doc-src/IsarImplementation/Thy/Prelim.thy
 author wenzelm Thu Oct 21 20:00:46 2010 +0100 (2010-10-21) changeset 39876 1ff9bce085bd parent 39866 5ec01d5acd0c child 40126 916cb4a28ffd permissions -rw-r--r--
preliminary material on "Concrete syntax and type-checking";
 wenzelm@29755  1 theory Prelim  wenzelm@29755  2 imports Base  wenzelm@29755  3 begin  wenzelm@18537  4 wenzelm@18537  5 chapter {* Preliminaries *}  wenzelm@18537  6 wenzelm@20429  7 section {* Contexts \label{sec:context} *}  wenzelm@18537  8 wenzelm@20429  9 text {*  wenzelm@20451  10  A logical context represents the background that is required for  wenzelm@20451  11  formulating statements and composing proofs. It acts as a medium to  wenzelm@20451  12  produce formal content, depending on earlier material (declarations,  wenzelm@20451  13  results etc.).  wenzelm@18537  14 wenzelm@20451  15  For example, derivations within the Isabelle/Pure logic can be  wenzelm@20451  16  described as a judgment @{text "\ \\<^sub>\ \"}, which means that a  wenzelm@20429  17  proposition @{text "\"} is derivable from hypotheses @{text "\"}  wenzelm@20429  18  within the theory @{text "\"}. There are logical reasons for  wenzelm@20451  19  keeping @{text "\"} and @{text "\"} separate: theories can be  wenzelm@20451  20  liberal about supporting type constructors and schematic  wenzelm@20451  21  polymorphism of constants and axioms, while the inner calculus of  wenzelm@20451  22  @{text "\ \ \"} is strictly limited to Simple Type Theory (with  wenzelm@20451  23  fixed type variables in the assumptions).  wenzelm@18537  24 wenzelm@20429  25  \medskip Contexts and derivations are linked by the following key  wenzelm@20429  26  principles:  wenzelm@20429  27 wenzelm@20429  28  \begin{itemize}  wenzelm@20429  29 wenzelm@20429  30  \item Transfer: monotonicity of derivations admits results to be  wenzelm@20451  31  transferred into a \emph{larger} context, i.e.\ @{text "\ \\<^sub>\  wenzelm@20451  32  \"} implies @{text "\' \\<^sub>\\<^sub>' \"} for contexts @{text "\'  wenzelm@20451  33  \ \"} and @{text "\' \ \"}.  wenzelm@18537  34 wenzelm@20429  35  \item Export: discharge of hypotheses admits results to be exported  wenzelm@20451  36  into a \emph{smaller} context, i.e.\ @{text "\' \\<^sub>\ \"}  wenzelm@20451  37  implies @{text "\ \\<^sub>\ \ \ \"} where @{text "\' \ \"} and  wenzelm@20451  38  @{text "\ = \' - \"}. Note that @{text "\"} remains unchanged here,  wenzelm@20451  39  only the @{text "\"} part is affected.  wenzelm@20429  40 wenzelm@20429  41  \end{itemize}  wenzelm@18537  42 wenzelm@20451  43  \medskip By modeling the main characteristics of the primitive  wenzelm@20451  44  @{text "\"} and @{text "\"} above, and abstracting over any  wenzelm@20451  45  particular logical content, we arrive at the fundamental notions of  wenzelm@20451  46  \emph{theory context} and \emph{proof context} in Isabelle/Isar.  wenzelm@20451  47  These implement a certain policy to manage arbitrary \emph{context  wenzelm@20451  48  data}. There is a strongly-typed mechanism to declare new kinds of  wenzelm@20429  49  data at compile time.  wenzelm@18537  50 wenzelm@20451  51  The internal bootstrap process of Isabelle/Pure eventually reaches a  wenzelm@20451  52  stage where certain data slots provide the logical content of @{text  wenzelm@20451  53  "\"} and @{text "\"} sketched above, but this does not stop there!  wenzelm@20451  54  Various additional data slots support all kinds of mechanisms that  wenzelm@20451  55  are not necessarily part of the core logic.  wenzelm@18537  56 wenzelm@20429  57  For example, there would be data for canonical introduction and  wenzelm@20429  58  elimination rules for arbitrary operators (depending on the  wenzelm@20429  59  object-logic and application), which enables users to perform  wenzelm@20451  60  standard proof steps implicitly (cf.\ the @{text "rule"} method  wenzelm@20451  61  \cite{isabelle-isar-ref}).  wenzelm@18537  62 wenzelm@20451  63  \medskip Thus Isabelle/Isar is able to bring forth more and more  wenzelm@20451  64  concepts successively. In particular, an object-logic like  wenzelm@20451  65  Isabelle/HOL continues the Isabelle/Pure setup by adding specific  wenzelm@20451  66  components for automated reasoning (classical reasoner, tableau  wenzelm@20451  67  prover, structured induction etc.) and derived specification  wenzelm@20451  68  mechanisms (inductive predicates, recursive functions etc.). All of  wenzelm@20451  69  this is ultimately based on the generic data management by theory  wenzelm@20451  70  and proof contexts introduced here.  wenzelm@18537  71 *}  wenzelm@18537  72 wenzelm@18537  73 wenzelm@18537  74 subsection {* Theory context \label{sec:context-theory} *}  wenzelm@18537  75 wenzelm@34921  76 text {* A \emph{theory} is a data container with explicit name and  wenzelm@34921  77  unique identifier. Theories are related by a (nominal) sub-theory  wenzelm@20451  78  relation, which corresponds to the dependency graph of the original  wenzelm@20451  79  construction; each theory is derived from a certain sub-graph of  wenzelm@34921  80  ancestor theories. To this end, the system maintains a set of  wenzelm@34921  81  symbolic identification stamps'' within each theory.  