(* $Id$ *)

theory Basics

imports Pure

begin

chapter {* The Isabelle system environment *}

text {*

  This manual describes Isabelle together with related tools and user

  interfaces as seen from an outside (system oriented) view.  See also

  the \emph{Isabelle/Isar Reference Manual}~\cite{isabelle-isar-ref}

  and the \emph{Isabelle Reference Manual}~\cite{isabelle-ref} for the

  actual Isabelle commands and related functions.

  \medskip The Isabelle system environment emerges from a few general

  concepts.

  \begin{enumerate}

  \item The \emph{Isabelle settings} mechanism provides environment

  variables to all Isabelle programs (including tools and user

  interfaces).

  \item The \emph{raw Isabelle process} (@{executable_ref

  "isabelle-process"}) runs logic sessions either interactively or in

  batch mode.  In particular, this view abstracts over the invocation

  of the actual ML system to be used.  Regular users rarely need to

  care about the low-level process.

  \item The \emph{Isabelle tools wrapper} (@{executable_ref isabelle})

  provides a generic startup environment Isabelle related utilities,

  user interfaces etc.  Such tools automatically benefit from the

  settings mechanism.

  \item The \emph{Isabelle interface wrapper} (@{executable_ref

  "isabelle-interface"}) provides some abstraction over the actual

  user interface to be used.  The de-facto standard interface for

  Isabelle is Proof~General \cite{proofgeneral}.

  \end{enumerate}

*}

section {* Isabelle settings \label{sec:settings} *}

text {*

  The Isabelle system heavily depends on the \emph{settings

  mechanism}\indexbold{settings}.  Essentially, this is a statically

  scoped collection of environment variables, such as @{setting

  ISABELLE_HOME}, @{setting ML_SYSTEM}, @{setting ML_HOME}.  These

  variables are \emph{not} intended to be set directly from the shell,

  though.  Isabelle employs a somewhat more sophisticated scheme of

  \emph{settings files} --- one for site-wide defaults, another for

  additional user-specific modifications.  With all configuration

  variables in at most two places, this scheme is more maintainable

  and user-friendly than global shell environment variables.

  In particular, we avoid the typical situation where prospective

  users of a software package are told to put several things into

  their shell startup scripts, before being able to actually run the

  program. Isabelle requires none such administrative chores of its

  end-users --- the executables can be invoked straight away.

  Occasionally, users would still want to put the @{"file"

  "$ISABELLE_HOME/bin"} directory into their shell's search path, but

  this is not required.

*}

subsection {* Building the environment *}

text {*

  Whenever any of the Isabelle executables is run, their settings

  environment is put together as follows.

  \begin{enumerate}

  \item The special variable @{setting_def ISABELLE_HOME} is

  determined automatically from the location of the binary that has

  been run.

  You should not try to set @{setting ISABELLE_HOME} manually. Also

  note that the Isabelle executables either have to be run from their

  original location in the distribution directory, or via the

  executable objects created by the @{tool install} utility.  Symbolic

  links are admissible, but a plain copy of the @{"file"

  "$ISABELLE_HOME/bin"} files will not work!

  \item The file @{"file" "$ISABELLE_HOME/etc/settings"} ist run as a

  @{executable_ref bash} shell script with the auto-export option for

  variables enabled.

  This file holds a rather long list of shell variable assigments,

  thus providing the site-wide default settings.  The Isabelle

  distribution already contains a global settings file with sensible

  defaults for most variables.  When installing the system, only a few

  of these may have to be adapted (probably @{setting ML_SYSTEM}

  etc.).

  \item The file @{verbatim "$ISABELLE_HOME_USER/etc/settings"} (if it

  exists) is run in the same way as the site default settings. Note

  that the variable @{setting ISABELLE_HOME_USER} has already been set

  before --- usually to @{verbatim "~/.isabelle"}.

  Thus individual users may override the site-wide defaults.  See also

  file @{"file" "$ISABELLE_HOME/etc/user-settings.sample"} in the

  distribution.  Typically, a user settings file would contain only a

  few lines, just the assigments that are really changed.  One should

  definitely \emph{not} start with a full copy the basic @{"file"

  "$ISABELLE_HOME/etc/settings"}. This could cause very annoying

  maintainance problems later, when the Isabelle installation is

  updated or changed otherwise.

