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-\begin{isabellebody}%
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-\isamarkupchapter{System integration%
-}
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-\isamarkupsection{Isar toplevel \label{sec:isar-toplevel}%
-}
-\isamarkuptrue%
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-\begin{isamarkuptext}%
-The Isar toplevel may be considered the centeral hub of the
- Isabelle/Isar system, where all key components and sub-systems are
- integrated into a single read-eval-print loop of Isar commands. We
- shall even incorporate the existing {\ML} toplevel of the compiler
- and run-time system (cf.\ \secref{sec:ML-toplevel}).
-
- Isabelle/Isar departs from the original ``LCF system architecture''
- where {\ML} was really The Meta Language for defining theories and
- conducting proofs. Instead, {\ML} now only serves as the
- implementation language for the system (and user extensions), while
- the specific Isar toplevel supports the concepts of theory and proof
- development natively. This includes the graph structure of theories
- and the block structure of proofs, support for unlimited undo,
- facilities for tracing, debugging, timing, profiling etc.
-
- \medskip The toplevel maintains an implicit state, which is
- transformed by a sequence of transitions -- either interactively or
- in batch-mode. In interactive mode, Isar state transitions are
- encapsulated as safe transactions, such that both failure and undo
- are handled conveniently without destroying the underlying draft
- theory (cf.~\secref{sec:context-theory}). In batch mode,
- transitions operate in a linear (destructive) fashion, such that
- error conditions abort the present attempt to construct a theory or
- proof altogether.
-
- The toplevel state is a disjoint sum of empty \isa{toplevel}, or
- \isa{theory}, or \isa{proof}. On entering the main Isar loop we
- start with an empty toplevel. A theory is commenced by giving a
- \isa{{\isasymTHEORY}} header; within a theory we may issue theory
- commands such as \isa{{\isasymDEFINITION}}, or state a \isa{{\isasymTHEOREM}} to be proven. Now we are within a proof state, with a
- rich collection of Isar proof commands for structured proof
- composition, or unstructured proof scripts. When the proof is
- concluded we get back to the theory, which is then updated by
- storing the resulting fact. Further theory declarations or theorem
- statements with proofs may follow, until we eventually conclude the
- theory development by issuing \isa{{\isasymEND}}. The resulting theory
- is then stored within the theory database and we are back to the
- empty toplevel.
-
- In addition to these proper state transformations, there are also
- some diagnostic commands for peeking at the toplevel state without
- modifying it (e.g.\ \isakeyword{thm}, \isakeyword{term},
- \isakeyword{print-cases}).%
-\end{isamarkuptext}%
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-\begin{isamarkuptext}%
-\begin{mldecls}
- \indexmltype{Toplevel.state}\verb|type Toplevel.state| \\
- \indexml{Toplevel.UNDEF}\verb|Toplevel.UNDEF: exn| \\
- \indexml{Toplevel.is\_toplevel}\verb|Toplevel.is_toplevel: Toplevel.state -> bool| \\
- \indexml{Toplevel.theory\_of}\verb|Toplevel.theory_of: Toplevel.state -> theory| \\
- \indexml{Toplevel.proof\_of}\verb|Toplevel.proof_of: Toplevel.state -> Proof.state| \\
- \indexml{Toplevel.debug}\verb|Toplevel.debug: bool ref| \\
- \indexml{Toplevel.timing}\verb|Toplevel.timing: bool ref| \\
- \indexml{Toplevel.profiling}\verb|Toplevel.profiling: int ref| \\
- \end{mldecls}
-
- \begin{description}
-
- \item \verb|Toplevel.state| represents Isar toplevel states,
- which are normally manipulated through the concept of toplevel
- transitions only (\secref{sec:toplevel-transition}). Also note that
- a raw toplevel state is subject to the same linearity restrictions
- as a theory context (cf.~\secref{sec:context-theory}).
-
- \item \verb|Toplevel.UNDEF| is raised for undefined toplevel
- operations. Many operations work only partially for certain cases,
- since \verb|Toplevel.state| is a sum type.
-
- \item \verb|Toplevel.is_toplevel|~\isa{state} checks for an empty
- toplevel state.
-
- \item \verb|Toplevel.theory_of|~\isa{state} selects the theory of
- a theory or proof (!), otherwise raises \verb|Toplevel.UNDEF|.
-
- \item \verb|Toplevel.proof_of|~\isa{state} selects the Isar proof
- state if available, otherwise raises \verb|Toplevel.UNDEF|.
-
- \item \verb|set Toplevel.debug| makes the toplevel print further
- details about internal error conditions, exceptions being raised
- etc.
-
- \item \verb|set Toplevel.timing| makes the toplevel print timing
- information for each Isar command being executed.
