%
\begin{isabellebody}%
\def\isabellecontext{First{\isaliteral{5F}{\isacharunderscore}}Order{\isaliteral{5F}{\isacharunderscore}}Logic}%
%
\isamarkupheader{Example: First-Order Logic%
}
\isamarkuptrue%
%
\isadelimvisible
%
\endisadelimvisible
%
\isatagvisible
\isacommand{theory}\isamarkupfalse%
\ First{\isaliteral{5F}{\isacharunderscore}}Order{\isaliteral{5F}{\isacharunderscore}}Logic\isanewline
\isakeyword{imports}\ Base\ \ \isanewline
\isakeyword{begin}%
\endisatagvisible
{\isafoldvisible}%
%
\isadelimvisible
%
\endisadelimvisible
%
\begin{isamarkuptext}%
\noindent In order to commence a new object-logic within
Isabelle/Pure we introduce abstract syntactic categories \isa{{\isaliteral{22}{\isachardoublequote}}i{\isaliteral{22}{\isachardoublequote}}}
for individuals and \isa{{\isaliteral{22}{\isachardoublequote}}o{\isaliteral{22}{\isachardoublequote}}} for object-propositions. The latter
is embedded into the language of Pure propositions by means of a
separate judgment.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{typedecl}\isamarkupfalse%
\ i\isanewline
\isacommand{typedecl}\isamarkupfalse%
\ o\isanewline
\isanewline
\isacommand{judgment}\isamarkupfalse%
\isanewline
\ \ Trueprop\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ prop{\isaliteral{22}{\isachardoublequoteclose}}\ \ \ \ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5F}{\isacharunderscore}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{5}}{\isaliteral{29}{\isacharparenright}}%
\begin{isamarkuptext}%
\noindent Note that the object-logic judgement is implicit in the
syntax: writing \isa{A} produces \isa{{\isaliteral{22}{\isachardoublequote}}Trueprop\ A{\isaliteral{22}{\isachardoublequote}}} internally.
From the Pure perspective this means ``\isa{A} is derivable in the
object-logic''.%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isamarkupsubsection{Equational reasoning \label{sec:framework-ex-equal}%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Equality is axiomatized as a binary predicate on individuals, with
reflexivity as introduction, and substitution as elimination
principle. Note that the latter is particularly convenient in a
framework like Isabelle, because syntactic congruences are
implicitly produced by unification of \isa{{\isaliteral{22}{\isachardoublequote}}B\ x{\isaliteral{22}{\isachardoublequote}}} against
expressions containing occurrences of \isa{x}.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ equal\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{infix}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{3D}{\isacharequal}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{5}}{\isadigit{0}}{\isaliteral{29}{\isacharparenright}}\isanewline
\isakeyword{where}\isanewline
\ \ refl\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ subst\ {\isaliteral{5B}{\isacharbrackleft}}elim{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B\ x\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B\ y{\isaliteral{22}{\isachardoublequoteclose}}%
\begin{isamarkuptext}%
\noindent Substitution is very powerful, but also hard to control in
full generality. We derive some common symmetry~/ transitivity
schemes of \isa{equal} as particular consequences.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{theorem}\isamarkupfalse%
\ sym\ {\isaliteral{5B}{\isacharbrackleft}}sym{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ {\isaliteral{22}{\isachardoublequoteopen}}y\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{with}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}y\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
\isanewline
%
\endisadelimproof
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ forw{\isaliteral{5F}{\isacharunderscore}}subst\ {\isaliteral{5B}{\isacharbrackleft}}trans{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}y\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ x{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ y{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}y\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ this\ \isakeyword{and}\ {\isaliteral{60}{\isacharbackquoteopen}}B\ x{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}B\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
\isanewline
%
\endisadelimproof
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ back{\isaliteral{5F}{\isacharunderscore}}subst\ {\isaliteral{5B}{\isacharbrackleft}}trans{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ y{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{60}{\isacharbackquoteclose}}\ \isakeyword{and}\ {\isaliteral{60}{\isacharbackquoteopen}}B\ x{\isaliteral{60}{\isacharbackquoteclose}}\isanewline
\ \ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}B\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
\isanewline
%
\endisadelimproof
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ trans\ {\isaliteral{5B}{\isacharbrackleft}}trans{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\ {\isaliteral{22}{\isachardoublequoteopen}}y\ {\isaliteral{3D}{\isacharequal}}\ z{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ z{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}y\ {\isaliteral{3D}{\isacharequal}}\ z{\isaliteral{60}{\isacharbackquoteclose}}\ \isakeyword{and}\ {\isaliteral{60}{\isacharbackquoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ y{\isaliteral{60}{\isacharbackquoteclose}}\isanewline
\ \ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{3D}{\isacharequal}}\ z{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isamarkupsubsection{Basic group theory%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
