Does the quantifier {0} make sense in some scenarios?

Question

Example:

/(?:Foo){0}bar/

I saw something like this in another answer. At first I thought \"what should that be\", but then, \"OK could make sense, kind of a

Answer 1

There are good uses of {0}. It allows you to define groups that you don't intend to capture at the moment. This can be useful in some cases:

• The best one - use of the group in recursive regular expressions (or other weird constructs). Perl, for example, has (?(DEFINE) ) for the same use.
  A quick example - in PHP, this will match barFoo (working example):

  preg_match("/(?:(Foo)){0}bar(?1)/", "barFoo", $matches);
  

• Adding a failed captured group (named or numbered) to the result matches.

• Keeping the indices of all groups intact in case the pattern was refactored.

Less good uses, as Peter suggested are useful in:

• Generated patterns.
• Readability - Patterns with certain duplication, where {0} and {1} may lead thinking in the right direction. (OK, not the best point)

These are all rare cases, and in most patterns it is a mistake.