Short answer: use `%hash{$var}`, not `%hash<$var>`.
When they are not in position to be less-than and greater-than comparison
operators, the pair of left and right angle brackets are a circumfix operator
that work like Perl 5’s “quote word” op: `qw()`.
In Perl 6, `<>` are used a lot, including as a shortcut in hash lookups.
The full form for looking up the constant key `acme` in %Vendors is to use
curly braces and to *quote* the key (single or double quote), or have the key
in a variable:
say %Vendors{'acme’};
say %Vendors{"acme”};
my $k = ‘acme’;
say %Vendors{$k};
The shortcut of replacing the curly braces with angle brackets only works for
constant strings:
say %Vendors<acme>;
Advanced note: Since `<>` produce a *list* of quoted words, you can use them to
extract multiple values from a hash:
my ( $acct, $cn ) = %Vendors{"acme"}{"AccountNo", "ContactName”};
my ( $acct, $cn ) = %Vendors<acme><AccountNo ContactName>;
say [:$acct, :$cn].perl;
--
Hope this helps,
Bruce Gray (Util of PerlMonks)
> On Jan 11, 2019, at 1:25 PM, ToddAndMargo via perl6-users
> <[email protected]> wrote:
>
> On 1/11/19 11:16 AM, Bruce Gray wrote:
>>> On Jan 11, 2019, at 12:41 PM, ToddAndMargo via perl6-users
>>> <[email protected]> wrote:
>>>
>>> Hi All,
>>>
>>> How do I do a hash inside a hash?
>>>
>>> So far I have:
>>>
>>> $ p6 'my %Vendors=("acme" => ( "ContactName" => "Larry, "AccountNo" => 1234
>>> ) ); say %Vendors;'
>>> ===SORRY!=== Error while compiling -e
>>>
>>>
>>> I want to be able to have both a Contact Name and and AccountNo
>>> associated with each key in %Vendors.
>>>
>>>
>>> Many thanks,
>>> -T
>> First, you need a double-quote after `Larry` (before the comma) to fix the
>> syntax error:
>> perl6 -e 'my %Vendors=("acme" => ( "ContactName" => "Larry",
>> "AccountNo" => 1234 ) ); say %Vendors;'
>> At this point, you have a Hash of List of Pairs. To change it into a Hash of
>> Hashes, change the inner parens to curly braces:
>> perl6 -e 'my %Vendors=("acme" => { "ContactName" => "Larry",
>> "AccountNo" => 1234 } ); say %Vendors; say %Vendors<acme><AccountNo>;'
>> Those inner parens were acting as an anonymous list constructor, but you
>> needed an anonymous *hash* constructor, which is what the curly braces do
>> (when they are not doing their code-block-ish job).
>> You could have also used `Hash(…)` or `%(…)` instead of `{…}`, but `{…} is
>> shortest, and most traditional from Perl 5.
>> —
>> Hope this helps,
>> Bruce Gray (Util of PerlMonks)
>
> Hi Bruce,
>
> Thank you!
>
> This works,
>
> $ p6 'my $x="Ace"; my %Vendors=("acme" => { "ContactName" => "Larry",
> "AccountNo" => 1234 }, "Ace" => { "ContactName" => "Mo", "AccountNo" =>
> "A102" } ); say "%Vendors<Ace><ContactName>" ~ "\t" ~
> "%Vendors<Ace><AccountNo>";'
> Mo A102
>
>
> but I have to access it by a variable. "Now" what am I doing wrong?
>
> $ p6 'my $x="Ace"; my %Vendors=("acme" => { "ContactName" => "Larry",
> "AccountNo" => 1234 }, "Ace" => { "ContactName" => "Mo", "AccountNo" =>
> "A102" } ); say "%Vendors<$Ace><ContactName>" ~ "\t" ~
> "%Vendors<$Ace><AccountNo>";'
> Use of uninitialized value of type Any in string context.
>
>
> Many thanks,
> -T