As an example for equational reasoning we consider some bits of
group theory. The subsequent locale definition postulates group
operations and axioms; we also derive some consequences of this
specification.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{locale}\isamarkupfalse%
\ group\ {\isaliteral{3D}{\isacharequal}}\isanewline
\ \ \isakeyword{fixes}\ prod\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ i{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{infix}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C636972633E}{\isasymcirc}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{7}}{\isadigit{0}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \ \ \isakeyword{and}\ inv\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ i{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{5F}{\isacharunderscore}}{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isaliteral{5B}{\isacharbrackleft}}{\isadigit{1}}{\isadigit{0}}{\isadigit{0}}{\isadigit{0}}{\isaliteral{5D}{\isacharbrackright}}\ {\isadigit{9}}{\isadigit{9}}{\isadigit{9}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \ \ \isakeyword{and}\ unit\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ i\ \ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{22}{\isachardoublequoteopen}}{\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isakeyword{assumes}\ assoc{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ y{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ z\ {\isaliteral{3D}{\isacharequal}}\ x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{28}{\isacharparenleft}}y\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ z{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \ \ \isakeyword{and}\ left{\isaliteral{5F}{\isacharunderscore}}unit{\isaliteral{3A}{\isacharcolon}}\ \ {\isaliteral{22}{\isachardoublequoteopen}}{\isadigit{1}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \ \ \isakeyword{and}\ left{\isaliteral{5F}{\isacharunderscore}}inv{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isakeyword{begin}\isanewline
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ right{\isaliteral{5F}{\isacharunderscore}}inv{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{28}{\isacharparenleft}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}unit\ {\isaliteral{5B}{\isacharbrackleft}}symmetric{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{3D}{\isacharequal}}\ {\isaliteral{28}{\isacharparenleft}}{\isadigit{1}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ assoc\ {\isaliteral{5B}{\isacharbrackleft}}symmetric{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isadigit{1}}\ {\isaliteral{3D}{\isacharequal}}\ {\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}inv\ {\isaliteral{5B}{\isacharbrackleft}}symmetric{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x\ {\isaliteral{3D}{\isacharequal}}\ {\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ assoc{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}inv{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{5C3C646F74733E}{\isasymdots}}{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{3D}{\isacharequal}}\ {\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{28}{\isacharparenleft}}{\isadigit{1}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ assoc{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isadigit{1}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}unit{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}inv{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{finally}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
\isanewline
%
\endisadelimproof
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ right{\isaliteral{5F}{\isacharunderscore}}unit{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isadigit{1}}\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isadigit{1}}\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}inv\ {\isaliteral{5B}{\isacharbrackleft}}symmetric{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{3D}{\isacharequal}}\ {\isaliteral{28}{\isacharparenleft}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ assoc\ {\isaliteral{5B}{\isacharbrackleft}}symmetric{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ right{\isaliteral{5F}{\isacharunderscore}}inv{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ left{\isaliteral{5F}{\isacharunderscore}}unit{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{finally}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isadigit{1}}\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\noindent Reasoning from basic axioms is often tedious. Our proofs
work by producing various instances of the given rules (potentially
the symmetric form) using the pattern ``\hyperlink{command.have}{\mbox{\isa{\isacommand{have}}}}~\isa{eq}~\hyperlink{command.by}{\mbox{\isa{\isacommand{by}}}}~\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{28}{\isacharparenleft}}rule\ r{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequote}}}'' and composing the chain of
results via \hyperlink{command.also}{\mbox{\isa{\isacommand{also}}}}/\hyperlink{command.finally}{\mbox{\isa{\isacommand{finally}}}}. These steps may
involve any of the transitivity rules declared in
\secref{sec:framework-ex-equal}, namely \isa{trans} in combining
the first two results in \isa{right{\isaliteral{5F}{\isacharunderscore}}inv} and in the final steps of
both proofs, \isa{forw{\isaliteral{5F}{\isacharunderscore}}subst} in the first combination of \isa{right{\isaliteral{5F}{\isacharunderscore}}unit}, and \isa{back{\isaliteral{5F}{\isacharunderscore}}subst} in all other calculational steps.
