Verified typechecker and evaluator for Simply Typed Lamda Calculus (STLC) in Idris inspired by this blogpost. The evaluator is based on the progress and preservation theorems which are also proved. Run the example (on Windows) by loading the example module into the Idris REPL with idris .\Example.idr -p pruviloj and evaluate and display the example with show (evalForget example).