Introduction to Lean for Programmers

Lean is an interactive proof assistant that provides programmers with an IDE-like experience for engaging with formal mathematics. The core concept explained is the Curry-Howard correspondence, which equates logical propositions to types and proofs to programs that inhabit those types. This principle is demonstrated by proving a logic theorem by writing a function with a corresponding type signature in both TypeScript and Lean. The tool is highly relevant in the AI field, with systems like DeepMind's AlphaProof and projects from OpenAI using Lean for formal verification and to solve complex mathematical problems.