--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc-src/IsarRef/ML_Tactic.thy Tue Aug 28 12:45:49 2012 +0200
@@ -0,0 +1,180 @@
+theory ML_Tactic
+imports Base Main
+begin
+
+chapter {* ML tactic expressions *}
+
+text {*
+ Isar Proof methods closely resemble traditional tactics, when used
+ in unstructured sequences of @{command "apply"} commands.
+ Isabelle/Isar provides emulations for all major ML tactics of
+ classic Isabelle --- mostly for the sake of easy porting of existing
+ developments, as actual Isar proof texts would demand much less
+ diversity of proof methods.
+
+ Unlike tactic expressions in ML, Isar proof methods provide proper
+ concrete syntax for additional arguments, options, modifiers etc.
+ Thus a typical method text is usually more concise than the
+ corresponding ML tactic. Furthermore, the Isar versions of classic
+ Isabelle tactics often cover several variant forms by a single
+ method with separate options to tune the behavior. For example,
+ method @{method simp} replaces all of @{ML simp_tac}~/ @{ML
+ asm_simp_tac}~/ @{ML full_simp_tac}~/ @{ML asm_full_simp_tac}, there
+ is also concrete syntax for augmenting the Simplifier context (the
+ current ``simpset'') in a convenient way.
+*}
+
+
+section {* Resolution tactics *}
+
+text {*
+ Classic Isabelle provides several variant forms of tactics for
+ single-step rule applications (based on higher-order resolution).
+ The space of resolution tactics has the following main dimensions.
+
+ \begin{enumerate}
+
+ \item The ``mode'' of resolution: intro, elim, destruct, or forward
+ (e.g.\ @{ML resolve_tac}, @{ML eresolve_tac}, @{ML dresolve_tac},
+ @{ML forward_tac}).
+
+ \item Optional explicit instantiation (e.g.\ @{ML resolve_tac} vs.\
+ @{ML res_inst_tac}).
+
+ \item Abbreviations for singleton arguments (e.g.\ @{ML resolve_tac}
+ vs.\ @{ML rtac}).
+
+ \end{enumerate}
+
+ Basically, the set of Isar tactic emulations @{method rule_tac},
+ @{method erule_tac}, @{method drule_tac}, @{method frule_tac} (see
+ \secref{sec:tactics}) would be sufficient to cover the four modes,
+ either with or without instantiation, and either with single or
+ multiple arguments. Although it is more convenient in most cases to
+ use the plain @{method_ref (Pure) rule} method, or any of its
+ ``improper'' variants @{method erule}, @{method drule}, @{method
+ frule}. Note that explicit goal addressing is only supported by the
+ actual @{method rule_tac} version.
+
+ With this in mind, plain resolution tactics correspond to Isar
+ methods as follows.
+
+ \medskip
+ \begin{tabular}{lll}
+ @{ML rtac}~@{text "a 1"} & & @{text "rule a"} \\
+ @{ML resolve_tac}~@{text "[a\<^sub>1, \<dots>] 1"} & & @{text "rule a\<^sub>1 \<dots>"} \\
+ @{ML res_inst_tac}~@{text "ctxt [(x\<^sub>1, t\<^sub>1), \<dots>] a 1"} & &
+ @{text "rule_tac x\<^sub>1 = t\<^sub>1 \<AND> \<dots> \<IN> a"} \\[0.5ex]
+ @{ML rtac}~@{text "a i"} & & @{text "rule_tac [i] a"} \\
+ @{ML resolve_tac}~@{text "[a\<^sub>1, \<dots>] i"} & & @{text "rule_tac [i] a\<^sub>1 \<dots>"} \\
+ @{ML res_inst_tac}~@{text "ctxt [(x\<^sub>1, t\<^sub>1), \<dots>] a i"} & &
+ @{text "rule_tac [i] x\<^sub>1 = t\<^sub>1 \<AND> \<dots> \<IN> a"} \\
+ \end{tabular}
+ \medskip
+
+ Note that explicit goal addressing may be usually avoided by
+ changing the order of subgoals with @{command "defer"} or @{command
+ "prefer"} (see \secref{sec:tactic-commands}).
+*}
+
+
+section {* Simplifier tactics *}
+
+text {*
+ The main Simplifier tactics @{ML simp_tac} and variants (cf.\
+ \cite{isabelle-ref}) are all covered by the @{method simp} and
+ @{method simp_all} methods (see \secref{sec:simplifier}). Note that
+ there is no individual goal addressing available, simplification
+ acts either on the first goal (@{method simp}) or all goals
+ (@{method simp_all}).
