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doc-src/IsarRef/generic.tex

author | wenzelm |

Wed, 04 Oct 2000 21:06:01 +0200 | |

changeset 10154 | 05d6ccb2f536 |

parent 10031 | 12fd0fcf755a |

child 10160 | bb8f9412fec6 |

permissions | -rw-r--r-- |

tuned;

\chapter{Generic Tools and Packages}\label{ch:gen-tools} \section{Axiomatic Type Classes}\label{sec:axclass} %FIXME % - qualified names % - class intro rules; % - class axioms; \indexisarcmd{axclass}\indexisarcmd{instance}\indexisarmeth{intro-classes} \begin{matharray}{rcl} \isarcmd{axclass} & : & \isartrans{theory}{theory} \\ \isarcmd{instance} & : & \isartrans{theory}{proof(prove)} \\ intro_classes & : & \isarmeth \\ \end{matharray} Axiomatic type classes are provided by Isabelle/Pure as a \emph{definitional} interface to type classes (cf.~\S\ref{sec:classes}). Thus any object logic may make use of this light-weight mechanism of abstract theories \cite{Wenzel:1997:TPHOL}. There is also a tutorial on using axiomatic type classes in isabelle \cite{isabelle-axclass} that is part of the standard Isabelle documentation. \begin{rail} 'axclass' classdecl (axmdecl prop comment? +) ; 'instance' (nameref '<' nameref | nameref '::' simplearity) comment? ; \end{rail} \begin{descr} \item [$\isarkeyword{axclass}~c < \vec c~axms$] defines an axiomatic type class as the intersection of existing classes, with additional axioms holding. Class axioms may not contain more than one type variable. The class axioms (with implicit sort constraints added) are bound to the given names. Furthermore a class introduction rule is generated, which is employed by method $intro_classes$ to support instantiation proofs of this class. \item [$\isarkeyword{instance}~c@1 < c@2$ and $\isarkeyword{instance}~t :: (\vec s)c$] setup a goal stating a class relation or type arity. The proof would usually proceed by $intro_classes$, and then establish the characteristic theorems of the type classes involved. After finishing the proof, the theory will be augmented by a type signature declaration corresponding to the resulting theorem. \item [$intro_classes$] repeatedly expands all class introduction rules of this theory. \end{descr} \section{Calculational proof}\label{sec:calculation} \indexisarcmd{also}\indexisarcmd{finally} \indexisarcmd{moreover}\indexisarcmd{ultimately} \indexisarcmd{print-trans-rules}\indexisaratt{trans} \begin{matharray}{rcl} \isarcmd{also} & : & \isartrans{proof(state)}{proof(state)} \\ \isarcmd{finally} & : & \isartrans{proof(state)}{proof(chain)} \\ \isarcmd{moreover} & : & \isartrans{proof(state)}{proof(state)} \\ \isarcmd{ultimately} & : & \isartrans{proof(state)}{proof(chain)} \\ \isarcmd{print_trans_rules}^* & : & \isarkeep{theory~|~proof} \\ trans & : & \isaratt \\ \end{matharray} Calculational proof is forward reasoning with implicit application of transitivity rules (such those of $=$, $\le$, $<$). Isabelle/Isar maintains an auxiliary register $calculation$\indexisarthm{calculation} for accumulating results obtained by transitivity composed with the current result. Command $\ALSO$ updates $calculation$ involving $this$, while $\FINALLY$ exhibits the final $calculation$ by forward chaining towards the next goal statement. Both commands require valid current facts, i.e.\ may occur only after commands that produce theorems such as $\ASSUMENAME$, $\NOTENAME$, or some finished proof of $\HAVENAME$, $\SHOWNAME$ etc. The $\MOREOVER$ and $\ULTIMATELY$ commands are similar to $\ALSO$ and $\FINALLY$, but only collect further results in $calculation$ without applying any rules yet. Also note that the automatic term abbreviation ``$\dots$'' has its canonical application with calculational proofs. It refers to the argument\footnote{The argument of a curried infix expression is its right-hand side.