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Re: [naive] hash assingment

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From:
Aureliano Guedes
Date:
July 14, 2021 19:38
Subject:
Re: [naive] hash assingment
Message ID:
CAG9gabQYrM=Jiad1PJhx15pMoB-u=YRRYz5sk9ZvyODro2rK9g@mail.gmail.com
Yes, it does help.

So, to create a new pair *k*ey/*v*alue on the fly in a hash given another
pair k/v, or even modify it will be a problem, then maybe will better
use an array instead of a hash.

> my @a = [ 1..5, 'a'..'e' ]
[1..5 "a".."e"]
> @a[2] = [@a[0][] ==> map( { .sqrt} )]
> @a[2]
[1 1.4142135623730951 1.7320508075688772 2 2.23606797749979]

On Wed, Jul 14, 2021 at 3:55 PM Clifton Wood <clifton.wood@gmail.com> wrote:

> Unfortunately, given this:
>
> my %a = 'column1' => [1...5], 'column2' => ['a'...'e']
>>
>
> column1 and column2 cannot yet be referenced to create column3.
>
> You need to do that on another line:
>
> %a<column3> = %a<column1>.map: { .sqrt };
>
> Which gives the following:
>
> > %a.gist.say
> # {column1 => [1 2 3 4 5], column2 => [a b c d e], column3 => (1
> 1.4142135623730951 1.7320508075688772 2 2.23606797749979)}
>
> Does this help?
>
> - X
>
> On Wed, Jul 14, 2021 at 2:32 PM Aureliano Guedes <
> guedes.aureliano@gmail.com> wrote:
>
>> Thanks JJ, Marcel, Matthew
>>
>> That's help me a lot to understand how Raku hashes work;
>> Little bit complex compared to Perl5.
>>
>> But now I got another question
>>
>> given
>> my %a = 'column1' => [1...5], 'column2' => ['a'...'e']
>>
>> I want to calculate sqrt and store in column3
>> > %a{'column1'}.map({ .sqrt })
>> (1 1.4142135623730951 1.7320508075688772 2 2.23606797749979)
>> > %a{'column3'} = %a{'column1'}.map({ .sqrt })
>> > %a{'column3'}
>> (1 1.4142135623730951 1.7320508075688772 2 2.23606797749979)
>> > %a.keys
>> (column1 column3 column2)
>>
>> But...
>> > %a{'column1'} ==> map( { .sqrt } )
>> (2.23606797749979)
>>
>> How I access the array's values within the hash?
>>
>>
>> On Wed, Jul 14, 2021 at 2:55 PM Marcel Timmerman <mt1957@gmail.com>
>> wrote:
>>
>>> On 7/14/21 7:43 PM, Aureliano Guedes wrote:
>>>
>>> Hi all,
>>>
>>> Trying to knowing a little bit more about Raku lang, I decided to write
>>> a simple (as possible) lib to became similar to R/dplyr or Python/Pandas
>>> method to data wrangle.
>>>
>>> So, Raku gives us the possibility to deal with data in a functional way,
>>> given the native pipe operator, which is wonderful for newbies.
>>> > @a = 1..100
>>> > @a ==> map( { .sqrt } )
>>> > @a ==> HYPER( { .sqrt } ) # faster map
>>> Even it is being *too verbose*, is good enough for the first moment to
>>> a data scientist.
>>>
>>> So I'm trying to decide the best way to abstract columns.
>>> First, I decide to use a hash where the key is the column name and the
>>> value is the oriented list ou array.
>>>
>>> > my %a = {'column1' => [1...5], 'column2' => ['a'...'e']}
>>> Potential difficulties:
>>>     Useless use of hash composer on right side of hash assignment; did
>>> you mean := instead?
>>>     at line 2
>>>     ------> <BOL>⏏<EOL>
>>> {column1 => [1 2 3 4 5], column2 => [a b c d e]}
>>>
>>> It is a warning, not an error!
>>>
>>> But let's obey the warning.
>>> > my %a = {'column1' := [1...5], 'column2' := ['a'...'e']}
>>> ===SORRY!=== Error while compiling:
>>> Cannot use bind operator with this left-hand side
>>> ------> n1' := [1...5], 'column2' := ['a'...'e']⏏}
>>>
>>>
>>> ':=' in the error is meant to replace the assignment so you are binding
>>> directly to the hash.
>>> So write,
>>>
>>> my %a := {'column1' => [1...5], 'column2' => ['a'...'e']}
>>>
>>> Without the binding you could write instead
>>>
>>> my %a = 'column1' => [1...5], 'column2' => ['a'...'e']
>>>
>>> See also https://docs.raku.org/type/Hash and
>>> https://docs.raku.org/routine/:=
>>>
>>>
>>> Now we got an error.
>>>
>>> Someone may explain me why I got this error??
>>>
>>> Thanks in advance
>>>
>>>
>>>
>>>
>>> --
>>> Aureliano Guedes
>>> skype: aureliano.guedes
>>> contato:  (11) 94292-6110
>>> whatsapp +5511942926110
>>>
>>>
>>>
>>
>> --
>> Aureliano Guedes
>> skype: aureliano.guedes
>> contato:  (11) 94292-6110
>> whatsapp +5511942926110
>>
>

-- 
Aureliano Guedes
skype: aureliano.guedes
contato:  (11) 94292-6110
whatsapp +5511942926110

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