“…An obvious question is then, could we build a verified compiler for Nuprl in Nuprl that generates reasonably fast code? Modern proof assistants that implement constructive type theories such as Coq [9,1], Isabelle [8,7], or Nuprl rely on unverified compilers. Even though the programs they generate, e.g., by extraction from proofs, are correct-by-construction, one could argue whether the machine code obtained after compilation is still correct.…”