Lambda the Ultimate

During the development of a language which allows formal verification I have experimented a lot with proof formats. First I have started with a proof language with tactics similar to Isabelle/HOL and Coq. But then I realized that such proofs are fairly difficult to read. In order to understand a proof one often writes down the state of the proof engine at intermediate positions of the tactics. Then I have introduced proof procedures stimulated by some examples in the dafny language.

Up to now I think that tactics are not appropriate to write down and document proofs. In the posts Boolean lattices, Predicates as sets and Complete lattices and closure systems I have used a proof format which I think is good to write down and document proofs.

Any opinions, remarks etc. are welcome.