theory Intro
imports Base
begin

chapter {* Introduction *}


text {*
   \begin{flushright}
  {\em
  ``My thesis is that programming is not at the bottom of the intellectual \\
  pyramid, but at the top. It's creative design of the highest order. It \\
  isn't monkey or donkey work; rather, as Edsger Dijkstra famously \\
  claimed, it's amongst the hardest intellectual tasks ever attempted.''} \\[1ex]
  Richard Bornat, In {\em Defence of Programming}. \cite{Bornat-lecture}
  \end{flushright}

  \medskip
  If your next project requires you to program on the ML-level of Isabelle,
  then this tutorial is for you. It will guide you through the first steps of
  Isabelle programming, and also explain tricks of the trade. The best way to
  get to know the ML-level of Isabelle is by experimenting with the many code
  examples included in the tutorial. The code is as far as possible checked
  against the Isabelle distribution.\footnote{\input{version}} If something does not work, 
  then please let us know. It is impossible for us to know every environment, 
  operating system or editor in which Isabelle is used. If you have comments, 
  criticism or like to add to the tutorial, please feel free---you are most 
  welcome! The tutorial is meant to be gentle and comprehensive. To achieve 
  this we need your feedback.
*}

section {* Intended Audience and Prior Knowledge *}

text {* 
  This tutorial targets readers who already know how to use Isabelle for
  writing theories and proofs. We also assume that readers are familiar with
  the functional programming language ML, the language in which most of
  Isabelle is implemented. If you are unfamiliar with either of these two
  subjects, then you should first work through the Isabelle/HOL tutorial
  \cite{isa-tutorial} or Paulson's book on ML \cite{paulson-ml2}.
*}

section {* Existing Documentation *}

text {*
  The following documentation about Isabelle programming already exists (and is
  part of the distribution of Isabelle):

  \begin{description}
  \item[The Isabelle/Isar Implementation Manual] describes Isabelle
  from a high-level perspective, documenting both the underlying
  concepts and some of the interfaces. 

  \item[The Isabelle Reference Manual] is an older document that used
  to be the main reference of Isabelle at a time when all proof scripts 
  were written on the ML-level. Many parts of this manual are outdated 
  now, but some  parts, particularly the chapters on tactics, are still 
  useful.

  \item[The Isar Reference Manual] provides specification material (like grammars,
  examples and so on) about Isar and its implementation.
  \end{description}

  Then of course there are:

  \begin{description}
  \item[The Isabelle sources.] They are the ultimate reference for how
  things really work. Therefore you should not hesitate to look at the
  way things are actually implemented. More importantly, it is often
  good to look at code that does similar things as you want to do and
  learn from it. This tutorial contains frequently pointers to the
  Isabelle sources. Still, the UNIX command \mbox{@{text "grep -R"}} is
  often your best friend while programming with Isabelle, or
  hypersearch if you program using jEdit under MacOSX. To understand the sources,
  it is often also necessary to track the change history of a file or
  files. The Mercurial repository\footnote{\url{http://isabelle.in.tum.de/repos/isabelle/}} 
  for Isabelle  provides convenient interfaces to query the history of
  files and ``change sets''.
  \end{description}
*}

section {* Typographic Conventions *}

text {*
  All ML-code in this tutorial is typeset in shaded boxes, like the following 
  simple ML-expression:

  \begin{isabelle}
  \begin{graybox}
  \isacommand{ML}~@{text "\<verbopen>"}\isanewline
  \hspace{5mm}@{ML "3 + 4"}\isanewline
  @{text "\<verbclose>"}
  \end{graybox}
  \end{isabelle}
  
  These boxes correspond to how code can be processed inside the interactive
  environment of Isabelle. It is therefore easy to experiment with what is 
  displayed. However, for better readability we will drop the enclosing 
  \isacommand{ML}~@{text "\<verbopen> \<dots> \<verbclose>"} and just write:


  @{ML [display,gray] "3 + 4"}
  
  Whenever appropriate we also show the response the code 
  generates when evaluated. This response is prefixed with a 
  @{text [quotes] ">"}, like:

  @{ML_response [display,gray] "3 + 4" "7"}

  The user-level commands of Isabelle (i.e., the non-ML code) are written
  in \isacommand{bold face} (e.g., \isacommand{lemma}, \isacommand{apply},
  \isacommand{foobar} and so on).  We use @{text "$ \<dots>"} to indicate that a
  command needs to be run in a UNIX-shell, for example:

  @{text [display] "$ grep -R ThyOutput *"}

  Pointers to further information and Isabelle files are typeset in 
  \textit{italic} and highlighted as follows:

  \begin{readmore}
  Further information or pointers to files.
  \end{readmore}

  The pointers to Isabelle files are hyperlinked to the tip of the Mercurial
  repository of Isabelle at \href{http://isabelle.in.tum.de/repos/isabelle/}
  {http://isabelle.in.tum.de/repos/isabelle/}.

