Re: <<>> question
On Thu, Oct 5, 2017 at 11:44 AM, Andy Bach wrote: > >> is ><<>> >> synonymous with >qw[] > ? `<<>>` is the same as `qqww<<>>` Which is short for `Q :qq :ww <<>>` the `:qq` is short for `:double`, that is it turns on double quote behaviour `:double` is short for `:scalar :array :hash :function :closure :backslash` the `:ww` is short for `:quotewords` which is similar to `:words` except it allows quoting to override where it splits the strings. `Q :quotewords < a 'b c' d >` turns into `( 'a', 'b c', 'd' )` Note that if you explicitly use `q` `qq` or `Q` that the brackets will not change how the construct works. (So even if you use `Q<<…>>` it will be the same as `Q'…'`)
RE: Perl 6 Object Construction - General Advice
Perl 6 (Timo),
In terms of new() uses… I’ve seen a clever use of new() that goes beyond
turning ‘positionals’ into ‘named’ in
https://github.com/retupmoca/P6-Net-SMTP/blob/master/lib/Net/SMTP.pm6. It
wraps methods for debugging. Pretty great, imo.
In terms of this thread’s subject… I am coming from a SysAdmin orientation,
where I implement large software suites with enough options to choke a pig.
I’m writing auto-deployment scripts that manage the trickier aspects of
installation & configuration. Also some Perl 6 apps supporting the products.
My primary desire is to specify defaults with ‘has’, which I consider concise,
convenient, easy to operate, and a great place to standardize specifying
attribute defaults. Then, while still in OC, have an opportunity to calculate
better attribute values before returning up the call stack to new() – all
without having to manage traits & defaults manually. Many of my classes simply
want to read a system command/file and provide an interface with accessors.
new() and its accompanying stack needs to slurp in all of the source
information, resulting in well-loaded attributes with accessors ready to answer
questions. If I can get new() to load up all attributes, then there will be no
need for a clunky new()->my-more-complete-init() in my classes. Hundreds of
classes…
Perl 6 provides a comprehensive simplest-case for Object Construction (OC) when
only attributes are specified -- defaults & traits are automatically managed.
#!/usr/bin/env perl6
class ITDT {
has $.itdt-path = '/usr/local/ITDT/itdt'; # nice!
has $.media-changer is required; # nice!
has %!robot = ( :ONE(1), :TWO(2) ); # nice!
method robot{ %!robot; }
}
my ITDT $tape_library_inventory .= new(:itdt-path,
:media-changer);
say 'itdt-path:= ' ~ $tape_library_inventory.itdt-path;
say 'media-changer = ' ~ $tape_library_inventory.media-changer;
print 'robot = '; dd $tape_library_inventory.robot;
# output:
itdt-path: = /opt/ITDT/itdt
media-changer = /dev/smc0
robot = Hash %!robot = {:ONE(1), :TWO(2)}
If you craft your own BUILD and/or TWEAK to perform more elaborate attribute
initializations, then you must manage all of that yourself, losing the elegant
‘has’ conveniences shown above.
I may have missed it. new(), BUILD(), TWEAK(), !initialize – none seem to
retain the magic of automatically managed defaults & traits. Please enlighten
me if it’s there and I’m not seeing it.
Thanks,
Mark
From: Timo Paulssen [mailto:t...@wakelift.de]
Sent: Sunday, October 1, 2017 16:56
To: perl6-users@perl.org
Subject: Re: Perl 6 Object Construction - General Advice
I wrote another more in-depth (but potentially less useful to you) mail about
this further down the thread, but I thought it'd be good to point this out near
the top:
I think the self.bless(|%args)!initialize idiom is a work-around for submethod
TWEAK not yet existing when this code was written. TWEAK works in a very
similar manner, with these differences:
1) Your "self" isn't fully built when TWEAK runs, therefore you can't call
regular methods on it
2) It will even be executed when a subclass of your class gets constructed,
whereas there's no simple way to get access to !initialize from a subclass.
