The Perl Short Questions Megathread: executable line noise

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Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

CanSpice posted:

If I have to go to my Programming Perl book to figure out what a special variable is for, I won't use it.

There are plenty of perfectly good arguments against just using special variables to golf, but does your system have neither perldoc nor google? perlvar is pretty readable and searchable

# ? Jan 12, 2010 21:52

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# ? May 17, 2024 04:04

Filburt Shellbach: Nov 6, 2007; Apni tackat say tujay aaj mitta juu gaa!

To be fair special variables are basically impossible to google for. The further explosion of punctuation is one reason I dislike Perl 6.

# ? Jan 12, 2010 22:17

Fenderbender: Oct 10, 2003; You have the right to remain silent.

Just going to reask this:

Fenderbender posted:

On that note, how would I go about altering the delagations (handles) for an attribute. My idea is to call the fields method on a Rose::DB::Object subclass and then push that all to a specific attribute's delegations. Haven't been able to figure out how to do this yet but it will solve a lot of upcoming issues I'm going to have to slave over if I don't do this now.

# ? Jan 12, 2010 22:30

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

Filburt Shellbach posted:

To be fair special variables are basically impossible to google for. The further explosion of punctuation is one reason I dislike Perl 6.

This is stupid. If you're within reach of Google, you're within reach of perlvar.

# ? Jan 12, 2010 22:40

Filburt Shellbach: Nov 6, 2007; Apni tackat say tujay aaj mitta juu gaa!

Triple Tech posted:

This is stupid. If you're within reach of Google, you're within reach of perlvar.

This is stupid. Google knows many orders of magnitude more about Perl than perldoc does.

# ? Jan 12, 2010 22:57

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

Did I mention the flip flop operator is cool as heck lately? Scraping function signatures from manpages:

code:

my ($start_decl, $end_decl) = (qr/[\s\*]$func\([^\)]/ , qr/\)/);
for (@lines) {
    if (/SYNOPSIS/ .. /DESCRIPTION/) {
        if (/$start_decl/ .. /$end_decl/) {
            $sig .= $_;
        }
    }
}

This replaced a whole bunch of stupid mess, and preserves whitespace to boot

# ? Jan 12, 2010 23:27

MolluskGoneBad: Feb 25, 2002

So I have a small project that needs to be distributed as a binary executable. It involves a lot of string manipulation.

It's been a few years since I programmed anything, I never did anything too complicated, and when I did it was C or C++. I was thinking I should use something friendlier for text than one of those, especially since the last developers of an analogous project used CPLAT and left an unmaintainable mess. Should I bother to learn Perl for this one, and is there an easy way to turn Perl scripts into binaries?

# ? Jan 13, 2010 06:00

ShoulderDaemon: Oct 9, 2003; support goon fund; Taco Defender

MolluskGoneBad posted:

is there an easy way to turn Perl scripts into binaries?

As long as you only want to distribute as a single file for ease-of-use purposes, you're probably best off using PAR to package your script and all its dependencies as a single executable; it works very well and is just about as seamless as you can get for users.

If you're hoping to get some sort of security from compiling to a binary, you're pretty much out of luck. But Perl isn't really any different from any other language in this regard; binaries from any language are not particularly hard to decompile for a motivated hacker.

# ? Jan 13, 2010 06:08

MolluskGoneBad: Feb 25, 2002

ShoulderDaemon posted:

As long as you only want to distribute as a single file for ease-of-use purposes, you're probably best off using PAR to package your script and all its dependencies as a single executable; it works very well and is just about as seamless as you can get for users.

If you're hoping to get some sort of security from compiling to a binary, you're pretty much out of luck. But Perl isn't really any different from any other language in this regard; binaries from any language are not particularly hard to decompile for a motivated hacker.

Ah perfect. Thanks.

Yeah, it's ease of use for our editors, some of whom require babysitting for anything trickier than "Click Here", some of whom would be wont to go and muck around with the scripts.

# ? Jan 13, 2010 16:12

CanSpice: Jan 12, 2002; GO CANUCKS GO

Triple Tech posted:

This is stupid. If you're within reach of Google, you're within reach of perlvar.