  A few exercises are scattered around the text. Their solutions are given 
  in Appendix~\ref{ch:solutions}. Of course, you learn most, if you first try
  to solve the exercises on your own, and then look at the solutions.
*}

section {* Aaaaargh! My Code Does not Work Anymore *}

text {*
  One unpleasant aspect of any code development inside a larger system is that
  one has to aim at a ``moving target''. Isabelle is no exception. Every 
  update lets potentially all hell break loose, because other developers have
  changed code you are relying on. Cursing is somewhat helpful in such situations, 
  but taking the view that incompatible code changes are a fact of life 
  might be more gratifying. Isabelle is a research project. In most circumstances 
  it is just impossible to make research backward compatible (imagine Darwin 
  attempting to make the Theory of Evolution backward compatible).

  However, there are a few steps you can take to mitigate unwanted
  interferences with code changes from other developers. First, you can base
  your code on the latest stable release of Isabelle (it is aimed to have one
  such release at least once every year). This might cut you off from the
  latest feature implemented in Isabelle, but at least you do not have to
  track side-steps or dead-ends in the Isabelle development. Of course this
  means also you have to synchronise your code at the next stable release. If
  you do not synchronise, be warned that code seems to ``rot'' very
  quickly. Another possibility is to get your code into the Isabelle
  distribution. For this you have to convince other developers that your code
  or project is of general interest. If you managed to do this, then the
  problem of the moving target goes away, because when checking in new code,
  developers are strongly urged to test it against Isabelle's code base. If
  your project is part of that code base, then maintenance is done by
  others. Unfortunately, this might not be a helpful advice for all types of
  projects. A lower threshold for inclusion has the Archive of Formalised
  Proofs, short AFP.\footnote{\url{http://afp.sourceforge.net/}} This archive
  has been created mainly for formalisations that are interesting but not
  necessarily of general interest. If you have ML-code as part of a
  formalisation, then this might be the right place for you. There is no
  problem with updating your code after submission. At the moment developers
  are not as diligent with checking their code against the AFP than with
  checking agains the distribution, but generally problems will be caught and
  the developer, who caused them, is expected to fix them. So also in this
  case code maintenance is done for you.
*}

section {* Some Naming Conventions in the Isabelle Sources *}

text {*
  There are a few naming conventions in the Isabelle code that might aid reading 
  and writing code. (Remember that code is written once, but read many 
  times.) The most important conventions are:

  \begin{itemize}
  \item @{text t}, @{text u}, @{text trm} for (raw) terms; ML-type: @{ML_type term}
  \item @{text ct}, @{text cu} for certified terms; ML-type: @{ML_type cterm}
  \item @{text "ty"}, @{text T}, @{text U} for (raw) types; ML-type: @{ML_type typ}
  \item @{text th}, @{text thm} for theorems; ML-type: @{ML_type thm}
  \item @{text "foo_tac"} for tactics; ML-type: @{ML_type tactic}
  \item @{text thy} for theories; ML-type: @{ML_type theory}
  \item @{text ctxt} for proof contexts; ML-type: @{ML_type Proof.context}
  \item @{text lthy} for local theories; ML-type: @{ML_type local_theory}
  \item @{text context} for generic contexts; ML-type @{ML_type Context.generic}
  \item @{text mx} for mixfix syntax annotations; ML-type @{ML_type mixfix}
  \item @{text prt} for pretty printing; ML-type @{ML_type Pretty.T}
  \end{itemize}
*}

section {* Acknowledgements *}

text {*
  Financial support for this tutorial was provided by the German 
  Research Council (DFG) under grant number URB 165/5-1. The following
  people contributed to the text:

  \begin{itemize}
  \item {\bf Stefan Berghofer} wrote nearly all of the ML-code of the
  \simpleinductive-package and the code for the @{text
  "chunk"}-antiquotation. He also wrote the first version of this chapter
  describing the package and has been helpful \emph{beyond measure} with
  answering questions about Isabelle.

  \item {\bf Jasmin Blanchette} helped greatly with section \ref{sec:pretty}.

  \item {\bf Sascha Böhme} contributed the recipes in \ref{rec:timeout}, 
  \ref{rec:external} and \ref{rec:oracle}. He also wrote section \ref{sec:conversion} 
  and helped with recipe \ref{rec:timing}. Parts of section \ref{sec:storing}
  are by him.

  \item {\bf Jeremy Dawson} wrote the first version of the chapter
  about parsing.

  \item {\bf Armin Heller} helped with recipe \ref{rec:sat}.

  \item {\bf Alexander Krauss} wrote the first version of the ``first-steps'' 
  chapter and also contributed the material on @{ML_functor Named_Thms}.

  \item {\bf Christian Sternagel} proofread the tutorial and made 
  many improvemets to the text. 
  \end{itemize}

  Please let me know of any omissions. Responsibility for any remaining
  errors lies with me.\bigskip

  \vspace{5cm}
  {\Large\bf
  This tutorial is still in the process of being written! All of the
  text is still under construction. Sections and 
  chapters that are under \underline{heavy} construction are marked 
  with TBD.}

  \vfill
  
  This document (version \input{tip}\hspace{-0.5ex}) was compiled with:\\
  \input{version}\\
  \input{pversion}
*}



end