A string of given length with an arbitrary (but >0) number of delimiters?

Question

Regular Expressions

I have already solved the problem without regexps, but now academic interest gnaws, I've been fighting all evening =)
We need to match strings from a given number of digits (let it be 6).
Numbers can be separated by an arbitrary number of delimiters (let it be [-]).
There must be at least one separator.
There should not be two separators in a row.
that is, it matches:
111-111
11-1111
1-111-11
does not match:
111111
-111111
111111-
111--111
11-11
1111-1111
This thing correctly matches the quantity, but does not take into account the obligatory nature of at least one separator:
(?<=\s)\d(?:[-]?\d){5}(?=\s)
https://regex101.com/r/9sHJSA/1
But this one takes into account the mandatory separator, but does not take into account the number:
(?<=\s)(?:\d+[-](?=\d))+\d+(?=\s)
https://regex101. com/r/83NFoD/1
How would they be combined into one rule?

Answer 1

You can take into account the obligatory nature of at least one separator by adding a positive forward check (?=\d{0,4}[-])
https://regex101.com/r/9sHJSA/2
Another option is to apply the trick with an empty retaining group and a back link to it.
It is based on the fact that an attempt to match against a backreference will fail if the matching retaining group has not yet participated in the match.
https://regex101.com/r/9sHJSA/3
This trick works in PHP, Perl, Python, Java and .NET, but JavaScript has its own rules for working with backlinks and this trick does not work.