Occasional substitutions in calculations are adequate, but should
not be over-emphasized. The other extreme is to compose a chain by
plain transitivity only, with replacements occurring always in
topmost position. For example:%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isadigit{1}}\ {\isaliteral{3D}{\isacharequal}}\ x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isaliteral{28}{\isacharparenleft}}x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{unfolding}\isamarkupfalse%
\ left{\isaliteral{5F}{\isacharunderscore}}inv\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{3D}{\isacharequal}}\ {\isaliteral{28}{\isacharparenleft}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{5C3C696E76657273653E}{\isasyminverse}}{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{unfolding}\isamarkupfalse%
\ assoc\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{3D}{\isacharequal}}\ {\isadigit{1}}\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{unfolding}\isamarkupfalse%
\ right{\isaliteral{5F}{\isacharunderscore}}inv\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{also}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C646F74733E}{\isasymdots}}\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{unfolding}\isamarkupfalse%
\ left{\isaliteral{5F}{\isacharunderscore}}unit\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{finally}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}x\ {\isaliteral{5C3C636972633E}{\isasymcirc}}\ {\isadigit{1}}\ {\isaliteral{3D}{\isacharequal}}\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\noindent Here we have re-used the built-in mechanism for unfolding
definitions in order to normalize each equational problem. A more
realistic object-logic would include proper setup for the Simplifier
(\secref{sec:simplifier}), the main automated tool for equational
reasoning in Isabelle. Then ``\hyperlink{command.unfolding}{\mbox{\isa{\isacommand{unfolding}}}}~\isa{left{\isaliteral{5F}{\isacharunderscore}}inv}~\hyperlink{command.ddot}{\mbox{\isa{\isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}}}}'' would become ``\hyperlink{command.by}{\mbox{\isa{\isacommand{by}}}}~\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{28}{\isacharparenleft}}simp\ only{\isaliteral{3A}{\isacharcolon}}\ left{\isaliteral{5F}{\isacharunderscore}}inv{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequote}}}'' etc.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{end}\isamarkupfalse%
%
\isamarkupsubsection{Propositional logic \label{sec:framework-ex-prop}%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
We axiomatize basic connectives of propositional logic: implication,
disjunction, and conjunction. The associated rules are modeled
after Gentzen's system of Natural Deduction \cite{Gentzen:1935}.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ imp\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{infixr}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{2}}{\isadigit{5}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ impI\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ impD\ {\isaliteral{5B}{\isacharbrackleft}}dest{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ B{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isanewline
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ disj\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{infixr}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6F723E}{\isasymor}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{3}}{\isadigit{0}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ disjI\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{1}}\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ disjI\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{2}}\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ disjE\ {\isaliteral{5B}{\isacharbrackleft}}elim{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{28}{\isacharparenleft}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{28}{\isacharparenleft}}B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isanewline
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ conj\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{infixr}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C616E643E}{\isasymand}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{3}}{\isadigit{5}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ conjI\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ conjD\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{1}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ conjD\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{2}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B{\isaliteral{22}{\isachardoublequoteclose}}%
\begin{isamarkuptext}%
\noindent The conjunctive destructions have the disadvantage that
decomposing \isa{{\isaliteral{22}{\isachardoublequote}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequote}}} involves an immediate decision which
component should be projected. The more convenient simultaneous
elimination \isa{{\isaliteral{22}{\isachardoublequote}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{28}{\isacharparenleft}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{22}{\isachardoublequote}}} can be derived as
follows:%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{theorem}\isamarkupfalse%
\ conjE\ {\isaliteral{5B}{\isacharbrackleft}}elim{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{obtains}\ A\ \isakeyword{and}\ B\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ A\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ conjD\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{1}}{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ B\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ conjD\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{2}}{\isaliteral{29}{\isacharparenright}}\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\noindent Here is an example of swapping conjuncts with a single
intermediate elimination step:%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\ \ \isacommand{assume}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{obtain}\isamarkupfalse%
\ B\ \isakeyword{and}\ A\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}B\ {\isaliteral{5C3C616E643E}{\isasymand}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\noindent Note that the analogous elimination rule for disjunction
``\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B\ {\isaliteral{5C3C4F425441494E533E}{\isasymOBTAINS}}\ A\ {\isaliteral{5C3C424241523E}{\isasymBBAR}}\ B{\isaliteral{22}{\isachardoublequote}}}'' coincides with
the original axiomatization of \isa{disjE}.