wenzelm@18537  82 wenzelm@34921  83  In order to avoid the full-scale overhead of explicit sub-theory  wenzelm@34921  84  identification of arbitrary intermediate stages, a theory is  wenzelm@34921  85  switched into @{text "draft"} mode under certain circumstances. A  wenzelm@34921  86  draft theory acts like a linear type, where updates invalidate  wenzelm@34921  87  earlier versions. An invalidated draft is called \emph{stale}.  wenzelm@20429  88 wenzelm@34921  89  The @{text "checkpoint"} operation produces a safe stepping stone  wenzelm@34921  90  that will survive the next update without becoming stale: both the  wenzelm@34921  91  old and the new theory remain valid and are related by the  wenzelm@34921  92  sub-theory relation. Checkpointing essentially recovers purely  wenzelm@34921  93  functional theory values, at the expense of some extra internal  wenzelm@34921  94  bookkeeping.  wenzelm@20447  95 wenzelm@20447  96  The @{text "copy"} operation produces an auxiliary version that has  wenzelm@20447  97  the same data content, but is unrelated to the original: updates of  wenzelm@20447  98  the copy do not affect the original, neither does the sub-theory  wenzelm@20447  99  relation hold.  wenzelm@20429  100 wenzelm@34921  101  The @{text "merge"} operation produces the least upper bound of two  wenzelm@34921  102  theories, which actually degenerates into absorption of one theory  wenzelm@34921  103  into the other (according to the nominal sub-theory relation).  wenzelm@34921  104 wenzelm@34921  105  The @{text "begin"} operation starts a new theory by importing  wenzelm@34921  106  several parent theories and entering a special mode of nameless  wenzelm@34921  107  incremental updates, until the final @{text "end"} operation is  wenzelm@34921  108  performed.  wenzelm@34921  109 wenzelm@20447  110  \medskip The example in \figref{fig:ex-theory} below shows a theory  wenzelm@20451  111  graph derived from @{text "Pure"}, with theory @{text "Length"}  wenzelm@20451  112  importing @{text "Nat"} and @{text "List"}. The body of @{text  wenzelm@20451  113  "Length"} consists of a sequence of updates, working mostly on  wenzelm@34921  114  drafts internally, while transaction boundaries of Isar top-level  wenzelm@34921  115  commands (\secref{sec:isar-toplevel}) are guaranteed to be safe  wenzelm@34921  116  checkpoints.  wenzelm@20447  117 wenzelm@20447  118  \begin{figure}[htb]  wenzelm@20447  119  \begin{center}  wenzelm@20429  120  \begin{tabular}{rcccl}  wenzelm@20447  121  & & @{text "Pure"} \\  wenzelm@20447  122  & & @{text "\"} \\  wenzelm@20447  123  & & @{text "FOL"} \\  wenzelm@18537  124  & $\swarrow$ & & $\searrow$ & \\  wenzelm@21852  125  @{text "Nat"} & & & & @{text "List"} \\  wenzelm@18537  126  & $\searrow$ & & $\swarrow$ \\  wenzelm@20447  127  & & @{text "Length"} \\  wenzelm@26864  128  & & \multicolumn{3}{l}{~~@{keyword "imports"}} \\  wenzelm@26864  129  & & \multicolumn{3}{l}{~~@{keyword "begin"}} \\  wenzelm@18537  130  & & $\vdots$~~ \\  wenzelm@20447  131  & & @{text "\"}~~ \\  wenzelm@20447  132  & & $\vdots$~~ \\  wenzelm@20447  133  & & @{text "\"}~~ \\  wenzelm@20447  134  & & $\vdots$~~ \\  wenzelm@26864  135  & & \multicolumn{3}{l}{~~@{command "end"}} \\  wenzelm@20429  136  \end{tabular}  wenzelm@20451  137  \caption{A theory definition depending on ancestors}\label{fig:ex-theory}  wenzelm@20447  138  \end{center}  wenzelm@20447  139  \end{figure}  wenzelm@20451  140 wenzelm@20451  141  \medskip There is a separate notion of \emph{theory reference} for  wenzelm@20451  142  maintaining a live link to an evolving theory context: updates on  wenzelm@39821  143  drafts are propagated automatically. Dynamic updating stops when  wenzelm@39821  144  the next @{text "checkpoint"} is reached.  wenzelm@20451  145 wenzelm@20451  146  Derived entities may store a theory reference in order to indicate  wenzelm@39821  147  the formal context from which they are derived. This implicitly  wenzelm@39821  148  assumes monotonic reasoning, because the referenced context may  wenzelm@39821  149  become larger without further notice.  