author | wenzelm |
Thu, 13 Nov 2008 21:59:02 +0100 | |
changeset 28774 | 0e25ef17b06b |
parent 28762 | f5d79aeffd81 |
child 28775 | d25fe9601dbd |
permissions | -rw-r--r-- |
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(* $Id$ *) |
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theory Outer_Syntax |
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imports Main |
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begin |
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chapter {* Outer syntax *} |
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text {* |
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The rather generic framework of Isabelle/Isar syntax emerges from |
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three main syntactic categories: \emph{commands} of the top-level |
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Isar engine (covering theory and proof elements), \emph{methods} for |
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general goal refinements (analogous to traditional ``tactics''), and |
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\emph{attributes} for operations on facts (within a certain |
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context). Subsequently we give a reference of basic syntactic |
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entities underlying Isabelle/Isar syntax in a bottom-up manner. |
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Concrete theory and proof language elements will be introduced later |
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on. |
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\medskip In order to get started with writing well-formed |
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Isabelle/Isar documents, the most important aspect to be noted is |
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the difference of \emph{inner} versus \emph{outer} syntax. Inner |
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syntax is that of Isabelle types and terms of the logic, while outer |
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syntax is that of Isabelle/Isar theory sources (specifications and |
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proofs). As a general rule, inner syntax entities may occur only as |
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\emph{atomic entities} within outer syntax. For example, the string |
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@{verbatim "\"x + y\""} and identifier @{verbatim z} are legal term |
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specifications within a theory, while @{verbatim "x + y"} without |
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quotes is not. |
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Printed theory documents usually omit quotes to gain readability |
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(this is a matter of {\LaTeX} macro setup, say via @{verbatim |
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"\\isabellestyle"}, see also \cite{isabelle-sys}). Experienced |
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users of Isabelle/Isar may easily reconstruct the lost technical |
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information, while mere readers need not care about quotes at all. |
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\medskip Isabelle/Isar input may contain any number of input |
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termination characters ``@{verbatim ";"}'' (semicolon) to separate |
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commands explicitly. This is particularly useful in interactive |
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shell sessions to make clear where the current command is intended |
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to end. Otherwise, the interpreter loop will continue to issue a |
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secondary prompt ``@{verbatim "#"}'' until an end-of-command is |
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clearly recognized from the input syntax, e.g.\ encounter of the |
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next command keyword. |
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More advanced interfaces such as Proof~General \cite{proofgeneral} |
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do not require explicit semicolons, the amount of input text is |
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determined automatically by inspecting the present content of the |
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Emacs text buffer. In the printed presentation of Isabelle/Isar |
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documents semicolons are omitted altogether for readability. |
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\begin{warn} |
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Proof~General requires certain syntax classification tables in |
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order to achieve properly synchronized interaction with the |
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Isabelle/Isar process. These tables need to be consistent with |
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the Isabelle version and particular logic image to be used in a |
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running session (common object-logics may well change the outer |
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syntax). The standard setup should work correctly with any of the |
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``official'' logic images derived from Isabelle/HOL (including |
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HOLCF etc.). Users of alternative logics may need to tell |
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Proof~General explicitly, e.g.\ by giving an option @{verbatim "-k ZF"} |
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(in conjunction with @{verbatim "-l ZF"}, to specify the default |
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logic image). Note that option @{verbatim "-L"} does both |
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of this at the same time. |
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\end{warn} |
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*} |
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section {* Lexical matters \label{sec:outer-lex} *} |
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text {* The Isabelle/Isar outer syntax provides token classes as |
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presented below; most of these coincide with the inner lexical |
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syntax as defined in \secref{sec:inner-lex}. |
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\begin{matharray}{rcl} |
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@{syntax_def ident} & = & letter\,quasiletter^* \\ |
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@{syntax_def longident} & = & ident (\verb,.,ident)^+ \\ |
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@{syntax_def symident} & = & sym^+ ~|~ \verb,\,\verb,<,ident\verb,>, \\ |
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@{syntax_def nat} & = & digit^+ \\ |
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@{syntax_def var} & = & ident ~|~ \verb,?,ident ~|~ \verb,?,ident\verb,.,nat \\ |
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@{syntax_def typefree} & = & \verb,',ident \\ |
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@{syntax_def typevar} & = & typefree ~|~ \verb,?,typefree ~|~ \verb,?,typefree\verb,.,nat \\ |
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@{syntax_def string} & = & \verb,", ~\dots~ \verb,", \\ |
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@{syntax_def altstring} & = & \backquote ~\dots~ \backquote \\ |
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@{syntax_def verbatim} & = & \verb,{*, ~\dots~ \verb,*,\verb,}, \\[1ex] |