I can get perlvar on my iPhone?

# ? Jan 13, 2010 21:16

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

CanSpice posted:

I can get perlvar on my iPhone?

You sho can, little boy! Just point yer Safaris to here!

# ? Jan 13, 2010 21:29

Paradox: May 19, 2003

I have a script that calls tar in a call to system(). While the script was running I decided to kill it with control c. What it did wasn't what I expected. Instead of killing the script it just killed tar and went straight to the next line in the script.

What is the mechanism that is causing this behavior and how can I make the script die like I want it to?

# ? Jan 14, 2010 01:51

Mario Incandenza: Aug 24, 2000; Tell me, small fry, have you ever heard of the golden Triumph Forks?

http://perldoc.perl.org/perlfaq8.html#How-do-I-make-a-system()-exit-on-control-C%3f

# ? Jan 14, 2010 02:26

Kidane: Dec 15, 2004; DANGER TO MANIFOLD

If I may be so bold: http://search.cpan.org/~bingos/Archive-Tar-1.54/lib/Archive/Tar.pm

For quick and dirty stuff system() and `` are fine, for anything I actually need to maintain I will find a module that does what I need (or write one). The one exception of course is ssh, I haven't been able to successfully install any pure-perl version of ssh on any system ever.

# ? Jan 14, 2010 11:18

Paradox: May 19, 2003

Mario Incandenza posted:

http://perldoc.perl.org/perlfaq8.html#How-do-I-make-a-system()-exit-on-control-C%3f

Well, that's easy enough to fix. Thanks. But it's not clear to me why that has to be the case. Any thoughts?

Kidane posted:

If I may be so bold: http://search.cpan.org/~bingos/Archive-Tar-1.54/lib/Archive/Tar.pm

For quick and dirty stuff system() and `` are fine, for anything I actually need to maintain I will find a module that does what I need (or write one). The one exception of course is ssh, I haven't been able to successfully install any pure-perl version of ssh on any system ever.

I've seen this module before. I've never used it but I have looked it over. The problem with it is that I am dealing with many archives on the order of tens of gigabytes. By its own admission it is quite slow and I really don't want to have to spend more time taring and untaring than I have to. As it is this script will already be spending an hour or two in tar alone, per run. Plus, this script will always be running on a machine with tar installed. If that ever changes then I am willing to spend the time to move it over to Archive::Tar.

I'm curious about what problems you've encountered when trying to install Net: :ssh:

:Perl. Usually installing perl modules is quite easy. What were the unique troubles with this one?

# ? Jan 14, 2010 18:35

Kidane: Dec 15, 2004; DANGER TO MANIFOLD

Paradox posted:

I'm curious about what problems you've encountered when trying to install Net::Perl. Usually installing perl modules is quite easy. What were the unique troubles with this one?

It's a very complex pure perl implementation of SSH, it requires a ton of nonstandard math and encryption libraries which need to be manually downloaded from some website, yada yada. Apparently there's a debian package for it so that might actually work. Unfortunately when I had cause to use that module I was using a Redhat system and was unable to find a package for it via yum (there may be one now, I haven't dealt with this in over a year).

I ended up using Expect.pm, which worked great, but anything I ever write using Expect feels like a hack.

# ? Jan 14, 2010 22:31

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

Dicking around on irc a lil earlier, something interesting was noted...

pre:

17:39 <@Sartak> .pl my %r = (a => 'b'); delete $r{a}; my $as_string = %r; "<$as_string>"
17:39 <+cheesebot> <0>
17:39 <@Sartak> .pl my %r = (a => 'b'); my $as_string = %r; "<$as_string>"
17:39 <+cheesebot> <1/8>
17:40 <@Sartak> oh ok cool
17:40 <@Sartak> so an empty hash in scalar context is probably always 0, good
17:40 <@Sartak> but a non-empty hash in scalar context has hilarious semantics
17:40 <@Sartak> 1/8 is buckets used/allocated

# ? Jan 15, 2010 00:09

Filburt Shellbach: Nov 6, 2007; Apni tackat say tujay aaj mitta juu gaa!

