perl.perl6.users

perl.perl6.users http://www.nntp.perl.org/group/perl.perl6.users/ ... Copyright 1998-2009 perl.org Sun, 05 Jul 2009 07:02:31 +0000 ask@perl.org Re: negative index in perl6 array by Matthew Walton On Sat, Jun 20, 2009 at 12:07 PM, Chas. Owens<chas.owens@gmail.com> wrote: > Hmm, I can't get [user-defined array indexes][1] working, and those > are a prerequisite for mixing subscripts (you can't mix normal and > user-defined indexes if you can't create user-defined indexes).  I > took a quick look at the tests and couldn't even find a test for > user-defined array indexes. > > [1] : http://perlcabal.org/syn/S09.html#User-defined_array_indexing That means it's not implemented yet, unfortunately. By the way, if you have trouble remembering that negative indexes for arrays are now *-n, recall that the * is generally called 'whatever', so it's 'whatever - 1', and the 'whatever' in this case fills in to be 'however many things are in the array, the precise value of which I really don't care about'. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1124.html Tue, 23 Jun 2009 23:24:31 +0000 Re: negative index in perl6 array by Chas. Owens On Sat, Jun 20, 2009 at 02:49, Aruna Goke<myklass@gmail.com> wrote: > Chas. Owens wrote: >> >> On Sat, Jun 20, 2009 at 00:58, Aruna Goke<myklass@gmail.com> wrote: >>> >>> is negative index not allowed in perl6? >>> >>> i tried >>> >>> my @test = (1 .. 20); >>> @test[-1].say; >>> >>> OUTPUT >>> Use of uninitialized value >>> >> >> You have to say >> >> @test[*-1].say; >> >> now >> >> http://perlcabal.org/syn/S09.html#Negative_and_differential_subscripts >> > Thanks Chas, > > however, i have been trying to run the example of Mixing subscripts under > S09. > > can you give me an example of using the Mixing subscripts? > > goksie > Hmm, I can't get [user-defined array indexes][1] working, and those are a prerequisite for mixing subscripts (you can't mix normal and user-defined indexes if you can't create user-defined indexes). I took a quick look at the tests and couldn't even find a test for user-defined array indexes. [1] : http://perlcabal.org/syn/S09.html#User-defined_array_indexing -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1123.html Sat, 20 Jun 2009 04:08:11 +0000 Re: negative index in perl6 array by Aruna Goke Chas. Owens wrote: > On Sat, Jun 20, 2009 at 00:58, Aruna Goke<myklass@gmail.com> wrote: >> is negative index not allowed in perl6? >> >> i tried >> >> my @test = (1 .. 20); >> @test[-1].say; >> >> OUTPUT >> Use of uninitialized value >> > > You have to say > > @test[*-1].say; > > now > > http://perlcabal.org/syn/S09.html#Negative_and_differential_subscripts > Thanks Chas, however, i have been trying to run the example of Mixing subscripts under S09. can you give me an example of using the Mixing subscripts? goksie http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1122.html Fri, 19 Jun 2009 23:52:30 +0000 Re: negative index in perl6 array by Chas. Owens On Sat, Jun 20, 2009 at 00:58, Aruna Goke<myklass@gmail.com> wrote: > is negative index not allowed in perl6? > > i tried > > my @test = (1 .. 20); > @test[-1].say; > > OUTPUT > Use of uninitialized value > You have to say @test[*-1].say; now http://perlcabal.org/syn/S09.html#Negative_and_differential_subscripts -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1121.html Fri, 19 Jun 2009 22:13:32 +0000 negative index in perl6 array by Aruna Goke is negative index not allowed in perl6? i tried my @test = (1 .. 20); @test[-1].say; OUTPUT Use of uninitialized value http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1120.html Fri, 19 Jun 2009 22:01:55 +0000 Rakudo Perl 6 development release #18 ("Pittsburgh") by Patrick R. Michaud On behalf of the Rakudo development team, I'm pleased to announce the June 2009 development release of Rakudo Perl #18 "Pittsburgh". Rakudo is an implementation of Perl 6 on the Parrot Virtual Machine [1]. The tarball for the June 2009 release is available from http://github.com/rakudo/rakudo/downloads . Due to the continued rapid pace of Rakudo development and the frequent addition of new Perl 6 features and bugfixes, we continue to recommend that people wanting to use or work with Rakudo obtain the latest source directly from the main repository at github. More details are available at http://rakudo.org/how-to-get-rakudo . Rakudo Perl follows a monthly release cycle, with each release code named after a Perl Mongers group. This release is named "Pittsburgh", which is the host for YAPC|10 (YAPC::NA 2009) [2] and the Parrot Virtual Machine Workshop [3]. Pittsburgh.pm has also sponsored hackathons for Rakudo Perl as part of the 2008 Pittsburgh Perl Workshop [4]. In this release of Rakudo Perl, we've focused our efforts on refactoring many of Rakudo's internals; these refactors improve performance, bring us closer to the Perl 6 specification, operate more cleanly with Parrot, and provide a stronger foundation for features to be implemented in the near future. Some of the specific major changes and improvements in this