doc-src/IsarTut/generated/Tutorial.tex

types complex and hcomplex are now instances of class ringpower:
omitting redundant lemmas

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\begin{isabellebody}%
\def\isabellecontext{Tutorial}%
\isamarkupfalse%
%
\isamarkupchapter{Introduction%
}
\isamarkuptrue%
%
\isamarkupchapter{Technical issues%
}
\isamarkuptrue%
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\isamarkupsection{Source texts%
}
\isamarkuptrue%
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\isamarkupsection{Interaction and debugging%
}
\isamarkuptrue%
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\isamarkupchapter{Calculational reasoning%
}
\isamarkuptrue%
%
\isamarkupchapter{Proof by cases and induction%
}
\isamarkuptrue%
%
\isamarkupchapter{General natural deduction%
}
\isamarkuptrue%
%
\isamarkupchapter{Example: FIXME%
}
\isamarkuptrue%
%
\isamarkupchapter{FIXME%
}
\isamarkuptrue%
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\isamarkupsection{Formal document preparation%
}
\isamarkuptrue%
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\isamarkupsubsection{Example%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
See this very document itself.%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isamarkupsubsection{Getting started%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
\verb"isatool mkdir Test && isatool make"%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isamarkupsection{Human-readable proof composition in Isar%
}
\isamarkuptrue%
%
\isamarkupsubsection{Getting started%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Claim a trivial goal in order to enter proof mode \isa{{\isasymdots}}%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isamarkupfalse%
%
\begin{isamarkuptxt}%
After the canonical initial refinement step we are left
    within an \emph{proof body}.%
\end{isamarkuptxt}%
\isamarkuptrue%
%
\begin{isamarkuptxt}%
Here we may augment the present local {proof context} as we
    please.%
\end{isamarkuptxt}%
\ \ \isamarkuptrue%
\isacommand{fix}\ something\isanewline
\ \ \isamarkupfalse%
\isacommand{assume}\ a{\isacharcolon}\ {\isachardoublequote}anything\ something{\isachardoublequote}\isamarkupfalse%
%
\begin{isamarkuptxt}%
Note that the present configuration may be inspected by
  several \emph{diagnostic commands}.%
\end{isamarkuptxt}%
\ \ \isamarkuptrue%
\isacommand{term}\ something\ \ %
\isamarkupcmt{\isa{something{\isasymColon}{\isacharprime}a}%
}
\isanewline
\ \ \isamarkupfalse%
\isacommand{term}\ anything\ \ %
\isamarkupcmt{\isa{anything{\isasymColon}{\isacharprime}a\ {\isasymRightarrow}\ bool}%
}
\isanewline
\ \ \isamarkupfalse%
\isacommand{thm}\ a\ \ %
\isamarkupcmt{\isa{anything\ something}%
}
\isamarkupfalse%
%
\begin{isamarkuptxt}%
We may state local (auxiliary) results as well.%
\end{isamarkuptxt}%
\ \ \isamarkuptrue%
\isacommand{have}\ True\ \isamarkupfalse%
\isacommand{proof}\ \isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptxt}%
We are now satisfied.%
\end{isamarkuptxt}%
\isamarkuptrue%
\isacommand{qed}\isamarkupfalse%
%
\isamarkupsubsection{Calculational Reasoning%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Isar is mainly about Natural Deduction, but Calculational Reasoning
  turns out as a simplified instance of that, so we demonstrate it
  first.%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isamarkupsubsubsection{Transitive chains%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Technique: establish a chain of local facts, separated by \cmd{also}
  and terminated by \cmd{finally}; another goal has to follow to point
  out the final result.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ {\isachardoublequote}x{\isadigit{1}}\ {\isacharequal}\ x{\isadigit{4}}{\isachardoublequote}\isanewline
\isamarkupfalse%
\isacommand{proof}\ {\isacharminus}\ \ %
\isamarkupcmt{do nothing yet%
}
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}x{\isadigit{1}}\ {\isacharequal}\ x{\isadigit{2}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}x{\isadigit{2}}\ {\isacharequal}\ x{\isadigit{3}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}x{\isadigit{3}}\ {\isacharequal}\ x{\isadigit{4}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{finally}\isanewline
\ \ \isamarkupfalse%
\isacommand{show}\ {\isachardoublequote}x{\isadigit{1}}\ {\isacharequal}\ x{\isadigit{4}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{{\isachardot}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptext}%
This may be written more succinctly, using the special term binds
  ``\isa{{\isasymdots}}'' (for the right-hand side of the last statement) and
  ``\isa{{\isacharquery}thesis}'' (for the original claim at the head of the
  proof).%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ {\isachardoublequote}x{\isadigit{1}}\ {\isacharequal}\ x{\isadigit{4}}{\isachardoublequote}\isanewline
\isamarkupfalse%
\isacommand{proof}\ {\isacharminus}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}x{\isadigit{1}}\ {\isacharequal}\ x{\isadigit{2}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isacharequal}\ x{\isadigit{3}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isacharequal}\ x{\isadigit{4}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{finally}\ \isamarkupfalse%