wenzelm@18537  150 *}  wenzelm@18537  151 wenzelm@20430  152 text %mlref {*  wenzelm@20447  153  \begin{mldecls}  wenzelm@20447  154  @{index_ML_type theory} \\  wenzelm@39837  155  @{index_ML Theory.eq_thy: "theory * theory -> bool"} \\  wenzelm@20447  156  @{index_ML Theory.subthy: "theory * theory -> bool"} \\  wenzelm@20447  157  @{index_ML Theory.checkpoint: "theory -> theory"} \\  wenzelm@20547  158  @{index_ML Theory.copy: "theory -> theory"} \\  wenzelm@34921  159  @{index_ML Theory.merge: "theory * theory -> theory"} \\  wenzelm@34921  160  @{index_ML Theory.begin_theory: "string -> theory list -> theory"} \\  wenzelm@39837  161  @{index_ML Theory.parents_of: "theory -> theory list"} \\  wenzelm@39837  162  @{index_ML Theory.ancestors_of: "theory -> theory list"} \\  wenzelm@20547  163  \end{mldecls}  wenzelm@20547  164  \begin{mldecls}  wenzelm@20447  165  @{index_ML_type theory_ref} \\  wenzelm@20447  166  @{index_ML Theory.deref: "theory_ref -> theory"} \\  wenzelm@24137  167  @{index_ML Theory.check_thy: "theory -> theory_ref"} \\  wenzelm@20447  168  \end{mldecls}  wenzelm@20447  169 wenzelm@20447  170  \begin{description}  wenzelm@20447  171 wenzelm@39864  172  \item Type @{ML_type theory} represents theory contexts. This is  wenzelm@39821  173  essentially a linear type, with explicit runtime checking.  wenzelm@39821  174  Primitive theory operations destroy the original version, which then  wenzelm@39821  175  becomes stale''. This can be prevented by explicit checkpointing,  wenzelm@39821  176  which the system does at least at the boundary of toplevel command  wenzelm@39821  177  transactions \secref{sec:isar-toplevel}.  wenzelm@20447  178 wenzelm@39837  179  \item @{ML "Theory.eq_thy"}~@{text "(thy\<^sub>1, thy\<^sub>2)"} check strict  wenzelm@39837  180  identity of two theories.  wenzelm@39837  181 wenzelm@34921  182  \item @{ML "Theory.subthy"}~@{text "(thy\<^sub>1, thy\<^sub>2)"} compares theories  wenzelm@34921  183  according to the intrinsic graph structure of the construction.  wenzelm@34921  184  This sub-theory relation is a nominal approximation of inclusion  wenzelm@34921  185  (@{text "\"}) of the corresponding content (according to the  wenzelm@34921  186  semantics of the ML modules that implement the data).  wenzelm@20447  187 wenzelm@20447  188  \item @{ML "Theory.checkpoint"}~@{text "thy"} produces a safe  wenzelm@34921  189  stepping stone in the linear development of @{text "thy"}. This  wenzelm@34921  190  changes the old theory, but the next update will result in two  wenzelm@34921  191  related, valid theories.  wenzelm@20447  192 wenzelm@20447  193  \item @{ML "Theory.copy"}~@{text "thy"} produces a variant of @{text  wenzelm@34921  194  "thy"} with the same data. The copy is not related to the original,  wenzelm@34921  195  but the original is unchanged.  wenzelm@34921  196 wenzelm@34921  197  \item @{ML "Theory.merge"}~@{text "(thy\<^sub>1, thy\<^sub>2)"} absorbs one theory  wenzelm@34921  198  into the other, without changing @{text "thy\<^sub>1"} or @{text "thy\<^sub>2"}.  wenzelm@34921  199  This version of ad-hoc theory merge fails for unrelated theories!  wenzelm@34921  200 wenzelm@34921  201  \item @{ML "Theory.begin_theory"}~@{text "name parents"} constructs  wenzelm@39825  202  a new theory based on the given parents. This ML function is  wenzelm@34921  203  normally not invoked directly.  wenzelm@20447  204 wenzelm@39837  205  \item @{ML "Theory.parents_of"}~@{text "thy"} returns the direct  wenzelm@39837  206  ancestors of @{text thy}.  wenzelm@39837  207 wenzelm@39837  208  \item @{ML "Theory.ancestors_of"}~@{text "thy"} returns all  wenzelm@39837  209  ancestors of @{text thy} (not including @{text thy} itself).  wenzelm@39837  210 wenzelm@39864  211  \item Type @{ML_type theory_ref} represents a sliding reference to  wenzelm@39864  212  an always valid theory; updates on the original are propagated  wenzelm@20447  213  automatically.  wenzelm@20447  214 wenzelm@24137  215  \item @{ML "Theory.deref"}~@{text "thy_ref"} turns a @{ML_type  wenzelm@24137  216  "theory_ref"} into an @{ML_type "theory"} value. As the referenced  wenzelm@24137  217  theory evolves monotonically over time, later invocations of @{ML  wenzelm@20451  218  "Theory.deref"} may refer to a larger context.  wenzelm@20447  219 wenzelm@24137  220  \item @{ML "Theory.check_thy"}~@{text "thy"} produces a @{ML_type  wenzelm@24137  221  "theory_ref"} from a valid @{ML_type "theory"} value.  