release include: * Rakudo is now passing 11,536 spectests, an increase of 194 passing tests since the May 2009 release. With this release Rakudo is now passing 68% of the available spectest suite. * Method dispatch has been substantially refactored; the new dispatcher is significantly faster and follows the Perl 6 specification more closely. * Object initialization via the BUILD and CREATE (sub)methods is substantially improved. * All return values are now type checked (previously only explicit 'return' statements would perform type checking). * String handling is significantly improved: fewer Unicode-related bugs exist, and parsing speed is greatly improved for some programs containing characters in the Latin-1 set. * The IO .lines and .get methods now follow the specification more closely. * User-defined operators now also receive some of their associated meta variants. * The 'is export' trait has been improved; more builtin functions and methods can be written in Perl 6 instead of PIR. * Many Parrot changes have improved performance and reduced overall memory leaks (although there's still much more improvement needed). The development team thanks all of our contributors and sponsors for making Rakudo Perl possible. If you would like to contribute, see http://rakudo.org/how-to-help , ask on the perl6-compiler@perl.org mailing list, or ask on IRC #perl6 on freenode. The next release of Rakudo (#19) is scheduled for July 23, 2009. A list of the other planned release dates and codenames for 2009 is available in the "docs/release_guide.pod" file. In general, Rakudo development releases are scheduled to occur two days after each Parrot monthly release. Parrot releases the third Tuesday of each month. Have fun! References: [1] Parrot, http://parrot.org/ [2] YAPC|10 http://yapc10.org/yn2009/ [3] Parrot Virtual Machine Workshop, http://yapc10.org/yn2009/talk/2045 [4] Pittsburgh Perl Workshop, http://pghpw.org/ppw2008/ http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1119.html Thu, 18 Jun 2009 22:26:20 +0000 [proto] installing a module if PARROT_DIR is a symlink by Moritz Lenz Since viklund++ added proto support to JSON yesterday, I wanted to try it - and I found some problem that I don't know how to fix. This is how my setup looks: rakudo (bleed) lives in ~/rakudo/. Parrot lives in ~/rakudo/parrot/, which is a symlink to ~/tmp/parrot-all/ ~/bin/ is in $PATH, and ~/bin/perl6 is a symlink to ~/rakudo/perl6. Now I cloned JSON, and tried this: moritz@trudi:~/src/json>perl6 Configure Configure.pm is preparing to make your Makefile. Found a PARROT_DIR to be /home/moritz/tmp/parrot-all but there is no Rakudo nearby. Please contact the proto people. Setting PARROT_DIR explicitly to ~/rakudo/parrot leads to exactly the same message. So, what should I do? I don't want proto to manage my rakudo or parrot installation for me, just the module build. Cheers, Moritz http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1118.html Sat, 13 Jun 2009 05:02:34 +0000 The Josephus Problem by Daniel Carrera Hello, Some list members may be interested in this blog post: http://daniel.carrera.bz/2009/06/perl-6-and-the-josephus-problem/ I use the Josephus Problem to compare the OOP syntax of Perl 6, Python and Ruby. It turns out that Perl 6 is *a bit* shorter and no less clear. The point is that one can no longer say that Perl's OOP is awkward. I put a lot of effort in writing the code the same way in all languages and I tried very hard to avoid any bias. Cheers, Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1117.html Fri, 12 Jun 2009 09:05:32 +0000 Re: the file slurping is not working by Smylers Tom Christiansen writes: > Larry wrote: > > > But we're trying very hard to get rid of most such special cases in > > Perl 6. Usually we can get the recommended Perl 6 code to just DWYM > > as a fallout of the general semantics, > > Oh. You mean like for directories containing a file whose name is the > 1-char string, "0", and that file pre-emptively terminating a readdir > loop the way it used to. I can't find it in the spec (link anybody?) but I'd expect the return value to be something which stringifies to "0" but boolifies to false, meaning it won't terminate the loop. That way we get the intuitive behaviour, but don't need a special case. And the general mechanism used to make this work is something available for all Perl programs to take advantage of, not an exception that requires baking into the core language internals. Smylers http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1116.html Wed, 10 Jun 2009 09:32:32 +0000 Re: rakudo-current loop 2-3 orders of magnitude slower than perl5? by Timothy S. Nelson On Thu, 4 Jun 2009, Fagyal Csongor wrote: > increase in the number of new Perl6ers at around < 100x slower. (That, and > the 10 "most important" Perl5 CPAN modules ported to Perl6 :)) Strangely enough, I was working on a list of things like this at one point. I'll format it up a bit, and include it below. -------------------------------------------- Category 1: Popular module types