\medskip We continue propositional logic by introducing absurdity
with its characteristic elimination. Plain truth may then be
defined as a proposition that is trivially true.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ false\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ o\ \ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ falseE\ {\isaliteral{5B}{\isacharbrackleft}}elim{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isanewline
\isacommand{definition}\isamarkupfalse%
\isanewline
\ \ true\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ o\ \ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C746F703E}{\isasymtop}}{\isaliteral{22}{\isachardoublequoteclose}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C746F703E}{\isasymtop}}\ {\isaliteral{5C3C65717569763E}{\isasymequiv}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ trueI\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C746F703E}{\isasymtop}}\isanewline
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{unfolding}\isamarkupfalse%
\ true{\isaliteral{5F}{\isacharunderscore}}def\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\medskip\noindent Now negation represents an implication towards
absurdity:%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{definition}\isamarkupfalse%
\isanewline
\ \ not\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}o\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{5F}{\isacharunderscore}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isaliteral{5B}{\isacharbrackleft}}{\isadigit{4}}{\isadigit{0}}{\isaliteral{5D}{\isacharbrackright}}\ {\isadigit{4}}{\isadigit{0}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A\ {\isaliteral{5C3C65717569763E}{\isasymequiv}}\ A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ notI\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{unfolding}\isamarkupfalse%
\ not{\isaliteral{5F}{\isacharunderscore}}def\isanewline
\isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \isacommand{assume}\isamarkupfalse%
\ A\isanewline
\ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ \isacommand{by}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ {\isaliteral{60}{\isacharbackquoteopen}}A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{60}{\isacharbackquoteclose}}{\isaliteral{29}{\isacharparenright}}\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
\isanewline
%
\endisadelimproof
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ notE\ {\isaliteral{5B}{\isacharbrackleft}}elim{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\ A\isanewline
\ \ \isakeyword{shows}\ B\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{2D}{\isacharminus}}\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{unfolding}\isamarkupfalse%
\ not{\isaliteral{5F}{\isacharunderscore}}def\ \isacommand{{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{from}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{60}{\isacharbackquoteclose}}\ \isakeyword{and}\ {\isaliteral{60}{\isacharbackquoteopen}}A{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ B\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isamarkupsubsection{Classical logic%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Subsequently we state the principle of classical contradiction as a
local assumption. Thus we refrain from forcing the object-logic
into the classical perspective. Within that context, we may derive
well-known consequences of the classical principle.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{locale}\isamarkupfalse%
\ classical\ {\isaliteral{3D}{\isacharequal}}\isanewline
\ \ \isakeyword{assumes}\ classical{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isakeyword{begin}\isanewline
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ double{\isaliteral{5F}{\isacharunderscore}}negation{\isaliteral{3A}{\isacharcolon}}\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ C\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ classical{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{assume}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{with}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ C\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
\isanewline
%
\endisadelimproof
\isanewline
\isacommand{theorem}\isamarkupfalse%
\ tertium{\isaliteral{5F}{\isacharunderscore}}non{\isaliteral{5F}{\isacharunderscore}}datur{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ {\isaliteral{28}{\isacharparenleft}}rule\ double{\isaliteral{5F}{\isacharunderscore}}negation{\isaliteral{29}{\isacharparenright}}\isanewline
\ \ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{28}{\isacharparenleft}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{assume}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{28}{\isacharparenleft}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \ \ \isacommand{assume}\isamarkupfalse%
\ C\ \isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \ \ \ \ \isacommand{with}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{28}{\isacharparenleft}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{29}{\isacharparenright}}{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{qed}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{with}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ {\isaliteral{28}{\isacharparenleft}}C\ {\isaliteral{5C3C6F723E}{\isasymor}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C{\isaliteral{29}{\isacharparenright}}{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\ \ \isacommand{qed}\isamarkupfalse%
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\noindent These examples illustrate both classical reasoning and
non-trivial propositional proofs in general. All three rules
characterize classical logic independently, but the original rule is
already the most convenient to use, because it leaves the conclusion
unchanged. Note that \isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ C\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{22}{\isachardoublequote}}} fits again into our
format for eliminations, despite the additional twist that the
context refers to the main conclusion. So we may write \isa{classical} as the Isar statement ``\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C4F425441494E533E}{\isasymOBTAINS}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ thesis{\isaliteral{22}{\isachardoublequote}}}''.
