doc-src/LaTeXsugar/Sugar/Sugar.thy
author nipkow
Fri Mar 13 12:32:29 2009 +0100 (2009-03-13)
changeset 30502 b80d2621caee
parent 27688 397de75836a1
child 32833 f3716d1a2e48
permissions -rw-r--r--
hiding numeric coercions in LaTeX
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(*<*)
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theory Sugar
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imports LaTeXsugar OptionalSugar
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begin
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(*>*)
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section "Introduction"
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text{* This document is for those Isabelle users who have mastered
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the art of mixing \LaTeX\ text and Isabelle theories and never want to
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typeset a theorem by hand anymore because they have experienced the
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bliss of writing \verb!@!\verb!{thm[display]setsum_cartesian_product[no_vars]}!
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and seeing Isabelle typeset it for them:
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@{thm[display,eta_contract=false] setsum_cartesian_product[no_vars]}
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No typos, no omissions, no sweat.
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If you have not experienced that joy, read Chapter 4, \emph{Presenting
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Theories}, \cite{LNCS2283} first.
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If you have mastered the art of Isabelle's \emph{antiquotations},
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i.e.\ things like the above \verb!@!\verb!{thm...}!, beware: in your vanity
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you may be tempted to think that all readers of the stunning ps or pdf
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documents you can now produce at the drop of a hat will be struck with
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awe at the beauty unfolding in front of their eyes. Until one day you
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come across that very critical of readers known as the ``common referee''.
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He has the nasty habit of refusing to understand unfamiliar notation
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like Isabelle's infamous @{text"\<lbrakk> \<rbrakk> \<Longrightarrow>"} no matter how many times you
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explain it in your paper. Even worse, he thinks that using @{text"\<lbrakk>
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\<rbrakk>"} for anything other than denotational semantics is a cardinal sin
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that must be punished by instant rejection.
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This document shows you how to make Isabelle and \LaTeX\ cooperate to
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produce ordinary looking mathematics that hides the fact that it was
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typeset by a machine. You merely need to load the right files:
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\begin{itemize}
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\item Import theory \texttt{LaTeXsugar} in the header of your own
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theory.  You may also want bits of \texttt{OptionalSugar}, which you can
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copy selectively into your own theory or import as a whole.  Both
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theories live in \texttt{HOL/Library} and are found automatically.
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\item Should you need additional \LaTeX\ packages (the text will tell
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you so), you include them at the beginning of your \LaTeX\ document,
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typically in \texttt{root.tex}. For a start, you should
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\verb!\usepackage{amssymb}! --- otherwise typesetting
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@{prop[source]"\<not>(\<exists>x. P x)"} will fail because the AMS symbol
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@{text"\<nexists>"} is missing.
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\end{itemize}
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*}
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section{* HOL syntax*}
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subsection{* Logic *}
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text{* 
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  The formula @{prop[source]"\<not>(\<exists>x. P x)"} is typeset as @{prop"~(EX x. P x)"}.
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The predefined constructs @{text"if"}, @{text"let"} and
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@{text"case"} are set in sans serif font to distinguish them from
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other functions. This improves readability:
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\begin{itemize}
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\item @{term"if b then e\<^isub>1 else e\<^isub>2"} instead of @{text"if b then e\<^isub>1 else e\<^isub>2"}.
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\item @{term"let x = e\<^isub>1 in e\<^isub>2"} instead of @{text"let x = e\<^isub>1 in e\<^isub>2"}.
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\item @{term"case x of True \<Rightarrow> e\<^isub>1 | False \<Rightarrow> e\<^isub>2"} instead of\\
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      @{text"case x of True \<Rightarrow> e\<^isub>1 | False \<Rightarrow> e\<^isub>2"}.
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\end{itemize}
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*}
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subsection{* Sets *}
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text{* Although set syntax in HOL is already close to
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standard, we provide a few further improvements:
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\begin{itemize}
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\item @{term"{x. P}"} instead of @{text"{x. P}"}.
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\item @{term"{}"} instead of @{text"{}"}, where
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 @{term"{}"} is also input syntax.
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\item @{term"insert a (insert b (insert c M))"} instead of @{text"insert a (insert b (insert c M))"}.
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\end{itemize}
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*}
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subsection{* Lists *}
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text{* If lists are used heavily, the following notations increase readability:
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\begin{itemize}
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\item @{term"x # xs"} instead of @{text"x # xs"},
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      where @{term"x # xs"} is also input syntax.
