--- 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