wenzelm@24137  222 wenzelm@20447  223  \end{description}  wenzelm@20430  224 *}  wenzelm@20430  225 wenzelm@39832  226 text %mlantiq {*  wenzelm@39832  227  \begin{matharray}{rcl}  wenzelm@39832  228  @{ML_antiquotation_def "theory"} & : & @{text ML_antiquotation} \\  wenzelm@39832  229  @{ML_antiquotation_def "theory_ref"} & : & @{text ML_antiquotation} \\  wenzelm@39832  230  \end{matharray}  wenzelm@39832  231 wenzelm@39832  232  \begin{rail}  wenzelm@39832  233  ('theory' | 'theory\_ref') nameref?  wenzelm@39832  234  ;  wenzelm@39832  235  \end{rail}  wenzelm@39832  236 wenzelm@39832  237  \begin{description}  wenzelm@39832  238 wenzelm@39832  239  \item @{text "@{theory}"} refers to the background theory of the  wenzelm@39832  240  current context --- as abstract value.  wenzelm@39832  241 wenzelm@39832  242  \item @{text "@{theory A}"} refers to an explicitly named ancestor  wenzelm@39832  243  theory @{text "A"} of the background theory of the current context  wenzelm@39832  244  --- as abstract value.  wenzelm@39832  245 wenzelm@39832  246  \item @{text "@{theory_ref}"} is similar to @{text "@{theory}"}, but  wenzelm@39832  247  produces a @{ML_type theory_ref} via @{ML "Theory.check_thy"} as  wenzelm@39832  248  explained above.  wenzelm@39832  249 wenzelm@39832  250  \end{description}  wenzelm@39832  251 *}  wenzelm@39832  252 wenzelm@18537  253 wenzelm@18537  254 subsection {* Proof context \label{sec:context-proof} *}  wenzelm@18537  255 wenzelm@34921  256 text {* A proof context is a container for pure data with a  wenzelm@39821  257  back-reference to the theory from which it is derived. The @{text  wenzelm@39821  258  "init"} operation creates a proof context from a given theory.  wenzelm@34921  259  Modifications to draft theories are propagated to the proof context  wenzelm@34921  260  as usual, but there is also an explicit @{text "transfer"} operation  wenzelm@34921  261  to force resynchronization with more substantial updates to the  wenzelm@34921  262  underlying theory.  wenzelm@20429  263 wenzelm@34921  264  Entities derived in a proof context need to record logical  wenzelm@20447  265  requirements explicitly, since there is no separate context  wenzelm@34921  266  identification or symbolic inclusion as for theories. For example,  wenzelm@34921  267  hypotheses used in primitive derivations (cf.\ \secref{sec:thms})  wenzelm@34921  268  are recorded separately within the sequent @{text "\ \ \"}, just to  wenzelm@34921  269  make double sure. Results could still leak into an alien proof  wenzelm@34921  270  context due to programming errors, but Isabelle/Isar includes some  wenzelm@34921  271  extra validity checks in critical positions, notably at the end of a  wenzelm@34921  272  sub-proof.  wenzelm@20429  273 wenzelm@20451  274  Proof contexts may be manipulated arbitrarily, although the common  wenzelm@20451  275  discipline is to follow block structure as a mental model: a given  wenzelm@20451  276  context is extended consecutively, and results are exported back  wenzelm@34921  277  into the original context. Note that an Isar proof state models  wenzelm@20451  278  block-structured reasoning explicitly, using a stack of proof  wenzelm@34921  279  contexts internally. For various technical reasons, the background  wenzelm@34921  280  theory of an Isar proof state must not be changed while the proof is  wenzelm@34921  281  still under construction!  wenzelm@18537  282 *}  wenzelm@18537  283 wenzelm@20449  284 text %mlref {*  wenzelm@20449  285  \begin{mldecls}  wenzelm@20449  286  @{index_ML_type Proof.context} \\  wenzelm@36611  287  @{index_ML ProofContext.init_global: "theory -> Proof.context"} \\  wenzelm@20449  288  @{index_ML ProofContext.theory_of: "Proof.context -> theory"} \\  wenzelm@20449  289  @{index_ML ProofContext.transfer: "theory -> Proof.context -> Proof.context"} \\  wenzelm@20449  290  \end{mldecls}  wenzelm@20449  291 wenzelm@20449  292  \begin{description}  wenzelm@20449  293 wenzelm@39864  294  \item Type @{ML_type Proof.context} represents proof contexts.  wenzelm@39864  295  Elements of this type are essentially pure values, with a sliding  wenzelm@39864  296  reference to the background theory.  wenzelm@20449  297 wenzelm@36611  298  \item @{ML ProofContext.init_global}~@{text "thy"} produces a proof context  wenzelm@20449  299  derived from @{text "thy"}, initializing all data.  wenzelm@20449  300 wenzelm@20449  301  \item @{ML ProofContext.theory_of}~@{text "ctxt"} selects the  wenzelm@20451  302  background theory from @{text "ctxt"}, dereferencing its internal  wenzelm@20451  303  @{ML_type theory_ref}.  wenzelm@20449  304 wenzelm@20449  305  \item @{ML ProofContext.transfer}~@{text "thy ctxt"} promotes the  wenzelm@20449  306  background theory of @{text "ctxt"} to the super theory @{text  wenzelm@20449  307  "thy"}.  