-
- \item \verb|Toplevel.profiling|~\verb|:=|~\isa{n} controls
- low-level profiling of the underlying {\ML} runtime system. For
- Poly/ML, \isa{n\ {\isacharequal}\ {\isadigit{1}}} means time and \isa{n\ {\isacharequal}\ {\isadigit{2}}} space
- profiling.
-
- \end{description}%
-\end{isamarkuptext}%
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-\isamarkupsubsection{Toplevel transitions \label{sec:toplevel-transition}%
-}
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-\begin{isamarkuptext}%
-An Isar toplevel transition consists of a partial function on the
- toplevel state, with additional information for diagnostics and
- error reporting: there are fields for command name, source position,
- optional source text, as well as flags for interactive-only commands
- (which issue a warning in batch-mode), printing of result state,
- etc.
-
- The operational part is represented as the sequential union of a
- list of partial functions, which are tried in turn until the first
- one succeeds. This acts like an outer case-expression for various
- alternative state transitions. For example, \isakeyword{qed} acts
- differently for a local proofs vs.\ the global ending of the main
- proof.
-
- Toplevel transitions are composed via transition transformers.
- Internally, Isar commands are put together from an empty transition
- extended by name and source position (and optional source text). It
- is then left to the individual command parser to turn the given
- concrete syntax into a suitable transition transformer that adjoin
- actual operations on a theory or proof state etc.%
-\end{isamarkuptext}%
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-\begin{mldecls}
- \indexml{Toplevel.print}\verb|Toplevel.print: Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.no\_timing}\verb|Toplevel.no_timing: Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.keep}\verb|Toplevel.keep: (Toplevel.state -> unit) ->|\isasep\isanewline%
-\verb| Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.theory}\verb|Toplevel.theory: (theory -> theory) ->|\isasep\isanewline%
-\verb| Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.theory\_to\_proof}\verb|Toplevel.theory_to_proof: (theory -> Proof.state) ->|\isasep\isanewline%
-\verb| Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.proof}\verb|Toplevel.proof: (Proof.state -> Proof.state) ->|\isasep\isanewline%
-\verb| Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.proofs}\verb|Toplevel.proofs: (Proof.state -> Proof.state Seq.seq) ->|\isasep\isanewline%
-\verb| Toplevel.transition -> Toplevel.transition| \\
- \indexml{Toplevel.end\_proof}\verb|Toplevel.end_proof: (bool -> Proof.state -> Proof.context) ->|\isasep\isanewline%
-\verb| Toplevel.transition -> Toplevel.transition| \\
- \end{mldecls}
-
- \begin{description}
-
- \item \verb|Toplevel.print|~\isa{tr} sets the print flag, which
- causes the toplevel loop to echo the result state (in interactive
- mode).
-
- \item \verb|Toplevel.no_timing|~\isa{tr} indicates that the
- transition should never show timing information, e.g.\ because it is
- a diagnostic command.
-
- \item \verb|Toplevel.keep|~\isa{tr} adjoins a diagnostic
- function.
-
- \item \verb|Toplevel.theory|~\isa{tr} adjoins a theory
- transformer.
-
- \item \verb|Toplevel.theory_to_proof|~\isa{tr} adjoins a global
- goal function, which turns a theory into a proof state. The theory
- may be changed before entering the proof; the generic Isar goal
- setup includes an argument that specifies how to apply the proven
- result to the theory, when the proof is finished.
-
- \item \verb|Toplevel.proof|~\isa{tr} adjoins a deterministic
- proof command, with a singleton result.
-
- \item \verb|Toplevel.proofs|~\isa{tr} adjoins a general proof
- command, with zero or more result states (represented as a lazy
- list).
-
- \item \verb|Toplevel.end_proof|~\isa{tr} adjoins a concluding
- proof command, that returns the resulting theory, after storing the
- resulting facts in the context etc.
-
- \end{description}%
-\end{isamarkuptext}%
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-\isamarkupsubsection{Toplevel control%
-}
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-\begin{isamarkuptext}%
-There are a few special control commands that modify the behavior
- the toplevel itself, and only make sense in interactive mode. Under
- normal circumstances, the user encounters these only implicitly as
- part of the protocol between the Isabelle/Isar system and a
- user-interface such as ProofGeneral.
-
- \begin{description}
-
- \item \isacommand{undo} follows the three-level hierarchy of empty
- toplevel vs.\ theory vs.\ proof: undo within a proof reverts to the
- previous proof context, undo after a proof reverts to the theory
- before the initial goal statement, undo of a theory command reverts
- to the previous theory value, undo of a theory header discontinues
- the current theory development and removes it from the theory
- database (\secref{sec:theory-database}).
-
- \item \isacommand{kill} aborts the current level of development:
- kill in a proof context reverts to the theory before the initial
- goal statement, kill in a theory context aborts the current theory
- development, removing it from the database.
