Raku Books / Perl 6 at a Glance / Operators

Method postfixes

There are a few syntactical elements in Perl 6, which start with a dot. These operators might look like a postfix operator, but they all are the forms of the calling a method on an object. Unlike Perl 5, the dot operator does not do any string concatenation.

.method calls a method on a variable. This works with both real objects and with those variables, which are not instances of any class, for example, built-in types like integers.

say "0.0".Numeric; # 0
say 42.Bool;       # True

class C {
    method m() {say "m()"}
}
my $c = C.new;
$c.m(); # m()

CodeBlockPlaceholder2raku-nobrowser class D { }

class C { method m() { return D.new; } }

my $o = C.new; say $o.WHAT; # (C)

$o.=m(); say $o.WHAT; # (D) CodeBlockPlaceholder3

.^method calls a method on the object’s metaobject. A metaobject is an instance of the HOW class and contains some additional information about the object. The following two operations, applied to the $i variable, are equivalent and print the list of the methods available for the Int variables.

my Int $i;
say $i.^methods();
say $i.HOW.methods($i);

↻ Runs in Rakudo; the in-browser engine (Raku++) doesn’t support this program yet — see the expected output above.

CodeBlockPlaceholder5raku-nobrowser class C { method m() {‘m’} }

my $c = C.new(); say $c.?m(); # m say $c.?n(); # Nil CodeBlockPlaceholder6

.+method makes an attempt to call all the methods with the given name on an object. This may be used, for example, when an instance is a part of the hierarchy of objects and its parent also has a method with the same name. More on the classes and class hierarchy in Chapter 4.

class A {
    method m($x) {"A::m($x)"}
}
class B is A {
    method m($x) {"B::m($x)"}
}

my $o = B.new;
my @a = $o.+m(7);
say @a; # Prints [B::m(7) A::m(7)]

↻ Runs in Rakudo; the in-browser engine (Raku++) doesn’t support this program yet — see the expected output above.

Here, the $o object has the m method in both its own class B and in its parent class A. The $o.+m(7) calls both of the methods and puts their results in a list.

If the method is not defined, an exception will be thrown.

.*method calls all the methods with the given method name and returns a parcel with the results. If the method is not defined, an empty list is returned. In the rest, it behaves like the .+ operator.

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