Snobol4【1】 语言实战：URL【2】 域名【3】合法性验证【4】实战
Snobol4 是一种古老的编程语言，最初在1962年由David J. Farber、Ralph E. Griswold 和 Ivan P. Polonsky 在贝尔实验室开发。它以其简洁的语法和强大的字符串处理【5】能力而闻名。尽管Snobol4在现代编程语言中并不常见，但它在处理字符串和文本方面仍然有其独特的优势。本文将探讨如何使用Snobol4语言实现一个简单的URL域名合法性验证器。
Snobol4 简介
Snobol4是一种高级编程语言，特别适合于文本处理和字符串操作。它的语法简洁，易于理解，但同时也非常强大。Snobol4程序由一系列规则【7】组成，这些规则定义了如何处理输入字符串。
URL域名合法性验证
URL（统一资源定位符）是互联网上用于定位资源的字符串。域名是URL的一部分，用于标识网站的所有者。为了验证域名的合法性，我们需要确保它符合以下规则：
1. 域名必须以字母或数字开始。
2. 域名可以包含字母、数字、连字符【8】（-）和点（.）。
3. 域名不能以连字符（-）或点（.）结束。
4. 域名中不能有两个连续的点（..）。
5. 域名长度不能超过253个字符。
以下是一个使用Snobol4编写的简单域名合法性验证器：
```snobol
:validateDomain
'http://'
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