By Kazuhiko Sakaguchi, Nov. 2011 - July 2020.

This is a formalization of the λ-calculus written in Coq and Agda2, and contains the following definitions and theorems:

• SKI combinator calculus: coq/CL.v
  • Confluence of weak reduction
• Untyped lambda calculus: coq/deBruijn/Untyped.v, agda/Lambda/*.agda
  • Confluence of beta reduction
• STLC (simply typed lambda calculus): coq/deBruijn/STLC.v
  • Subject reduction (type preservation) theorem
  • Strong normalization theorem (three different proofs are available)
• System F (second order typed lambda calculus): coq/deBruijn/F.v
  • Subject reduction (type preservation) theorem
  • Strong normalization theorem (three different proofs are available)

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