} of the preceding statement. Isabelle/Isar calculations are implicitly subject to block structure in the sense that new threads of calculational reasoning are commenced for any new block (as opened by a local goal, for example). This means that, apart from being able to nest calculations, there is no separate \emph{begin-calculation} command required. \medskip The Isar calculation proof commands may be defined as follows:\footnote{Internal bookkeeping such as proper handling of block-structure has been suppressed.} \begin{matharray}{rcl} \ALSO@0 & \equiv & \NOTE{calculation}{this} \\ \ALSO@{n+1} & \equiv & \NOTE{calculation}{trans~[OF~calculation~this]} \\[0.5ex] \FINALLY & \equiv & \ALSO~\FROM{calculation} \\ \MOREOVER & \equiv & \NOTE{calculation}{calculation~this} \\ \ULTIMATELY & \equiv & \MOREOVER~\FROM{calculation} \\ \end{matharray} \begin{rail} ('also' | 'finally') transrules? comment? ; ('moreover' | 'ultimately') comment? ; 'trans' (() | 'add' | 'del') ; transrules: '(' thmrefs ')' interest? ; \end{rail} \begin{descr} \item [$\ALSO~(\vec a)$] maintains the auxiliary $calculation$ register as follows. The first occurrence of $\ALSO$ in some calculational thread initializes $calculation$ by $this$. Any subsequent $\ALSO$ on the same level of block-structure updates $calculation$ by some transitivity rule applied to $calculation$ and $this$ (in that order). Transitivity rules are picked from the current context plus those given as explicit arguments (the latter have precedence). \item [$\FINALLY~(\vec a)$] maintaining $calculation$ in the same way as $\ALSO$, and concludes the current calculational thread. The final result is exhibited as fact for forward chaining towards the next goal. Basically, $\FINALLY$ just abbreviates $\ALSO~\FROM{calculation}$. Note that ``$\FINALLY~\SHOW{}{\Var{thesis}}~\DOT$'' and ``$\FINALLY~\HAVE{}{\phi}~\DOT$'' are typical idioms for concluding calculational proofs. \item [$\MOREOVER$ and $\ULTIMATELY$] are analogous to $\ALSO$ and $\FINALLY$, but collect results only, without applying rules. \item [$\isarkeyword{print_trans_rules}$] prints the list of transitivity rules declared in the current context. \item [$trans$] declares theorems as transitivity rules. \end{descr} \section{Named local contexts (cases)}\label{sec:cases} \indexisarcmd{case}\indexisarcmd{print-cases} \indexisaratt{case-names}\indexisaratt{params} \begin{matharray}{rcl} \isarcmd{case} & : & \isartrans{proof(state)}{proof(state)} \\ \isarcmd{print_cases}^* & : & \isarkeep{proof} \\ case_names & : & \isaratt \\ params & : & \isaratt \\ \end{matharray} Basically, Isar proof contexts are built up explicitly using commands like $\FIXNAME$, $\ASSUMENAME$ etc.\ (see \S\ref{sec:proof-context}). In typical verification tasks this can become hard to manage, though. In particular, a large number of local contexts may emerge from case analysis or induction over inductive sets and types. \medskip The $\CASENAME$ command provides a shorthand to refer to certain parts of logical context symbolically. Proof methods may provide an environment of named ``cases'' of the form $c\colon \vec x, \vec \phi$. Then the effect of $\CASE{c}$ is exactly the same as $\FIX{\vec x}~\ASSUME{c}{\vec\phi}$. It is important to note that $\CASENAME$ does \emph{not} provide any means to peek at the current goal state, which is treated as strictly non-observable in Isar! Instead, the cases considered here usually emerge in a canonical way from certain pieces of specification that appear in the theory somewhere else (e.g.\ in an inductive definition, or recursive function). See also \S\ref{sec:induct-method} for more details of how this works in HOL. \medskip Named cases may be exhibited in the current proof context only if both the proof method and the rules involved support this. Case names and parameters of basic rules may be declared by hand as well, by using appropriate attributes. Thus variant versions of rules that have been derived manually may be used in advanced case analysis later. \railalias{casenames}{case\_names} \railterm{casenames} \begin{rail} 'case' nameref attributes? ; casenames (name + ) ; 'params' ((name * ) + 'and') ; \end{rail} %FIXME bug in rail \begin{descr} \item [$\CASE{c}$] invokes a named local context $c\colon \vec x, \vec \phi$, as provided by an appropriate proof method (such as $cases$ and $induct$ in Isabelle/HOL, see \S\ref{sec:induct-method}). The command $\CASE{c}$ abbreviates $\FIX{\vec x}~\ASSUME{c}{\vec\phi}$. \item [$\isarkeyword{print_cases}$] prints all local contexts of the current state, using Isar proof language notation. This is a diagnostic command; $undo$ does not apply. \item [$case_names~\vec c$] declares names for the local contexts of premises of some theorem; $\vec c$ refers to the \emph{suffix} of the list premises. \item [$params~\vec p@1 \dots \vec p@n$] renames the innermost parameters of premises $1, \dots, n$ of some theorem. An empty list of names may be given to skip positions, leaving the present parameters unchanged. Note that the default usage of case rules does \emph{not} directly expose parameters to the proof context (see also \S\ref{sec:induct-method-proper}). \end{descr} \section{Generalized existence}\label{sec:obtain} \indexisarcmd{obtain} \begin{matharray}{rcl} \isarcmd{obtain} & : & \isartrans{proof(state)}{proof(prove)} \\ \end{matharray} Generalized existence means that additional elements with certain properties may introduced in the current context. Technically, the $\OBTAINNAME$ language element is like a declaration of $\FIXNAME$ and $\ASSUMENAME$ (see also see \S\ref{sec:proof-context}), together with a soundness proof of its additional claim. According to the nature of existential reasoning, assumptions get eliminated from any result exported from the context later, provided that the corresponding parameters do \emph{not} occur in the conclusion. \begin{rail} 'obtain' (vars + 'and') comment? \\ 'where' (assm comment? + 'and') ; \end{rail} $\OBTAINNAME$ is defined as a derived Isar command as follows, where $\vec b$ shall refer to (optional) facts indicated for forward chaining. \begin{matharray}{l} \langle facts~\vec b\rangle \\ \OBTAIN{\vec x}{a}{\vec \phi}~~\langle proof\rangle \equiv {} \\[1ex] \quad \BG \\ \qquad \FIX{thesis} \\ \qquad \ASSUME{that [simp, intro]}{\All{\vec x} \vec\phi \Imp thesis} \\ \qquad \FROM{\vec b}~\HAVE{}{thesis}~~\langle proof\rangle \\ \quad \EN \\ \quad \FIX{\vec x}~\ASSUMENAME^\ast~a\colon~\vec\phi \\ \end{matharray} Typically, the soundness proof is relatively straight-forward, often just by canonical automated tools such as $\BY{simp}$ (see \S\ref{sec:simp}) or $\BY{blast}$ (see \S\ref{sec:classical-auto}). Accordingly, the ``$that$'' reduction above is declared as simplification and introduction rule. \medskip In a sense, $\OBTAINNAME$ represents at the level of Isar proofs what would be meta-logical existential quantifiers and conjunctions. This concept has a broad range of useful applications, ranging from plain elimination (or even introduction) of object-level existentials and conjunctions, to elimination over results of symbolic evaluation of recursive definitions, for example. Also note that $\OBTAINNAME$ without parameters acts much like $\HAVENAME$, where the result is treated as an assumption. \section{Miscellaneous methods and attributes}\label{sec:misc-methods} \indexisarmeth{unfold}\indexisarmeth{fold}\indexisarmeth{insert} \indexisarmeth{erule}\indexisarmeth{drule}\indexisarmeth{frule} \indexisarmeth{fail}\indexisarmeth{succeed} \begin{matharray}{rcl} unfold & : & \isarmeth \\ fold & : & \isarmeth \\[0.5ex] insert^* & : & \isarmeth \\[0.5ex] erule^* & : & \isarmeth \\ drule^* & : & \isarmeth \\ frule^* & : & \isarmeth \\[0.5ex] succeed & : & \isarmeth \\ fail & : & \isarmeth \\ \end{matharray} \begin{rail} ('fold' | 'unfold' | 'insert' | 'erule' | 'drule' | 'frule') thmrefs ; \end{rail} \begin{descr} \item [$unfold~\vec a$ and $fold~\vec a$] expand and fold back again the given meta-level definitions throughout all goals; any facts provided are inserted into the goal and subject to rewriting as