not covered by the Perl6 specs - Tree/Datapath API module type (include DBI access, PathTools, maybe URI) - Template module type (ie. HTML::Mason/Text::Template) - Protocol module type requires: - Grammars - Event-loop framework (see below) - Finite state machine Category 2: Other popular purposes that aren't already covered by perl features (eg. grammars or testing): - Images (ie. GD) - Archive/Encoding/Encryption - Interfaces for specific software Category 3: Covered well by the specs - Time/Date -- see Temporal.pod Category 4: Covered sketchily by the specs - Event-loop framework -- will go in S17 - See POE-basic, AnyEvent, etc. -------------------------------------------- I generated the ideas in the above list by looking at some list of the top 100 Perl5 modules (Phalanx or something), and trying to extract out what I thought the common themes were. But I haven't explained some of them very well. I've gone on enough about the Tree/Datapath stuff often enough that those who followed it will have some idea of what I'm on about, but if not, let me know. The "Protocol" module mentioned is an idea for a suite of modules like Perl5's Net::Cmd, but better; inbuilt stuff for dealing with some of the basic kinds of protocol, whether basic call/response like POP, or numbered responses like SMTP, or the xAP style format used in IMAP and ACAP, or the MIME-encoded stuff in HTTP. Hopefully most of the rest should be fairly obvious, but if not, let me know. HTH, --------------------------------------------------------------------- | Name: Tim Nelson | Because the Creator is, | | E-mail: wayland@wayland.id.au | I am | --------------------------------------------------------------------- ----BEGIN GEEK CODE BLOCK---- Version 3.12 GCS d+++ s+: a- C++$ U+++$ P+++$ L+++ E- W+ N+ w--- V- PE(+) Y+>++ PGP->+++ R(+) !tv b++ DI++++ D G+ e++>++++ h! y- -----END GEEK CODE BLOCK----- http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1115.html Tue, 09 Jun 2009 05:51:20 +0000 Re: RPN calculator in Perl 6 by Daniel Ruoso Em Sáb, 2009-06-06 às 19:51 +0200, Daniel Carrera escreveu: > Daniel Ruoso wrote: > > Yes... that's what wasn't implemented... But now it is ;) > > http://sial.org/pbot/37085 > Close, but... > % perl6 rpn.pl "5 4 + 3 / 5 3 - *" > -6 > That should be a positive 6. Fixed now! http://sial.org/pbot/37088 (with a op trace included, so one can see what's happening...) > Are you planning to write a post explaining how your program works? Maybe, but if you want to beat me to it, feel free ;) > I figure that the explanation is as useful as the example. I sure > spent a lot of time writing the blog post. I'm not sure I'll have the time to write it soon, but it will certainly be on my list, unless you kindly post about it first ;) daniel http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1114.html Mon, 08 Jun 2009 10:16:30 +0000 Re: RPN calculator in Perl 6 by Daniel Ruoso Em Sáb, 2009-06-06 às 18:22 +0200, Daniel Carrera escreveu: > Daniel Ruoso wrote: > > er... that's because I didn't tried to implement it... but it > certainly > > is possible to, just by declaring the :(@a, Num $a) variant... > Well, * is implemented, so I guess you are talking about complex > expressions. Yes... that's what wasn't implemented... But now it is ;) http://sial.org/pbot/37085 daniel http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1113.html Mon, 08 Jun 2009 09:59:36 +0000 Re: RPN calculator in Perl 6 by Daniel Ruoso Em Sáb, 2009-06-06 às 14:06 +0200, Daniel Carrera escreveu: > I just wrote a blog post showing how to make a reverse polish notation > calculator in Perl 6. In the process I show some of Perl 6's grammar > features. TIMTOWTDI ;) http://sial.org/pbot/37075 daniel http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1112.html Mon, 08 Jun 2009 09:31:17 +0000 Re: RPN calculator in Perl 6 by Geoffrey Broadwell On Sat, 2009-06-06 at 13:18 -0300, Daniel Ruoso wrote: > http://sial.org/pbot/37077 > A slightly improved syntax, as per jnthn++ suggestion... My list mail has been very delayed, so this may be out of sequence, but in case no one mentioned it yet: http://sial.org/pbot/37102 (That's ruoso++'s later 37100 paste with a couple small tweaks by me.) I wanted to shrink that even further by replacing the given/when with a direct call of the correct op variant, but I couldn't figure out how to do that in current Rakudo. (And just using eval inside a multi seemed to be broken.) -'f http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1111.html Mon, 08 Jun 2009 09:19:54 +0000 Re: RPN calculator in Perl 6 by Daniel Ruoso Em Dom, 2009-06-07 às 00:07 +0200, Daniel Carrera escreveu: > Daniel Ruoso wrote: > >> Are you planning to write a post explaining how your program works? > > Maybe, but if you want to beat me to it, feel free ;) > >> I figure that the explanation is as useful as the example. I sure > >> spent a lot of time writing the blog post. > > I'm not sure I'll have the time to write it soon, but it will certainly > > be on my list, unless you kindly post about it first ;) > Honestly, I don't really know how your version works. I'll take the code as in http://sial.org/pbot/37089 Feel free to post it if you like... Ok, I think I can skip the first part, where I declare a token Num, since your example explain it in great detail. At first I'm using multi subs, the declaration is just multi name ($a, $b) {...