In Operators§
See primary documentation in context for infix but
multi infix:<but>(Mu , Mu ) is assoc<non>multi infix:<but>(Mu , Mu ) is assoc<non>
Creates a copy of $obj
with $role
mixed in. Since $obj
is not modified, but
can be used to create immutable values with mixins.
If $role
supplies exactly one attribute, an initializer can be passed in parentheses:
my = 'Life, the Universe and Everything' but Answerable(42);say ; # OUTPUT: «Life, the Universe and Everything»say .^name; # OUTPUT: «Str+{Answerable}»say .answer; # OUTPUT: «42»
Instead of a role, you can provide an instantiated object. In this case, the operator will create a role for you automatically. The role will contain a single method named the same as $obj.^name
and that returns $obj
:
my = 42 but 'forty two';say +33; # OUTPUT: «75»say .^name; # OUTPUT: «Int+{<anon|1>}»say .Str; # OUTPUT: «forty two»
Calling ^name
shows that the variable is an Int
with an anonymous object mixed in. However, that object is of type Str
, so the variable, through the mixin, is endowed with a method with that name, which is what we use in the last sentence.
We can also mixin classes, even created on the fly.
my = 12 but .new;say .Warbles.hi; # OUTPUT: «hello»say + 42; # OUTPUT: «54»
To access the mixed-in class, as above, we use the class name as is shown in the second sentence. If methods of the same name are present already, the last mixed in role takes precedence. A list of methods can be provided in parentheses separated by comma. In this case conflicts will be reported at runtime.