well. \item [$erule~\vec a$, $drule~\vec a$, and $frule~\vec a$] are similar to the basic $rule$ method (see \S\ref{sec:pure-meth-att}), but apply rules by elim-resolution, destruct-resolution, and forward-resolution, respectively \cite{isabelle-ref}. These are improper method, mainly for experimentation and emulating tactic scripts. Different modes of basic rule application are usually expressed in Isar at the proof language level, rather than via implicit proof state manipulations. For example, a proper single-step elimination would be done using the basic $rule$ method, with forward chaining of current facts. \item [$insert~\vec a$] inserts theorems as facts into all goals of the proof state. Note that current facts indicated for forward chaining are ignored. \item [$succeed$] yields a single (unchanged) result; it is the identity of the ``\texttt{,}'' method combinator (cf.\ \S\ref{sec:syn-meth}). \item [$fail$] yields an empty result sequence; it is the identity of the ``\texttt{|}'' method combinator (cf.\ \S\ref{sec:syn-meth}). \end{descr} \indexisaratt{standard} \indexisaratt{elim-format} \indexisaratt{no-vars} \indexisaratt{THEN}\indexisaratt{COMP} \indexisaratt{where}\indexisaratt{tagged}\indexisaratt{untagged} \indexisaratt{unfolded}\indexisaratt{folded}\indexisaratt{exported} \begin{matharray}{rcl} tagged & : & \isaratt \\ untagged & : & \isaratt \\[0.5ex] THEN & : & \isaratt \\ COMP & : & \isaratt \\[0.5ex] where & : & \isaratt \\[0.5ex] unfolded & : & \isaratt \\ folded & : & \isaratt \\[0.5ex] standard & : & \isaratt \\ elim_format & : & \isaratt \\ no_vars^* & : & \isaratt \\ exported^* & : & \isaratt \\ \end{matharray} \begin{rail} 'tagged' (nameref+) ; 'untagged' name ; ('THEN' | 'COMP') ('[' nat ']')? thmref ; 'where' (name '=' term * 'and') ; ('unfolded' | 'folded') thmrefs ; \end{rail} \begin{descr} \item [$tagged~name~args$ and $untagged~name$] add and remove $tags$ of some theorem. Tags may be any list of strings that serve as comment for some tools (e.g.\ $\LEMMANAME$ causes the tag ``$lemma$'' to be added to the result). The first string is considered the tag name, the rest its arguments. Note that untag removes any tags of the same name. \item [$THEN~n~a$ and $COMP~n~a$] compose rules. $THEN$ resolves with the $n$-th premise of $a$; the $COMP$ version skips the automatic lifting process that is normally intended (cf.\ \texttt{RS} and \texttt{COMP} in \cite[\S5]{isabelle-ref}). \item [$where~\vec x = \vec t$] perform named instantiation of schematic variables occurring in a theorem. Unlike instantiation tactics such as $rule_tac$ (see \S\ref{sec:tactic-commands}), actual schematic variables have to be specified (e.g.\ $\Var{x@3}$). \item [$unfolded~\vec a$ and $folded~\vec a$] expand and fold back again the given meta-level definitions throughout a rule. \item [$standard$] puts a theorem into the standard form of object-rules, just as the ML function \texttt{standard} (see \cite[\S5]{isabelle-ref}). \item [$elim_format$] turns a destruction rule into elimination rule format; see also the ML function \texttt{make\_elim} (see \cite{isabelle-ref}). \item [$no_vars$] replaces schematic variables by free ones; this is mainly for tuning output of pretty printed theorems. \item [$exported$] lifts a local result out of the current proof context, generalizing all fixed variables and discharging all assumptions. Note that proper incremental export is already done as part of the basic Isar machinery. This attribute is mainly for experimentation. \end{descr} \section{Tactic emulations}\label{sec:tactics} The following improper proof methods emulate traditional tactics. These admit direct access to the goal state, which is normally considered harmful! In particular, this may involve both numbered goal addressing (default 1), and dynamic instantiation within the scope of some subgoal. \begin{warn} Dynamic instantiations are read and type-checked according to a subgoal of the current dynamic goal state, rather