raku - 如何显示值的类型层次结构？

Question

在 Perl5 和 Moose 中，线性 isa 或线性化 isa 有助于理解类层次结构。

方法WHAT显示值的具体类型:

> 42.WHAT
(Int)

我如何显示类似的东西

> 42.hypothetical-type-hierarchy
(Int) ┬ is (Cool) ─ is (Any) ─ is (Mu)
      └ does (Real) ─ does (Numeric)

...可能为每个消耗的角色提供更多行？

编辑:具有两股角色的示例

class Beta {}
role Delta {}
role Gamma does Delta {}
role Eta {}
role Zeta does Eta {}
role Epsilon does Zeta {}
class Alpha is Beta does Gamma does Epsilon {}

# (Alpha) ┬ is (Beta)
#         ├ does (Gamma) ─ does (Delta)
#         └ does (Epsilon) ─ does (Zeta) ─ does (Eta)

my $ai = Alpha.new
$ai.^mro        # ((Alpha) (Beta) (Any) (Mu))

$ai.^roles      # ((Epsilon) (Zeta) (Eta) (Gamma) (Delta))
                # flat list, not two-element list of a tuple and triple‽

Answer 1

您可以查询元对象

> 42.^mro
((Int) (Cool) (Any) (Mu))

哪里 mro代表方法解析顺序和

> 42.^roles
((Real) (Numeric))

您可以通过副词 :local 控制返回哪些角色。 (排除从父类继承的角色 - 仅适用于类)和 :!transitive (排除通过另一个角色组成的角色 - 可用于角色和类)。

以下应该让你开始:

my $depth = 0;
for Alpha.^mro {
    say "is {.^name}";
    (sub {
        ++$depth;
        for @_ {
            say '  ' x $depth ~ "does {.^name}";
            &?ROUTINE(.^roles(:!transitive)); # recursive call of anon sub
        }
        --$depth;
    })(.^roles(:local, :!transitive));
}

鉴于您的示例代码略有修改

role Delta {}
role Gamma does Delta {}
role Eta {}
role Zeta does Eta {}
role Epsilon does Zeta {}
class Beta does Gamma {}
class Alpha is Beta does Gamma does Epsilon {}

它产生输出

is Alpha
  does Epsilon
    does Zeta
      does Eta
  does Gamma
    does Delta
is Beta
  does Gamma
    does Delta
is Any
is Mu