} and is just a shortcut for our multi sub name ($a, $b) {...} which means we're declaring a sub named '&name' which will also be registered in the current package (our), with the signature inside the parens. This will work mostly as multis work in other languages, it will invoke the variant which signature matches the parameters. The second point is the use of the "infix:<rpn>" name in the multi. This is how you declare new operators in Perl 6. infix describe the syntatic category of the operator, in this specific case, it means the operator stays between two values. So, after defining the multi sub, I could just use: 5 rpn 4 and this would invoke infix:<rpn>(5, 4) If you're following until here, you probably realize that I could also do ((5 rpn 4) rpn '+') rpn 3 but Perl 6 has the "reduce meta operator", which takes any infix operator and builds the above grouping for an arbitrary list, and that's the last line of the code [rpn] @*ARGS[0].words; This takes the list of words in @*ARGS[0] (which means I require a space between every token) and reduces it using the infix:<rpn> operator, which is implemented by each of the variants in the code. The reduce meta-op works by taking the first two elements of the list and running the infix:<rpn> with them as parameters, take the result of that and the next element of the list and call it again, then do it again until the list ends. The last thing you need to know to understand this is about subsets, as used in the signature of most variants multi infix:<rpn> ($a where /<Num>/, $b where /<Num>/) {...} This signature will take two arguments where both must match the Num token. This happens to be the variant that matches the start of the list, and it is the only one that doesn't expect an Array as the first argument, because it will itself return an Array with the two numbers. As the reduce metaop takes the result from this call and the next element on the list to call the sub again, the next call will receive an array with the two first numbers as the first argument and the next token as second argument, then the signature match does its trick and we go on until we reach the end of the list, and the last calculation is made. This solution is mostly a functional solution. Probably if you ask the LISP guys to work on a program to do RPN, it will probably look like this... daniel http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1110.html Mon, 08 Jun 2009 09:05:19 +0000 Re: RPN calculator in Perl 6 by Daniel Ruoso Em Sáb, 2009-06-06 às 19:45 -0400, Minimiscience escreveu: > my $ls = @a.shift; > my $rs = @a.shift; > To: > my $rs = @a.pop; > my $ls = @a.pop; Thanks... this was already solved in the latest version I sent http://sial.org/pbot/37089 daniel http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1109.html Mon, 08 Jun 2009 09:05:18 +0000 Re: RPN calculator in Perl 6 by Daniel Ruoso http://sial.org/pbot/37077 A slightly improved syntax, as per jnthn++ suggestion... Em Sáb, 2009-06-06 às 18:08 +0200, Daniel Carrera escreveu: > Daniel Carrera wrote > > Ok, try again: > > % perl6 rpn.pl "2 2+" > > 2 2 > You can probably fix that with a different split() line. I tried using > <ws> instead of \s+ but the program just hangs forever. Hmm.. it certainly is in the split, I'm not sure how to get the barrier between the 2 and the +.... > I also tried a more complex expression, and the calculator didn't like it: > % perl6 rpn.pl "5 4 + 3 / 5 3 - *" > Error parsing expression near * er... that's because I didn't tried to implement it... but it certainly is possible to, just by declaring the :(@a, Num $a) variant... daniel http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1108.html Mon, 08 Jun 2009 08:56:56 +0000 Re: How to speed up a grammar by Leon Timmermans On Sun, Jun 7, 2009 at 1:44 AM, Minimiscience<minimiscience@gmail.com> wrote: > > This is just a wild, uneducated, possibly delusional guess, but I don't > think that vertical bar before the '/>' should be there.  