  \end{enumerate}

  Since settings files are regular GNU @{executable_def bash} scripts,

  one may use complex shell commands, such as @{verbatim "if"} or

  @{verbatim "case"} statements to set variables depending on the

  system architecture or other environment variables.  Such advanced

  features should be added only with great care, though. In

  particular, external environment references should be kept at a

  minimum.

  \medskip A few variables are somewhat special:

  \begin{itemize}

  \item @{setting_def ISABELLE_PROCESS} and @{setting_def ISABELLE_TOOL} are set

  automatically to the absolute path names of the @{executable

  "isabelle-process"} and @{executable isabelle} executables,

  respectively.

  \item @{setting_ref ISABELLE_OUTPUT} will have the identifiers of

  the Isabelle distribution (cf.\ @{setting ISABELLE_IDENTIFIER}) and

  the ML system (cf.\ @{setting ML_IDENTIFIER}) appended automatically

  to its value.

  \end{itemize}

  \medskip Note that the settings environment may be inspected with

  the Isabelle tool @{tool getenv}.  This might help to figure out the

  effect of complex settings scripts.

*}

subsection{* Common variables *}

text {*

  This is a reference of common Isabelle settings variables. Note that

  the list is somewhat open-ended. Third-party utilities or interfaces

  may add their own selection. Variables that are special in some

  sense are marked with @{text "\<^sup>*"}.

  \begin{description}

  \item[@{setting_def ISABELLE_HOME}@{text "\<^sup>*"}] is the

  location of the top-level Isabelle distribution directory. This is

  automatically determined from the Isabelle executable that has been

  invoked.  Do not attempt to set @{setting ISABELLE_HOME} yourself

  from the shell!

  \item[@{setting_def ISABELLE_HOME_USER}] is the user-specific

  counterpart of @{setting ISABELLE_HOME}. The default value is

  @{verbatim "~/.isabelle"}, under rare circumstances this may be

  changed in the global setting file.  Typically, the @{setting

  ISABELLE_HOME_USER} directory mimics @{setting ISABELLE_HOME} to

  some extend. In particular, site-wide defaults may be overridden by

  a private @{verbatim "$ISABELLE_HOME_USER/etc/settings"}.

  \item[@{setting_def ISABELLE_PROCESS}@{text "\<^sup>*"}, @{setting

  ISABELLE_TOOL}@{text "\<^sup>*"}] are automatically set to the full path

  names of the @{executable "isabelle-process"} and @{executable

  isabelle} executables, respectively.  Thus other tools and scripts

  need not assume that the @{"file" "$ISABELLE_HOME/bin"} directory is

  on the current search path of the shell.

  \item[@{setting_def ISABELLE_IDENTIFIER}@{text "\<^sup>*"}] refers

  to the name of this Isabelle distribution, e.g.\ ``@{verbatim

  Isabelle2008}''.

  \item[@{setting_def ML_SYSTEM}, @{setting_def ML_HOME},

  @{setting_def ML_OPTIONS}, @{setting_def ML_PLATFORM}, @{setting_def

  ML_IDENTIFIER}@{text "\<^sup>*"}] specify the underlying ML system

  to be used for Isabelle.  There is only a fixed set of admissable

  @{setting ML_SYSTEM} names (see the @{"file"

  "$ISABELLE_HOME/etc/settings"} file of the distribution).

  The actual compiler binary will be run from the directory @{setting

  ML_HOME}, with @{setting ML_OPTIONS} as first arguments on the

  command line.  The optional @{setting ML_PLATFORM} may specify the

  binary format of ML heap images, which is useful for cross-platform

  installations.  The value of @{setting ML_IDENTIFIER} is

  automatically obtained by composing the values of @{setting

  ML_SYSTEM}, @{setting ML_PLATFORM} and the Isabelle version values.

  \item[@{setting_def ISABELLE_PATH}] is a list of directories

  (separated by colons) where Isabelle logic images may reside.  When

  looking up heaps files, the value of @{setting ML_IDENTIFIER} is

  appended to each component internally.

  \item[@{setting_def ISABELLE_OUTPUT}@{text "\<^sup>*"}] is a

  directory where output heap files should be stored by default. The

  ML system and Isabelle version identifier is appended here, too.

