--- a/doc-src/TutorialI/Recdef/document/Nested1.tex Wed Aug 30 18:05:20 2000 +0200
+++ b/doc-src/TutorialI/Recdef/document/Nested1.tex Wed Aug 30 18:09:20 2000 +0200
@@ -1,11 +1,11 @@
%
\begin{isabellebody}%
-\isacommand{consts}\ trev\ \ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}b{\isacharparenright}term\ {\isacharequal}{\isachargreater}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}b{\isacharparenright}term{\isachardoublequote}%
+\isacommand{consts}\ trev\ \ {\isacharcolon}{\isacharcolon}\ {\isachardoublequote}{\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}b{\isacharparenright}term\ {\isasymRightarrow}\ {\isacharparenleft}{\isacharprime}a{\isacharcomma}{\isacharprime}b{\isacharparenright}term{\isachardoublequote}%
\begin{isamarkuptext}%
\noindent
Although the definition of \isa{trev} is quite natural, we will have
overcome a minor difficulty in convincing Isabelle of is termination.
-It is precisely this difficulty that is the \textit{rasion d'\^etre} of
+It is precisely this difficulty that is the \textit{raison d'\^etre} of
this subsection.
Defining \isa{trev} by \isacommand{recdef} rather than \isacommand{primrec}
@@ -13,31 +13,30 @@
suggested at the end of \S\ref{sec:nested-datatype}:%
\end{isamarkuptext}%
\isacommand{recdef}\ trev\ {\isachardoublequote}measure\ size{\isachardoublequote}\isanewline
-\ {\isachardoublequote}trev\ {\isacharparenleft}Var\ x{\isacharparenright}\ {\isacharequal}\ Var\ x{\isachardoublequote}\isanewline
+\ {\isachardoublequote}trev\ {\isacharparenleft}Var\ x{\isacharparenright}\ \ \ \ {\isacharequal}\ Var\ x{\isachardoublequote}\isanewline
\ {\isachardoublequote}trev\ {\isacharparenleft}App\ f\ ts{\isacharparenright}\ {\isacharequal}\ App\ f\ {\isacharparenleft}rev{\isacharparenleft}map\ trev\ ts{\isacharparenright}{\isacharparenright}{\isachardoublequote}%
\begin{isamarkuptext}%
-FIXME: recdef should complain and generate unprovable termination condition!
-moveto todo
-
+\noindent
Remember that function \isa{size} is defined for each \isacommand{datatype}.
-However, the definition does not succeed. Isabelle complains about an unproved termination
-condition
+However, the definition does not succeed. Isabelle complains about an
+unproved termination condition
\begin{quote}
\begin{isabelle}%
-\mbox{t}\ {\isasymin}\ set\ \mbox{ts}\ {\isasymlongrightarrow}\ size\ \mbox{t}\ {\isacharless}\ Suc\ {\isacharparenleft}term{\isacharunderscore}size\ \mbox{ts}{\isacharparenright}
+\mbox{t}\ {\isasymin}\ set\ \mbox{ts}\ {\isasymlongrightarrow}\ size\ \mbox{t}\ {\isacharless}\ Suc\ {\isacharparenleft}term{\isacharunderscore}list{\isacharunderscore}size\ \mbox{ts}{\isacharparenright}
\end{isabelle}%
\end{quote}
-where \isa{set} returns the set of elements of a list---no special knowledge of sets is
-required in the following.
-First we have to understand why the recursive call of \isa{trev} underneath \isa{map} leads
-to the above condition. The reason is that \isacommand{recdef} ``knows'' that \isa{map} will
-apply \isa{trev} only to elements of \isa{\mbox{ts}}. Thus the above condition expresses that
-the size of the argument \isa{\mbox{t}\ {\isasymin}\ set\ \mbox{ts}} of any recursive call of \isa{trev} is strictly
-less than \isa{size\ {\isacharparenleft}App\ \mbox{f}\ \mbox{ts}{\isacharparenright}\ {\isacharequal}\ Suc\ {\isacharparenleft}term{\isacharunderscore}size\ \mbox{ts}{\isacharparenright}}.
-We will now prove the termination condition and continue with our definition.
-Below we return to the question of how \isacommand{recdef} ``knows'' about \isa{map}.%
+where \isa{set} returns the set of elements of a list (no special
+knowledge of sets is required in the following) and \isa{term{\isacharunderscore}list{\isacharunderscore}size\ {\isacharcolon}{\isacharcolon}\ term\ list\ {\isasymRightarrow}\ nat} is an auxiliary function automatically defined by Isabelle
+(when \isa{term} was defined). First we have to understand why the
+recursive call of \isa{trev} underneath \isa{map} leads to the above
+condition. The reason is that \isacommand{recdef} ``knows'' that \isa{map}
+will apply \isa{trev} only to elements of \isa{\mbox{ts}}. Thus the above
+condition expresses that the size of the argument \isa{\mbox{t}\ {\isasymin}\ set\ \mbox{ts}} of any
+recursive call of \isa{trev} is strictly less than \isa{size\ {\isacharparenleft}App\ \mbox{f}\ \mbox{ts}{\isacharparenright}\ {\isacharequal}\ Suc\ {\isacharparenleft}term{\isacharunderscore}list{\isacharunderscore}size\ \mbox{ts}{\isacharparenright}}. We will now prove the termination condition and
+continue with our definition. Below we return to the question of how
+\isacommand{recdef} ``knows'' about \isa{map}.%
\end{isamarkuptext}%
\end{isabellebody}%
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