3) TWEAK gets passed the named parameters that bless was called with
method new is useful only if you want to take positional parameters for the
.new — the default new you get from Mu only accepts named arguments and passes
them on as-is to self.bless. They then get passed to every BUILD and TWEAK in
the inheritance chain. The named parameters don't have to correspond to
attribute names, as you can do any private attribute assignment in TWEAK that
you like.
I hope that helps
- Timo
RE: Perl 6 Object Construction - General Advice
Timo, Oops. You're right. (I was unconditionally sending an argument in my test that zeroed it out the attribute that I was watching -- doh!) Now I can confirm that TWEAK is the logical place to further initialize attributes. I now see the light! Thanks, Mark -Original Message- From: Timo Paulssen [mailto:t...@wakelift.de] Sent: Thursday, October 5, 2017 13:56 To: Mark Devine ; perl6-users@perl.org Subject: Re: Perl 6 Object Construction - General Advice The main difference between BUILD and TWEAK is that BUILD will replace all default and requiredness handling, while TWEAK keeps it intact. TWEAK gets run after these aspects had their turn, so if you have an "is required" attribute that doesn't get a value passed, the BUILDALL process will throw the corresponding exception before TWEAK even gets invoked. Don't forget that with the assignment syntax for attribute defaults you're allowed to do calculations, too! You can even refer to other attributes in there, as long as you use the $!foo syntax. hope that helps - Timo
Re: Perl 6 Object Construction - General Advice
The main difference between BUILD and TWEAK is that BUILD will replace all default and requiredness handling, while TWEAK keeps it intact. TWEAK gets run after these aspects had their turn, so if you have an "is required" attribute that doesn't get a value passed, the BUILDALL process will throw the corresponding exception before TWEAK even gets invoked. Don't forget that with the assignment syntax for attribute defaults you're allowed to do calculations, too! You can even refer to other attributes in there, as long as you use the $!foo syntax. hope that helps - Timo
Re: <<>> question
> is
<<>>
> synonymous with
qw[]
?
IIUC - close, it like qqw:
https://docs.perl6.org/language/quoting#index-entry-quote_qqww-quote_
<<_>>-quote_«_»-Word_quoting_with_interpolation_and_quote_protection:_qqww
It's actually synonymous w/ qqww but depending upon your use of quotes w/i
the list elements, it works out the same as qqww ... except for that whole
"allomorph" aspect
> my $a = 42
42
> say qww{"$a b" c}.perl
("42 b", "c")
> say qw{"$a b" c}.perl
("\"\$a", "b\"", "c")
> say qqw{"$a b" c}.perl
("\"42", "b\"", "c")
> say qqww{"$a b" c}.perl
("42 b", "c")
> say <<"$a b" c>>.perl
("42 b", "c")
> say <<$a b c>>.perl
(IntStr.new(42, "42"), "b", "c")
> say qw{$a b c}.perl
("\$a", "b", "c")
> say qqw{$a b c}.perl
("42", "b", "c")
> say qqww{$a b c}.perl
("42", "b", "c")
> say qww{$a b c}.perl
("\$a", "b", "c")
On Wed, Oct 4, 2017 at 10:22 PM, Todd Chester wrote:
> On 10/04/2017 08:20 PM, Todd Chester wrote:
>
>> So in this context "{$x}" means insert (interpolate) a
>> variable into the list? I was thinking it meant to
>> insert a variable into a string. Did saying <<>>
>> automatically tell Perl6 that this was a list
>> and not a sting?
>>
>
>
> is
><<>>
> synonymous with
>qw[]
> ?
>
--
a
Andy Bach,
afb...@gmail.com
608 658-1890 cell
608 261-5738 wk
Re: <<>> question
MIME Is The Sacha Guitry Picture.
On Oct 4, 2017 8:23 PM, "Todd Chester" wrote:
> On 10/04/2017 08:20 PM, Todd Chester wrote:
>
>> So in this context "{$x}" means insert (interpolate) a
>> variable into the list? I was thinking it meant to
>> insert a variable into a string. Did saying <<>>
>> automatically tell Perl6 that this was a list
>> and not a sting?
>>
>
>
> is
><<>>
> synonymous with
>qw[]
> ?
>
