An interactive tool that checks math proofs with strict type rules.
Lean is a math teacher with a red pen. Every proof step needs a reason. “Trust me” gets zero points.
Its small core checks each step. People use it for math proofs and safe software.
Formalized Mathematics
Lean writes math claims as proofs a machine can check.
Formal Methods
Lean can prove that software follows its rules.
ATP
ATP tools can help Lean fill in some proof steps.