test of retrieve r v = retrieve (bsimp r) (decode bsimp r code v)

removed C(c) The retrieve and code in the previous version is still not correct and will crash. no prob now.

The C(Char) construct is incompatible with the code and retrieve in Fahad's thesis. This causes the exception. Two ways of fixing this: delete C(C) construct (easy way around) or amend retrieve code etc. since the C(C) construct is intended for decoding Pred, and we don't use pred now, we shall delete this. This is the last veersion that contains C(CHAR)

exp and proof

augmented version of proof sketch

pf