(* $Id$ *)
theory integration imports base begin
chapter {* System integration *}
section {* Isar toplevel \label{sec:isar-toplevel} *}
text {* 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 @{text toplevel}, or
@{text theory}, or @{text proof}. On entering the main Isar loop we
start with an empty toplevel. A theory is commenced by giving a
@{text \<THEORY>} header; within a theory we may issue theory
commands such as @{text \<DEFINITION>}, or state a @{text
\<THEOREM>} 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 @{text \<END>}. 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}).
*}
text %mlref {*
\begin{mldecls}
@{index_ML_type Toplevel.state} \\
@{index_ML Toplevel.UNDEF: "exn"} \\
@{index_ML Toplevel.is_toplevel: "Toplevel.state -> bool"} \\
@{index_ML Toplevel.theory_of: "Toplevel.state -> theory"} \\
@{index_ML Toplevel.proof_of: "Toplevel.state -> Proof.state"} \\
@{index_ML Toplevel.debug: "bool ref"} \\
@{index_ML Toplevel.timing: "bool ref"} \\
@{index_ML Toplevel.profiling: "int ref"} \\
\end{mldecls}
\begin{description}
\item @{ML_type 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 @{ML Toplevel.UNDEF} is raised for undefined toplevel
operations. Many operations work only partially for certain cases,
since @{ML_type Toplevel.state} is a sum type.
\item @{ML Toplevel.is_toplevel}~@{text "state"} checks for an empty
toplevel state.
\item @{ML Toplevel.theory_of}~@{text "state"} selects the theory of
a theory or proof (!), otherwise raises @{ML Toplevel.UNDEF}.
\item @{ML Toplevel.proof_of}~@{text "state"} selects the Isar proof
state if available, otherwise raises @{ML Toplevel.UNDEF}.
\item @{ML "set Toplevel.debug"} makes the toplevel print further
details about internal error conditions, exceptions being raised
etc.
\item @{ML "set Toplevel.timing"} makes the toplevel print timing
information for each Isar command being executed.
\item @{ML Toplevel.profiling}~@{verbatim ":="}~@{text "n"} controls
low-level profiling of the underlying {\ML} runtime system. For
Poly/ML, @{text "n = 1"} means time and @{text "n = 2"} space
profiling.
\end{description}
*}
subsection {* Toplevel transitions \label{sec:toplevel-transition} *}
text {*
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.
*}
text %mlref {*
\begin{mldecls}
@{index_ML Toplevel.print: "Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.no_timing: "Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.keep: "(Toplevel.state -> unit) ->
Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.theory: "(theory -> theory) ->
Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.theory_to_proof: "(theory -> Proof.state) ->
Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.proof: "(Proof.state -> Proof.state) ->
Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.proofs: "(Proof.state -> Proof.state Seq.seq) ->
Toplevel.transition -> Toplevel.transition"} \\
@{index_ML Toplevel.end_proof: "(bool -> Proof.state -> Proof.context) ->
Toplevel.transition -> Toplevel.transition"} \\
\end{mldecls}
\begin{description}
\item @{ML Toplevel.print}~@{text "tr"} sets the print flag, which
causes the toplevel loop to echo the result state (in interactive
mode).
\item @{ML Toplevel.no_timing}~@{text "tr"} indicates that the
transition should never show timing information, e.g.\ because it is
a diagnostic command.
\item @{ML Toplevel.keep}~@{text "tr"} adjoins a diagnostic
function.
\item @{ML Toplevel.theory}~@{text "tr"} adjoins a theory
transformer.
\item @{ML Toplevel.theory_to_proof}~@{text "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 @{ML Toplevel.proof}~@{text "tr"} adjoins a deterministic
proof command, with a singleton result.
\item @{ML Toplevel.proofs}~@{text "tr"} adjoins a general proof
command, with zero or more result states (represented as a lazy
list).
\item @{ML Toplevel.end_proof}~@{text "tr"} adjoins a concluding
proof command, that returns the resulting theory, after storing the
resulting facts in the context etc.
\end{description}
*}
subsection {* Toplevel control *}
text {*
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}
*}
section {* ML toplevel \label{sec:ML-toplevel} *}
text {*
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}).
*}
text %mlref {*
\begin{mldecls}
@{index_ML the_context: "unit -> theory"} \\
@{index_ML "Context.>> ": "(theory -> theory) -> unit"} \\
\end{mldecls}
\begin{description}
\item @{ML "the_context ()"} refers to the theory context of the
{\ML} toplevel --- at compile time! {\ML} code needs to take care
to refer to @{ML "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 @{ML_type
theory_ref} (cf.\ \secref{sec:context-theory}).