-
- \item \isacommand{exit} drops out of the Isar toplevel into the
- underlying {\ML} toplevel (\secref{sec:ML-toplevel}). The Isar
- toplevel state is preserved and may be continued later.
-
- \item \isacommand{quit} terminates the Isabelle/Isar process without
- saving.
-
- \end{description}%
-\end{isamarkuptext}%
-\isamarkuptrue%
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-\isamarkupsection{ML toplevel \label{sec:ML-toplevel}%
-}
-\isamarkuptrue%
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-\begin{isamarkuptext}%
-The {\ML} toplevel provides a read-compile-eval-print loop for {\ML}
- values, types, structures, and functors. {\ML} declarations operate
- on the global system state, which consists of the compiler
- environment plus the values of {\ML} reference variables. There is
- no clean way to undo {\ML} declarations, except for reverting to a
- previously saved state of the whole Isabelle process. {\ML} input
- is either read interactively from a TTY, or from a string (usually
- within a theory text), or from a source file (usually loaded from a
- theory).
-
- Whenever the {\ML} toplevel is active, the current Isabelle theory
- context is passed as an internal reference variable. Thus {\ML}
- code may access the theory context during compilation, it may even
- change the value of a theory being under construction --- while
- observing the usual linearity restrictions
- (cf.~\secref{sec:context-theory}).%
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-\begin{mldecls}
- \indexml{the\_context}\verb|the_context: unit -> theory| \\
- \indexml{Context.$>$$>$ }\verb|Context.>> : (Context.generic -> Context.generic) -> unit| \\
- \end{mldecls}
-
- \begin{description}
-
- \item \verb|the_context ()| refers to the theory context of the
- {\ML} toplevel --- at compile time! {\ML} code needs to take care
- to refer to \verb|the_context ()| correctly. Recall that
- evaluation of a function body is delayed until actual runtime.
- Moreover, persistent {\ML} toplevel bindings to an unfinished theory
- should be avoided: code should either project out the desired
- information immediately, or produce an explicit \verb|theory_ref| (cf.\ \secref{sec:context-theory}).
-
- \item \verb|Context.>>|~\isa{f} applies context transformation
- \isa{f} to the implicit context of the {\ML} toplevel.
-
- \end{description}
-
- It is very important to note that the above functions are really
- restricted to the compile time, even though the {\ML} compiler is
- invoked at runtime! The majority of {\ML} code uses explicit
- functional arguments of a theory or proof context instead. Thus it
- may be invoked for an arbitrary context later on, without having to
- worry about any operational details.
-
- \bigskip
-
- \begin{mldecls}
- \indexml{Isar.main}\verb|Isar.main: unit -> unit| \\
- \indexml{Isar.loop}\verb|Isar.loop: unit -> unit| \\
- \indexml{Isar.state}\verb|Isar.state: unit -> Toplevel.state| \\
- \indexml{Isar.exn}\verb|Isar.exn: unit -> (exn * string) option| \\
- \indexml{Isar.context}\verb|Isar.context: unit -> Proof.context| \\
- \indexml{Isar.goal}\verb|Isar.goal: unit -> thm| \\
- \end{mldecls}
-
- \begin{description}
-
- \item \verb|Isar.main ()| invokes the Isar toplevel from {\ML},
- initializing an empty toplevel state.
-
- \item \verb|Isar.loop ()| continues the Isar toplevel with the
- current state, after having dropped out of the Isar toplevel loop.
-
- \item \verb|Isar.state ()| and \verb|Isar.exn ()| get current
- toplevel state and error condition, respectively. This only works
- after having dropped out of the Isar toplevel loop.
-
- \item \verb|Isar.context ()| produces the proof context from \verb|Isar.state ()|, analogous to \verb|Context.proof_of|
- (\secref{sec:generic-context}).
-
- \item \verb|Isar.goal ()| picks the tactical goal from \verb|Isar.state ()|, represented as a theorem according to
- \secref{sec:tactical-goals}.
-
- \end{description}%
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-\isamarkupsection{Theory database \label{sec:theory-database}%
-}
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-The theory database maintains a collection of theories, together
- with some administrative information about their original sources,
- which are held in an external store (i.e.\ some directory within the
- regular file system).
-
- The theory database is organized as a directed acyclic graph;
- entries are referenced by theory name. Although some additional
- interfaces allow to include a directory specification as well, this
- is only a hint to the underlying theory loader. The internal theory
- name space is flat!
-
- Theory \isa{A} is associated with the main theory file \isa{A}\verb,.thy,, which needs to be accessible through the theory
- loader path. Any number of additional {\ML} source files may be
- associated with each theory, by declaring these dependencies in the
- theory header as \isa{{\isasymUSES}}, and loading them consecutively
- within the theory context. The system keeps track of incoming {\ML}
- sources and associates them with the current theory. The file
- \isa{A}\verb,.ML, is loaded after a theory has been concluded, in
- order to support legacy proof {\ML} proof scripts.
