Thanks. But I am actually confused by the use of colon in
Sort: { ... }
What does it mean in the above statement? I have done several experiments like:
p6 'say sort({$^a <=> $^b}, < 3 5 2 1>)' # (1 2 3 5)
p6 'say <3 5 2 1>.sort({$^a <=> $^b})' # it works.
p6 'say <3 5 2 1>.sort: {$^a <=> $^b}' # it works.
But I don't know what the colon here mean, although I know it works.
If I write something like this,
p6 'say sort: {$^a <=> $^b} < 3 5 2 1> ' # It doesn't work.
But why? Why the colon works in one form, but not in another form? So I want to
know the meaning of the colon when it works.
Regards
Xin
> On Jun 9, 2018, at 3:01 PM, Brandon Allbery <[email protected]> wrote:
>
> The ".=" operator means call the method on the right, with the thing on the
> left as invocant, and assign the result back to the thing on the left. So
>
> @x .= sort: ...
>
> is the same as
>
> @x = @x.sort(...)
>
> So you're being confused by the syntactic "magic" of ".=".
>
> On Sat, Jun 9, 2018 at 2:58 PM Xin Cheng <[email protected]
> <mailto:[email protected]>> wrote:
> I got the point for //.
>
> Another question is about calling the method sort with a code block. I can
> understand
>
> @x .= sort({ ... });
>
> But I don't quite understand why this form also works.
>
> @x .= sort: { ... };
>
> I look into the documentation for infix ":", https://docs.perl6.org/routine/:
> <https://docs.perl6.org/routine/:> , and it explains something like this:
>
> Used as an argument separator just like infix , and marks the argument to its
> left as the invocant. That turns what would otherwise be a function call into
> a method call.
>
> substr('abc': 1); # same as 'abc'.substr(1)
> Infix : is only allowed after the first argument of a non-method call. In
> other positions, it's a syntax error.
>
>
> How does the above explanation related to the case in hand @x .= sort: { ...
> }; ? Is sort an invocant? Or I miss something.
>
> Regards
>
> Xin
>
>
>
>> On Jun 9, 2018, at 12:44 PM, Brandon Allbery <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> More precisely, at that point you have a bunch of numbers, but possibly not
>> as many as expected if some of the components weren't numeric (or all of
>> them, as when there are files present that aren't the expected logs). Which
>> means some or all of those variables will be undefined instead of numbers.
>> The // replaces those with the following value (0), so they do something
>> sensible when sorted instead of producing warnings.
>>
>> On Sat, Jun 9, 2018 at 11:40 AM Xin Cheng <[email protected]
>> <mailto:[email protected]>> wrote:
>> This is very interesting. But I wonder how it works. I can understand the
>> first line
>>
>> my ($month, $day, $year, $hour, $minute, $second) = .comb(/\d+/);
>>
>> Which extract the variables from $_. What is the second line doing, it is
>> very concise.
>>
>> ($year // 0, $month // 0, $day // 0, $hour // 0, $minute // 0,
>> $second // 0, $_);
>>
>> Could somebody explain in some more words.? What does // do? Why it sorts
>> the array?
>>
>> Regards
>>
>> Xin
>>
>>> On Jun 9, 2018, at 12:51 AM, Timo Paulssen <[email protected]
>>> <mailto:[email protected]>> wrote:
>>>
>>> That's unnecessarily long and complicated, here's how you can do it much
>>> easier:
>>>
>>> @x.sort: {
>>> my ($month, $day, $year, $hour, $minute, $second) = .comb(/\d+/);
>>> ($year // 0, $month // 0, $day // 0, $hour // 0, $minute // 0,
>>> $second // 0, $_);
>>> }
>>>
>>> Trying it on some input data:
>>>
>>> cimtrak.log.06-08-2018_16:07:39.zip
>>> cimtrak.log.06-08-2018_17:07:39.zip
>>> cimtrak.log.07-08-2018_06:07:39.zip
>>> cimtrak.log.07-08-2018_16:07:39.zip
>>> cimtrak.log.12-08-2016_06:07:39.zip
>>> cookies
>>> asbestos
>>> fire engine
>>> perl6
>>> butterflies
>>>
>>> results in:
>>>
>>> asbestos
>>> butterflies
>>> cookies
>>> fire engine
>>> perl6
>>> cimtrak.log.12-08-2016_06:07:39.zip
>>> cimtrak.log.06-08-2018_16:07:39.zip
>>> cimtrak.log.06-08-2018_17:07:39.zip
>>> cimtrak.log.07-08-2018_06:07:39.zip
>>> cimtrak.log.07-08-2018_16:07:39.zip
>>>
>>> This is the schwartzian transform that was mentioned in another mail.
>>> why it wasn't actually shown, i have no clue :)
>>>
>>> Hope that helps
>>> - Timo
>>
>>
>>
>> --
>> brandon s allbery kf8nh sine nomine associates
>> [email protected] <mailto:[email protected]>
>> [email protected] <mailto:[email protected]>
>> unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net
>> <http://sinenomine.net/>
>
>
> --
> brandon s allbery kf8nh sine nomine associates
> [email protected] <mailto:[email protected]>
> [email protected] <mailto:[email protected]>
> unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net
> <http://sinenomine.net/>