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If you prefer more space around the $\cdot$ you have to redefine
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\verb!\isasymcdot! in \LaTeX:
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\verb!\renewcommand{\isasymcdot}{\isamath{\,\cdot\,}}!
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\item @{term"length xs"} instead of @{text"length xs"}.
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\item @{term"nth xs n"} instead of @{text"nth xs n"},
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      the $n$th element of @{text xs}.
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\item Human readers are good at converting automatically from lists to
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sets. Hence \texttt{OptionalSugar} contains syntax for suppressing the
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conversion function @{const set}: for example, @{prop[source]"x \<in> set xs"}
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becomes @{prop"x \<in> set xs"}.
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\item The @{text"@"} operation associates implicitly to the right,
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which leads to unpleasant line breaks if the term is too long for one
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line. To avoid this, \texttt{OptionalSugar} contains syntax to group
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@{text"@"}-terms to the left before printing, which leads to better
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line breaking behaviour:
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@{term[display]"term\<^isub>0 @ term\<^isub>1 @ term\<^isub>2 @ term\<^isub>3 @ term\<^isub>4 @ term\<^isub>5 @ term\<^isub>6 @ term\<^isub>7 @ term\<^isub>8 @ term\<^isub>9 @ term\<^isub>1\<^isub>0"}
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\end{itemize}
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*}
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subsection{* Numbers *}
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text{* Coercions between numeric types are alien to mathematicians who
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consider, for example, @{typ nat} as a subset of @{typ int}.
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\texttt{OptionalSugar} contains syntax for suppressing numeric coercions such
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as @{const int} @{text"::"} @{typ"nat \<Rightarrow> int"}. For example,
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@{term[source]"int 5"} is printed as @{term "int 5"}. Embeddings of types
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@{typ nat}, @{typ int}, @{typ real} are covered; non-injective coercions such
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as @{const nat} @{text"::"} @{typ"int \<Rightarrow> nat"} are not and should not be
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hidden. *}
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section "Printing theorems"
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subsection "Question marks"
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text{* If you print anything, especially theorems, containing
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schematic variables they are prefixed with a question mark:
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\verb!@!\verb!{thm conjI}! results in @{thm conjI}. Most of the time
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you would rather not see the question marks. There is an attribute
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\verb!no_vars! that you can attach to the theorem that turns its
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schematic into ordinary free variables: \verb!@!\verb!{thm conjI[no_vars]}!
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results in @{thm conjI[no_vars]}.
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This \verb!no_vars! business can become a bit tedious.
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If you would rather never see question marks, simply put
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\begin{verbatim}
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reset show_question_marks;
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\end{verbatim}
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at the beginning of your file \texttt{ROOT.ML}.
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The rest of this document is produced with this flag reset.
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Hint: Resetting \verb!show_question_marks! only suppresses question
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marks; variables that end in digits, e.g. @{text"x1"}, are still
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printed with a trailing @{text".0"}, e.g. @{text"x1.0"}, their
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internal index. This can be avoided by turning the last digit into a
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subscript: write \verb!x\<^isub>1! and obtain the much nicer @{text"x\<^isub>1"}. *}
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(*<*)ML"reset show_question_marks"(*>*)
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subsection {*Qualified names*}
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text{* If there are multiple declarations of the same name, Isabelle prints
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the qualified name, for example @{text "T.length"}, where @{text T} is the
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theory it is defined in, to distinguish it from the predefined @{const[source]
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"List.length"}. In case there is no danger of confusion, you can insist on
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short names (no qualifiers) by setting \verb!short_names!, typically
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in \texttt{ROOT.ML}:
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\begin{verbatim}
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set short_names;
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\end{verbatim}
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*}
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subsection {*Variable names\label{sec:varnames}*}
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text{* It sometimes happens that you want to change the name of a
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variable in a theorem before printing it. This can easily be achieved
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with the help of Isabelle's instantiation attribute \texttt{where}:
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@{thm conjI[where P = \<phi> and Q = \<psi>]} is the result of
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\begin{quote}
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\verb!@!\verb!{thm conjI[where P = \<phi> and Q = \<psi>]}!
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\end{quote}
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To support the ``\_''-notation for irrelevant variables
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the constant \texttt{DUMMY} has been introduced:
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@{thm fst_conv[where b = DUMMY]} is produced by
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\begin{quote}
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\verb!@!\verb!{thm fst_conv[where b = DUMMY]}!
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\end{quote}
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*}
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subsection "Inference rules"
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text{* To print theorems as inference rules you need to include Didier
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R\'emy's \texttt{mathpartir} package~\cite{mathpartir}
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for typesetting inference rules in your \LaTeX\ file.