-
- The basic internal actions of the theory database are \isa{update}, \isa{outdate}, and \isa{remove}:
-
- \begin{itemize}
-
- \item \isa{update\ A} introduces a link of \isa{A} with a
- \isa{theory} value of the same name; it asserts that the theory
- sources are now consistent with that value;
-
- \item \isa{outdate\ A} invalidates the link of a theory database
- entry to its sources, but retains the present theory value;
-
- \item \isa{remove\ A} deletes entry \isa{A} from the theory
- database.
-
- \end{itemize}
-
- These actions are propagated to sub- or super-graphs of a theory
- entry as expected, in order to preserve global consistency of the
- state of all loaded theories with the sources of the external store.
- This implies certain causalities between actions: \isa{update}
- or \isa{outdate} of an entry will \isa{outdate} all
- descendants; \isa{remove} will \isa{remove} all descendants.
-
- \medskip There are separate user-level interfaces to operate on the
- theory database directly or indirectly. The primitive actions then
- just happen automatically while working with the system. In
- particular, processing a theory header \isa{{\isasymTHEORY}\ A\ {\isasymIMPORTS}\ B\isactrlsub {\isadigit{1}}\ {\isasymdots}\ B\isactrlsub n\ {\isasymBEGIN}} ensures that the
- sub-graph of the collective imports \isa{B\isactrlsub {\isadigit{1}}\ {\isasymdots}\ B\isactrlsub n}
- is up-to-date, too. Earlier theories are reloaded as required, with
- \isa{update} actions proceeding in topological order according to
- theory dependencies. There may be also a wave of implied \isa{outdate} actions for derived theory nodes until a stable situation
- is achieved eventually.%
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-\begin{mldecls}
- \indexml{theory}\verb|theory: string -> theory| \\
- \indexml{use\_thy}\verb|use_thy: string -> unit| \\
- \indexml{use\_thys}\verb|use_thys: string list -> unit| \\
- \indexml{ThyInfo.touch\_thy}\verb|ThyInfo.touch_thy: string -> unit| \\
- \indexml{ThyInfo.remove\_thy}\verb|ThyInfo.remove_thy: string -> unit| \\[1ex]
- \indexml{ThyInfo.begin\_theory}\verb|ThyInfo.begin_theory|\verb|: ... -> bool -> theory| \\
- \indexml{ThyInfo.end\_theory}\verb|ThyInfo.end_theory: theory -> unit| \\
- \indexml{ThyInfo.register\_theory}\verb|ThyInfo.register_theory: theory -> unit| \\[1ex]
- \verb|datatype action = Update |\verb,|,\verb| Outdate |\verb,|,\verb| Remove| \\
- \indexml{ThyInfo.add\_hook}\verb|ThyInfo.add_hook: (ThyInfo.action -> string -> unit) -> unit| \\
- \end{mldecls}
-
- \begin{description}
-
- \item \verb|theory|~\isa{A} retrieves the theory value presently
- associated with name \isa{A}. Note that the result might be
- outdated.
-
- \item \verb|use_thy|~\isa{A} ensures that theory \isa{A} is fully
- up-to-date wrt.\ the external file store, reloading outdated
- ancestors as required.
-
- \item \verb|use_thys| is similar to \verb|use_thy|, but handles
- several theories simultaneously. Thus it acts like processing the
- import header of a theory, without performing the merge of the
- result, though.
-
- \item \verb|ThyInfo.touch_thy|~\isa{A} performs and \isa{outdate} action
- on theory \isa{A} and all descendants.
-
- \item \verb|ThyInfo.remove_thy|~\isa{A} deletes theory \isa{A} and all
- descendants from the theory database.
-
- \item \verb|ThyInfo.begin_theory| is the basic operation behind a
- \isa{{\isasymTHEORY}} header declaration. This is {\ML} functions is
- normally not invoked directly.
-
- \item \verb|ThyInfo.end_theory| concludes the loading of a theory
- proper and stores the result in the theory database.
-
- \item \verb|ThyInfo.register_theory|~\isa{text\ thy} registers an
- existing theory value with the theory loader database. There is no
- management of associated sources.
-
- \item \verb|ThyInfo.add_hook|~\isa{f} registers function \isa{f} as a hook for theory database actions. The function will be
- invoked with the action and theory name being involved; thus derived
- actions may be performed in associated system components, e.g.\
- maintaining the state of an editor for the theory sources.
-
- The kind and order of actions occurring in practice depends both on
- user interactions and the internal process of resolving theory
- imports. Hooks should not rely on a particular policy here! Any
- exceptions raised by the hook are ignored.
-
- \end{description}%
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