Perl 6正则表达式与语法解析深入指南：构建强大解析器

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"《Perl 6正则表达式与文法解析：递归下降入解析》是一本由Perl 6专家Moritz Lenz编写的教程，他也是Rakudo核心贡献者之一。本书旨在引导读者理解和掌握Perl 6编程语言中的正则表达式（Regexes）和语法解析（Grammars）。从基础的正则表达式概念开始，作者逐步深入探讨如何在Perl 6中有效地运用这些技术。书中首先介绍了正则表达式的搜索、解析和验证功能，强调了Perl 6中的Grammar扩展，使其成为解析任务的理想工具。作者解释了正则表达式的阅读性和灵活性，以及它们相对于传统Perl兼容正则表达式的增强特性，如更好的可重用性和回溯控制。通过这些，读者能够学会编写完整的解析器，处理各种复杂的输入格式。随着内容的深化，书中涵盖了如何构建可复用的命名正则表达式和语法，这对于在更大的文法结构中实现代码复用至关重要。对于更复杂的数据格式，作者展示了如何设计和实现解析器，包括错误报告和实际案例研究，使理论知识得以实际应用。《Perl 6正则表达式与文法解析》不仅是寻找文本模式、验证输入的有效工具，更是带领读者步入高级解析技术的桥梁。它适合对Perl 6感兴趣的开发者、语言学习者，以及希望提升正则表达式能力的专业人士。通过跟随本书的指导，读者将掌握如何在Perl 6的世界中优雅地进行文本处理和复杂数据解析，从而提升编程技能和项目效率。"

Validation

Most applications face untrusted user input. Web applications in particular

are confronted with a lot of untrusted input. This input must be validated

before applying any further logic to it or storing it in, for example, a database.

Regexes are a common first step toward validation. They make it trivial

to check for simple things such as digits, and verifying the minimal and

maximal length of input. At the same time, they allow the programmer to

do much more precise and sophisticated checks.

All the web application programmer needs to provide is a regex and

associate it with an input field. The web framework can then validate form

input against all configured regexes and automatically generate error

messages for the end user, so that the web application programmer does

not need to deal with the workflow of rejecting the input and re-generating

the form.

Parsing

Regexes alone are not very suitable for parsing complex input data. Perl 6,

however, adds some features that make it well suited for this task. These

extensions include easy-to-use backtracking control and composability

through named regexes.

The result of a successful regex match is a match object, which contains

all the necessary metadata to extract the interesting bits from the parsed text.

There are also some features that make it easy to turn a match object into an

abstract syntax tree or AST, a data structure suitable for use outside the parser.

Chapter 1 What are regexes andgrammars?

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Perl 6正则表达式与语法解析深入指南：构建强大解析器

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