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Q&A Vim: how to search for all instances of a string, except for those that are between two specific strings

As @Quasímodo‭ has shown, the search pattern \(abc.*\)\@&lt;!bird\|bird\(.*xyz\)\@! solves your problem. But, why does it work, and why does your original approach not work? What you want to achi...

posted 8mo ago by Dirk Herrmann‭

Answer
#1: Initial revision by user avatar Dirk Herrmann‭ · 2022-06-10T16:55:43Z (8 months ago)
As @Quasímodo‭ has shown, the search pattern `\(abc.*\)\@<!bird\|bird\(.*xyz\)\@!` solves your problem.  But, why does it work, and why does your original approach not work?

What you want to achieve is to find all occurrences of "bird" for which the following holds:

    "bird" if not between "abc" and "xyz"

Which can be re-phrased as

    "bird" if not ((preceded by "abc") and (followed by "xyz"))

Or, using De Morgan's law:

    "bird" if ((not preceded by "abc") or (not followed by "xyz"))
    <==> (bird if not preceded by "abc") or (bird if not followed by "xyz")

This is why @Quasímodo‭'s answer works.

Your search pattern `/\(abc.*\)\@<!bird\(.*xyz\)\@!`, however, has the following meaning:

    bird, if ((not preceded by "abc") AND (not followed by "xyz"))

In other words, an occurrence of "bird" will be ignored if there is a preceding "abc" or a following "xyz".  You will see this when trying your original expression on the following line:

    foo bird bar

This occurrence of bird will be found.