Solving regex crosswords with Z3

Nelson Elhage · 21 Oct 2025 · blog.nelhage.com ↗

2 korrents from this piece

Nelson Elhage did not write this page.

Every claim below was made in this piece, quoted word for word and numbered in the order the piece makes them, so you can read it there rather than take our word for it. The sentence above each quote is our reading of the claim, not their wording. Each quote was checked against a stored copy of the page at build time; where the two differ, the quote is the fact.

Our reading
Augmenting a general-purpose solver with domain-specific heuristics commonly gives it a meaningful performance boost.

Their wordsMy sense is that this hybrid is fairly common in practice; solvers aren't magical and if you can deduce additional structure using domain-specific analysis, it will often give the solver an important boost.
Our reading
When a tool has first-class, native support for a problem domain, that is the best place to start before building a custom encoding.

Their wordsI suspect the pattern generalizes: If Z3 has first-class support for your problem domain, it's worth starting there!