than the static proof context! In particular, locally fixed variables and term abbreviations may not be included in the term specifications. Thus schematic variables are left to be solved by unification with certain parts of the subgoal involved. \end{warn} Note that the tactic emulation proof methods in Isabelle/Isar are consistently named $foo_tac$. \indexisarmeth{rule-tac}\indexisarmeth{erule-tac} \indexisarmeth{drule-tac}\indexisarmeth{frule-tac} \indexisarmeth{cut-tac}\indexisarmeth{thin-tac} \indexisarmeth{subgoal-tac}\indexisarmeth{rename-tac} \indexisarmeth{rotate-tac}\indexisarmeth{tactic} \begin{matharray}{rcl} rule_tac^* & : & \isarmeth \\ erule_tac^* & : & \isarmeth \\ drule_tac^* & : & \isarmeth \\ frule_tac^* & : & \isarmeth \\ cut_tac^* & : & \isarmeth \\ thin_tac^* & : & \isarmeth \\ subgoal_tac^* & : & \isarmeth \\ rename_tac^* & : & \isarmeth \\ rotate_tac^* & : & \isarmeth \\ tactic^* & : & \isarmeth \\ \end{matharray} \railalias{ruletac}{rule\_tac} \railterm{ruletac} \railalias{eruletac}{erule\_tac} \railterm{eruletac} \railalias{druletac}{drule\_tac} \railterm{druletac} \railalias{fruletac}{frule\_tac} \railterm{fruletac} \railalias{cuttac}{cut\_tac} \railterm{cuttac} \railalias{thintac}{thin\_tac} \railterm{thintac} \railalias{subgoaltac}{subgoal\_tac} \railterm{subgoaltac} \railalias{renametac}{rename\_tac} \railterm{renametac} \railalias{rotatetac}{rotate\_tac} \railterm{rotatetac} \begin{rail} ( ruletac | eruletac | druletac | fruletac | cuttac | thintac ) goalspec? ( insts thmref | thmrefs ) ; subgoaltac goalspec? (prop +) ; renametac goalspec? (name +) ; rotatetac goalspec? int? ; 'tactic' text ; insts: ((name '=' term) + 'and') 'in' ; \end{rail} \begin{descr} \item [$rule_tac$ etc.] do resolution of rules with explicit instantiation. This works the same way as the ML tactics \texttt{res_inst_tac} etc. (see \cite[\S3]{isabelle-ref}). Note that multiple rules may be only given there is no instantiation. Then $rule_tac$ is the same as \texttt{resolve_tac} in ML (see \cite[\S3]{isabelle-ref}). \item [$cut_tac$] inserts facts into the proof state as assumption of a subgoal, see also \texttt{cut_facts_tac} in \cite[\S3]{isabelle-ref}. Note that the scope of schmatic variables is spread over the main goal statement. Instantiations may be given as well, see also ML tactic \texttt{cut_inst_tac} in \cite[\S3]{isabelle-ref}. \item [$thin_tac~\phi$] deletes the specified assumption from a subgoal; note that $\phi$ may contain schematic variables. See also \texttt{thin_tac} in \cite[\S3]{isabelle-ref}. \item [$subgoal_tac~\phi$] adds $\phi$ as an assumption to a subgoal. See also \texttt{subgoal_tac} and \texttt{subgoals_tac} in \cite[\S3]{isabelle-ref}. \item [$rename_tac~\vec x$] renames parameters of a goal according to the list $\vec x$, which refers to the \emph{suffix} of variables. \item [$rotate_tac~n$] rotates the assumptions of a goal by $n$ positions: from right to left if $n$ is positive, and from left to right if $n$ is negative; the default value is $1$. See also \texttt{rotate_tac} in \cite[\S3]{isabelle-ref}. \item [$tactic~text$] produces a proof method from any ML text of type \texttt{tactic}. Apart from the usual ML environment and the current implicit theory context, the ML code may refer to the following locally bound values: %%FIXME ttbox produces too much trailing space (why?) {\footnotesize\begin{verbatim} val ctxt : Proof.context val facts : thm list val thm : string -> thm val thms : string -> thm list \end{verbatim}} Here \texttt{ctxt} refers to the current proof context, \texttt{facts} indicates any current facts for forward-chaining, and \texttt{thm}~/~\texttt{thms} retrieve named facts (including global theorems) from the context. \end{descr} \section{The Simplifier}\label{sec:simplifier} \subsection{Simplification methods}\label{sec:simp} \indexisarmeth{simp}\indexisarmeth{simp-all} \begin{matharray}{rcl} simp & : & \isarmeth \\ simp_all & : & \isarmeth \\ \end{matharray} \railalias{simpall}{simp\_all} \railterm{simpall} \railalias{noasm}{no\_asm} \railterm{noasm} \railalias{noasmsimp}{no\_asm\_simp} \railterm{noasmsimp} \railalias{noasmuse}{no\_asm\_use} \railterm{noasmuse} \begin{rail} ('simp' | simpall) ('!' ?) opt? (simpmod * ) ; opt: '(' (noasm | noasmsimp | noasmuse) ')' ; simpmod: ('add' | 'del' | 'only' | 'cong' (() | 'add' | 'del') | 'split' (() | 'add' | 'del')) ':' thmrefs ; \end{rail} \begin{descr} \item [$simp$] invokes Isabelle's simplifier, after declaring additional rules according to the arguments given. Note that the \railtterm{only} modifier first removes all other rewrite rules, congruences, and looper tactics (including splits), and then behaves like \railtterm{add}. \medskip The \railtterm{cong} modifiers add or delete Simplifier congruence rules (see also \cite{isabelle-ref}), the default is to add. \medskip The \railtterm{split} modifiers add or delete rules for the Splitter (see also \cite{isabelle-ref}), the default is to add. This works only if the Simplifier method has been properly setup to include the Splitter (all major object logics such HOL, HOLCF, FOL, ZF do this already). \item [$simp_all$] is similar to $simp$, but acts on all goals. \end{descr} By default, the Simplifier methods are based on \texttt{asm_full_simp_tac} internally \cite[\S10]{isabelle-ref}, which means that assumptions are both simplified as well as used in simplifying the conclusion. In structured proofs this is usually quite well behaved in practice: just the local premises of the actual goal are involved, additional facts may inserted via explicit forward-chaining (using $\THEN$, $\FROMNAME$ etc.). The full context of assumptions is only included if the ``$!$'' (bang) argument is given, which should be used with some care, though. Additional Simplifier options may be specified to tune the behavior even further: $(no_asm)$ means assumptions are ignored completely (cf.\ \texttt{simp_tac}), $(no_asm_simp)$ means assumptions are used in the simplification of the conclusion but are not themselves simplified (cf.\ \texttt{asm_simp_tac}), and $(no_asm_use)$ means assumptions are simplified but are not used in the simplification of each other or the conclusion (cf. \texttt{full_simp_tac}). \medskip The Splitter package is usually configured to work as part of the Simplifier. The effect of repeatedly applying \texttt{split_tac} can be simulated by $(simp~only\colon~split\colon~\vec a)$. There is also a separate $split$ method available for single-step case splitting, see \S\ref{sec:basic-eq}. \subsection{Declaring rules} \indexisarcmd{print-simpset} \indexisaratt{simp}\indexisaratt{split}\indexisaratt{cong} \begin{matharray}{rcl} print_simpset^* & : & \isarkeep{theory~|~proof} \\ simp & : & \isaratt \\ cong & : & \isaratt \\ split & : & \isaratt \\ \end{matharray} \begin{rail} ('simp' | 'cong' | 'split') (() | 'add' | 'del') ; \end{rail} \begin{descr} \item [$print_simpset$] prints the collection of rules declared to the Simplifier, which is also known as ``simpset'' internally \cite{isabelle-ref}. This is a diagnostic command; $undo$ does not apply. \item [$simp$] declares simplification rules. \item [$cong$] declares congruence rules. \item [$split$] declares case split rules. \end{descr} \subsection{Forward simplification} \indexisaratt{simplified} \begin{matharray}{rcl} simplified & : & \isaratt \\ \end{matharray} \begin{rail} 'simplified' opt? ; opt: '(' (noasm | noasmsimp | noasmuse) ')' ; \end{rail} \begin{descr} \item [$simplified$] causes a theorem to be simplified according to the current Simplifier context (there are no separate arguments for declaring additional rules). By default the result is fully simplified, including assumptions and conclusion. The options $no_asm$ etc.