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Writing \verb!@!\verb!{thm[mode=Rule] conjI}! produces
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@{thm[mode=Rule] conjI}, even in the middle of a sentence.
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If you prefer your inference rule on a separate line, maybe with a name,
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\begin{center}
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@{thm[mode=Rule] conjI} {\sc conjI}
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\end{center}
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is produced by
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\begin{quote}
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\verb!\begin{center}!\\
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\verb!@!\verb!{thm[mode=Rule] conjI} {\sc conjI}!\\
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\verb!\end{center}!
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\end{quote}
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It is not recommended to use the standard \texttt{display} option
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together with \texttt{Rule} because centering does not work and because
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the line breaking mechanisms of \texttt{display} and \texttt{mathpartir} can
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clash.
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Of course you can display multiple rules in this fashion:
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\begin{quote}
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\verb!\begin{center}!\\
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\verb!@!\verb!{thm[mode=Rule] conjI} {\sc conjI} \\[1ex]!\\
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\verb!@!\verb!{thm[mode=Rule] conjE} {\sc disjI$_1$} \qquad!\\
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\verb!@!\verb!{thm[mode=Rule] disjE} {\sc disjI$_2$}!\\
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\verb!\end{center}!
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\end{quote}
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yields
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\begin{center}\small
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@{thm[mode=Rule] conjI} {\sc conjI} \\[1ex]
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@{thm[mode=Rule] disjI1} {\sc disjI$_1$} \qquad
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@{thm[mode=Rule] disjI2} {\sc disjI$_2$}
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\end{center}
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The \texttt{mathpartir} package copes well if there are too many
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premises for one line:
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\begin{center}
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@{prop[mode=Rule] "\<lbrakk> A \<longrightarrow> B; B \<longrightarrow> C; C \<longrightarrow> D; D \<longrightarrow> E; E \<longrightarrow> F; F \<longrightarrow> G;
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 G \<longrightarrow> H; H \<longrightarrow> I; I \<longrightarrow> J; J \<longrightarrow> K \<rbrakk> \<Longrightarrow> A \<longrightarrow> K"}
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\end{center}
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Limitations: 1. Premises and conclusion must each not be longer than
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the line.  2. Premises that are @{text"\<Longrightarrow>"}-implications are again
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displayed with a horizontal line, which looks at least unusual.
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In case you print theorems without premises no rule will be printed by the
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\texttt{Rule} print mode. However, you can use \texttt{Axiom} instead:
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\begin{quote}
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\verb!\begin{center}!\\
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\verb!@!\verb!{thm[mode=Axiom] refl} {\sc refl}! \\
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\verb!\end{center}!
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\end{quote}
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yields
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\begin{center}
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@{thm[mode=Axiom] refl} {\sc refl} 
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\end{center}
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*}
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subsection "Displays and font sizes"
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text{* When displaying theorems with the \texttt{display} option, e.g.
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\verb!@!\verb!{thm[display] refl}! @{thm[display] refl} the theorem is
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set in small font. It uses the \LaTeX-macro \verb!\isastyle!,
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which is also the style that regular theory text is set in, e.g. *}
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lemma "t = t"
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(*<*)oops(*>*)
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text{* \noindent Otherwise \verb!\isastyleminor! is used,
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which does not modify the font size (assuming you stick to the default
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\verb!\isabellestyle{it}! in \texttt{root.tex}). If you prefer
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normal font size throughout your text, include
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\begin{quote}
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\verb!\renewcommand{\isastyle}{\isastyleminor}!
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\end{quote}
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in \texttt{root.tex}. On the other hand, if you like the small font,
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just put \verb!\isastyle! in front of the text in question,
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e.g.\ at the start of one of the center-environments above.
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The advantage of the display option is that you can display a whole
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list of theorems in one go. For example,
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\verb!@!\verb!{thm[display] foldl.simps}!
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generates @{thm[display] foldl.simps}
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*}
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subsection "If-then"
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text{* If you prefer a fake ``natural language'' style you can produce
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the body of
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\newtheorem{theorem}{Theorem}
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\begin{theorem}
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@{thm[mode=IfThen] le_trans}
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\end{theorem}
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by typing
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\begin{quote}
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\verb!@!\verb!{thm[mode=IfThen] le_trans}!
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\end{quote}
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In order to prevent odd line breaks, the premises are put into boxes.