Fix cheesebot already so I don't have to resort to <>, thanks.

# ? Jan 15, 2010 00:15

Mario Incandenza: Aug 24, 2000; Tell me, small fry, have you ever heard of the golden Triumph Forks?

Paradox posted:

Well, that's easy enough to fix. Thanks. But it's not clear to me why that has to be the case. Any thoughts?

It's because when you call system(), Perl does the equivalent of:

code:

$SIG{INT} = 'IGNORE';

So if you want your program to also catch those signals, you need to roll your own version of system() that doesn't fiddle with signal handlers.

# ? Jan 15, 2010 03:41

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

Are there any initiatives to get Perl5 or Perl6 onto .NET? It seems like there used to be for Perl5, but I think it's dead now.

I use C# at work and I'm a junkie now, I love it. Perl6 looks good in the way Duke Nukem Forever looks good.

# ? Jan 19, 2010 19:58

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

There's been more progress with 6 and with Parrot in the last year or so to the point that the Rakudo people think they can have something generally usable as a beta out by April ('Rakudo Star')

I haven't seen any plans to get it onto .Net though :/

# ? Jan 19, 2010 20:41

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

I've been listening the FLOSS Weekly podcast and I heard about IronPython, Jython, and IronRuby, etc... It made me think, wow, this is almost as bad/crazy as Parrot!

And now I feel like making a chart... Here are all the VMs, .NET, JVM, Parrot, and here are all the languages on top of it... And you can have crazy permutations!

C# on Parrot
IronPerl
JPHP

Although I don't know any sane person that would want to redo the abortion that is PHP. :smug:

# ? Jan 19, 2010 21:12

SynVisions: Jun 29, 2003

nevermind, got it

SynVisions fucked around with this message at 01:07 on Jan 21, 2010

# ? Jan 21, 2010 00:55

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Quick question about nested data structures: I have a hash that contains a bunch of data in various formats. This one part is a little tricky to wrap my brain around and I want to be sure what I'm doing makes sense. I am generating a 2D array that is not keyed off of integer values, but rather specific floats that each line of the matrix is keyed off of. I just want to be sure that I am accessing each individual scalar correctly. Basically what I have is:

code:

#if for example &example_hash{y_direction_array} = [0.01, 0.03, 0.08, 0.15]
#and &example_hash{x_direction_array} = [10, 20, 40, 70, 90]


for($i = 0; $i <= $#example_hash{y_direction_array}; $i++){
     for($j = 0; $j <= $#example_hash{x_direction_array}; $j++){
          $example_hash{matrix}{$example_hash{y_direction_array}[$i]}[$j] = some_number;
     }
}

Does this make sense? Is there a better way to go about this?

# ? Jan 21, 2010 20:45

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

Just because you can jam everything on to one line doesn't mean you have to.

What's matrix?

# ? Jan 21, 2010 21:07

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Triple Tech posted:

Just because you can jam everything on to one line doesn't mean you have to.

What's matrix?

How would you set it up? I'm really not that experienced with perl so I'm not really sure about the best way to show what I'm doing. matrix is my name for the 2D array that I'm trying to set up.

# ? Jan 21, 2010 21:15

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

Captain Frigate, could you describe the problem at a bit higher level of abstraction? I'm not quite sure what your goal is and I think we're having an x/y problem here ("I want to do x, y seems like a way to do x, I'll ask about y rather than x")

# ? Jan 21, 2010 21:30

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

So... you want to set up a 2D array. Super, that's pretty straight forward. And I'm guessing "matrix" is a key. It should really be quoted to make it more clear. Keys for hashes should be quoted since they are strings/scalars.

If you're doing a 2D array, why would you need a hash? If it's a single value hash/dictionary, that doesn't really make sense. Why not start just at the 2D array?

A 2D array in Perl is not unlike the way it's done in other languages. It's literally an array of arrays. Except that Perl does not support typed or first class 2D arrays (where it isn't an array OF arrays but a native, 2-dimensional data structure with two indices).