This also explains nicely how classical reasoning really works:
whatever the main \isa{thesis} might be, we may always assume its
negation!%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{end}\isamarkupfalse%
%
\isamarkupsubsection{Quantifiers \label{sec:framework-ex-quant}%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
Representing quantifiers is easy, thanks to the higher-order nature
of the underlying framework. According to the well-known technique
introduced by Church \cite{church40}, quantifiers are operators on
predicates, which are syntactically represented as \isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C6C616D6264613E}{\isasymlambda}}{\isaliteral{22}{\isachardoublequote}}}-terms
of type \isa{{\isaliteral{22}{\isachardoublequote}}i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequote}}}. Binder notation turns \isa{{\isaliteral{22}{\isachardoublequote}}All\ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C6C616D6264613E}{\isasymlambda}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequote}}} into \isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequote}}} etc.%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ All\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{binder}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{1}}{\isadigit{0}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ allI\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C416E643E}{\isasymAnd}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ allD\ {\isaliteral{5B}{\isacharbrackleft}}dest{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B\ a{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\isanewline
\isacommand{axiomatization}\isamarkupfalse%
\isanewline
\ \ Ex\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}i\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ o{\isaliteral{22}{\isachardoublequoteclose}}\ \ {\isaliteral{28}{\isacharparenleft}}\isakeyword{binder}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}{\isaliteral{22}{\isachardoublequoteclose}}\ {\isadigit{1}}{\isadigit{0}}{\isaliteral{29}{\isacharparenright}}\ \isakeyword{where}\isanewline
\ \ exI\ {\isaliteral{5B}{\isacharbrackleft}}intro{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ a\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{29}{\isacharparenright}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\isanewline
\ \ exE\ {\isaliteral{5B}{\isacharbrackleft}}elim{\isaliteral{5D}{\isacharbrackright}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C416E643E}{\isasymAnd}}x{\isaliteral{2E}{\isachardot}}\ B\ x\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ C{\isaliteral{22}{\isachardoublequoteclose}}%
\begin{isamarkuptext}%
\noindent The statement of \isa{exE} corresponds to ``\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ {\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x\ {\isaliteral{5C3C4F425441494E533E}{\isasymOBTAINS}}\ x\ {\isaliteral{5C3C57484552453E}{\isasymWHERE}}\ B\ x{\isaliteral{22}{\isachardoublequote}}}'' in Isar. In the
subsequent example we illustrate quantifier reasoning involving all
four rules:%
\end{isamarkuptext}%
\isamarkuptrue%
\isacommand{theorem}\isamarkupfalse%
\isanewline
\ \ \isakeyword{assumes}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ {\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}y{\isaliteral{2E}{\isachardot}}\ R\ x\ y{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isakeyword{shows}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}y{\isaliteral{2E}{\isachardot}}\ {\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ R\ x\ y{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
\isacommand{proof}\isamarkupfalse%
\ \ \ \ %
\isamarkupcmt{\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}{\isaliteral{22}{\isachardoublequote}}} introduction%
}
\isanewline
\ \ \isacommand{obtain}\isamarkupfalse%
\ x\ \isakeyword{where}\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}y{\isaliteral{2E}{\isachardot}}\ R\ x\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{using}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ {\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}y{\isaliteral{2E}{\isachardot}}\ R\ x\ y{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\ \ \ \ %
\isamarkupcmt{\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}{\isaliteral{22}{\isachardoublequote}}} elimination%
}
\isanewline
\ \ \isacommand{fix}\isamarkupfalse%
\ y\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}R\ x\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{using}\isamarkupfalse%
