GoKawiilDeveloper formalizes DFA textbook proof using Lean and Mathlib
A software engineer walked through a theory-of-computation textbook exercise asking for a proof, via finite automata, of a language property, then reformalized that informal constructive proof in the Lean proof assistant. The write-up builds a deterministic finite automaton (DFA) and leans on existing theorems in Lean's Mathlib library to formally verify it recognizes the target language.