\isacommand{show}\ {\isacharquery}thesis\ \isamarkupfalse%
\isacommand{{\isachardot}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptext}%
The (implicit) forward-chaining steps involved in \cmd{also} and
  \cmd{finally} are declared in the current context.  The main library
  of Isabelle/HOL already knows about (mixed) transitivities of \isa{{\isacharequal}}, \isa{{\isacharless}}, \isa{{\isasymle}} etc.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ {\isachardoublequote}{\isacharparenleft}x{\isadigit{1}}{\isacharcolon}{\isacharcolon}nat{\isacharparenright}\ {\isacharless}\ x{\isadigit{6}}{\isachardoublequote}\isanewline
\ \ %
\isamarkupcmt{restriction to type \isa{nat} ensures that \isa{{\isacharless}} is really transitive%
}
\isanewline
\isamarkupfalse%
\isacommand{proof}\ {\isacharminus}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}x{\isadigit{1}}\ {\isacharless}\ x{\isadigit{2}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isasymle}\ x{\isadigit{3}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isacharequal}\ x{\isadigit{4}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isacharless}\ x{\isadigit{5}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isacharequal}\ x{\isadigit{6}}{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{finally}\ \isamarkupfalse%
\isacommand{show}\ {\isacharquery}thesis\ \isamarkupfalse%
\isacommand{{\isachardot}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptext}%
We may also calculate on propositions.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymlongrightarrow}\ B\ {\isasymlongrightarrow}\ C{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ A\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ B\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{finally}\ \isamarkupfalse%
\isacommand{have}\ C\ \isamarkupfalse%
\isacommand{{\isachardot}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptext}%
This is getting pretty close to Dijkstra's preferred proof style.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isacharbrackleft}trans{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}{\isasymAnd}X\ Y\ Z{\isachardot}\ X\ {\isasymlongrightarrow}\ Y\ {\isasymLongrightarrow}\ Y\ {\isasymlongrightarrow}\ Z\ {\isasymLongrightarrow}\ X\ {\isasymlongrightarrow}\ Z{\isachardoublequote}\ \isamarkupfalse%
\isacommand{by}\ rules\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymlongrightarrow}\ B{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isasymlongrightarrow}\ C{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{also}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymdots}\ {\isasymlongrightarrow}\ D{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{finally}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymlongrightarrow}\ D{\isachardoublequote}\ \isamarkupfalse%
\isacommand{{\isachardot}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\isamarkupsubsubsection{Degenerate calculations and bigstep reasoning%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Instead of \cmd{also}/\cmd{finally} we may use degenerative steps
  \cmd{moreover}/\cmd{ultimately} to accumulate facts, without
  applying any forward rules yet.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ A\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{moreover}\ \isamarkupfalse%
\isacommand{have}\ B\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{moreover}\ \isamarkupfalse%
\isacommand{have}\ C\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{ultimately}\ \isamarkupfalse%
\isacommand{have}\ A\ \isakeyword{and}\ B\ \isakeyword{and}\ C\ \isamarkupfalse%
\isacommand{{\isachardot}}\ \ %
\isamarkupcmt{Pretty obvious, right?%
}
\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptext}%
Both kinds of calculational elements may be used together.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \isamarkupfalse%
\isacommand{assume}\ reasoning{\isacharunderscore}pattern\ {\isacharbrackleft}trans{\isacharbrackright}{\isacharcolon}\ {\isachardoublequote}A\ {\isasymLongrightarrow}\ B\ {\isasymLongrightarrow}\ C\ {\isasymLongrightarrow}\ D{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ A\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{moreover}\ \isamarkupfalse%
\isacommand{have}\ B\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{moreover}\ \isamarkupfalse%
\isacommand{have}\ C\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{finally}\ \isamarkupfalse%
\isacommand{have}\ D\ \isamarkupfalse%
\isacommand{{\isachardot}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\isamarkupsubsection{Natural deduction%
}
\isamarkuptrue%
%
\isamarkupsubsubsection{Primitive patterns%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
The default theory context admits to perform canonical single-step