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letter & = & latin ~|~ \verb,\,\verb,<,latin\verb,>, ~|~ \verb,\,\verb,<,latin\,latin\verb,>, ~|~ greek ~|~ \\ |
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& & \verb,\<^isub>, ~|~ \verb,\<^isup>, \\ |
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quasiletter & = & letter ~|~ digit ~|~ \verb,_, ~|~ \verb,', \\ |
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latin & = & \verb,a, ~|~ \dots ~|~ \verb,z, ~|~ \verb,A, ~|~ \dots ~|~ \verb,Z, \\ |
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digit & = & \verb,0, ~|~ \dots ~|~ \verb,9, \\ |
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sym & = & \verb,!, ~|~ \verb,#, ~|~ \verb,$, ~|~ \verb,%, ~|~ \verb,&, ~|~ |
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\verb,*, ~|~ \verb,+, ~|~ \verb,-, ~|~ \verb,/, ~|~ \\ |
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& & \verb,<, ~|~ \verb,=, ~|~ \verb,>, ~|~ \verb,?, ~|~ \texttt{\at} ~|~ |
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\verb,^, ~|~ \verb,_, ~|~ \verb,|, ~|~ \verb,~, \\ |
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greek & = & \verb,\<alpha>, ~|~ \verb,\<beta>, ~|~ \verb,\<gamma>, ~|~ \verb,\<delta>, ~| \\ |
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& & \verb,\<epsilon>, ~|~ \verb,\<zeta>, ~|~ \verb,\<eta>, ~|~ \verb,\<theta>, ~| \\ |
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& & \verb,\<iota>, ~|~ \verb,\<kappa>, ~|~ \verb,\<mu>, ~|~ \verb,\<nu>, ~| \\ |
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& & \verb,\<xi>, ~|~ \verb,\<pi>, ~|~ \verb,\<rho>, ~|~ \verb,\<sigma>, ~|~ \verb,\<tau>, ~| \\ |
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& & \verb,\<upsilon>, ~|~ \verb,\<phi>, ~|~ \verb,\<chi>, ~|~ \verb,\<psi>, ~| \\ |
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& & \verb,\<omega>, ~|~ \verb,\<Gamma>, ~|~ \verb,\<Delta>, ~|~ \verb,\<Theta>, ~| \\ |
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& & \verb,\<Lambda>, ~|~ \verb,\<Xi>, ~|~ \verb,\<Pi>, ~|~ \verb,\<Sigma>, ~| \\ |
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& & \verb,\<Upsilon>, ~|~ \verb,\<Phi>, ~|~ \verb,\<Psi>, ~|~ \verb,\<Omega>, \\ |
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\end{matharray} |
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The syntax of @{syntax string} admits any characters, including |
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newlines; ``@{verbatim "\""}'' (double-quote) and ``@{verbatim |
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"\\"}'' (backslash) need to be escaped by a backslash; arbitrary |
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character codes may be specified as ``@{verbatim "\\"}@{text ddd}'', |
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with three decimal digits. Alternative strings according to |
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@{syntax altstring} are analogous, using single back-quotes instead. |
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The body of @{syntax verbatim} may consist of any text not |
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containing ``@{verbatim "*"}@{verbatim "}"}''; this allows |
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convenient inclusion of quotes without further escapes. The greek |
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letters do \emph{not} include @{verbatim "\<lambda>"}, which is already used |
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differently in the meta-logic. |
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Common mathematical symbols such as @{text \<forall>} are represented in |
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Isabelle as @{verbatim \<forall>}. There are infinitely many Isabelle |
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symbols like this, although proper presentation is left to front-end |
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tools such as {\LaTeX} or Proof~General with the X-Symbol package. |
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A list of standard Isabelle symbols that work well with these tools |
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is given in \cite[appendix~A]{isabelle-sys}. |
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Source comments take the form @{verbatim "(*"}~@{text |
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"\<dots>"}~@{verbatim "*)"} and may be nested, although user-interface |
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tools might prevent this. Note that this form indicates source |
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comments only, which are stripped after lexical analysis of the |
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input. The Isar syntax also provides proper \emph{document |
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comments} that are considered as part of the text (see |
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\secref{sec:comments}). |
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*} |
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section {* Common syntax entities *} |
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text {* |
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We now introduce several basic syntactic entities, such as names, |
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terms, and theorem specifications, which are factored out of the |
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actual Isar language elements to be described later. |
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*} |
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subsection {* Names *} |
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text {* |
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Entity \railqtok{name} usually refers to any name of types, |
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constants, theorems etc.\ that are to be \emph{declared} or |
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\emph{defined} (so qualified identifiers are excluded here). Quoted |
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strings provide an escape for non-identifier names or those ruled |
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out by outer syntax keywords (e.g.\ quoted @{verbatim "\"let\""}). |
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Already existing objects are usually referenced by |
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\railqtok{nameref}. |
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\indexoutertoken{name}\indexoutertoken{parname}\indexoutertoken{nameref} |
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\indexoutertoken{int} |
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\begin{rail} |
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name: ident | symident | string | nat |
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parname: '(' name ')' |
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; |
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nameref: name | longident |
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; |
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int: nat | '-' nat |
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; |
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\end{rail} |
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*} |
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subsection {* Comments \label{sec:comments} *} |
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text {* |
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Large chunks of plain \railqtok{text} are usually given |
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\railtok{verbatim}, i.e.\ enclosed in @{verbatim "{"}@{verbatim |
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"*"}~@{text "\<dots>"}~@{verbatim "*"}@{verbatim "}"}. For convenience, |
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any of the smaller text units conforming to \railqtok{nameref} are |
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admitted as well. A marginal \railnonterm{comment} is of the form |