I think it might > be causing the grammar engine to check whether it can omit the ending of > each tag and attach it to the enclosing tag instead, which it can't confirm > without examining the whole file at least once for each tag. > In Perl 5 regexps that would be a problem, but in Perl 6 it shouldn't AFAIK. See "Nothing is illegal" in S05. Leon http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1107.html Sun, 07 Jun 2009 10:46:13 +0000 Re: RPN calculator in Perl 6 by Minimiscience [I just realized I sent this directly to Daniel rather than to the list, so for the benefit of onlookers...] On Jun 6, 2009, at 1:51 PM, Daniel Carrera wrote: > Daniel Ruoso wrote: >> Yes... that's what wasn't implemented... But now it is ;) >> http://sial.org/pbot/37085 > > Close, but... > > % perl6 rpn.pl "5 4 + 3 / 5 3 - *" > -6 > > That should be a positive 6. I think I see the problem (assuming it hasn't already been pointed out off-list). The infix:<rpn>(@a, $op where ...) operators call .shift on the arrays to get the operands, yet the infix:<rpn>(... , $b where / <Num>/) operators place the numbers on the *end* of the stack, where the next reverse-polish operator should read them from. Thus, when the '-' is processed, the stack is "3 5 3", where the first three is the result of "5 4 + 3 /", and the first two numbers are shifted off for subtraction rather than the last two. In order to fix this, either change the first two infix:<rpn>() functions so that they place new numbers at the *beginning* of the array, or else change each occurrence of my $ls = @a.shift; my $rs = @a.shift; To: my $rs = @a.pop; my $ls = @a.pop; (Note that, in addition to the use of .pop, $rs is now acquired before $ls.) At least, I think that's how it works. -- Minimiscience http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1106.html Sat, 06 Jun 2009 16:46:08 +0000 Re: How to speed up a grammar by Minimiscience On Jun 6, 2009, at 10:32 AM, Richard Hainsworth wrote: > rule element { > '<' <name> <attribute>* > [ > | '/>' > | '>' <element>* '</' $<name> '>' > ] > } This is just a wild, uneducated, possibly delusional guess, but I don't think that vertical bar before the '/>' should be there. I think it might be causing the grammar engine to check whether it can omit the ending of each tag and attach it to the enclosing tag instead, which it can't confirm without examining the whole file at least once for each tag. -- Minimiscience http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1105.html Sat, 06 Jun 2009 16:44:27 +0000 Re: RPN calculator in Perl 6 by Daniel Carrera Daniel Ruoso wrote: >> Are you planning to write a post explaining how your program works? > > Maybe, but if you want to beat me to it, feel free ;) > >> I figure that the explanation is as useful as the example. I sure >> spent a lot of time writing the blog post. > > I'm not sure I'll have the time to write it soon, but it will certainly > be on my list, unless you kindly post about it first ;) Honestly, I don't really know how your version works. Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1104.html Sat, 06 Jun 2009 15:08:00 +0000 Re: RPN calculator in Perl 6 by Daniel Carrera Daniel Ruoso wrote: > Yes... that's what wasn't implemented... But now it is ;) > > http://sial.org/pbot/37085 Close, but... % perl6 rpn.pl "5 4 + 3 / 5 3 - *" -6 That should be a positive 6. Are you planning to write a post explaining how your program works? I figure that the explanation is as useful as the example. I sure spent a lot of time writing the blog post. Cheers, Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1103.html Sat, 06 Jun 2009 10:51:48 +0000 Re: RPN calculator in Perl 6 by Daniel Carrera Daniel Ruoso wrote: >> You can probably fix that with a different split() line. I tried using >> <ws> instead of \s+ but the program just hangs forever. > > Hmm.. it certainly is in the split, I'm not sure how to get the barrier > between the 2 and the +.... Does Perl 6 still have the word barrier \b regex? Maybe some sort of character class that matches spaces and word boundaries? I dunno... >> I also tried a more complex expression, and the calculator didn't like it: >> % perl6 rpn.pl "5 4 + 3 / 5 3 - *" >> Error parsing expression near * > > er... that's because I didn't tried to implement it... but it certainly > is possible to, just by declaring the :(@a, Num $a) variant... Well, * is implemented, so I guess you are talking about complex expressions. Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1102.html Sat, 06 Jun 2009 09:23:06 +0000 Re: RPN calculator in Perl 6 by Daniel Carrera Daniel Carrera wrote > Ok, try again: > > % perl6 rpn.pl "2 2+" > 2 2 You can probably fix that with a different split() line. I tried using <ws> instead of \s+ but the program just hangs forever. I also tried a more complex expression, and the calculator didn't like it: % perl6 rpn.pl "5 4 + 3 / 5 3 - *" Error parsing expression near * :-( Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1101.html Sat, 06 Jun 2009 09:08:24 +0000 Re: RPN calculator in Perl 6 by Daniel Carrera Daniel Carrera wrote: >> http://sial.org/pbot/37075 > > % perl rpn.pl "2 2 +" Tee hee... that should have been "perl6". :-) Ok, try again: % perl6 rpn.pl "2 2+" 2 2 http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1100.html Sat, 06 Jun 2009 09:00:36 +0000 Re: RPN calculator in Perl 6 by Daniel Carrera Daniel Ruoso wrote: > TIMTOWTDI ;) The objective of the blog was more about the learning + teaching experience than anything else. > http://sial.org/pbot/37075 % perl rpn.pl "2 2 +" Semicolon seems to be missing at rpn.pl line 2. String found where operator expected at rpn.pl line 13, near "where '+'" (Do you need to predeclare where?) Array found where operator expected at rpn.pl line 