如何将使用三元运算符的 C++ 代码移植到 Rust? [英] How can I port C++ code that uses the ternary operator to Rust?

问题描述

如何将此 C++ 代码移植到 Rust:

How can I port this C++ code to Rust:

auto sgnR = (R >= 0.) ? 1. : -1.;

我看过一些带有 match 关键字的例子，但我不明白它是如何工作的.

I have seen some examples with the match keyword, but I don't understand how it works.

推荐答案

Rust 没有三元运算符，因为它不需要.一切都会评估为某个值，if/else 语句也不例外:

Rust does not have the ternary operator because it's not needed. Everything evaluates to some value, and if / else statements are no exception:

let r = 42.42;
let sgn_r = if r >= 0. { 1. } else { -1. };

您会注意到，我还将您的变量名称更改为惯用的 Rust.标识符使用snake_case.

You'll note that I've also changed your variable names to be idiomatic Rust. Identifiers use snake_case.

不要被 Rust 确实 拥有的 ? 操作符弄糊涂了.这是 称为尝试操作符"，用于传播错误.

Do not be confused by the ? operator that Rust does have. This is called the "try operator" and is used to propagate errors.

特别是对于这个代码，您可能应该使用f64::signum:

Specifically for this code, it's likely you should use f64::signum:

let r = 42.42_f64;
let sgn_r = r.signum();

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