\item @{ML "Context.>>"}~@{text f} applies theory transformation
@{text f} to the current theory of the {\ML} toplevel. In order to
work as expected, the theory should be still under construction, and
the Isar language element that invoked the {\ML} compiler in the
first place should be ready to accept the changed theory value
(e.g.\ \isakeyword{ML-setup}, but not plain \isakeyword{ML}).
Otherwise the theory becomes stale!
\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}
@{index_ML Isar.main: "unit -> unit"} \\
@{index_ML Isar.loop: "unit -> unit"} \\
@{index_ML Isar.state: "unit -> Toplevel.state"} \\
@{index_ML Isar.exn: "unit -> (exn * string) option"} \\
@{index_ML Isar.context: "unit -> Proof.context"} \\
@{index_ML Isar.goal: "unit -> thm list * thm"} \\
\end{mldecls}
\begin{description}
\item @{ML "Isar.main ()"} invokes the Isar toplevel from {\ML},
initializing an empty toplevel state.
\item @{ML "Isar.loop ()"} continues the Isar toplevel with the
current state, after having dropped out of the Isar toplevel loop.
\item @{ML "Isar.state ()"} and @{ML "Isar.exn ()"} get current
toplevel state and error condition, respectively. This only works
after having dropped out of the Isar toplevel loop.
\item @{ML "Isar.context ()"} produces the proof context from @{ML
"Isar.state ()"}, analogous to @{ML Context.proof_of}
(\secref{sec:generic-context}).
\item @{ML "Isar.goal ()"} picks the goal configuration from @{ML
"Isar.state ()"}, consisting on the current facts and the goal
represented as a theorem according to \secref{sec:tactical-goals}.
\end{description}
*}
section {* Theory database \label{sec:theory-database} *}
text {*
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 @{text A} is associated with the main theory file @{text
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 @{text \<USES>}, 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
@{text 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 @{text
"update"}, @{text "outdate"}, and @{text "remove"}:
\begin{itemize}
\item @{text "update A"} introduces a link of @{text "A"} with a
@{text "theory"} value of the same name; it asserts that the theory
sources are now consistent with that value;
\item @{text "outdate A"} invalidates the link of a theory database
entry to its sources, but retains the present theory value;
\item @{text "remove A"} deletes entry @{text "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: @{text "update"}
or @{text "outdate"} of an entry will @{text "outdate"} all
descendants; @{text "remove"} will @{text "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 @{text "\<THEORY> A
\<IMPORTS> B\<^sub>1 \<dots> B\<^sub>n \<BEGIN>"} ensures that the
sub-graph of the collective imports @{text "B\<^sub>1 \<dots> B\<^sub>n"}
is up-to-date, too. Earlier theories are reloaded as required, with
@{text update} actions proceeding in topological order according to
theory dependencies. There may be also a wave of implied @{text
outdate} actions for derived theory nodes until a stable situation
is achieved eventually.
*}
text %mlref {*
\begin{mldecls}
@{index_ML theory: "string -> theory"} \\
@{index_ML use_thy: "string -> unit"} \\
@{index_ML use_thys: "string list -> unit"} \\
@{index_ML touch_thy: "string -> unit"} \\
@{index_ML remove_thy: "string -> unit"} \\[1ex]
@{index_ML ThyInfo.begin_theory}@{verbatim ": ... -> bool -> theory"} \\
@{index_ML ThyInfo.end_theory: "theory -> theory"} \\
@{index_ML ThyInfo.register_theory: "theory -> unit"} \\[1ex]
@{verbatim "datatype action = Update | Outdate | Remove"} \\
@{index_ML ThyInfo.add_hook: "(ThyInfo.action -> string -> unit) -> unit"} \\
\end{mldecls}
\begin{description}
\item @{ML theory}~@{text A} retrieves the theory value presently
associated with name @{text A}. Note that the result might be
outdated.
\item @{ML use_thy}~@{text A} ensures that theory @{text A} is fully
up-to-date wrt.\ the external file store, reloading outdated
ancestors as required.
\item @{ML use_thys} is similar to @{ML 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 @{ML touch_thy}~@{text A} performs and @{text outdate} action
on theory @{text A} and all descendants.
\item @{ML remove_thy}~@{text A} deletes theory @{text A} and all
descendants from the theory database.
\item @{ML ThyInfo.begin_theory} is the basic operation behind a
@{text \<THEORY>} header declaration. This is {\ML} functions is
normally not invoked directly.
\item @{ML ThyInfo.end_theory} concludes the loading of a theory
proper. An attached theory {\ML} file may be still loaded later on.
This is function is normally not invoked directly.
\item @{ML ThyInfo.register_theory}~@{text "text thy"} registers an
existing theory value with the theory loader database. There is no
management of associated sources.
\item @{ML "ThyInfo.add_hook"}~@{text f} registers function @{text
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}
*}
end