+
+ \medskip
+ \begin{tabular}{lll}
+ @{ML asm_full_simp_tac}~@{text "@{simpset} 1"} & & @{method simp} \\
+ @{ML ALLGOALS}~(@{ML asm_full_simp_tac}~@{text "@{simpset}"}) & & @{method simp_all} \\[0.5ex]
+ @{ML simp_tac}~@{text "@{simpset} 1"} & & @{method simp}~@{text "(no_asm)"} \\
+ @{ML asm_simp_tac}~@{text "@{simpset} 1"} & & @{method simp}~@{text "(no_asm_simp)"} \\
+ @{ML full_simp_tac}~@{text "@{simpset} 1"} & & @{method simp}~@{text "(no_asm_use)"} \\
+ @{ML asm_lr_simp_tac}~@{text "@{simpset} 1"} & & @{method simp}~@{text "(asm_lr)"} \\
+ \end{tabular}
+ \medskip
+*}
+
+
+section {* Classical Reasoner tactics *}
+
+text {* The Classical Reasoner provides a rather large number of
+ variations of automated tactics, such as @{ML blast_tac}, @{ML
+ fast_tac}, @{ML clarify_tac} etc. The corresponding Isar methods
+ usually share the same base name, such as @{method blast}, @{method
+ fast}, @{method clarify} etc.\ (see \secref{sec:classical}). *}
+
+
+section {* Miscellaneous tactics *}
+
+text {*
+ There are a few additional tactics defined in various theories of
+ Isabelle/HOL, some of these also in Isabelle/FOL or Isabelle/ZF.
+ The most common ones of these may be ported to Isar as follows.
+
+ \medskip
+ \begin{tabular}{lll}
+ @{ML stac}~@{text "a 1"} & & @{text "subst a"} \\
+ @{ML hyp_subst_tac}~@{text 1} & & @{text hypsubst} \\
+ @{ML strip_tac}~@{text 1} & @{text "\<approx>"} & @{text "intro strip"} \\
+ @{ML split_all_tac}~@{text 1} & & @{text "simp (no_asm_simp) only: split_tupled_all"} \\
+ & @{text "\<approx>"} & @{text "simp only: split_tupled_all"} \\
+ & @{text "\<lless>"} & @{text "clarify"} \\
+ \end{tabular}
+*}
+
+
+section {* Tacticals *}
+
+text {*
+ Classic Isabelle provides a huge amount of tacticals for combination
+ and modification of existing tactics. This has been greatly reduced
+ in Isar, providing the bare minimum of combinators only: ``@{text
+ ","}'' (sequential composition), ``@{text "|"}'' (alternative
+ choices), ``@{text "?"}'' (try), ``@{text "+"}'' (repeat at least
+ once). These are usually sufficient in practice; if all fails,
+ arbitrary ML tactic code may be invoked via the @{method tactic}
+ method (see \secref{sec:tactics}).
+
+ \medskip Common ML tacticals may be expressed directly in Isar as
+ follows:
+
+ \medskip
+ \begin{tabular}{lll}
+ @{text "tac\<^sub>1"}~@{ML_text THEN}~@{text "tac\<^sub>2"} & & @{text "meth\<^sub>1, meth\<^sub>2"} \\
+ @{text "tac\<^sub>1"}~@{ML_text ORELSE}~@{text "tac\<^sub>2"} & & @{text "meth\<^sub>1 | meth\<^sub>2"} \\
+ @{ML TRY}~@{text tac} & & @{text "meth?"} \\
+ @{ML REPEAT1}~@{text tac} & & @{text "meth+"} \\
+ @{ML REPEAT}~@{text tac} & & @{text "(meth+)?"} \\
+ @{ML EVERY}~@{text "[tac\<^sub>1, \<dots>]"} & & @{text "meth\<^sub>1, \<dots>"} \\
+ @{ML FIRST}~@{text "[tac\<^sub>1, \<dots>]"} & & @{text "meth\<^sub>1 | \<dots>"} \\
+ \end{tabular}
+ \medskip
+
+ \medskip @{ML CHANGED} (see \cite{isabelle-implementation}) is
+ usually not required in Isar, since most basic proof methods already
+ fail unless there is an actual change in the goal state.
+ Nevertheless, ``@{text "?"}'' (try) may be used to accept
+ \emph{unchanged} results as well.
+
+ \medskip @{ML ALLGOALS}, @{ML SOMEGOAL} etc.\ (see
+ \cite{isabelle-implementation}) are not available in Isar, since
+ there is no direct goal addressing. Nevertheless, some basic
+ methods address all goals internally, notably @{method simp_all}
+ (see \secref{sec:simplifier}). Also note that @{ML ALLGOALS} can be
+ often replaced by ``@{text "+"}'' (repeat at least once), although
+ this usually has a different operational behavior: subgoals are
+ solved in a different order.
+
+ \medskip Iterated resolution, such as
+ @{ML_text "REPEAT (FIRSTGOAL (resolve_tac ...))"}, is usually better
+ expressed using the @{method intro} and @{method elim} methods of
+ Isar (see \secref{sec:classical}).
+*}
+
+end