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@{verbatim "--"} \railqtok{text}. Any number of these may occur |
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within Isabelle/Isar commands. |
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\indexoutertoken{text}\indexouternonterm{comment} |
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\begin{rail} |
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text: verbatim | nameref |
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; |
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comment: '--' text |
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; |
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\end{rail} |
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*} |
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subsection {* Type classes, sorts and arities *} |
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text {* |
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Classes are specified by plain names. Sorts have a very simple |
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inner syntax, which is either a single class name @{text c} or a |
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list @{text "{c\<^sub>1, \<dots>, c\<^sub>n}"} referring to the |
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intersection of these classes. The syntax of type arities is given |
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directly at the outer level. |
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\indexouternonterm{sort}\indexouternonterm{arity} |
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\indexouternonterm{classdecl} |
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\begin{rail} |
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classdecl: name (('<' | subseteq) (nameref + ','))? |
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; |
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sort: nameref |
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; |
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arity: ('(' (sort + ',') ')')? sort |
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; |
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\end{rail} |
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*} |
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subsection {* Types and terms \label{sec:types-terms} *} |
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text {* |
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The actual inner Isabelle syntax, that of types and terms of the |
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logic, is far too sophisticated in order to be modelled explicitly |
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at the outer theory level. Basically, any such entity has to be |
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quoted to turn it into a single token (the parsing and type-checking |
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is performed internally later). For convenience, a slightly more |
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liberal convention is adopted: quotes may be omitted for any type or |
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term that is already atomic at the outer level. For example, one |
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may just write @{verbatim x} instead of quoted @{verbatim "\"x\""}. |
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Note that symbolic identifiers (e.g.\ @{verbatim "++"} or @{text |
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"\<forall>"} are available as well, provided these have not been superseded |
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by commands or other keywords already (such as @{verbatim "="} or |
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@{verbatim "+"}). |
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\indexoutertoken{type}\indexoutertoken{term}\indexoutertoken{prop} |
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\begin{rail} |
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type: nameref | typefree | typevar |
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; |
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term: nameref | var |
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; |
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prop: term |
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; |
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\end{rail} |
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Positional instantiations are indicated by giving a sequence of |
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terms, or the placeholder ``@{text _}'' (underscore), which means to |
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skip a position. |
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\indexoutertoken{inst}\indexoutertoken{insts} |
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\begin{rail} |
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inst: underscore | term |
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; |
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insts: (inst *) |
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; |
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\end{rail} |
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Type declarations and definitions usually refer to |
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\railnonterm{typespec} on the left-hand side. This models basic |
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type constructor application at the outer syntax level. Note that |
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only plain postfix notation is available here, but no infixes. |
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\indexouternonterm{typespec} |
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\begin{rail} |
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typespec: (() | typefree | '(' ( typefree + ',' ) ')') name |
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; |
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\end{rail} |
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*} |
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subsection {* Term patterns and declarations \label{sec:term-decls} *} |
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text {* |
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Wherever explicit propositions (or term fragments) occur in a proof |
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text, casual binding of schematic term variables may be given |
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specified via patterns of the form ``@{text "(\<IS> p\<^sub>1 \<dots> |
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p\<^sub>n)"}''. This works both for \railqtok{term} and \railqtok{prop}. |
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\indexouternonterm{termpat}\indexouternonterm{proppat} |
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\begin{rail} |
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termpat: '(' ('is' term +) ')' |
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; |
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proppat: '(' ('is' prop +) ')' |
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; |
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\end{rail} |
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\medskip Declarations of local variables @{text "x :: \<tau>"} and |
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logical propositions @{text "a : \<phi>"} represent different views on |
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the same principle of introducing a local scope. In practice, one |
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may usually omit the typing of \railnonterm{vars} (due to |
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type-inference), and the naming of propositions (due to implicit |
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references of current facts). In any case, Isar proof elements |