\ restrict the Simplifier in the same way as the for the $simp$ method (see \S\ref{sec:simp}). The $simplified$ operation should be used only very rarely, usually for experimentation only. \end{descr} \section{Basic equational reasoning}\label{sec:basic-eq} \indexisarmeth{subst}\indexisarmeth{hypsubst}\indexisarmeth{split}\indexisaratt{symmetric} \begin{matharray}{rcl} subst & : & \isarmeth \\ hypsubst^* & : & \isarmeth \\ split & : & \isarmeth \\ symmetric & : & \isaratt \\ \end{matharray} \begin{rail} 'subst' thmref ; 'split' ('(' 'asm' ')')? thmrefs ; \end{rail} These methods and attributes provide basic facilities for equational reasoning that are intended for specialized applications only. Normally, single step reasoning would be performed by calculation (see \S\ref{sec:calculation}), while the Simplifier is the canonical tool for automated normalization (see \S\ref{sec:simplifier}). \begin{descr} \item [$subst~thm$] performs a single substitution step using rule $thm$, which may be either a meta or object equality. \item [$hypsubst$] performs substitution using some assumption. \item [$split~thms$] performs single-step case splitting using rules $thms$. By default, splitting is performed in the conclusion of a goal; the $asm$ option indicates to operate on assumptions instead. Note that the $simp$ method already involves repeated application of split rules as declared in the current context (see \S\ref{sec:simp}). \item [$symmetric$] applies the symmetry rule of meta or object equality. \end{descr} \section{The Classical Reasoner}\label{sec:classical} \subsection{Basic methods}\label{sec:classical-basic} \indexisarmeth{rule}\indexisarmeth{intro} \indexisarmeth{elim}\indexisarmeth{default}\indexisarmeth{contradiction} \begin{matharray}{rcl} rule & : & \isarmeth \\ intro & : & \isarmeth \\ elim & : & \isarmeth \\ contradiction & : & \isarmeth \\ \end{matharray} \begin{rail} ('rule' | 'intro' | 'elim') thmrefs? ; \end{rail} \begin{descr} \item [$rule$] as offered by the classical reasoner is a refinement over the primitive one (see \S\ref{sec:pure-meth-att}). In case that no rules are provided as arguments, it automatically determines elimination and introduction rules from the context (see also \S\ref{sec:classical-mod}). This is made the default method for basic proof steps, such as $\PROOFNAME$ and ``$\DDOT$'' (two dots), see also \S\ref{sec:proof-steps} and \S\ref{sec:pure-meth-att}. \item [$intro$ and $elim$] repeatedly refine some goal by intro- or elim-resolution, after having inserted any facts. Omitting the arguments refers to any suitable rules declared in the context, otherwise only the explicitly given ones may be applied. The latter form admits better control of what actually happens, thus it is very appropriate as an initial method for $\PROOFNAME$ that splits up certain connectives of the goal, before entering the actual sub-proof. \item [$contradiction$] solves some goal by contradiction, deriving any result from both $\neg A$ and $A$. Facts, which are guaranteed to participate, may appear in either order. \end{descr} \subsection{Automated methods}\label{sec:classical-auto} \indexisarmeth{blast}\indexisarmeth{fast}\indexisarmeth{slow} \indexisarmeth{best}\indexisarmeth{safe}\indexisarmeth{clarify} \begin{matharray}{rcl} blast & : & \isarmeth \\ fast & : & \isarmeth \\ slow & : & \isarmeth \\ best & : & \isarmeth \\ safe & : & \isarmeth \\ clarify & : & \isarmeth \\ \end{matharray} \begin{rail} 'blast' ('!' ?) nat? (clamod * ) ; ('fast' | 'slow' | 'best' | 'safe' | 'clarify') ('!' ?) (clamod * ) ; clamod: (('intro' | 'elim' | 'dest') ('!' | () | '?') | 'del') ':' thmrefs ; \end{rail} \begin{descr} \item [$blast$] refers to the classical tableau prover (see \texttt{blast_tac} in \cite[\S11]{isabelle-ref}). The optional argument specifies a user-supplied search bound (default 20). Note that $blast$ is the only classical proof procedure in Isabelle that can handle actual object-logic rules as local assumptions ($fast$ etc.