perl6/doc/lib/EnumMap
doc src
(title) class EnumMap
class EnumMap does Associative is Iterable { }
An EnumMap is an immutable mapping from string keys to values of arbitrary
types. It serves as a base class for L<Hash>, which is mutable.
In list context an EnumMap behaves as a list of L<Pair> objects.
Note that the order in which keys, values and pairs are retrieved is
generally arbitrary, but the keys , values and pairs methods
return them always in the same order when called on the same object.
my %e := EnumMap.new('a', 1, 'b', 2);
say %e.keys; # can print "a b\n" or "b a\n";
say %e.values; # prints "1 2\n" if the previous line
# printed "a b\n", "b a\n" otherwise
Methods
(head2) new
proto method new(*@, *%) {*}
multi method new(*@args, *%pairs)
Creates a new EnumMap from a list of alternating keys and values, with
the same semantics as described for hash assigning in the L<Hash>
documentation.
(head2) elems
method elems(EnumMap:D:) returns Int:D:
Returns the number of pairs stored in the EnumMap.
(head2) ACCEPTS
multi method ACCEPTS(EnumMap:D: Positional $topic)
multi method ACCEPTS(EnumMap:D: Cool:D $topic)
multi method ACCEPTS(EnumMap:D: Regex $topic)
multi method ACCEPTS(EnumMap:D: Any $topic)
Used in smart-matching if the right-hand side is an
EnumMap .
If the topic is list-like (L<Positional>), returns True if
any of the list elements exist as a key in the EnumMap.
If the topic is of type
Cool (strings, integers etc.),
returns True if the topic exists as a key.
If the topic is a regex, returns True if any of the keys match
the regex.
As a fallback, the topic is coerced to a list, and the
Positional
behavior is applied.
To retrieve a value from the EnumMap by key, use the
{ } postcircumfix
operator:
my $value = $enummap{$key};
To check whether a given key is stored in an EnumMap, modify the access
with the :exists adverb:
if %h{$key}:exists {
say "%h{} has key $key";
}
Note that Rakudo does not yet implement operator adverbs. As a workaround
you can use the non-standard exists method.
(head2) keys
method keys(EnumMap:D:) returns List:D
Returns a list of all keys in the EnumMap.
(head2) values
method values(EnumMap:D:) returns List:D
Returns a list of all values in the EnumMap.
(head2) pairs
method pairs(EnumMap:D:) returns List:D
Returns a list of all pairs in the EnumMap.
(head2) invert
method invert(EnumMap:D:) returns List:D
Returns a list of pairs, but with key and value exchanged.
(head2) kv
method kv(EnumMap:D:) returns List:D
Returns a list of keys and values interleaved.
EnumMap.new('a', 1, 'b', 2).kv # a, 1, b, 2 OR b, 2, a, 1