# ? Jan 21, 2010 21:37

Erasmus Darwin: Mar 6, 2001

Triple Tech posted:

If you're doing a 2D array, why would you need a hash?

I thought he explained that pretty clearly in his first post. One of the array indices is a float, not an integer.

# ? Jan 21, 2010 22:06

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Well the issue for me is that the array would look like this:

code:

matrix      10        20         40         70         90
0.01      (value)  (value)     (value)    (value)    (value)
0.03      (value)  (value)     (value)    (value)    (value)
0.08      (value)  (value)     (value)    (value)    (value)
0.15      (value)  (value)     (value)    (value)    (value)

So I am trying to make it use hashes so that I can iterate through the column key values (0.01, 0.03, etc) and the row key values (10, 20, 40 etc.) in a loop, using two arrays that I have that are [0.01, 0.03, 0.08, 0.15] and [10, 20, 40, 70, 90]. I'm just not sure how best to organize it.

# ? Jan 21, 2010 22:07

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

Well if both values aren't indices starting at zero, it's not really an array, is it? I mean, the storage mechanism could be anything (AoA) but accessing it is a whole different story.

Storing the 10th and 20th values of something results in what, a 20 element array or a 2 element array?

You want a hash of hashes, each key happening to be a number.

code:

$matrix{$x}{$y} = 3.14159

Unless these values are ordered in some significant way and you need easy access to these ordered slices...

Edit: Alternatively, you could have an x_lookup and a y_lookup and a 2D array for storing the values themselves. But that's three data structures instead of one monster one.

# ? Jan 21, 2010 22:24

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Triple Tech posted:

Well if both values aren't indices starting at zero, it's not really an array, is it? I mean, the storage mechanism could be anything (AoA) but accessing it is a whole different story.

Storing the 10th and 20th values of something results in what, a 20 element array or a 2 element array?

You want a hash of hashes, each key happening to be a number.
code:
$matrix{$x}{$y} = 3.14159
Unless these values are ordered in some significant way and you need easy access to these ordered slices...

Edit: Alternatively, you could have an x_lookup and a y_lookup and a 2D array for storing the values themselves. But that's three data structures instead of one monster one.

Well, they do have to be in ascending order, so what I have now are the two arrays, which give me the keys which happen to be numbers. I did it like that so I can iterate on them, making sure I get the numbers in the right order. So instead of directly iterating on the hash, I can iterate on the array, and use the value of the array as the key for the hash.

I'm also not sure what you mean by having an x_lookup and a y_lookup.

# ? Jan 21, 2010 22:39

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

If you value iterating over them cell by cell in order, then a 2D array is the way to go. What I meant by the lookups is that the array indices will have no semantic value to you. Hence the lookup table to provide a mapping between semantic index and array index.

code:

     10  20
.34   1   7
.72   2   5

Stored as

@matrix = [ [ 1, 7 ], [ 2, 5 ] ]

%x = { .34 => 0, .72 => 1 }
%y = {  10 => 0,  20 => 1 }

# ? Jan 21, 2010 22:49

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Triple Tech posted:

If you value iterating over them cell by cell in order, then a 2D array is the way to go. What I meant by the lookups is that the array indices will have no semantic value to you. Hence the lookup table to provide a mapping between semantic index and array index.
code:
     10  20
.34   1   7
.72   2   5

Stored as

@matrix = [ [ 1, 7 ], [ 2, 5 ] ]

%x = { .34 => 0, .72 => 1 }
%y = {  10 => 0,  20 => 1 }

Ok so what you have here is pretty much the opposite of what I have already as far as array vs hash goes, and I think I understand what you're doing, but how do you make sure to print out %x and %y in order?

# ? Jan 21, 2010 23:13

Triple Tech: Jul 28, 2006; So what, are you quitting to join Homo Explosion?

I'm assuming you have you x keys and your y keys already in an ordered list (or some sort of source). If not, then you need to keep sorting them if you iterate over the keys in the lookup hash or keep a regular list of values in their significant order.