14, near "] " (Missing operator before ?) Scalar found where operator expected at rpn.pl line 14, near "@($a" (Missing operator before $a?) String found where operator expected at rpn.pl line 17, near "where '-'" (Do you need to predeclare where?) Array found where operator expected at rpn.pl line 18, near "] " (Missing operator before ?) Scalar found where operator expected at rpn.pl line 18, near "@($a" (Missing operator before $a?) String found where operator expected at rpn.pl line 21, near "where '*'" (Do you need to predeclare where?) Array found where operator expected at rpn.pl line 22, near "*] " (Missing operator before ?) Scalar found where operator expected at rpn.pl line 22, near "@($a" (Missing operator before $a?) Semicolon seems to be missing at rpn.pl line 24. String found where operator expected at rpn.pl line 25, near "where '/'" (Do you need to predeclare where?) Semicolon seems to be missing at rpn.pl line 28. String found where operator expected at rpn.pl line 30, near "fail 'Error parsing expression near '" (Do you need to predeclare fail?) Array found where operator expected at rpn.pl line 33, near "] " (Missing operator before ?) Bareword found where operator expected at rpn.pl line 33, near "@*ARGS" (Missing operator before ARGS?) Operator or semicolon missing before *ARGS at rpn.pl line 33. Ambiguous use of * resolved as operator * at rpn.pl line 33. syntax error at rpn.pl line 1, near "\." Missing right curly or square bracket at rpn.pl line 34, at end of line Execution of rpn.pl aborted due to compilation errors. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1099.html Sat, 06 Jun 2009 08:58:05 +0000 How to speed up a grammar by Richard Hainsworth Leon Timmermans wrote: > If you want to write a fast parser for XML, preventing backtracking is > going to be quite essential. I suspect the problem is your grammar, > not the grammar engine itself. You could post it to perl6-users and > ask for advice on it. > > Leon Below is the grammar. I am only interested in tag names <xs1:text> <xs1:playlist> (and within playlist) <xs1:item> The only attributes I want are 'author', 'title', and 'id' grammar sony_grammar; rule TOP { ^ <xmldecl>? <root=element> $ } rule xmldecl { '<?xml' 'version' '=' '"' $<version>=<-[\"]>+ '"' 'encoding' '=' '"' $<encoding>=<-[\"]>+ '"' '?>' } rule element { '<' <name> <attribute>* [ | '/>' | '>' <element>* '</' $<name> '>' ] } rule attribute { <name> '=' '"' $<value>=<-["]>* '"' } token name { <namespace>? $<ename>=<ident> } token namespace { <ident> ':' } http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1098.html Sat, 06 Jun 2009 07:33:11 +0000 RPN calculator in Perl 6 by Daniel Carrera Hi all, I just wrote a blog post showing how to make a reverse polish notation calculator in Perl 6. In the process I show some of Perl 6's grammar features. Someone in IRC thought it was good, so I decided to post here in the off chance that someone else finds it interesting or useful. http://daniel.carrera.bz/2009/06/rpn-calculator-in-perl-6/ Cheers, Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1097.html Sat, 06 Jun 2009 05:06:32 +0000 Re: the file slurping is not working by Tom Christiansen Larry wrote: » Indeed, that preference is why Perl 6 can (we hope) get away with » autochomping, where Perl 5 can't (as easily). Or more accurately, » we choose not to special-case "while (<>)" as Perl 5 does (because » even Perl 5 has difficulties with files that are accidentally » "autochomped" by omitting the final newline in the file). I don't understand what you mean, Larry. Sure, Perl *4* had such difficulties, since having only chop(), not an RS-aware chomp(), you'd get a: substr($line,-1) = q() whether you "needed" it or not (although it returns the old LHS not the new RHS). It's not conditional, except that it won't give you negatively lengthed null lines. And so those folks who deemed textfiles as \n-SEPARATED sequences of lines, not \n-TERMINATED sequences, would therefore shorten their files by a character if they didn't check first. But with Perl *5*, since chomp() is RS-aware in that it instead looks for it leaps--er, checks before it chomps--so I'm don't at all understand what you mean when you say » even Perl 5 has difficulties with files that are accidentally » "autochomped" by omitting the final newline in the file). I don't see where you see Perl 5 having that problem. This seems safe enough, which to a first approximation about this: $line =~ s[ ${RS} \z ][]x; Even when $RS = q!!, making for squishy record terminators for both readline() and also for chomp(), I see no destructive action. Often enough I set $RS = "%%\n", and sometimes I remember to put a %% at the end, and sometimes I don't, but no harm done. The only place I can see there being a "problem" is with something like % perl -i'IBACKUP/*' lpe 's/foo/bar/g' file* and some of those files start out without their terminator. Here though the problem is opposite what you mention, in that once Perl's had its way with them, all files are canonically terminated