perl6 “P6opaque, Str"vs 简单的“Str"类型 [英] perl6 "P6opaque, Str" vs simple "Str" types

问题描述

我试图从用户输入中获取一个列表，执行我常用的代码，但有时会由于此错误而意外失败:

I was trying to obtain a list from user input doing my usual codes, but sometimes it fails unpredictably due to this error:

This type cannot unbox to a native integer: P6opaque, Str

代码行是

my @a = prompt("Enter list: ").words || (1,2,3);

只有当我只输入一个数字时才会失败.

It failed only if I enter only one number.

何时将 Str 转换为P6opaque, Str"?没有用户意识?我不能使用 +@a[0] 或 @a[0].Int 来转换这个P6opaque, Str"到一个 Int.我在这里错过了什么?

When is a Str converted to "P6opaque, Str" without user awareness? I cannot use +@a[0] or @a[0].Int to convert this "P6opaque, Str" to an Int. What am I missing here?

推荐答案

TL;DR 提到 P6Opaque 主要是一个红鲱鱼.某些代码试图将字符串分配给 int.您需要先将其强制为 Int.我知道你已经试过了.剩下的就是找出需要完成的地方.希望这个答案能引导我们到那里.

TL;DR The mention of P6Opaque is a mostly a red herring. Some code is trying to assign a string to an int. You'll need to coerce it to an Int first. I know you've tried that. All that's left is to find out where it needs to be done. Hopefully this answer will guide us there.

将字符串分配给 Int 或 int 是错误的:

It's an error to assign a string to an Int or an int:

my Int $a = '1'; # Type check failed ... expected Int but got Str
my int $a = '1'; # This type cannot unbox to a native integer: P6opaque, Str

分配给 Int 的错误被高级机器捕获，它以高级错误消息进行响应.对于 int，它是低级机制，它以低级消息进行响应.我们将在下面仔细研究这种差异，但就解决您的问题而言，这是一个红鲱鱼.

The error on assigning to an Int is caught by high level machinery which responds with a high level error message. For int it's low level machinery which responds with a low level message. We'll take a closer look at this difference below, but it's a red herring as far as fixing your problem is concerned.

要解决此问题，您需要找到字符串被分配或绑定到具有本机整数类型约束(如 int)的变量的位置，然后在分配之前使用如下内容进行强制:

To fix this problem you'll need to find where a string is being assigned or bound to a variable with a native integer type constraint like int and then coerce before the assignment with something like this:

my int $a = +'1' # Works

我知道您已经尝试过类似的方法.我不知道为什么它不起作用，因为您尚未共享导致问题的代码部分.

I know you've tried something like that. I don't know why it hasn't worked because you haven't yet shared the part of your code that's causing the problem.

必须直接在您的代码中使用本机整数(即您明确指定本机整数类型，全小写类型，如 int、int32、uint 等)或在您的代码使用的某些代码中.

There must be some use of a native integer that's either directly in your code (i.e. you explicitly specified a native integer type, an all lowercase type like int, int32, uint etc.) or in some code your code uses.

因此，请先搜索您的代码.

So, search your code first.

如果您仍然没有找到它，那么请分享足够多的代码以便我们重现问题，最好是在阅读 StackOverflow 的新命名/URL 页面之后 如何创建一个最小的、可重现的示例.TIA.

If you still haven't found it, then please share enough of your code that we can reproduce the problem, preferably after reading StackOverflow's freshly Named/URLed page How to create a Minimal, Reproducible Example. TIA.

P6opaque, Str" vs 简单的Str"类型

"P6opaque, Str" vs simple "Str" types

他们是一样的.P6opaque, Str 是对与 Str 完全相同的类型的引用.

They're the same. P6opaque, Str is a reference to exactly the same type as Str.

Str 何时在用户不知情的情况下转换为P6opaque, Str"?

When is a Str converted to "P6opaque, Str" without user awareness?

不是.

引用 是repr和本地表示:

Quoting is repr and native representations:

P6opaque 是 Perl 6 中所有对象使用的默认表示.

P6opaque is the default representation used for all objects in Perl 6.

表示是在计算机内存中表示类型的一组规则.

A representation is a set of rules for representing a type in a computer's memory.

与 P6 对象相关的错误通常由 P6 语言/编译器的高级前端"处理.高级错误消息没有提及表示，因为大多数普通 P6 对象都具有相同的表示 (P6Opaque)，即使它们没有，表示仍然不相关.

Errors related to P6 objects are generally handled by the high level "front end" of the P6 language/compiler. High level error messages don't mention representations because most ordinary P6 objects have the same one (P6Opaque) and even when they don't the representation still won't be relevant.

但这里我们正在处理一个由 MoarVM 处理的错误.

But here we're dealing with an error handled by MoarVM.

如果 MoarVM 的错误消息被认为不相关，则不会提及该表示.例如:

MoarVM's error messages don't mention the representation if it's deemed irrelevant. For example:

my int64  $a = 2⁶³

显示 a Moar 错误关于表示为 P6bigint 的 bigint 类型的消息:

Cannot unbox 64 bit wide bigint into native integer

此错误消息未提及表示形式 (P6bigint).

This error message doesn't mention the representation (P6bigint).

但是 MoarVM 对尝试将整数以外的任何内容放入本机整数的响应是 一个 MoarVM 异常，确实提到了这种表示.例如，如果您尝试分配一个 Str，它是:

But the MoarVM response to trying to put anything other than an integer into a native integer is a MoarVM exception which does mention the representation. For example, if you attempt to assign an Str it's:

This type cannot unbox to a native integer: P6opaque, Str

如果有人不知道表述，这个消息有点不透明，又名长期协议.但是，在删除表示消除了混淆的同时，它也删除了可能很重要的信息:

If someone doesn't know about representations, this message is bit opaque aka LTA. But while removing the representation removes the confusion it also removes information that might be important:

This type cannot unbox to a native integer: Str

我不相信这实际上更好和/或值得，但如果您对此有强烈的看法，请随时使用 LTA 标签提交有关此问题的 MoarVM 错误.

I'm not convinced that that is actually better and/or worthwhile but if you feel strongly about it, feel free to file a MoarVM bug about this with an LTA tag.

这篇关于perl6 “P6opaque, Str"vs 简单的“Str"类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！