wenzelm@20449  308 wenzelm@20449  309  \end{description}  wenzelm@20449  310 *}  wenzelm@20449  311 wenzelm@39832  312 text %mlantiq {*  wenzelm@39832  313  \begin{matharray}{rcl}  wenzelm@39832  314  @{ML_antiquotation_def "context"} & : & @{text ML_antiquotation} \\  wenzelm@39832  315  \end{matharray}  wenzelm@39832  316 wenzelm@39832  317  \begin{description}  wenzelm@39832  318 wenzelm@39832  319  \item @{text "@{context}"} refers to \emph{the} context at  wenzelm@39832  320  compile-time --- as abstract value. Independently of (local) theory  wenzelm@39832  321  or proof mode, this always produces a meaningful result.  wenzelm@39832  322 wenzelm@39832  323  This is probably the most common antiquotation in interactive  wenzelm@39832  324  experimentation with ML inside Isar.  wenzelm@39832  325 wenzelm@39832  326  \end{description}  wenzelm@39832  327 *}  wenzelm@39832  328 wenzelm@20430  329 wenzelm@20451  330 subsection {* Generic contexts \label{sec:generic-context} *}  wenzelm@20429  331 wenzelm@20449  332 text {*  wenzelm@20449  333  A generic context is the disjoint sum of either a theory or proof  wenzelm@20451  334  context. Occasionally, this enables uniform treatment of generic  wenzelm@20450  335  context data, typically extra-logical information. Operations on  wenzelm@20449  336  generic contexts include the usual injections, partial selections,  wenzelm@20449  337  and combinators for lifting operations on either component of the  wenzelm@20449  338  disjoint sum.  wenzelm@20449  339 wenzelm@20449  340  Moreover, there are total operations @{text "theory_of"} and @{text  wenzelm@20449  341  "proof_of"} to convert a generic context into either kind: a theory  wenzelm@20451  342  can always be selected from the sum, while a proof context might  wenzelm@34921  343  have to be constructed by an ad-hoc @{text "init"} operation, which  wenzelm@34921  344  incurs a small runtime overhead.  wenzelm@20449  345 *}  wenzelm@20430  346 wenzelm@20449  347 text %mlref {*  wenzelm@20449  348  \begin{mldecls}  wenzelm@20449  349  @{index_ML_type Context.generic} \\  wenzelm@20449  350  @{index_ML Context.theory_of: "Context.generic -> theory"} \\  wenzelm@20449  351  @{index_ML Context.proof_of: "Context.generic -> Proof.context"} \\  wenzelm@20449  352  \end{mldecls}  wenzelm@20449  353 wenzelm@20449  354  \begin{description}  wenzelm@20430  355 wenzelm@39864  356  \item Type @{ML_type Context.generic} is the direct sum of @{ML_type  wenzelm@20451  357  "theory"} and @{ML_type "Proof.context"}, with the datatype  wenzelm@20451  358  constructors @{ML "Context.Theory"} and @{ML "Context.Proof"}.  wenzelm@20449  359 wenzelm@20449  360  \item @{ML Context.theory_of}~@{text "context"} always produces a  wenzelm@20449  361  theory from the generic @{text "context"}, using @{ML  wenzelm@20449  362  "ProofContext.theory_of"} as required.  wenzelm@20449  363 wenzelm@20449  364  \item @{ML Context.proof_of}~@{text "context"} always produces a  wenzelm@20449  365  proof context from the generic @{text "context"}, using @{ML  wenzelm@36611  366  "ProofContext.init_global"} as required (note that this re-initializes the  wenzelm@20451  367  context data with each invocation).  wenzelm@20449  368 wenzelm@20449  369  \end{description}  wenzelm@20449  370 *}  wenzelm@20437  371 wenzelm@20476  372 wenzelm@20476  373 subsection {* Context data \label{sec:context-data} *}  wenzelm@20447  374 wenzelm@33524  375 text {* The main purpose of theory and proof contexts is to manage  wenzelm@33524  376  arbitrary (pure) data. New data types can be declared incrementally  wenzelm@33524  377  at compile time. There are separate declaration mechanisms for any  wenzelm@33524  378  of the three kinds of contexts: theory, proof, generic.  wenzelm@20449  379 wenzelm@33524  380  \paragraph{Theory data} declarations need to implement the following  wenzelm@33524  381  SML signature:  wenzelm@20449  382 wenzelm@20449  383  \medskip  wenzelm@20449  384  \begin{tabular}{ll}  wenzelm@22869  385  @{text "\ T"} & representing type \\  wenzelm@22869  386  @{text "\ empty: T"} & empty default value \\  wenzelm@22869  387  @{text "\ extend: T \ T"} & re-initialize on import \\  wenzelm@22869  388  @{text "\ merge: T \ T \ T"} & join on import \\  wenzelm@20449  389  \end{tabular}  wenzelm@20449  390  \medskip  wenzelm@20449  391 wenzelm@39861  392  The @{text "empty"} value acts as initial default for \emph{any}  wenzelm@39861  393  theory that does not declare actual data content; @{text "extend"}  wenzelm@39861  394  is acts like a unitary version of @{text "merge"}.  