Hi all,
Andy Bach contacted me off list, to say my postscript comment about
"prepending" (versus "appending") to a hash object was nonsensical. I
agree.
Hashes in Raku/Perl6 are guaranteed to be unordered upon return. So
once they are declared, it doesn't make sense to think of them as a
(double-ended) linear array of pairs.
--Bill.
P.S. Link to the ",=" Postfix operator:
https://docs.raku.org/routine/,=
On Thu, Mar 19, 2020 at 10:33 AM William Michels wrote:
>
> Okay, here's another (simpler?) approach using the ",= " postfix operator:
>
> mbook:~ homedir$ perl6
> To exit type 'exit' or '^D'
> > my %stash;
> {}
> > my @monsters = << godzilla grendel wormface blob >>;
> [godzilla grendel wormface blob]
> > my @rabbits = << bugs peter easter >>;
> [bugs peter easter]
> > %stash ,= monsters => @monsters
> {monsters => [godzilla grendel wormface blob]}
> > %stash ,= :@rabbits
> {monsters => [godzilla grendel wormface blob], rabbits => [bugs peter easter]}
> > say %stash
> {monsters => [godzilla grendel wormface blob], rabbits => [bugs peter easter]}
> > exit
> mbook:~ homedir$ perl6 -v
> This is Rakudo version 2019.07.1 built on MoarVM version 2019.07.1
> implementing Perl 6.d.
>
> HTH, Bill.
>
> PS. Note, above shows how to 'postfix' (i.e. append), but I'm still
> unclear on how to prepend to a pre-existing hash.
>
>
> On Tue, Mar 17, 2020 at 11:15 AM Joseph Brenner wrote:
> >
> > Yes you're right: I could've sworn I tried that in the repl a minute
> > ago and it worked, but actually it's a no-op and appends nothing to
> > the hash.
> >
> > This is okay, doing it the other way (without the inner parens around
> > the colonpair) is not:
> >
> > ny %stash;
> > my @monsters = << godzilla grendel wormface blob >>;
> > my @rabbits = << bugs peter easter >>;
> >
> > %stash.append( (:@monsters) );
> > %stash.append( (:@rabbits) );
> >
> > say %stash;
> >
> >
> > On 3/17/20, Vadim Belman wrote:
> > >
> > > Joseph, you've got yourself into a trap I fell into yesterday.
> > > %stash.append( :@stuff ) syntax is about calling append method with a
> > > named
> > > parameter stuff whereas append works with positionals only. So, your case
> > > should be written:
> > >
> > > %stash.append( (:@stuff) );
> > >
> > > Which is apparently more cumbersome. In either case, use of colons is not
> > > always about saving a character or two. Sometimes it's about readability,
> > > sometimes about elegance. Overuse is surely bad, but overuse of anything
> > > is
> > > bad, for that matter. :)
> > >
> > > Best regards,
> > > Vadim Belman
> > >
> > >> On Mar 17, 2020, at 1:09 PM, Joseph Brenner wrote:
> > >>
> > >>> Though I've no idea what those colons are/are not doing.
> > >>
> > >> Those are "colon pairs" (which I've relearned around three times now...):
> > >>
> > >> https://docs.raku.org/language/glossary#index-entry-Colon_Pair
> > >>
> > >>
> > >> Except for this colon:
> > >>
> > >> %stash.append: (rocks => @rocks);
> > >>
> > >> Which is a short hand for this:
> > >>
> > >> %stash.append( (rocks => @rocks) );
> > >>
> > >> As an aside: it's a minor style point, but I think a lot of
> > >> us overuse that trick-- it saves a character, but the explicit
> > >> parens are more flexible.
> > >>
> > >> Notably this works fine, so here it doesn't even save any
> > >> characters:
> > >>
> > >> %stash.append( :@stuff );
> > >>
> > >>
> > >
> > >
