Table of Contents

This book is an introduction to programming language theory using the proof assistant Agda.

Comments on all matters—organisation, material to add, material to remove, parts that require better explanation, good exercises, errors, and typos—are welcome. The book repository is on GitHub. Pull requests are encouraged.

Front matter

Part 1: Logical Foundations

Part 2: Programming Language Foundations

  • Lambda: Introduction to Lambda Calculus
  • Properties: Progress and Preservation
  • DeBruijn: Inherently typed De Bruijn representation
  • More: Additional constructs of simply-typed lambda calculus
  • Bisimulation : Relating reductions systems
  • Inference: Bidirectional type inference
  • Untyped: Untyped lambda calculus with full normalisation


  • A paper describing the book appears in SBMF.
  • Courses taught from the textbook:
    • Philip Wadler, University of Edinburgh, 2018
    • David Darais, University of Vermont, 2018
    • John Leo, Google Seattle, 2018–2019