pack function

[TS xx]

Hi there,


I am trying to translate some old perl 5 code and I am having trouble with a 
particular line.


I used to have this in perl 5 to translate multibyte encoding like "%C3%A1":


$value =~ s/%([\dA-Fa-f][\dA-Fa-f])/pack("C", hex($1))/eg;


And I have translated the regex to something like this:


$value ~~ 
s:g/[\%(<[\dA..Fa..f]><[\dA..Fa..f]>)]+/{pack().decode()}/;


So I thought I could just change the base of the matching hex bytes and pack 
them, but the pack function is not working as it did in perl 5.

I tried many things and the closest solution I came to implied using the 
"template" argument of the pack function like this:

print pack("CC", 195, 161).decode();


This produces the character "á".


As you can see, I am adding as many "C"s as bytes there be. And I can count the 
elements in the regex match to construct the template, but I'm wondering if 
there is a better approach.


All of your comments on the matter would be much appreciated.


Kind Regards,

Emiliano

Re: Need help with Nil values

[TS xx]

Thanks,

That was it.
Somtimes I get confused with the way other languages treat undefined/null/nil 
values.

Regards,
Emiliano


From: Timo Paulssen 
Sent: Tuesday, February 23, 2016 2:20 AM
To: perl6-users@perl.org
Subject: Re: Need help with Nil values

Hello Emiliano,

In this case, I think you may want to use just "Str" instead of "Nil".
"Str" is the "type object" for Str objects, and you can check whether
it's a string like "foo" or just the Str object by checking $!value.defined.

There's a FAQ answer that's about "Any", but it works the same way for
"Str":

 http://doc.perl6.org/language/faq#What_is_%28Any%29%3F

And there's the classtut that talks about this a bit more in depth,
search for "type object":

 http://doc.perl6.org/language/classtut


I hope this'll get you towards your goal. If not, just keep asking :)

Have fun with Perl 6!
   - Timo

RE: Constants as members of a class

[TS xx]

Thanks Liz,

I will stick with the method aproach.

Regards,
Emiliano

> Subject: Re: Constants as members of a class
> From: l...@dijkmat.nl
> Date: Fri, 18 Dec 2015 23:49:53 +0100
> To: perl6-users@perl.org
> 
> > On 18 Dec 2015, at 23:37, TS xx <maringa...@hotmail.com> wrote:
> > 
> > Hi Liz, thanks for your reply.
> > 
> > Can I call the method from static context?
> > I mean: MyClass.FOO
> 
> In general, yes:
> 
> class A {
> method FOO { 42 }   # note the method doesn’t reference any attributes
> }
> say A.FOO;
> say A.new.FOO;  # also works on instances
> 
> You can even have a method to be called in case of a static (class) context, 
> and one to be called in the case of an instance:
> 
> class B {
> has $.FOO = 666;
> multi method FOO(B:U:) { 42 } # B is the class, :U is undefined, 
> final : for self
> multi method FOO(B:D:) { $!FOO }  # :D is defined, 
> }
> say B.FOO; # 42
> say B.new.FOO; # 666
> say B.new(FOO => 3.14).FOO;# 3.14
> 
> 
> Hope this helps!
> 
> 
> 
> Liz
  

RE: Constants as members of a class

[TS xx]

Hi Liz, thanks for your reply.