whether they began that way or not. » But we're trying very hard to get rid of most such special » cases in Perl 6. Usually we can get the recommended Perl » 6 code to just DWYM as a fallout of the general semantics, » but in this particular case, if you really want to read » your input with while, there's a slight "regression" from » Perl 5 insofar as you must explicitly use defined(). This » de-huffmanization is intended as a subtle encouragement to » move from Item-Think towards List-Think. :) Oh. You mean like for directories containing a file whose name is the 1-char string, "0", and that file pre-emptively terminating a readdir loop the way it used to. Whereas nowadays, our compassionate compiler, spotting an incorrectly tested assignment governing a while's conditional: while ( $thingie = <read{dir,lin[ke]}>() ) { ;;; } graciously inserts a defined() opcode for you. Wasn't the reasoning that whenever there's something each and every program must without fail do if it's to be a correct program, that something is too important to be left up to the programmer to forget? Is this rationale no longer sound? It still makes sense to me. Then again, folks can still confuse interating using a while with iterating using foreach. They often appear act the same, so the wrong mental model is held. People grow complacent, having seen the misleading apparent interchangeability between while ( $src = <*.[Cchy]> ) { } foreach $src ( <*.[Cchy]> ) { } or while ( $datum = <$yafh> ) { } foreach $datum ( <$yafh> ) { } They then get quite hung up when these aren't the same: foreach $item (@someitems) { ;;; } while ( $item = shift(@someitems) ) { ;;; } I guess removing special awareness for <read{dir,lin[ke]}> might prod them into thinking more about the whole thing. After all, no special blessing of an inserted defined() op can save them here, condering that this: while ( defined( $item = shift(@someitems) ) ) { ;;; } still isn't the same as this: while (@someitems) { $item = shift(@someitems); ;;; } Still, whenever there's something everyone has to do for a program to function correctly, shouldn't Perl be doing it for them whenever possible, lest they sometimes forget? Think of the Python programs that die because they forget to pre-extend their lists to grow it by one. Perl after all never makes you write: if ($#someitems < $index) { $#someitems = $index; } $sometimes[$index] = $value; EACH AND EVERY $@%&* time you want to write $sometimes[$index] = $value; but Python does. But perhaps this is something for the <ITERATOR> to see to tkaing care of, or the I/O aka line-discipline, or whatever model you prefer. --tom http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1096.html Sat, 06 Jun 2009 04:39:46 +0000 Re: the file slurping is not working by Larry Wall On Fri, Jun 05, 2009 at 01:39:02PM +0200, Carl Mäsak wrote: : Daniel (>), Leon (>>), Daniel (>>>): : >>> Then why is it that .get works fine for $*IN? : >>> : >>> while $*IN.get -> $line { : >>>       say $line : >>> } : >>> : >> : >> Because you're using a while loop instead of a for loop ;-) : > : > Worse. The code I wrote has a subtle but horrible error. The condition will : > fail as soon as you hit a blank line!! : : Which, I think, summarizes why the 'for $*IN.lines' idiom is preferred : in Perl 6. Indeed, that preference is why Perl 6 can (we hope) get away with autochomping, where Perl 5 can't (as easily). Or more accurately, we choose not to special-case "while (<>)" as Perl 5 does (because even Perl 5 has difficulties with files that are accidentally "autochomped" by omitting the final newline in the file). But we're trying very hard to get rid of most such special cases in Perl 6. Usually we can get the recommended Perl 6 code to just DWYM as a fallout of the general semantics, but in this particular case, if you really want to read your input with while, there's a slight "regression" from Perl 5 insofar as you must explicitly use defined(). This de-huffmanization is intended as a subtle encouragement to move from Item-Think towards List-Think. :) Larry http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1095.html Fri, 05 Jun 2009 11:32:24 +0000 Re: the file slurping is not working by Carl Mäsak Daniel (>), Leon (>>), Daniel (>>>): >>> Then why is it that .get works fine for $*IN? >>> >>> while $*IN.get -> $line { >>>       say $line >>> } >>> >> >> Because you're using a while loop instead of a for loop ;-) > > Worse. The code I wrote has a subtle but horrible error. The condition will > fail as soon as you hit a blank line!! Which, I think, summarizes why the 'for $*IN.lines' idiom is preferred in Perl 6. // Carl http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1094.html Fri, 05 Jun 2009 04:39:15 +0000 Re: the file slurping is not working by Daniel Carrera Leon Timmermans wrote: >> Then why is it that .get works fine for $*IN? >> >> while $*IN.get -> $line { >> say $line >> } >> > > Because you're using a while loop instead of a for loop ;-) Worse. The code I wrote has a subtle but horrible error. The condition will fail as soon as you hit a blank line!! Daniel. