Raku 中 (Any) 的含义是什么 - 特别是 ()? [英] What is the meaning of (Any) in Raku - specifically the ()?

问题描述

这是 Raku 的实验:

Here is an experiment with Raku:

> my $x
(Any)
> my $y=1
1
> my @a=[1, 2]
[1 2]
> my %h=a=>'b'
{a => b}
> say "nil" unless $x
nil

我可以看到 [] 表示数组文字，{} 表示哈希文字.

I can see that [] indicates an array literal, {} a hash literal.

我还可以看到 (Any) 的行为类似于 nil - 在上面显示的布尔上下文中返回 false.

I can also see that (Any) behaves like nil - returning false in the boolean context shown above.

我觉得 (Any) 很有趣.文档告诉我 Any 只是 Raku 中的神类之一.但是 Any 周围的括号 () 告诉我什么?

I find the (Any) interesting. The documentation tells me that Any is just one of the god classes in Raku. But what do the parenthesis () around Any tell me?

推荐答案

当您使用 REPL 时，使用 say 显示表达式的结果.say 函数调用表达式上的 .gist 函数.

When you use the REPL, the result of the expression is shown using say. The say function calls the .gist function on the expression.

Any 是一个类型对象.类型对象有一个 .gist 方法，将括号放在它们周围.

Any is a type-object. Type-objects have a .gist method that puts the parentheses around them.

put 函数与say 函数几乎相同，但它在表达式上调用了.Str 函数.这会产生警告，因为您无法真正对类型对象进行字符串化.观察差异:

The put function is almost the same as the say function, but it calls the .Str function on the expression. And that produces a warning, because you cannot really stringify a type object. Observe the difference:

$ raku -e 'say Any'
(Any)

# raku -e 'put Any'
Use of uninitialized value of type Any in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in block <unit> at -e line 1

请参阅类和对象、类型系统, 输入对象了解更多信息.

See Classes and Objects, Type System, Type Objects for more information.

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