\ {\isaliteral{60}{\isacharbackquoteopen}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}y{\isaliteral{2E}{\isachardot}}\ R\ x\ y{\isaliteral{60}{\isacharbackquoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\ \ \ \ %
\isamarkupcmt{\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}{\isaliteral{22}{\isachardoublequote}}} destruction%
}
\isanewline
\ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ R\ x\ y{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\ \ \ \ %
\isamarkupcmt{\isa{{\isaliteral{22}{\isachardoublequote}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}{\isaliteral{22}{\isachardoublequote}}} introduction%
}
\isanewline
\isacommand{qed}\isamarkupfalse%
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isamarkupsubsection{Canonical reasoning patterns%
}
\isamarkuptrue%
%
\begin{isamarkuptext}%
The main rules of first-order predicate logic from
\secref{sec:framework-ex-prop} and \secref{sec:framework-ex-quant}
can now be summarized as follows, using the native Isar statement
format of \secref{sec:framework-stmt}.
\medskip
\begin{tabular}{l}
\isa{{\isaliteral{22}{\isachardoublequote}}impI{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ B\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ B{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}impD{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ B\ {\isaliteral{5C3C414E443E}{\isasymAND}}\ A\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ B{\isaliteral{22}{\isachardoublequote}}} \\[1ex]
\isa{{\isaliteral{22}{\isachardoublequote}}disjI\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{1}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}disjI\isaliteral{5C3C5E697375623E}{}\isactrlisub {\isadigit{2}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ B\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}disjE{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B\ {\isaliteral{5C3C4F425441494E533E}{\isasymOBTAINS}}\ A\ {\isaliteral{5C3C424241523E}{\isasymBBAR}}\ B{\isaliteral{22}{\isachardoublequote}}} \\[1ex]
\isa{{\isaliteral{22}{\isachardoublequote}}conjI{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C414E443E}{\isasymAND}}\ B\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}conjE{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B\ {\isaliteral{5C3C4F425441494E533E}{\isasymOBTAINS}}\ A\ {\isaliteral{5C3C414E443E}{\isasymAND}}\ B{\isaliteral{22}{\isachardoublequote}}} \\[1ex]
\isa{{\isaliteral{22}{\isachardoublequote}}falseE{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ A{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}trueI{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ {\isaliteral{5C3C746F703E}{\isasymtop}}{\isaliteral{22}{\isachardoublequote}}} \\[1ex]
\isa{{\isaliteral{22}{\isachardoublequote}}notI{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ A\ {\isaliteral{5C3C4C6F6E6772696768746172726F773E}{\isasymLongrightarrow}}\ {\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}notE{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ {\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A\ {\isaliteral{5C3C414E443E}{\isasymAND}}\ A\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ B{\isaliteral{22}{\isachardoublequote}}} \\[1ex]
\isa{{\isaliteral{22}{\isachardoublequote}}allI{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ {\isaliteral{5C3C416E643E}{\isasymAnd}}x{\isaliteral{2E}{\isachardot}}\ B\ x\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ {\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}allE{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ {\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ B\ a{\isaliteral{22}{\isachardoublequote}}} \\[1ex]
\isa{{\isaliteral{22}{\isachardoublequote}}exI{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ B\ a\ {\isaliteral{5C3C53484F57533E}{\isasymSHOWS}}\ {\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequote}}} \\
\isa{{\isaliteral{22}{\isachardoublequote}}exE{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{5C3C415353554D45533E}{\isasymASSUMES}}\ {\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x\ {\isaliteral{5C3C4F425441494E533E}{\isasymOBTAINS}}\ a\ {\isaliteral{5C3C57484552453E}{\isasymWHERE}}\ B\ a{\isaliteral{22}{\isachardoublequote}}}
\end{tabular}
\medskip
\noindent This essentially provides a declarative reading of Pure
rules as Isar reasoning patterns: the rule statements tells how a
canonical proof outline shall look like. Since the above rules have
already been declared as \hyperlink{attribute.Pure.intro}{\mbox{\isa{intro}}}, \hyperlink{attribute.Pure.elim}{\mbox{\isa{elim}}}, \hyperlink{attribute.Pure.dest}{\mbox{\isa{dest}}} --- each according to its
