什么是 Ruby 正则表达式中的“?-mix" [英] What is '?-mix' in a Ruby Regular Expression

问题描述

只是想在 ruby​​ 中调试一个正则表达式.当我打印正则表达式的内容时，即使这些字符不是表达式的一部分，它也会在正则表达式的开头显示 ?-mix.请参阅以下 IRB 输出以查看此说明

Just trying to debug a regular expression in ruby. When I print the contents of a regular expression, it shows ?-mix at the beginning of the regular expression even though those characters were not part of the expression. Please see the following IRB output to see this illustrated

irb(main):028:0* EXPR = /^a$/
=> /^a$/
irb(main):029:0> EXPR
=> /^a$/
irb(main):030:0> puts EXPR
(?-mix:^a$)
=> nil

如您所见，当您使用puts 打印出正则表达式的内容时，开头是?-mix.我应该担心这个吗?它来自哪里?

As you can see, when you use puts to print out the contents of a regular expression, there is ?-mix at the beginning. Should I be concerned by this? Where is it coming from?

推荐答案

mix 不是英文单词 mix，它是 Regexp 的选项.

mix is not the English word mix, it's options of Regexp.

参见Regexp#to_s:

返回一个包含正则表达式及其选项的字符串(使用 (?opts:source) 表示法.

Returns a string containing the regular expression and its options (using the (?opts:source) notation.

在您的示例中，m 用于多行模式，i 用于不区分大小写，x 用于扩展模式.破折号前的选项打开，后面的选项关闭(默认).问题的示例 ?-mix 已关闭所有选项.

In your example, m is for multiline mode, i is for case insensitive, and x is for extended mode. Options before the dash are on, those after are off (default). The question's example, ?-mix, has all options off.

您可以像这样打开它们:

You can turn them on like:

puts /^a$/mix
# =>(?mix:^a$)

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