  reasoning (similar to Gentzen) without further ado.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ True\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ False\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ C\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymnot}\ A{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{assume}\ A\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ False\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}{\isasymnot}\ A{\isachardoublequote}\ \isakeyword{and}\ A\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ C\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymlongrightarrow}\ B{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{assume}\ A\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ B\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}A\ {\isasymlongrightarrow}\ B{\isachardoublequote}\ \isakeyword{and}\ A\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ B\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymand}\ B{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ A\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ B\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}A\ {\isasymand}\ B{\isachardoublequote}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ A\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}A\ {\isasymand}\ B{\isachardoublequote}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ B\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ A\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymor}\ B{\isachardoublequote}\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ B\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}A\ {\isasymor}\ B{\isachardoublequote}\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}A\ {\isasymor}\ B{\isachardoublequote}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ C\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \ \ \isamarkupfalse%
\isacommand{assume}\ A\isanewline
\ \ \ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{show}\ {\isacharquery}thesis\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{next}\isanewline
\ \ \ \ \ \ \isamarkupfalse%
\isacommand{assume}\ B\isanewline
\ \ \ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{show}\ {\isacharquery}thesis\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{qed}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymforall}x{\isachardot}\ P\ x{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{fix}\ x\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ {\isachardoublequote}P\ x{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}{\isasymforall}x{\isachardot}\ P\ x{\isachardoublequote}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}P\ t{\isachardoublequote}\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}{\isasymexists}x{\isachardot}\ P\ x{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ {\isachardoublequote}P\ t{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\ \ \isanewline
\ \ \isamarkupfalse%
\isacommand{{\isacharbraceleft}}\ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}{\isasymexists}x{\isachardot}\ P\ x{\isachardoublequote}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{then}\ \isamarkupfalse%
\isacommand{obtain}\ x\ \isakeyword{where}\ {\isachardoublequote}P\ x{\isachardoublequote}\ \isamarkupfalse%
\isacommand{{\isachardot}{\isachardot}}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{note}\ nothing\ \ %
\isamarkupcmt{relax%
}
\ \isamarkupfalse%
\isacommand{{\isacharbraceright}}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\begin{isamarkuptext}%
Certainly, this works with derived rules for defined concepts in the
  same manner.  E.g.\ use the simple-typed set-theory of Isabelle/HOL.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{lemma}\ True\isanewline
\isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}y\ {\isasymin}\ {\isacharparenleft}{\isasymInter}x\ {\isasymin}\ A{\isachardot}\ B\ x{\isacharparenright}{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{fix}\ x\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{assume}\ {\isachardoublequote}x\ {\isasymin}\ A{\isachardoublequote}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ {\isachardoublequote}y\ {\isasymin}\ B\ x{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\isanewline
\ \ \isamarkupfalse%
\isacommand{have}\ {\isachardoublequote}y\ {\isasymin}\ {\isacharparenleft}{\isasymUnion}x\ {\isasymin}\ A{\isachardot}\ B\ x{\isacharparenright}{\isachardoublequote}\isanewline
\ \ \isamarkupfalse%
\isacommand{proof}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ {\isachardoublequote}a\ {\isasymin}\ A{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \ \ \isamarkupfalse%
\isacommand{show}\ {\isachardoublequote}y\ {\isasymin}\ B\ a{\isachardoublequote}\ \isamarkupfalse%
\isacommand{sorry}\isanewline
\ \ \isamarkupfalse%
\isacommand{qed}\isanewline
\isamarkupfalse%
\isacommand{qed}\isamarkupfalse%
%
\isamarkupsubsubsection{Variations in structure%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
The design of the Isar language takes the user seriously%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isamarkupsubsubsection{Generalized elimination%
}
\isamarkuptrue%
%
\isamarkupsubsubsection{Scalable cases and induction%
}
\isamarkuptrue%
%
\isamarkupsection{Assimilating the old tactical style%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Improper commands: 
  Observation: every Isar subproof may start with a ``script'' of%
\end{isamarkuptext}%
\isamarkuptrue%
\isamarkupfalse%
\end{isabellebody}%
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