  \item[@{setting_def ISABELLE_BROWSER_INFO}] is the directory where

  theory browser information (HTML text, graph data, and printable

  documents) is stored (see also \secref{sec:info}).  The default

  value is @{verbatim "$ISABELLE_HOME_USER/browser_info"}.

  \item[@{setting_def ISABELLE_LOGIC}] specifies the default logic to

  load if none is given explicitely by the user.  The default value is

  @{verbatim HOL}.

  \item[@{setting_def ISABELLE_LINE_EDITOR}] specifies the default

  line editor for the @{tool_ref tty} interface.

  \item[@{setting_def ISABELLE_USEDIR_OPTIONS}] is implicitly prefixed

  to the command line of any @{tool_ref usedir} invocation. This

  typically contains compilation options for object-logics --- @{tool

  usedir} is the basic utility for managing logic sessions (cf.\ the

  @{verbatim IsaMakefile}s in the distribution).

  \item[@{setting_def ISABELLE_FILE_IDENT}] specifies a shell command

  for producing a source file identification, based on the actual

  content instead of the full physical path and date stamp (which is

  the default). A typical identification would produce a ``digest'' of

  the text, using a cryptographic hash function like SHA-1, for

  example.

  \item[@{setting_def ISABELLE_LATEX}, @{setting_def

  ISABELLE_PDFLATEX}, @{setting_def ISABELLE_BIBTEX}, @{setting_def

  ISABELLE_DVIPS}] refer to {\LaTeX} related tools for Isabelle

  document preparation (see also \secref{sec:tool-latex}).

  \item[@{setting_def ISABELLE_TOOLS}] is a colon separated list of

  directories that are scanned by @{executable isabelle} for external

  utility programs (see also \secref{sec:isabelle-tool}).

  \item[@{setting_def ISABELLE_DOCS}] is a colon separated list of

  directories with documentation files.

  \item[@{setting_def ISABELLE_DOC_FORMAT}] specifies the preferred

  document format, typically @{verbatim dvi} or @{verbatim pdf}.

  \item[@{setting_def DVI_VIEWER}] specifies the command to be used

  for displaying @{verbatim dvi} files.

  \item[@{setting_def PDF_VIEWER}] specifies the command to be used

  for displaying @{verbatim pdf} files.

  \item[@{setting_def PRINT_COMMAND}] specifies the standard printer

  spool command, which is expected to accept @{verbatim ps} files.

  \item[@{setting_def ISABELLE_TMP_PREFIX}@{text "\<^sup>*"}] is the

  prefix from which any running @{executable "isabelle-process"}

  derives an individual directory for temporary files.  The default is

  somewhere in @{verbatim "/tmp"}.

  \item[@{setting_def ISABELLE_INTERFACE}] is an identifier that

  specifies the actual user interface that the capital @{executable

  Isabelle} or @{executable "isabelle-interface"} should invoke.  See

  \secref{sec:interface} for more details.

  \end{description}

*}

section {* The raw Isabelle process *}

text {*

  The @{executable_def "isabelle-process"} executable runs bare-bones

  Isabelle logic sessions --- either interactively or in batch mode.

  It provides an abstraction over the underlying ML system, and over

  the actual heap file locations.  Its usage is:

\begin{ttbox}

Usage: isabelle-process [OPTIONS] [INPUT] [OUTPUT]

  Options are:

    -C           tell ML system to copy output image

    -I           startup Isar interaction mode

    -P           startup Proof General interaction mode

    -S           secure mode -- disallow critical operations

    -W OUTPUT    startup process wrapper, with messages going to OUTPUT stream

    -X           startup PGIP interaction mode

    -c           tell ML system to compress output image

    -e MLTEXT    pass MLTEXT to the ML session

    -f           pass 'Session.finish();' to the ML session

    -m MODE      add print mode for output

    -q           non-interactive session

    -r           open heap file read-only

    -u           pass 'use"ROOT.ML";' to the ML session

    -w           reset write permissions on OUTPUT

  INPUT (default "\$ISABELLE_LOGIC") and OUTPUT specify in/out heaps.