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1093.html Fri, 05 Jun 2009 03:58:00 +0000 Re: rakudo-current loop 2-3 orders of magnitude slower than perl 5? by Steffen Schwigon Parrot Raiser <1parrota@gmail.com> writes: > If Sun's propaganda about Dtrace : > http://www.sun.com/bigadmin/content/dtrace/ is anywhere near true Which I can confirm. DTrace *is* cool. Steffen -- Steffen Schwigon <ss5@renormalist.net> Dresden Perl Mongers <http://dresden-pm.org/> Deutscher Perl-Workshop <http://www.perl-workshop.de/> http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1092.html Fri, 05 Jun 2009 03:46:23 +0000 Re: the file slurping is not working by Leon Timmermans > > Then why is it that .get works fine for $*IN? > > while $*IN.get -> $line { >        say $line > } > Because you're using a while loop instead of a for loop ;-) Leon http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1091.html Fri, 05 Jun 2009 03:42:37 +0000 Re: the file slurping is not working by Daniel Carrera Carl Mäsak wrote: > Aruna (>): >> I tested the below code on parrot-1.1.0 and it read all the lines in the >> file and tested same code on the latest git update (4th June 2009), it >> outputs only the first line. > > That's what C<$file.get> does -- it gives you one line per default. > You want C<$file.lines>. Then why is it that .get works fine for $*IN? while $*IN.get -> $line { say $line } http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1090.html Fri, 05 Jun 2009 03:17:37 +0000 Re: the file slurping is not working by Aruna Goke Carl Mäsak wrote: > Aruna (>): >> I tested the below code on parrot-1.1.0 and it read all the lines in the >> file and tested same code on the latest git update (4th June 2009), it >> outputs only the first line. > > That's what C<$file.get> does -- it gives you one line per default. > You want C<$file.lines>. > > // Carl > Thanks. http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1089.html Fri, 05 Jun 2009 03:14:55 +0000 Re: the file slurping is not working by Carl Mäsak Aruna (>): > I tested the below code on parrot-1.1.0 and it read all the lines in the > file and tested same code on the latest git update (4th June 2009), it > outputs only the first line. That's what C<$file.get> does -- it gives you one line per default. You want C<$file.lines>. // Carl http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1088.html Fri, 05 Jun 2009 03:08:38 +0000 Announcing pun (Re: rakudo-current loop 2-3 orders of magnitude slower than perl 5?) by Carl Mäsak Steffen (>), Fagyal (>>): >> However, performance is an issue. I would not mind running into >> bugs, writing some extra code to work around missing stuff, etc., >> but right now it is just hard to find any projects (for me - YMMV) >> where performance would not be a blocker. > > I suggest to start using it as replacement for sysadmin automation > tasks. The same way Perl started to replace sh/sed/awk. This would not > need all the funky OO or FP features you get with Perl 6 but many of > those tasks are not speed critical and still of practical use and > would already benefit from the syntax cleanup compared to Perl 5. I'll take this opportunity to announce 'pun', a small Perl 6 project to emulate the behaviour of the -p and -n flags in Rakudo. (The name 'pun', believe it or not, doesn't stand for anything in particular.) pun <http://github.com/masak/pun/> The principle behind it is easy: you just type 'perl6n' instead of 'perl6 -n'. Same thing for 'perl6p' and 'perl6 -p'. $ ./perl6p -e .=flip # here's a rev clone I CAN HAZ BACKWARDS? ?SDRAWKCAB ZAH NAC I ^D I find this is an excellent way to start using Perl 6 for simple sed/awk-like tasks today. Maybe some of you will too. If you try pun and would like to comment, critique, patch, document, or otherwise improve the software for the greater good of the Perl 6 community, please don't hesitate to contact me, via email or #perl6 on freenode. // Carl http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1087.html Fri, 05 Jun 2009 03:02:47 +0000 the file slurping is not working by Aruna Goke I tested the below code on parrot-1.1.0 and it read all the lines in the file and tested same code on the latest git update (4th June 2009), it outputs only the first line. #!/usr/bin/perl6 use v6; my $fname = 'README'; if my $file = open($fname, :r) { for $file.get-> $line { say $line; } } else { say "could not open $fname bcos : $!"; } close($file); what is happening? http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1086.html Fri, 05 Jun 2009 02:58:49 +0000 Re: rakudo-current loop 2-3 orders of magnitude slower than perl 5? by Parrot Raiser If Sun's propaganda about Dtrace : http://www.sun.com/bigadmin/content/dtrace/ is anywhere near true, it sounds as though it's a wheel we won't have to invent for Parrot/Rakudo. It is apparently also available for Mac OS (Leopard) http://tinyurl.com/2xas7q http://www.nntp.perl.org/group/perl.perl6.users/2009/06/msg1085.html Fri, 05 Jun 2009 02:26:27 +0000