Lecture
This lecture covers the concepts of type checking and type reconstruction in lambda calculus, focusing on transforming judgements into equations and using unification to find type solutions. It also explores soundness and completeness of type systems, the Hindley/Milner system, polymorphism, and the translation of programs into System F. The instructor explains the limitations of Hindley/Milner, the essence of let expressions, and the importance of principal types in type schemes.