wenzelm@20449  395 wenzelm@34921  396  Implementing @{text "merge"} can be tricky. The general idea is  wenzelm@34921  397  that @{text "merge (data\<^sub>1, data\<^sub>2)"} inserts those parts of @{text  wenzelm@34921  398  "data\<^sub>2"} into @{text "data\<^sub>1"} that are not yet present, while  wenzelm@34921  399  keeping the general order of things. The @{ML Library.merge}  wenzelm@34921  400  function on plain lists may serve as canonical template.  wenzelm@34921  401 wenzelm@34921  402  Particularly note that shared parts of the data must not be  wenzelm@34921  403  duplicated by naive concatenation, or a theory graph that is like a  wenzelm@34921  404  chain of diamonds would cause an exponential blowup!  wenzelm@34921  405 wenzelm@33524  406  \paragraph{Proof context data} declarations need to implement the  wenzelm@33524  407  following SML signature:  wenzelm@20449  408 wenzelm@20449  409  \medskip  wenzelm@20449  410  \begin{tabular}{ll}  wenzelm@22869  411  @{text "\ T"} & representing type \\  wenzelm@22869  412  @{text "\ init: theory \ T"} & produce initial value \\  wenzelm@20449  413  \end{tabular}  wenzelm@20449  414  \medskip  wenzelm@20449  415 wenzelm@39861  416  The @{text "init"} operation is supposed to produce a pure value  wenzelm@39861  417  from the given background theory and should be somehow  wenzelm@34921  418  immediate''. Whenever a proof context is initialized, which  wenzelm@34921  419  happens frequently, the the system invokes the @{text "init"}  wenzelm@39821  420  operation of \emph{all} theory data slots ever declared. This also  wenzelm@39821  421  means that one needs to be economic about the total number of proof  wenzelm@39821  422  data declarations in the system, i.e.\ each ML module should declare  wenzelm@39821  423  at most one, sometimes two data slots for its internal use.  wenzelm@39821  424  Repeated data declarations to simulate a record type should be  wenzelm@39821  425  avoided!  wenzelm@20449  426 wenzelm@20451  427  \paragraph{Generic data} provides a hybrid interface for both theory  wenzelm@33524  428  and proof data. The @{text "init"} operation for proof contexts is  wenzelm@33524  429  predefined to select the current data value from the background  wenzelm@33524  430  theory.  wenzelm@20449  431 wenzelm@39821  432  \bigskip Any of the above data declarations over type @{text "T"}  wenzelm@39821  433  result in an ML structure with the following signature:  wenzelm@20449  434 wenzelm@20449  435  \medskip  wenzelm@20449  436  \begin{tabular}{ll}  wenzelm@20449  437  @{text "get: context \ T"} \\  wenzelm@20449  438  @{text "put: T \ context \ context"} \\  wenzelm@20449  439  @{text "map: (T \ T) \ context \ context"} \\  wenzelm@20449  440  \end{tabular}  wenzelm@20449  441  \medskip  wenzelm@20449  442 wenzelm@39861  443  These other operations provide exclusive access for the particular  wenzelm@39861  444  kind of context (theory, proof, or generic context). This interface  wenzelm@39861  445  observes the ML discipline for types and scopes: there is no other  wenzelm@39861  446  way to access the corresponding data slot of a context. By keeping  wenzelm@39861  447  these operations private, an Isabelle/ML module may maintain  wenzelm@39861  448  abstract values authentically. *}  wenzelm@20447  449 wenzelm@20450  450 text %mlref {*  wenzelm@20450  451  \begin{mldecls}  wenzelm@33524  452  @{index_ML_functor Theory_Data} \\  wenzelm@33524  453  @{index_ML_functor Proof_Data} \\  wenzelm@33524  454  @{index_ML_functor Generic_Data} \\  wenzelm@20450  455  \end{mldecls}  wenzelm@20450  456 wenzelm@20450  457  \begin{description}  wenzelm@20450  458 wenzelm@33524  459  \item @{ML_functor Theory_Data}@{text "(spec)"} declares data for  wenzelm@20450  460  type @{ML_type theory} according to the specification provided as  wenzelm@20451  461  argument structure. The resulting structure provides data init and  wenzelm@20451  462  access operations as described above.  wenzelm@20450  463 wenzelm@33524  464  \item @{ML_functor Proof_Data}@{text "(spec)"} is analogous to  wenzelm@33524  465  @{ML_functor Theory_Data} for type @{ML_type Proof.context}.  wenzelm@20450  466 wenzelm@33524  467  \item @{ML_functor Generic_Data}@{text "(spec)"} is analogous to  wenzelm@33524  468  @{ML_functor Theory_Data} for type @{ML_type Context.generic}.  wenzelm@20450  469 wenzelm@20450  470  \end{description}  wenzelm@20450  471 *}  wenzelm@20450  472 wenzelm@34928  473 text %mlex {*  wenzelm@34928  474  The following artificial example demonstrates theory  wenzelm@34928  475  data: we maintain a set of terms that are supposed to be wellformed  wenzelm@34928  476  wrt.