如何使用正则表达式从可选的匹配中排除单词

Question

I want to be able to match the following:

top of pole
top of existing pole
existing top of pole

but not

proposed top of pole

I tried to use ((?=proposed)\s)*top\sof\s(existing\s)?pole with look back, but it doesn't quite work, still matching proposed top of pole.

How to exclude certain word when it is optional?

Answer 1

You can exclude a certain word like this:

(\w+\s(?<!proposed\s))?top\sof\s(existing\s)?hole

There are a couple of things going on in this solution:

• \w+\s matches a word and 1 whitespace character,

• The negative lookbehind (?<!proposed\s) gurantees that, once the regex is at this position after the word and space, looking backwards we do not match "proposed ".

• The (...)? makes the (word, space, and no "proposed ") match optional.

For a more detailed walkthrough: https://regex101.com/r/LLs2zA/1