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usually admit to introduce multiple such items simultaneously. |
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\indexouternonterm{vars}\indexouternonterm{props} |
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\begin{rail} |
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vars: (name+) ('::' type)? |
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; |
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props: thmdecl? (prop proppat? +) |
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; |
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\end{rail} |
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The treatment of multiple declarations corresponds to the |
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complementary focus of \railnonterm{vars} versus |
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\railnonterm{props}. In ``@{text "x\<^sub>1 \<dots> x\<^sub>n :: \<tau>"}'' |
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the typing refers to all variables, while in @{text "a: \<phi>\<^sub>1 \<dots> |
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\<phi>\<^sub>n"} the naming refers to all propositions collectively. |
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Isar language elements that refer to \railnonterm{vars} or |
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\railnonterm{props} typically admit separate typings or namings via |
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another level of iteration, with explicit @{keyword_ref "and"} |
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separators; e.g.\ see @{command "fix"} and @{command "assume"} in |
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\secref{sec:proof-context}. |
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*} |
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|
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subsection {* Attributes and theorems \label{sec:syn-att} *} |
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text {* Attributes have their own ``semi-inner'' syntax, in the sense |
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that input conforming to \railnonterm{args} below is parsed by the |
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attribute a second time. The attribute argument specifications may |
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be any sequence of atomic entities (identifiers, strings etc.), or |
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properly bracketed argument lists. Below \railqtok{atom} refers to |
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any atomic entity, including any \railtok{keyword} conforming to |
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\railtok{symident}. |
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\indexoutertoken{atom}\indexouternonterm{args}\indexouternonterm{attributes} |
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\begin{rail} |
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atom: nameref | typefree | typevar | var | nat | keyword |
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; |
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arg: atom | '(' args ')' | '[' args ']' |
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; |
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args: arg * |
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; |
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attributes: '[' (nameref args * ',') ']' |
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; |
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\end{rail} |
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Theorem specifications come in several flavors: |
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\railnonterm{axmdecl} and \railnonterm{thmdecl} usually refer to |
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axioms, assumptions or results of goal statements, while |
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\railnonterm{thmdef} collects lists of existing theorems. Existing |
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theorems are given by \railnonterm{thmref} and |
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\railnonterm{thmrefs}, the former requires an actual singleton |
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result. |
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There are three forms of theorem references: |
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\begin{enumerate} |
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\item named facts @{text "a"}, |
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\item selections from named facts @{text "a(i)"} or @{text "a(j - k)"}, |
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\item literal fact propositions using @{syntax_ref altstring} syntax |
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@{verbatim "`"}@{text "\<phi>"}@{verbatim "`"} (see also method |
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@{method_ref fact}). |
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\end{enumerate} |
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Any kind of theorem specification may include lists of attributes |
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both on the left and right hand sides; attributes are applied to any |
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immediately preceding fact. If names are omitted, the theorems are |
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not stored within the theorem database of the theory or proof |
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context, but any given attributes are applied nonetheless. |
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An extra pair of brackets around attributes (like ``@{text |
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"[[simproc a]]"}'') abbreviates a theorem reference involving an |
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internal dummy fact, which will be ignored later on. So only the |
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effect of the attribute on the background context will persist. |
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This form of in-place declarations is particularly useful with |
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commands like @{command "declare"} and @{command "using"}. |
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\indexouternonterm{axmdecl}\indexouternonterm{thmdecl} |
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\indexouternonterm{thmdef}\indexouternonterm{thmref} |
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\indexouternonterm{thmrefs}\indexouternonterm{selection} |
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\begin{rail} |
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axmdecl: name attributes? ':' |
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; |
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thmdecl: thmbind ':' |
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; |
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thmdef: thmbind '=' |
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; |
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thmref: (nameref selection? | altstring) attributes? | '[' attributes ']' |
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; |
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thmrefs: thmref + |
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; |
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thmbind: name attributes | name | attributes |
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; |
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selection: '(' ((nat | nat '-' nat?) + ',') ')' |
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; |
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\end{rail} |
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*} |
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end |