  These are either names to be searched in the Isabelle path, or

  actual file names (containing at least one /).

  If INPUT is "RAW_ML_SYSTEM", just start the bare bones ML system.

\end{ttbox}

  Input files without path specifications are looked up in the

  @{setting ISABELLE_PATH} setting, which may consist of multiple

  components separated by colons --- these are tried in the given

  order with the value of @{setting ML_IDENTIFIER} appended

  internally.  In a similar way, base names are relative to the

  directory specified by @{setting ISABELLE_OUTPUT}.  In any case,

  actual file locations may also be given by including at least one

  slash (@{verbatim "/"}) in the name (hint: use @{verbatim "./"} to

  refer to the current directory).

*}

subsubsection {* Options *}

text {*

  If the input heap file does not have write permission bits set, or

  the @{verbatim "-r"} option is given explicitely, then the session

  started will be read-only.  That is, the ML world cannot be

  committed back into the image file.  Otherwise, a writable session

  enables commits into either the input file, or into another output

  heap file (if that is given as the second argument on the command

  line).

  The read-write state of sessions is determined at startup only, it

  cannot be changed intermediately. Also note that heap images may

  require considerable amounts of disk space (approximately

  50--200~MB). Users are responsible for themselves to dispose their

  heap files when they are no longer needed.

  \medskip The @{verbatim "-w"} option makes the output heap file

  read-only after terminating.  Thus subsequent invocations cause the

  logic image to be read-only automatically.

  \medskip The @{verbatim "-c"} option tells the underlying ML system

  to compress the output heap (fully transparently).  On Poly/ML for

  example, the image is garbage collected and all stored values are

  maximally shared, resulting in up to @{text "50%"} less disk space

  consumption.

  \medskip The @{verbatim "-C"} option tells the ML system to produce

  a completely self-contained output image, probably including a copy

  of the ML runtime system itself.

  \medskip Using the @{verbatim "-e"} option, arbitrary ML code may be

  passed to the Isabelle session from the command line. Multiple

  @{verbatim "-e"}'s are evaluated in the given order. Strange things

  may happen when errorneous ML code is provided. Also make sure that

  the ML commands are terminated properly by semicolon.

  \medskip The @{verbatim "-u"} option is a shortcut for @{verbatim

  "-e"} passing ``@{verbatim "use \"ROOT.ML\";"}'' to the ML session.

  The @{verbatim "-f"} option passes ``@{verbatim

  "Session.finish();"}'', which is intended mainly for administrative

  purposes.

  \medskip The @{verbatim "-m"} option adds identifiers of print modes

  to be made active for this session. Typically, this is used by some

  user interface, e.g.\ to enable output of proper mathematical

  symbols.

  \medskip Isabelle normally enters an interactive top-level loop

  (after processing the @{verbatim "-e"} texts). The @{verbatim "-q"}

  option inhibits interaction, thus providing a pure batch mode

  facility.

  \medskip The @{verbatim "-I"} option makes Isabelle enter Isar

  interaction mode on startup, instead of the primitive ML top-level.

  The @{verbatim "-P"} option configures the top-level loop for

  interaction with the Proof General user interface, and the

  @{verbatim "-X"} option enables XML-based PGIP communication.  The

  @{verbatim "-W"} option makes Isabelle enter a special process

  wrapper for interaction via an external program; the protocol is a

  stripped-down version of Proof General the interaction mode, see

  also @{"file" "~~/src/Pure/Tools/isabelle_process.ML"} and @{"file"

  "~~/src/Pure/Tools/isabelle_process.scala"}.

  \medskip The @{verbatim "-S"} option makes the Isabelle process more

  secure by disabling some critical operations, notably runtime

  compilation and evaluation of ML source code.

*}

subsubsection {* Examples *}

text {*

  Run an interactive session of the default object-logic (as specified

  by the @{setting ISABELLE_LOGIC} setting) like this:

\begin{ttbox}

isabelle-process

\end{ttbox}

  Usually @{setting ISABELLE_LOGIC} refers to one of the standard

  logic images, which are read-only by default.  A writable session

  --- based on @{verbatim FOL}, but output to @{verbatim Foo} (in the

  directory specified by the @{setting ISABELLE_OUTPUT} setting) ---

  may be invoked as follows:

\begin{ttbox}

isabelle-process FOL Foo

\end{ttbox}

  Ending this session normally (e.g.\ by typing control-D) dumps the

  whole ML system state into @{verbatim Foo}. Be prepared for several

  tens of megabytes.

  The @{verbatim Foo} session may be continued later (still in

  writable state) by:

\begin{ttbox}

isabelle-process Foo

\end{ttbox}

  A read-only @{verbatim Foo} session may be started by:

\begin{ttbox}

isabelle-process -r Foo

\end{ttbox}

  \medskip Note that manual session management like this does

  \emph{not} provide proper setup for theory presentation.  This would

  require the @{tool usedir} utility.

  \bigskip The next example demonstrates batch execution of Isabelle.

  We retrieve the @{verbatim FOL} theory value from the theory loader

  within ML:

\begin{ttbox}

isabelle-process -e 'theory "FOL";' -q -r FOL

\end{ttbox}

  Note that the output text will be interspersed with additional junk

  messages by the ML runtime environment.  The @{verbatim "-W"} option

  allows to communicate with the Isabelle process via an external

  program in a more robust fashion.

*}

section {* The Isabelle tools wrapper \label{sec:isabelle-tool} *}

text {*

  All Isabelle related tools and interfaces are called via a common

  wrapper --- @{executable isabelle}:

\begin{ttbox}

Usage: isabelle TOOL [ARGS ...]

  Start Isabelle tool NAME with ARGS; pass "-?" for tool specific help.

  Available tools are:

    browser - Isabelle graph browser

    \dots

\end{ttbox}

  In principle, Isabelle tools are ordinary executable scripts that

  are run within the Isabelle settings environment, see

  \secref{sec:settings}.  The set of available tools is collected by

  @{executable isabelle} from the directories listed in the @{setting

  ISABELLE_TOOLS} setting.  Do not try to call the scripts directly

  from the shell.  Neither should you add the tool directories to your

  shell's search path!

*}

subsubsection {* Examples *}

text {*

  Show the list of available documentation of the current Isabelle

  installation like this:

\begin{ttbox}

  isabelle doc

\end{ttbox}

  View a certain document as follows:

\begin{ttbox}

  isabelle doc isar-ref

\end{ttbox}

  Create an Isabelle session derived from HOL (see also

  \secref{sec:tool-mkdir} and \secref{sec:tool-make}):

\begin{ttbox}

  isabelle mkdir HOL Test && isabelle make

\end{ttbox}

  Note that @{verbatim "isabelle mkdir"} is usually only invoked once;

  existing sessions (including document output etc.) are then updated

  by @{verbatim "isabelle make"} alone.

*}

section {* The Isabelle interface wrapper \label{sec:interface} *}

text {*

  Isabelle is a generic theorem prover, even w.r.t.\ its user

  interface.  The @{executable_def Isabelle} (or @{executable_def

  "isabelle-interface"}) executable provides a uniform way for

  end-users to invoke a certain interface; which one to start is

  determined by the @{setting_ref ISABELLE_INTERFACE} setting

  variable, which should give a full path specification to the actual

  executable.

  Presently, the most prominent Isabelle interface is Proof

  General~\cite{proofgeneral}\index{user interface!Proof General}.

  The Proof General distribution includes an interface wrapper script

  for the regular Isar toplevel, see @{verbatim

  "ProofGeneral/isar/interface"}.  The canonical settings for

  Isabelle/Isar are as follows:

\begin{ttbox}

ISABELLE_INTERFACE=\$ISABELLE_HOME/contrib/ProofGeneral/isar/interface

PROOFGENERAL_OPTIONS=""

\end{ttbox}

  Thus @{executable Isabelle} would automatically invoke Emacs with

  proper setup of the Proof General Lisp packages.  There are some

  options available, such as @{verbatim "-l"} for passing the logic

  image to be used by default, or @{verbatim "-m"} to tune the

  standard print mode.

  \medskip Note that the world may be also seen the other way round:

  Emacs may be started first (with proper setup of Proof General

  mode), and @{executable "isabelle-process"} run from within.  This

  requires further Emacs Lisp configuration, see the Proof General

  documentation \cite{proofgeneral} for more information.

*}

end