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At times this is too drastic:
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\begin{theorem}
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@{prop[mode=IfThen] "longpremise \<Longrightarrow> longerpremise \<Longrightarrow> P(f(f(f(f(f(f(f(f(f(x)))))))))) \<Longrightarrow> longestpremise \<Longrightarrow> conclusion"}
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\end{theorem}
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In which case you should use \texttt{IfThenNoBox} instead of
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\texttt{IfThen}:
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\begin{theorem}
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@{prop[mode=IfThenNoBox] "longpremise \<Longrightarrow> longerpremise \<Longrightarrow> P(f(f(f(f(f(f(f(f(f(x)))))))))) \<Longrightarrow> longestpremise \<Longrightarrow> conclusion"}
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\end{theorem}
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*}
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subsection{* Doing it yourself\label{sec:yourself}*}
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text{* If for some reason you want or need to present theorems your
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own way, you can extract the premises and the conclusion explicitly
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and combine them as you like:
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\begin{itemize}
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\item \verb!@!\verb!{thm_style prem1! $thm$\verb!}!
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prints premise 1 of $thm$ (and similarly up to \texttt{prem9}).
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\item \verb!@!\verb!{thm_style concl! $thm$\verb!}!
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prints the conclusion of $thm$.
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\end{itemize}
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For example, ``from @{thm_style prem2 conjI} and
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@{thm_style prem1 conjI} we conclude @{thm_style concl conjI}''
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is produced by
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\begin{quote}
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\verb!from !\verb!@!\verb!{thm_style prem2 conjI}! \verb!and !\verb!@!\verb!{thm_style prem1 conjI}!\\
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\verb!we conclude !\verb!@!\verb!{thm_style concl conjI}!
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\end{quote}
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Thus you can rearrange or hide premises and typeset the theorem as you like.
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The \verb!thm_style! antiquotation is a general mechanism explained
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in \S\ref{sec:styles}.
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*}
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subsection "Patterns"
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text {*
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  In \S\ref{sec:varnames} we shows how to create patterns containing
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  ``@{term DUMMY}''.
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  You can drive this game even further and extend the syntax of let
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  bindings such that certain functions like @{term fst}, @{term hd}, 
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  etc.\ are printed as patterns. \texttt{OptionalSugar} provides the
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  following:
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  \begin{center}
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  \begin{tabular}{l@ {~~produced by~~}l}
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  @{term "let x = fst p in t"} & \verb!@!\verb!{term "let x = fst p in t"}!\\
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  @{term "let x = snd p in t"} & \verb!@!\verb!{term "let x = snd p in t"}!\\
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  @{term "let x = hd xs in t"} & \verb!@!\verb!{term "let x = hd xs in t"}!\\
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  @{term "let x = tl xs in t"} & \verb!@!\verb!{term "let x = tl xs in t"}!\\
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  @{term "let x = the y in t"} & \verb!@!\verb!{term "let x = the y in t"}!\\
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  \end{tabular}
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  \end{center}
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*}
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section "Proofs"
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text {* Full proofs, even if written in beautiful Isar style, are
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likely to be too long and detailed to be included in conference
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papers, but some key lemmas might be of interest.
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It is usually easiest to put them in figures like the one in Fig.\
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\ref{fig:proof}. This was achieved with the \isakeyword{text\_raw} command:
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*}
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text_raw {*
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  \begin{figure}
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  \begin{center}\begin{minipage}{0.6\textwidth}  
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  \isastyleminor\isamarkuptrue
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*}
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lemma True
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proof -
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  -- "pretty trivial"
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  show True by force
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qed
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text_raw {*    
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  \end{minipage}\end{center}
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  \caption{Example proof in a figure.}\label{fig:proof}
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  \end{figure}
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*}
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text {*
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\begin{quote}
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\small
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\verb!text_raw {!\verb!*!\\
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\verb!  \begin{figure}!\\
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\verb!  \begin{center}\begin{minipage}{0.6\textwidth}!\\
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\verb!  \isastyleminor\isamarkuptrue!\\
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\verb!*!\verb!}!\\
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\verb!lemma True!\\
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\verb!proof -!\\
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\verb!  -- "pretty trivial"!\\
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\verb!  show True by force!\\
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\verb!qed!\\
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\verb!text_raw {!\verb!*!\\
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\verb!  \end{minipage}\end{center}!\\
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\verb!  \caption{Example proof in a figure.}\label{fig:proof}!\\
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\verb!  \end{figure}!\\
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\verb!*!\verb!}!
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\end{quote}
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Other theory text, e.g.\ definitions, can be put in figures, too.