particular shape --- we can immediately write Isar proof texts as
follows:%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isadelimproof
%
\endisadelimproof
%
\isatagproof
%
\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{assume}\isamarkupfalse%
\ A\isanewline
\ \ \ \ \isacommand{show}\isamarkupfalse%
\ B%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{qed}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6C6F6E6772696768746172726F773E}{\isasymlongrightarrow}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\ A%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ B\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\\[3ex]\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ A%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
\isanewline
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ B%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C6F723E}{\isasymor}}\ B{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ C\isanewline
\ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{assume}\isamarkupfalse%
\ A\isanewline
\ \ \ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ C%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{next}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{assume}\isamarkupfalse%
\ B\isanewline
\ \ \ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ C%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{qed}\isamarkupfalse%
%
\end{minipage}\\[3ex]\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ A\ \isakeyword{and}\ B%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}A\ {\isaliteral{5C3C616E643E}{\isasymand}}\ B{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{obtain}\isamarkupfalse%
\ A\ \isakeyword{and}\ B\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\\[3ex]\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ A\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C746F703E}{\isasymtop}}{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\\[3ex]\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{assume}\isamarkupfalse%
\ A\isanewline
\ \ \ \ \isacommand{then}\isamarkupfalse%
\ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C626F74746F6D3E}{\isasymbottom}}{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{qed}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6E6F743E}{\isasymnot}}\ A{\isaliteral{22}{\isachardoublequoteclose}}\ \isakeyword{and}\ A%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ B\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\\[3ex]\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{fix}\isamarkupfalse%
\ x\isanewline
\ \ \ \ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}B\ x{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{qed}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}B\ a{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}\\[3ex]\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequoteclose}}\isanewline
\ \ \isacommand{proof}\isamarkupfalse%
\isanewline
\ \ \ \ \isacommand{show}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}B\ a{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{qed}\isamarkupfalse%
%
\end{minipage}\qquad\begin{minipage}[t]{0.4\textwidth}
\isanewline
\ \ \isacommand{have}\isamarkupfalse%
\ {\isaliteral{22}{\isachardoublequoteopen}}{\isaliteral{5C3C6578697374733E}{\isasymexists}}x{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{22}{\isachardoublequoteclose}}%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\isadelimnoproof
\ %
\endisadelimnoproof
%
\isatagnoproof
\isacommand{sorry}\isamarkupfalse%
%
\endisatagnoproof
{\isafoldnoproof}%
%
\isadelimnoproof
\isanewline
%
\endisadelimnoproof
%
\isadelimproof
\ \ %
\endisadelimproof
%
\isatagproof
\isacommand{then}\isamarkupfalse%
\ \isacommand{obtain}\isamarkupfalse%
\ a\ \isakeyword{where}\ {\isaliteral{22}{\isachardoublequoteopen}}B\ a{\isaliteral{22}{\isachardoublequoteclose}}\ \isacommand{{\isaliteral{2E}{\isachardot}}{\isaliteral{2E}{\isachardot}}}\isamarkupfalse%
%
\end{minipage}
%
\endisatagproof
{\isafoldproof}%
%
\isadelimproof
%
\endisadelimproof
%
\begin{isamarkuptext}%
\bigskip\noindent Of course, these proofs are merely examples. As
sketched in \secref{sec:framework-subproof}, there is a fair amount
of flexibility in expressing Pure deductions in Isar. Here the user
is asked to express himself adequately, aiming at proof texts of
literary quality.%
\end{isamarkuptext}%
\isamarkuptrue%
%
\isadelimvisible
%
\endisadelimvisible
%
\isatagvisible
\isacommand{end}\isamarkupfalse%
%
\endisatagvisible
{\isafoldvisible}%
%
\isadelimvisible
%
\endisadelimvisible
\isanewline
\end{isabellebody}%
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