diff -r c8ff97d9f8da -r 7edbd5657702 Paper/Paper.thy --- a/Paper/Paper.thy Sun Jan 20 16:01:16 2013 +0000 +++ b/Paper/Paper.thy Tue Jan 22 14:38:56 2013 +0000 @@ -1,6 +1,6 @@ (*<*) theory Paper -imports "../thys/uncomputable" +imports "../thys/recursive" begin (* @@ -66,7 +66,7 @@ The only satisfying way out of this problem in a theorem prover based on classical logic is to formalise a theory of computability. Norrish -provided such a formalisation for the HOL4. He choose +provided such a formalisation for the HOL. He choose the $\lambda$-calculus as the starting point for his formalisation of computability theory, because of its ``simplicity'' \cite[Page 297]{Norrish11}. Part of his formalisation is a clever infrastructure @@ -90,13 +90,13 @@ of register machines) and recursive functions. To see the difficulties involved with this work, one has to understand that Turing machine programs can be completely \emph{unstructured}, behaving -similar to Basic's infamous goto \cite{Dijkstra68}. This precludes in the +similar Basic programs involving the infamous goto \cite{Dijkstra68}. This precludes in the general case a compositional Hoare-style reasoning about Turing -programs. We provide such Hoare-rules for when it is possible to +programs. We provide such Hoare-rules for when it \emph{is} possible to reason in a compositional manner (which is fortunately quite often), but also tackle the more complicated case when we translate abacus programs into -Turing programs. This aspect of reasoning about computability theory -is usually completely left out in the informal literature, e.g.~\cite{Boolos87}. +Turing programs. These difficulties when reasoning about computability theory +are usually completely left out in the informal literature, e.g.~\cite{Boolos87}. %To see the difficulties %involved with this work, one has to understand that interactive