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Re: [naive] hash assingment

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From:
Marcel Timmerman
Date:
July 14, 2021 17:55
Subject:
Re: [naive] hash assingment
Message ID:
c5fd8908-e6f0-2f77-3c4b-2682b7069081@gmail.com
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


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