\ would just ignore non-atomic facts). \item [$fast$, $slow$, $best$, $safe$, and $clarify$] refer to the generic classical reasoner. See \texttt{fast_tac}, \texttt{slow_tac}, \texttt{best_tac}, \texttt{safe_tac}, and \texttt{clarify_tac} in \cite[\S11]{isabelle-ref} for more information. \end{descr} Any of above methods support additional modifiers of the context of classical rules. Their semantics is analogous to the attributes given in \S\ref{sec:classical-mod}. Facts provided by forward chaining are inserted\footnote{These methods usually cannot make proper use of actual rules inserted that way, though.} into the goal before doing the search. The ``!''~argument causes the full context of assumptions to be included as well. This is slightly less hazardous than for the Simplifier (see \S\ref{sec:simp}). \subsection{Combined automated methods}\label{sec:clasimp} \indexisarmeth{auto}\indexisarmeth{force}\indexisarmeth{clarsimp} \indexisarmeth{fastsimp}\indexisarmeth{slowsimp}\indexisarmeth{bestsimp} \begin{matharray}{rcl} auto & : & \isarmeth \\ force & : & \isarmeth \\ clarsimp & : & \isarmeth \\ fastsimp & : & \isarmeth \\ slowsimp & : & \isarmeth \\ bestsimp & : & \isarmeth \\ \end{matharray} \begin{rail} 'auto' '!'? (nat nat)? (clasimpmod * ) ; ('force' | 'clarsimp' | 'fastsimp' | 'slowsimp' | 'bestsimp') '!'? (clasimpmod * ) ; clasimpmod: ('simp' (() | 'add' | 'del' | 'only') | ('cong' | 'split') (() | 'add' | 'del') | 'iff' (((() | 'add') '?'?) | 'del') | (('intro' | 'elim' | 'dest') ('!' | () | '?') | 'del')) ':' thmrefs \end{rail} \begin{descr} \item [$auto$, $force$, $clarsimp$, $fastsimp$, $slowsimp$, and $bestsimp$] provide access to Isabelle's combined simplification and classical reasoning tactics. These correspond to \texttt{auto_tac}, \texttt{force_tac}, \texttt{clarsimp_tac}, and Classical Reasoner tactics with the Simplifier added as wrapper, see \cite[\S11]{isabelle-ref} for more information. The modifier arguments correspond to those given in \S\ref{sec:simp} and \S\ref{sec:classical-auto}. Just note that the ones related to the Simplifier are prefixed by \railtterm{simp} here. Facts provided by forward chaining are inserted into the goal before doing the search. The ``!''~argument causes the full context of assumptions to be included as well. \end{descr} \subsection{Declaring rules}\label{sec:classical-mod} \indexisarcmd{print-claset} \indexisaratt{intro}\indexisaratt{elim}\indexisaratt{dest} \indexisaratt{iff}\indexisaratt{rule} \begin{matharray}{rcl} print_claset^* & : & \isarkeep{theory~|~proof} \\ intro & : & \isaratt \\ elim & : & \isaratt \\ dest & : & \isaratt \\ rule & : & \isaratt \\ iff & : & \isaratt \\ \end{matharray} \begin{rail} ('intro' | 'elim' | 'dest') ('!' | () | '?') ; 'rule' 'del' ; 'iff' (((() | 'add') '?'?) | 'del') ; \end{rail} \begin{descr} \item [$print_claset$] prints the collection of rules declared to the Classical Reasoner, which is also known as ``simpset'' internally \cite{isabelle-ref}. This is a diagnostic command; $undo$ does not apply. \item [$intro$, $elim$, and $dest$] declare introduction, elimination, and destruct rules, respectively. By default, rules are considered as \emph{unsafe} (i.e.\ not applied blindly without backtracking), while a single ``!'' classifies as \emph{safe}, and ``?'' as \emph{extra} (i.e.\ not applied in the search-oriented automated methods, but only in single-step methods such as $rule$). \item [$rule~del$] deletes introduction, elimination, or destruct rules from the context. \item [$iff$] declares equivalence rules to the context. The default behavior is to declare a rewrite rule to the Simplifier, and the two corresponding implications to the Classical Reasoner (as ``safe'' rules that are used aggressively, which would normally be indicated by ``!''). The ``?'' version of $iff$ declares ``extra'' Classical Reasoner rules only, and omits the Simplifier declaration. Thus the declaration does not have any effect on automated proof tools, but only on simple methods such as $rule$ (see \S\ref{sec:misc-methods}). \end{descr} %%% Local Variables: %%% mode: latex %%% TeX-master: "isar-ref" %%% End: