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author | wenzelm |

Sun, 15 Feb 2009 18:53:41 +0100 | |

changeset 29743 | 86c57ef80ba3 |

parent 29742 | 8edd5198dedb |

child 29744 | 37785fa3826d |

removed obsolete section "User interfaces";
removed obsolete section "Isabelle/Isar theories", moved parts to beginning of Spec.thy;
removed obsolete section "How to write Isar proofs anyway?";
tuned;

--- a/doc-src/IsarRef/Thy/Introduction.thy Sun Feb 15 18:50:51 2009 +0100 +++ b/doc-src/IsarRef/Thy/Introduction.thy Sun Feb 15 18:53:41 2009 +0100 @@ -10,27 +10,27 @@ The \emph{Isabelle} system essentially provides a generic infrastructure for building deductive systems (programmed in Standard ML), with a special focus on interactive theorem proving in - higher-order logics. In the olden days even end-users would refer - to certain ML functions (goal commands, tactics, tacticals etc.) to - pursue their everyday theorem proving tasks - \cite{isabelle-intro,isabelle-ref}. + higher-order logics. Many years ago, even end-users would refer to + certain ML functions (goal commands, tactics, tacticals etc.) to + pursue their everyday theorem proving tasks. In contrast \emph{Isar} provides an interpreted language environment of its own, which has been specifically tailored for the needs of theory and proof development. Compared to raw ML, the Isabelle/Isar top-level provides a more robust and comfortable development - platform, with proper support for theory development graphs, - single-step transactions with unlimited undo, etc. The - Isabelle/Isar version of the \emph{Proof~General} user interface - \cite{proofgeneral,Aspinall:TACAS:2000} provides an adequate - front-end for interactive theory and proof development in this - advanced theorem proving environment. + platform, with proper support for theory development graphs, managed + transactions with unlimited undo etc. The Isabelle/Isar version of + the \emph{Proof~General} user interface + \cite{proofgeneral,Aspinall:TACAS:2000} provides a decent front-end + for interactive theory and proof development in this advanced + theorem proving environment, even though it is somewhat biased + towards old-style proof scripts. \medskip Apart from the technical advances over bare-bones ML programming, the main purpose of the Isar language is to provide a conceptually different view on machine-checked proofs - \cite{Wenzel:1999:TPHOL,Wenzel-PhD}. ``Isar'' stands for - ``Intelligible semi-automated reasoning''. Drawing from both the + \cite{Wenzel:1999:TPHOL,Wenzel-PhD}. \emph{Isar} stands for + \emph{Intelligible semi-automated reasoning}. Drawing from both the traditions of informal mathematical proof texts and high-level programming languages, Isar offers a versatile environment for structured formal proof documents. Thus properly written Isar @@ -45,15 +45,15 @@ Despite its grand design of structured proof texts, Isar is able to assimilate the old tactical style as an ``improper'' sub-language. This provides an easy upgrade path for existing tactic scripts, as - well as additional means for interactive experimentation and - debugging of structured proofs. Isabelle/Isar supports a broad - range of proof styles, both readable and unreadable ones. + well as some means for interactive experimentation and debugging of + structured proofs. Isabelle/Isar supports a broad range of proof + styles, both readable and unreadable ones. \medskip The generic Isabelle/Isar framework (see - \chref{ch:isar-framework}) should work reasonably well for any - Isabelle object-logic that conforms to the natural deduction view of - the Isabelle/Pure framework. Specific language elements introduced - by the major object-logics are described in \chref{ch:hol} + \chref{ch:isar-framework}) works reasonably well for any Isabelle + object-logic that conforms to the natural deduction view of the + Isabelle/Pure framework. Specific language elements introduced by + the major object-logics are described in \chref{ch:hol} (Isabelle/HOL), \chref{ch:holcf} (Isabelle/HOLCF), and \chref{ch:zf} (Isabelle/ZF). The main language elements are already provided by the Isabelle/Pure framework. Nevertheless, examples given in the @@ -70,194 +70,4 @@ context; other commands emulate old-style tactical theorem proving. *} - -section {* User interfaces *} - -subsection {* Terminal sessions *} - -text {* - The Isabelle \texttt{tty} tool provides a very interface for running - the Isar interaction loop, with some support for command line - editing. For example: -\begin{ttbox} -isabelle tty\medskip -{\out Welcome to Isabelle/HOL (Isabelle2008)}\medskip -theory Foo imports Main begin; -definition foo :: nat where "foo == 1"; -lemma "0 < foo" by (simp add: foo_def); -end; -\end{ttbox} - - Any Isabelle/Isar command may be retracted by @{command undo}. - See the Isabelle/Isar Quick Reference (\appref{ap:refcard}) for a - comprehensive overview of available commands and other language - elements. -*} - - -subsection {* Emacs Proof General *} - -text {* - Plain TTY-based interaction as above used to be quite feasible with - traditional tactic based theorem proving, but developing Isar - documents really demands some better user-interface support. The - Proof~General environment by David Aspinall - \cite{proofgeneral,Aspinall:TACAS:2000} offers a generic Emacs - interface for interactive theorem provers that organizes all the - cut-and-paste and forward-backward walk through the text in a very - neat way. In Isabelle/Isar, the current position within a partial - proof document is equally important than the actual proof state. - Thus Proof~General provides the canonical working environment for - Isabelle/Isar, both for getting acquainted (e.g.\ by replaying - existing Isar documents) and for production work. -*} - - -subsubsection{* Proof~General as default Isabelle interface *} - -text {* - The Isabelle interface wrapper script provides an easy way to invoke - Proof~General (including XEmacs or GNU Emacs). The default - configuration of Isabelle is smart enough to detect the - Proof~General distribution in several canonical places (e.g.\ - @{verbatim "$ISABELLE_HOME/contrib/ProofGeneral"}). Thus the - capital @{verbatim Isabelle} executable would already refer to the - @{verbatim "ProofGeneral/isar"} interface without further ado. The - Isabelle interface script provides several options; pass @{verbatim - "-?"} to see its usage. - - With the proper Isabelle interface setup, Isar documents may now be edited by - visiting appropriate theory files, e.g.\ -\begin{ttbox} -Isabelle \({\langle}isabellehome{\rangle}\)/src/HOL/Isar_examples/Summation.thy -\end{ttbox} - Beginners may note the tool bar for navigating forward and backward - through the text (this depends on the local Emacs installation). - Consult the Proof~General documentation \cite{proofgeneral} for - further basic command sequences, in particular ``@{verbatim "C-c C-return"}'' - and ``@{verbatim "C-c u"}''. - - \medskip Proof~General may be also configured manually by giving - Isabelle settings like this (see also \cite{isabelle-sys}): - -\begin{ttbox} -ISABELLE_INTERFACE=\$ISABELLE_HOME/contrib/ProofGeneral/isar/interface -PROOFGENERAL_OPTIONS="" -\end{ttbox} - You may have to change @{verbatim - "$ISABELLE_HOME/contrib/ProofGeneral"} to the actual installation - directory of Proof~General. - - \medskip Apart from the Isabelle command line, defaults for - interface options may be given by the @{verbatim PROOFGENERAL_OPTIONS} - setting. For example, the Emacs executable to be used may be - configured in Isabelle's settings like this: -\begin{ttbox} -PROOFGENERAL_OPTIONS="-p xemacs-mule" -\end{ttbox} - - Occasionally, a user's @{verbatim "~/.emacs"} file contains code - that is incompatible with the (X)Emacs version used by - Proof~General, causing the interface startup to fail prematurely. - Here the @{verbatim "-u false"} option helps to get the interface - process up and running. Note that additional Lisp customization - code may reside in @{verbatim "proofgeneral-settings.el"} of - @{verbatim "$ISABELLE_HOME/etc"} or @{verbatim - "$ISABELLE_HOME_USER/etc"}. -*} - - -subsubsection {* The X-Symbol package *} - -text {* - Proof~General incorporates a version of the Emacs X-Symbol package - \cite{x-symbol}, which handles proper mathematical symbols displayed - on screen. Pass option @{verbatim "-x true"} to the Isabelle - interface script, or check the appropriate Proof~General menu - setting by hand. The main challenge of getting X-Symbol to work - properly is the underlying (semi-automated) X11 font setup. - - \medskip Using proper mathematical symbols in Isabelle theories can - be very convenient for readability of large formulas. On the other - hand, the plain ASCII sources easily become somewhat unintelligible. - For example, @{text "\<Longrightarrow>"} would appear as @{verbatim "\<Longrightarrow>"} according - the default set of Isabelle symbols. Nevertheless, the Isabelle - document preparation system (see \chref{ch:document-prep}) will be - happy to print non-ASCII symbols properly. It is even possible to - invent additional notation beyond the display capabilities of Emacs - and X-Symbol. -*} - - -section {* Isabelle/Isar theories *} - -text {* - Isabelle/Isar offers the following main improvements over classic - Isabelle. - - \begin{enumerate} - - \item A \emph{theory format} that integrates specifications and - proofs, supporting interactive development and unlimited undo - operation. - - \item A \emph{formal proof document language} designed to support - intelligible semi-automated reasoning. Instead of putting together - unreadable tactic scripts, the author is enabled to express the - reasoning in way that is close to usual mathematical practice. The - old tactical style has been assimilated as ``improper'' language - elements. - - \item A simple document preparation system, for typesetting formal - developments together with informal text. The resulting - hyper-linked PDF documents are equally well suited for WWW - presentation and as printed copies. - - \end{enumerate} - - The Isar proof language is embedded into the new theory format as a - proper sub-language. Proof mode is entered by stating some - @{command theorem} or @{command lemma} at the theory level, and - left again with the final conclusion (e.g.\ via @{command qed}). - A few theory specification mechanisms also require some proof, such - as HOL's @{command typedef} which demands non-emptiness of the - representing sets. -*} - - -section {* How to write Isar proofs anyway? \label{sec:isar-howto} *} - -text {* - This is one of the key questions, of course. First of all, the - tactic script emulation of Isabelle/Isar essentially provides a - clarified version of the very same unstructured proof style of - classic Isabelle. Old-time users should quickly become acquainted - with that (slightly degenerative) view of Isar. - - Writing \emph{proper} Isar proof texts targeted at human readers is - quite different, though. Experienced users of the unstructured - style may even have to unlearn some of their habits to master proof - composition in Isar. In contrast, new users with less experience in - old-style tactical proving, but a good understanding of mathematical - proof in general, often get started easier. - - \medskip The present text really is only a reference manual on - Isabelle/Isar, not a tutorial. Nevertheless, we will attempt to - give some clues of how the concepts introduced here may be put into - practice. Especially note that \appref{ap:refcard} provides a quick - reference card of the most common Isabelle/Isar language elements. - - Further issues concerning the Isar concepts are covered in the - literature - \cite{Wenzel:1999:TPHOL,Wiedijk:2000:MV,Bauer-Wenzel:2000:HB,Bauer-Wenzel:2001}. - The author's PhD thesis \cite{Wenzel-PhD} presently provides the - most complete exposition of Isar foundations, techniques, and - applications. A number of example applications are distributed with - Isabelle, and available via the Isabelle WWW library (e.g.\ - \url{http://isabelle.in.tum.de/library/}). The ``Archive of Formal - Proofs'' \url{http://afp.sourceforge.net/} also provides plenty of - examples, both in proper Isar proof style and unstructured tactic - scripts. -*} - end