Can I call the method from static context?
I mean: MyClass.FOO



> Subject: Re: Constants as members of a class
> From: l...@dijkmat.nl
> Date: Fri, 18 Dec 2015 10:23:11 +0100
> To: perl6-users@perl.org
> 
> 
> > On 18 Dec 2015, at 03:46, TS xx <maringa...@hotmail.com> wrote:
> > 
> > Hello dear perl6 users,
> > 
> > I was in the need of declaring a member variable as a constant integer. 
> > After many syntax tryouts I came to this one:
> > 
> > class MyClass {
> > has int $.myConst;
> > 
> > method new () {
> > return self.bless();
> > }
> > 
> > submethod BUILD () {
> > constant $!myConst = 1;
> > }
> > 
> > method showMyConst () {
> > print $!myConst;
> > }
> > }
> > 
> > But I'm getting the followinf error message: "Twigil-Variable constants not 
> > yet implemented. Sorry."
> > 
> > The only place in the docs where I have found any reference to constants is 
> > in here: https://doc.perl6.org/language/variables#The_%3F_Twigil
> > But it's not what I am looking for :/
> > 
> > So my questions are:
> > Is the syntax right and the thing isn't implemented yet?
> > Is the syntax (or the full concept) wrong?
> > Do I have and old interpreter (This is perl6 version 2015.02 built on 
> > MoarVM version 2015.02)?
> 
> Yes, that is ancient in rakudo years  :-)
> 
> The question you should ask you: is the constant different for each 
> instantiated object or not.
> 
> If not, and you only need it inside of your class, you can just make it a 
> constant in the mainline of the class:
> 
> class MyClass {
> constant FOO = 42;
> …
> }
> 
> If you need to expose a method returning such a constant:
> 
> class MyClass {
> method FOO { 42 }
> …
> }
> 
> Otherwise, you probably just need to add an attribute.
> 
> 
> 
> Liz
  

RE: Constants as members of a class

[TS xx]

Thanks anyway

The new method is there just to state the example.

Date: Thu, 17 Dec 2015 22:58:32 -0500
Subject: Re: Constants as members of a class
From: awwa...@thelackthereof.org
To: maringa...@hotmail.com
CC: perl6-users@perl.org

Two things jump out at me. One is that I think you don't need that "new" 
method. Second -- yes, this is a very old interpreter. I unfortunately don't 
know about the twigil variable constant things.
--Brock

On Thu, Dec 17, 2015 at 9:46 PM, TS xx <maringa...@hotmail.com> wrote:



Hello dear perl6 users,

I was in the need of declaring a member variable as a constant integer. After 
many syntax tryouts I came to this one:

class MyClass {
has int $.myConst;

method new () {
return self.bless();
}

submethod BUILD () {
constant $!myConst = 1;
}

method showMyConst () {
print $!myConst;
}
}

But I'm getting the followinf error message: "Twigil-Variable constants not yet 
implemented. Sorry."

The only place in the docs where I have found any reference to constants is in 
here: https://doc.perl6.org/language/variables#The_%3F_Twigil
But it's not what I am looking for :/

So my questions are:
Is the syntax right and the thing isn't implemented yet?
Is the syntax (or the full concept) wrong?
Do I have and old interpreter (This is perl6 version 2015.02 built on MoarVM 
version 2015.02)?

Thanks to all.

Kind Regards,
Emiliano
  

  

Constants as members of a class

[TS xx]

Hello dear perl6 users,

I was in the need of declaring a member variable as a constant integer. After 
many syntax tryouts I came to this one:

class MyClass {
has int $.myConst;

method new () {
return self.bless();
}

submethod BUILD () {
constant $!myConst = 1;
}

method showMyConst () {
print $!myConst;
}
}

But I'm getting the followinf error message: "Twigil-Variable constants not yet 
implemented. Sorry."

The only place in the docs where I have found any reference to constants is in 
here: https://doc.perl6.org/language/variables#The_%3F_Twigil
But it's not what I am looking for :/

So my questions are:
Is the syntax right and the thing isn't implemented yet?
Is the syntax (or the full concept) wrong?
Do I have and old interpreter (This is perl6 version 2015.02 built on MoarVM 
version 2015.02)?

Thanks to all.

Kind Regards,
Emiliano
  

How to call a super class method?

[TS xx]

Hello fellow perl users,

I have been trying to understand perl 6 oop implementation, and one thing I 
still can't figure out is how to call super class methods from lower classes.
Let's say we have two classes, Person and Employee, and the method I am trying 
to access is the object constructor:

class Person {
method new ($argument) {
#do some things
}
}

class Employee is Person {
method new () {
#call here Person's method new
#do more things
}
}

Can I call the Person's constructor (in non static context), pass the required 
parameter and do more things before returning?


Regards,
Emiliano