There are so many ways of tackling this problem and the answer is IT DEPENDS on your use case. Are you building this structure, are you reading it, does it need to be fast, how are you reading it, etc. All of these things matter and I have no idea what you want.

PS - If building and arbitrary reading are all important, consider making or finding a matrix class that provides ordered and random access, implementation be damned.

# ? Jan 21, 2010 23:39

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

Captain Frigate posted:

Ok so what you have here is pretty much the opposite of what I have already as far as array vs hash goes, and I think I understand what you're doing, but how do you make sure to print out %x and %y in order?

I'll give you a hint based on how you do it with a one-dimensional hash:

code:

use warnings;
use strict;

my %foo = (0.01 => 'hello', 0.03 => 'how', 0.08 => 'are', 0.18 => 'you', 0.24 => 'doing');

print "$_ -> $foo{$_}\n" for keys %foo;
print "\n\n";
print "$_ -> $foo{$_}\n" for sort {$a <=> $b} keys %foo;

(see output: http://codepad.org/jMQq8eGq )

# ? Jan 22, 2010 01:09

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Well I appreciate the help, and I think I was able to improve some bits of the code with your advice! But I have another smallish question: I am running a number of for-loops iterating through these kinds of constructs and I keep running into a syntax error and I'm not sure what to do with it. The code looks like:

code:

for($i = 0; $i <= $#array_of_hashes_of_arrays; $i++;){
     for($j = 0; $j <= $#array_of_hashes_of_arrays[$i]{some_array}; $j++;){
          print $#array_of_hashes_of_arrays[$i]{some_array}[$j];
     }
}

I gives me a syntax error on the second for-loop but not the first one. Any idea why?

# ? Jan 22, 2010 16:27

Erasmus Darwin: Mar 6, 2001

You've got an extra semi-colon after $j++.

Edit: Actually, you've got an extra one after $i++, so that isn't the problem. It is unnecessary though. So it's probably the conditional clause that's causing trouble ("$j <= $#array_of_hashes_of_arrays[$i]{some_array}"). Let me do some testing.

# ? Jan 22, 2010 16:37

Captain Frigate: Apr 30, 2007; you cant have it, you dont have nuff teef to chew it

Erasmus Darwin posted:

You've got an extra semi-colon after $j++.

Edit: Actually, you've got an extra one after $i++, so that isn't the problem. It is unnecessary though. So it's probably the conditional clause that's causing trouble ("$j <= $#array_of_hashes_of_arrays[$i]{some_array}"). Let me do some testing.

Actually the first semicolon was a typo. When I leave out the semicolon on the second one I get an error, and when I put one on the first one I get an error. The way I have it now is:

code:

for($i = 0; $i <= $#array_of_hashes_of_arrays; $i++){
     for($j = 0; $j <= $#array_of_hashes_of_arrays[$i]{some_array}; $j++;){
          print $#array_of_hashes_of_arrays[$i]{some_array}[$j];
     }
}

I get errors that specifically mention the conditional and not any other part of it.

# ? Jan 22, 2010 16:42

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# ? May 17, 2024 04:04

Mithaldu: Sep 25, 2007; Let's cuddle.

You need to stop golfing your stuff so hard. Try it like this.

code:

my @array_of_hashes_of_arrays;

for my $i ( 0 .. $#array_of_hashes_of_arrays ){
    
    my $hash_ref = $array_of_hashes_of_arrays[$i];
    
    my $some_array_ref = $hash_ref->{some_array};
    my $last_index_of_some_array = $#{ $some_array_ref };
    
    for my $j ( 0 .. $last_index_of_some_array ){
        print $some_array_ref->[$j];
    }
}

I am in fact dumb. This is how you do it right:

code:

my @array_of_hashes_of_arrays;

for my $hash_ref ( @array_of_hashes_of_arrays ){
    
    my $some_array_ref = $hash_ref->{some_array};
    
    for my $value ( @{ $some_array_ref } ){
        print $value;
    }
}

Same thing as above, but actually readable.

Mithaldu fucked around with this message at 16:48 on Jan 22, 2010

# ? Jan 22, 2010 16:44

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > The Perl Short Questions Megathread: executable line noise

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