. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 6.5 Coroutines and concurrency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 6.6 Integration are almost as simple as synchronous code, but without the expense of a thread. They also make concurrency easier to reason about by reducing the number of places where a context switch can happen. Example: coroutines: – are generally faster. – can use async for and async with statements which make some patterns much simpler. – do not run at all unless you await or yield them. Decorated coroutines can start

IOStream connection factory tornado.tcpserver — Basic IOStream-based TCP server Coroutines and concurrency tornado.gen — Generator-based coroutines tornado.locks – Synchronization primitives tornado.queues Examples Coroutines Native vs decorated coroutines How it works How to call a coroutine Coroutine patterns Calling blocking functions Parallelism Interleaving Looping Running in the background Queue example are almost as simple as synchronous code, but without the expense of a thread. They also make concurrency easier [https://glyph.twistedmatrix.com/2014/02/unyielding.html] to reason about by reducing the

look like?  It has little technical debt.  It is built according to good, extensible design patterns and uses well-accepted standards.  It is loosely coupled—pieces of it can be easily exchanged good monitoring tools in place.  It is coded in a way that resists hard-to-find defects like concurrency errors. Build Versus Buy Everyone knows that in every case under the sun, in any example one custom development is falling: More and more logic is abstracted away by frameworks and design patterns. Incremental delivery and staged investments reduce cost and risk.  Custom code is almost not

误： $ cargo run Compiling enums v0.1.0 (file:///projects/enums) error[E0004]: non-exhaustive patterns: `None` not covered --> src/main.rs:3:15 | 3 | match x { | ^ pattern 出现的特定情况，不正确的代码会直接编 译失败并提供解释问题的错误信息。因此，你可以在开发时修复代码，而不是在部署到生产环 境后修复代码。我们给 Rust 的这一部分起了一个绰号无畏并发（fearless concurrency）。无畏 并发令你的代码免于出现诡异的 bug 并可以轻松重构且无需担心会引入新的 bug。 注意：出于简洁的考虑，我们将很多问题归类为并发，而不是更准确的区分并发和/或 并行。对于本章，当我们谈到并发时，请自行脑内替换为 375/562Rust 程序设计语言 简体中文版 这正是 Rust 的 async 抽象所提供的。不过在讲解它们在实践中如何工作之前，让我们稍微绕 个远路来了解一下并行（parallelism）和并发（concurrency）的区别。 并行与并发 在上一章中，我们大致将并行和并发视为可以互换的概念。但现在我们需要更加精确地区分它 们，因为它们的区别将在实际工作中显现出来。 思考一下不同的团队分割方法来开发

Redefining Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 12.6 Design Patterns with Parametric Methods . . . . . . . . . . . . . . . . . . . . . . . 160 12.7 Parametrically-constrained by the longest sequence of 8-bit code units that matches the start of one of the following bit patterns (each x can be 0 or 1): • 0xxxxxxx; • 110xxxxx 10xxxxxx; • 1110xxxx 10xxxxxx 10xxxxxx; • 11110xxx do know it will look something like YYYY-MM-DD. Regular expressions allow you to specify these patterns and search for them. Julia uses version 2 of Perl-compatible regular expressions (regexes), as

Redefining Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 12.6 Design Patterns with Parametric Methods . . . . . . . . . . . . . . . . . . . . . . . 160 12.7 Parametrically-constrained by the longest sequence of 8-bit code units that matches the start of one of the following bit patterns (each x can be 0 or 1): • 0xxxxxxx; • 110xxxxx 10xxxxxx; • 1110xxxx 10xxxxxx 10xxxxxx; • 11110xxx do know it will look something like YYYY-MM-DD. Regular expressions allow you to specify these patterns and search for them. Julia uses version 2 of Perl-compatible regular expressions (regexes), as

Redefining Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 13.6 Design Patterns with Parametric Methods . . . . . . . . . . . . . . . . . . . . . . . 168 13.7 Parametrically-constrained by the longest sequence of 8-bit code units that matches the start of one of the following bit patterns (each x can be 0 or 1): • 0xxxxxxx; • 110xxxxx 10xxxxxx; • 1110xxxx 10xxxxxx 10xxxxxx; • 11110xxx do know it will look something like YYYY-MM-DD. Regular expressions allow you to specify these patterns and search for them. Julia uses version 2 of Perl-compatible regular expressions (regexes), as

Redefining Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 13.6 Design Patterns with Parametric Methods . . . . . . . . . . . . . . . . . . . . . . . 168 13.7 Parametrically-constrained by the longest sequence of 8-bit code units that matches the start of one of the following bit patterns (each x can be 0 or 1): • 0xxxxxxx; • 110xxxxx 10xxxxxx; • 1110xxxx 10xxxxxx 10xxxxxx; • 11110xxx do know it will look something like YYYY-MM-DD. Regular expressions allow you to specify these patterns and search for them. Julia uses version 2 of Perl-compatible regular expressions (regexes), as

Redefining Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 13.6 Design Patterns with Parametric Methods . . . . . . . . . . . . . . . . . . . . . . . 168 13.7 Parametrically-constrained by the longest sequence of 8-bit code units that matches the start of one of the following bit patterns (each x can be 0 or 1): • 0xxxxxxx; • 110xxxxx 10xxxxxx; • 1110xxxx 10xxxxxx 10xxxxxx; • 11110xxx do know it will look something like YYYY-MM-DD. Regular expressions allow you to specify these patterns and search for them. Julia uses version 2 of Perl-compatible regular expressions (regexes), as

Redefining Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 13.6 Design Patterns with Parametric Methods . . . . . . . . . . . . . . . . . . . . . . . 168 13.7 Parametrically-constrained by the longest sequence of 8-bit code units that matches the start of one of the following bit patterns (each x can be 0 or 1): • 0xxxxxxx; • 110xxxxx 10xxxxxx; • 1110xxxx 10xxxxxx 10xxxxxx; • 11110xxx do know it will look something like YYYY-MM-DD. Regular expressions allow you to specify these patterns and search for them. Julia uses version 2 of Perl-compatible regular expressions (regexes), as