\ the enclosing theory. The public interface is as follows:  wenzelm@34928  477 *}  wenzelm@34928  478 wenzelm@34928  479 ML {*  wenzelm@34928  480  signature WELLFORMED_TERMS =  wenzelm@34928  481  sig  wenzelm@34928  482  val get: theory -> term list  wenzelm@34928  483  val add: term -> theory -> theory  wenzelm@34928  484  end;  wenzelm@34928  485 *}  wenzelm@34928  486 wenzelm@39861  487 text {* The implementation uses private theory data internally, and  wenzelm@39861  488  only exposes an operation that involves explicit argument checking  wenzelm@39861  489  wrt.\ the given theory. *}  wenzelm@34928  490 wenzelm@34928  491 ML {*  wenzelm@34928  492  structure Wellformed_Terms: WELLFORMED_TERMS =  wenzelm@34928  493  struct  wenzelm@34928  494 wenzelm@34928  495  structure Terms = Theory_Data  wenzelm@34928  496  (  wenzelm@39687  497  type T = term Ord_List.T;  wenzelm@34928  498  val empty = [];  wenzelm@34928  499  val extend = I;  wenzelm@34928  500  fun merge (ts1, ts2) =  wenzelm@39687  501  Ord_List.union Term_Ord.fast_term_ord ts1 ts2;  wenzelm@39861  502  );  wenzelm@34928  503 wenzelm@34928  504  val get = Terms.get;  wenzelm@34928  505 wenzelm@34928  506  fun add raw_t thy =  wenzelm@39821  507  let  wenzelm@39821  508  val t = Sign.cert_term thy raw_t;  wenzelm@39821  509  in  wenzelm@39821  510  Terms.map (Ord_List.insert Term_Ord.fast_term_ord t) thy  wenzelm@39821  511  end;  wenzelm@34928  512 wenzelm@34928  513  end;  wenzelm@34928  514 *}  wenzelm@34928  515 wenzelm@39864  516 text {* Type @{ML_type "term Ord_List.T"} is used for reasonably  wenzelm@39864  517  efficient representation of a set of terms: all operations are  wenzelm@39864  518  linear in the number of stored elements. Here we assume that users  wenzelm@39864  519  of this module do not care about the declaration order, since that  wenzelm@39864  520  data structure forces its own arrangement of elements.  wenzelm@34928  521 wenzelm@34928  522  Observe how the @{verbatim merge} operation joins the data slots of  wenzelm@39687  523  the two constituents: @{ML Ord_List.union} prevents duplication of  wenzelm@34928  524  common data from different branches, thus avoiding the danger of  wenzelm@39821  525  exponential blowup. Plain list append etc.\ must never be used for  wenzelm@39821  526  theory data merges!  wenzelm@34928  527 wenzelm@34928  528  \medskip Our intended invariant is achieved as follows:  wenzelm@34928  529  \begin{enumerate}  wenzelm@34928  530 wenzelm@34928  531  \item @{ML Wellformed_Terms.add} only admits terms that have passed  wenzelm@34928  532  the @{ML Sign.cert_term} check of the given theory at that point.  wenzelm@34928  533 wenzelm@34928  534  \item Wellformedness in the sense of @{ML Sign.cert_term} is  wenzelm@34928  535  monotonic wrt.\ the sub-theory relation. So our data can move  wenzelm@34928  536  upwards in the hierarchy (via extension or merges), and maintain  wenzelm@34928  537  wellformedness without further checks.  wenzelm@34928  538 wenzelm@34928  539  \end{enumerate}  wenzelm@34928  540 wenzelm@34928  541  Note that all basic operations of the inference kernel (which  wenzelm@34928  542  includes @{ML Sign.cert_term}) observe this monotonicity principle,  wenzelm@34928  543  but other user-space tools don't. For example, fully-featured  wenzelm@34928  544  type-inference via @{ML Syntax.check_term} (cf.\  wenzelm@34928  545  \secref{sec:term-check}) is not necessarily monotonic wrt.\ the  wenzelm@34928  546  background theory, since constraints of term constants can be  wenzelm@39821  547  modified by later declarations, for example.  wenzelm@34928  548 wenzelm@34928  549  In most cases, user-space context data does not have to take such  wenzelm@34928  550  invariants too seriously. The situation is different in the  wenzelm@34928  551  implementation of the inference kernel itself, which uses the very  wenzelm@34928  552  same data mechanisms for types, constants, axioms etc.  wenzelm@34928  553 *}  wenzelm@34928  554 wenzelm@20447  555 wenzelm@39865  556 subsection {* Configuration options \label{sec:config-options} *}  wenzelm@39865  557 wenzelm@39865  558 text {* A \emph{configuration option} is a named optional value of  wenzelm@39865  559  some basic type (Boolean, integer, string) that is stored in the  wenzelm@39865  560  context. It is a simple application of general context data  wenzelm@39865  561  (\secref{sec:context-data}) that is sufficiently common to justify  wenzelm@39865  562  customized setup, which includes some concrete declarations for  wenzelm@39865  563  end-users using existing notation for attributes (cf.\  wenzelm@39865  564  \secref{sec:attributes}).  