thank
It is now more clear.
And I like this notation |%a<column1> ==> map({.sqrt});
less is more sometimes
On Wed, Jul 14, 2021 at 4:41 PM Daniel Sockwell <dan...@codesections.com>
wrote:
> To expand slightly on what Clifton said, the reason that
>
> > %a<column3> = %a<column1>.map: { .sqrt };
> > # (1 1.4142135623730951 1.7320508075688772 2 2.23606797749979)
>
> does what you mean but
>
> > %a{'column1'} ==> map( { .sqrt } )
> > # (2.23606797749979)
>
> does not is that the method .map maps over *each item* in the Array,
> whereas
> ==> map maps over the Array as *one collection*. When taking the square
> root,
> an Array needs to be treated as an number, which for Raku means treating
> it as
> a count of how many elements it has (i.e., its length).
>
> So `%a{'column1'} ==> map({.sqrt})` is the same as
> `%a{'column1'}.elems.map({.sqrt})`
>
> If want to map over each item in the Array when using the ==> operator,
> you need to
> slip the items out of the Array before feeding them on. You can do that
> with either
> of the following (equivalent) lines:
>
> > %a{'column1'}.Slip ==> map({.sqrt});
> > |%a{'column1>'}==> map({.sqrt});
>
> (Also, you may already know this, but when the keys of your hash are
> strings, you
> can write %a<column1> instead of %a{'column1'} )
>
> Hope that helps!
>
> –codesections
>
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Aureliano Guedes
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