perl 5 semantics on Parrot. (As well, I expect 80% of the core Perl 5 tests will port to Perl 6 with surprisingly little work.)
how to invest, a novice's guide