使用分组时，如何使用gsub在Ruby正则表达式(regex)中进行反向引用? [英] How to backreference in Ruby regular expression (regex) with gsub when I use grouping?

问题描述

我想修补从网页提取的一些文本数据. 样本:

I would like to patch some text data extracted from web pages. sample:

t="First sentence. Second sentence.Third sentence."

第二句结尾处的点后没有空格.这表明我在原始文档中第3句话在一行中(在br标签之后).

There is no space after the point at the end of the second sentence. This sign me that the 3rd sentence was in a separate line (after a br tag) in the original document.

我想使用此正则表达式在适当的位置插入"\ n"字符并修补我的文本. 我的正则表达式:

I want to use this regexp to insert "\n" character into the proper places and patch my text. My regex:

t2=t.gsub(/([.\!?])([A-Z1-9])/,$1+"\n"+$2)

但是不幸的是，它不起作用:"NoMethodError:nil:NilClass的未定义方法'+'" 如何正确回溯匹配的组? 在Microsoft Word中是如此简单，我只需要使用\ 1和\ 2符号.

But unfortunately it doesn't work: "NoMethodError: undefined method `+' for nil:NilClass" How can I properly backreference to the matched groups? It was so easy in Microsoft Word, I just had to use \1 and \2 symbols.

推荐答案

您可以使用\1向后替换字符串中的反向引用(以匹配捕获组1).

You can backreference in the substitution string with \1 (to match capture group 1).

t = "First sentence. Second sentence.Third sentence!Fourth sentence?Fifth sentence."
t.gsub(/([.!?])([A-Z1-9])/, "\\1\n\\2") # => "First sentence. Second sentence.\nThird sentence!\nFourth sentence?\nFifth sentence."

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