正则表达式查找是否只有一个代码块 [英] Regex to find if there is only one block of code

问题描述

我的输入是一个字符串，我想验证只有一个 first-level 代码块.

My input is a string, I want to validate that there is only one first-level block of code.

示例:

{ abc }              TRUE
{ a { bc } }         TRUE
{ a {{}} }           TRUE
{ abc {efg}{hij}}    TRUE
{ a b cde }{aa}      FALSE

/^ \ {.* \} $/对这5种情况有效，您能帮我找到对最后一种情况无效的正则表达式吗?

/^\{.*\}$/ is valid for the 5 cases, can you help me to find a regex invalid for the last case ?

语言是JavaScript.

Language is JavaScript.

推荐答案

编辑:在指定JavaScript之前，我开始编写答案.将其保留为记录，因为它完整解释了正则表达式.

I started writing the answer before JavaScript was specified. Will leave it as for the record as it fully explains the regex.

简而言之:在JavaScript中，我想不出一个可靠的解决方案.在其他引擎中，有几种选择:

In short: In JavaScript I cannot think of a reliable solution. In other engines there are several options:

• 递归(我将在下面进行扩展)
• 平衡组(.NET)

对于解决方案2(无论如何在JS中也不起作用)，我将带您参考此问题

For solutions 2 (which anyhow won't work in JS either), I'll refer you to the example in this question

在Perl，PCRE(例如Notepad ++，PHP，R)和Matthew Barnett的Python的 regex 模块中，您可以使用:

In Perl, PCRE (e.g. Notepad++, PHP, R) and the Matthew Barnett's regex module for Python, you can use:

^({(?:[^{}]++|(?1))*})$

这个想法是要精确地匹配一组嵌套的花括号.还有什么使正则表达式失败.

The idea is to match exactly one set of nested braces. Anything more makes the regex fail.

在 Regex演示 中查看哪些匹配项和失败的内容.

See what matches and fails in the Regex Demo.

说明

• ^ 锚断言我们位于字符串的开头
• 外部括号定义第1组(或子例程1)
• {匹配左括号
• (?: ...)* 零次或多次，我们将...
• [^ {}] ++ 匹配所有不是 {或}
的字符
• 或 |
• (?1)重复子例程1的表达式
• } 匹配右括号
• $ 锚断言我们位于字符串的末尾.因此，

• The ^ anchor asserts that we are at the beginning of the string
• The outer parentheses define Group 1 (or Subroutine 1)
• { match the opening brace
• (?: ... )* zero or more times, we will...
• [^{}]++ match any chars that are not { or }
• OR |
• (?1) repeat the expression of subroutine 1
• } match closing brace
• The $ anchor asserts that we are at the end of the string. Therefore,

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