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*}
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section {*Styles\label{sec:styles}*}
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text {*
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  The \verb!thm! antiquotation works nicely for single theorems, but
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  sets of equations as used in definitions are more difficult to
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  typeset nicely: people tend to prefer aligned @{text "="} signs.
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  To deal with such cases where it is desirable to dive into the structure
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  of terms and theorems, Isabelle offers antiquotations featuring
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  ``styles'':
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    \begin{quote}
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    \verb!@!\verb!{thm_style stylename thm}!\\
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    \verb!@!\verb!{term_style stylename term}!
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    \end{quote}
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  A ``style'' is a transformation of propositions. There are predefined
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  styles, namely \verb!lhs! and \verb!rhs!, \verb!prem1! up to \verb!prem9!, and \verb!concl!.
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  For example, 
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  the output
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  \begin{center}
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  \begin{tabular}{l@ {~~@{text "="}~~}l}
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  @{thm_style lhs foldl_Nil} & @{thm_style rhs foldl_Nil}\\
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  @{thm_style lhs foldl_Cons} & @{thm_style rhs foldl_Cons}
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  \end{tabular}
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  \end{center}
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  is produced by the following code:
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  \begin{quote}
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    \verb!\begin{center}!\\
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    \verb!\begin{tabular}{l@ {~~!\verb!@!\verb!{text "="}~~}l}!\\
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    \verb!@!\verb!{thm_style lhs foldl_Nil} & @!\verb!{thm_style rhs foldl_Nil}!\\
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    \verb!@!\verb!{thm_style lhs foldl_Cons} & @!\verb!{thm_style rhs foldl_Cons}!\\
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    \verb!\end{tabular}!\\
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    \verb!\end{center}!
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  \end{quote}
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  Note the space between \verb!@! and \verb!{! in the tabular argument.
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  It prevents Isabelle from interpreting \verb!@ {~~...~~}! 
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  as an antiquotation. The styles \verb!lhs! and \verb!rhs!
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  extract the left hand side (or right hand side respectively) from the
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  conclusion of propositions consisting of a binary operator
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  (e.~g.~@{text "="}, @{text "\<equiv>"}, @{text "<"}).
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  Likewise, \verb!concl! may be used as a style to show just the
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  conclusion of a proposition. For example, take \verb!hd_Cons_tl!:
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  \begin{center}
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    @{thm [show_types] hd_Cons_tl}
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  \end{center}
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  To print just the conclusion,
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  \begin{center}
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    @{thm_style [show_types] concl hd_Cons_tl}
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  \end{center}
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  type
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  \begin{quote}
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    \verb!\begin{center}!\\
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    \verb!@!\verb!{thm_style [show_types] concl hd_Cons_tl}!\\
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    \verb!\end{center}!
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  \end{quote}
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  Beware that any options must be placed \emph{before}
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  the name of the style, as in this example.
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  Further use cases can be found in \S\ref{sec:yourself}.
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  If you are not afraid of ML, you may also define your own styles.
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  A style is implemented by an ML function of type
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  \verb!Proof.context -> term -> term!.
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  Have a look at the following example:
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*}
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(*<*)
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setup {*
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let
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  fun my_concl ctxt = Logic.strip_imp_concl
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  in TermStyle.add_style "my_concl" my_concl
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end;
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*}
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(*>*)
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text {*
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  \begin{quote}
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    \verb!setup {!\verb!*!\\
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    \verb!let!\\
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    \verb!  fun my_concl ctxt = Logic.strip_imp_concl!\\
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    \verb!  in TermStyle.add_style "my_concl" my_concl!\\
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    \verb!end;!\\
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    \verb!*!\verb!}!\\
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  \end{quote}
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  \noindent
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  This example shows how the \verb!concl! style is implemented
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  and may be used as as a ``copy-and-paste'' pattern to write your own styles.
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  The code should go into your theory file, separate from the \LaTeX\ text.
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  The \verb!let! expression avoids polluting the
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  ML global namespace. Each style receives the current proof context
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  as first argument; this is helpful in situations where the
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  style has some object-logic specific behaviour for example.
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  The mapping from identifier name to the style function
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  is done by the @{ML TermStyle.add_style} expression which expects the desired
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  style name and the style function as arguments.
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  After this \verb!setup!,
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  there will be a new style available named \verb!my_concl!, thus allowing
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  antiquoations like \verb!@!\verb!{thm_style my_concl hd_Cons_tl}!
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  yielding @{thm_style my_concl hd_Cons_tl}.
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*}
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(*<*)
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end
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(*>*)