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<main>
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<h1 id="返回值和错误处理"><a class="header" href="#返回值和错误处理">返回值和错误处理</a></h1>
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<p>飞鸽传书、八百里加急，自古以来，掌权者最需要的就是及时获得对某个事物的信息反馈，在此过程中，也定义了相应的应急处理措施。</p>
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<p>社会演变至今，这种思想依然没变，甚至来到计算中的微观世界，也是如此。及时、准确的获知系统在发生什么，是程序设计的重中之重。因此能够准确的分辨函数返回值是正确的还是错误的、以及在发生错误时该怎么快速处理，成了程序设计语言的必备功能。</p>
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<p>Go 语言为人诟病的其中一点就是 <strong><em>if err != nil {}</em></strong> 的大量使用，缺乏一些程序设计的美感，不过我倒是觉得这种简单的方式也有其好处，就是阅读代码时的流畅感很强，你不需要过多的思考各种语法是什么意思。与 Go 语言不同，Rust 博采众家之长，实现了颇具自身色彩的返回值和错误处理体系，本章我们就高屋建瓴地来学习，更加深入的讲解见<a href="https://course.rs/advance/errors.html">错误处理</a>。</p>
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<h2 id="rust-的错误哲学"><a class="header" href="#rust-的错误哲学">Rust 的错误哲学</a></h2>
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<p>错误对于软件来说是不可避免的，因此一门优秀的编程语言必须有其完整的错误处理哲学。在很多情况下，Rust 需要你承认自己的代码可能会出错，并提前采取行动，来处理这些错误。</p>
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<p>Rust 中的错误主要分为两类：</p>
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<ul>
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<li><strong>可恢复错误</strong>，通常用于从系统全局角度来看可以接受的错误，例如处理用户的访问、操作等错误，这些错误只会影响某个用户自身的操作进程，而不会对系统的全局稳定性产生影响</li>
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<li><strong>不可恢复错误</strong>，刚好相反，该错误通常是全局性或者系统性的错误，例如数组越界访问，系统启动时发生了影响启动流程的错误等等，这些错误的影响往往对于系统来说是致命的</li>
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</ul>
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<p>很多编程语言，并不会区分这些错误，而是直接采用异常的方式去处理。Rust 没有异常，但是 Rust 也有自己的卧龙凤雏：<code>Result<T, E></code> 用于可恢复错误，<code>panic!</code> 用于不可恢复错误。</p>
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