Lean 99: Ninety-Nine Lean Problems

Lean is a theorem prover, but it is also a programming language. Moreover, it is the best functional language ever! Let's learn functional programming with Lean. 😎

These are Lean translations of Ninety-Nine Haskell Problems, which are themselves translations of Ninety-Nine Lisp Problems.

How to Play

• Every Lean code block in this book has a button to jump to the Lean web playground. Replace the sorry with your own code so that the test code passes.

• You can see an answer by clicking on the button in the top right-hand corner of each page.

Good luck! 👍