wenzelm@39865  565 wenzelm@39865  566  For example, the predefined configuration option @{attribute  wenzelm@39865  567  show_types} controls output of explicit type constraints for  wenzelm@39876  568  variables in printed terms (cf.\ \secref{sec:read-print}). Its  wenzelm@39865  569  value can be modified within Isar text like this:  wenzelm@39865  570 *}  wenzelm@39865  571 wenzelm@39865  572 declare [[show_types = false]]  wenzelm@39865  573  -- {* declaration within (local) theory context *}  wenzelm@39865  574 wenzelm@39865  575 example_proof  wenzelm@39865  576  note [[show_types = true]]  wenzelm@39865  577  -- {* declaration within proof (forward mode) *}  wenzelm@39865  578  term x  wenzelm@39865  579 wenzelm@39865  580  have "x = x"  wenzelm@39865  581  using [[show_types = false]]  wenzelm@39865  582  -- {* declaration within proof (backward mode) *}  wenzelm@39865  583  ..  wenzelm@39865  584 qed  wenzelm@39865  585 wenzelm@39865  586 text {* Configuration options that are not set explicitly hold a  wenzelm@39865  587  default value that can depend on the application context. This  wenzelm@39865  588  allows to retrieve the value from another slot within the context,  wenzelm@39865  589  or fall back on a global preference mechanism, for example.  wenzelm@39865  590 wenzelm@39865  591  The operations to declare configuration options and get/map their  wenzelm@39865  592  values are modeled as direct replacements for historic global  wenzelm@39865  593  references, only that the context is made explicit. This allows  wenzelm@39865  594  easy configuration of tools, without relying on the execution order  wenzelm@39865  595  as required for old-style mutable references. *}  wenzelm@39865  596 wenzelm@39865  597 text %mlref {*  wenzelm@39865  598  \begin{mldecls}  wenzelm@39865  599  @{index_ML Config.get: "Proof.context -> 'a Config.T -> 'a"} \\  wenzelm@39865  600  @{index_ML Config.map: "'a Config.T -> ('a -> 'a) -> Proof.context -> Proof.context"} \\  wenzelm@39865  601  @{index_ML Attrib.config_bool: "string -> (Context.generic -> bool) ->  wenzelm@39865  602  bool Config.T * (theory -> theory)"} \\  wenzelm@39865  603  @{index_ML Attrib.config_int: "string -> (Context.generic -> int) ->  wenzelm@39865  604  int Config.T * (theory -> theory)"} \\  wenzelm@39865  605  @{index_ML Attrib.config_string: "string -> (Context.generic -> string) ->  wenzelm@39865  606  string Config.T * (theory -> theory)"} \\  wenzelm@39865  607  \end{mldecls}  wenzelm@39865  608 wenzelm@39865  609  \begin{description}  wenzelm@39865  610 wenzelm@39865  611  \item @{ML Config.get}~@{text "ctxt config"} gets the value of  wenzelm@39865  612  @{text "config"} in the given context.  wenzelm@39865  613 wenzelm@39865  614  \item @{ML Config.map}~@{text "config f ctxt"} updates the context  wenzelm@39865  615  by updating the value of @{text "config"}.  wenzelm@39865  616 wenzelm@39865  617  \item @{text "(config, setup) ="}~@{ML Attrib.config_bool}~@{text  wenzelm@39865  618  "name default"} creates a named configuration option of type  wenzelm@39865  619  @{ML_type bool}, with the given @{text "default"} depending on the  wenzelm@39865  620  application context. The resulting @{text "config"} can be used to  wenzelm@39865  621  get/map its value in a given context. The @{text "setup"} function  wenzelm@39865  622  needs to be applied to the theory initially, in order to make  wenzelm@39865  623  concrete declaration syntax available to the user.  wenzelm@39865  624 wenzelm@39865  625  \item @{ML Attrib.config_int} and @{ML Attrib.config_string} work  wenzelm@39865  626  like @{ML Attrib.config_bool}, but for types @{ML_type int} and  wenzelm@39865  627  @{ML_type string}, respectively.  wenzelm@39865  628 wenzelm@39865  629  \end{description}  wenzelm@39865  630 *}  wenzelm@39865  631 wenzelm@39865  632 text %mlex {* The following example shows how to declare and use a  wenzelm@39865  633  Boolean configuration option called @{text "my_flag"} with constant  wenzelm@39865  634  default value @{ML false}. *}  wenzelm@39865  635 wenzelm@39865  636 ML {*  wenzelm@39865  637  val (my_flag, my_flag_setup) =  wenzelm@39865  638  Attrib.config_bool "my_flag" (K false)  wenzelm@39865  639 *}  wenzelm@39865  640 setup my_flag_setup  wenzelm@39865  641 wenzelm@39865  642 text {* Now the user can refer to @{attribute my_flag} in  wenzelm@39865  643  declarations, while we can retrieve the current value from the  wenzelm@39865  644  context via @{ML Config.get}. *}  wenzelm@39865  645 wenzelm@39866  646 ML_val {* @{assert} (Config.get @{context} my_flag = false) *}  wenzelm@39865  647 wenzelm@39865  648 declare [[my_flag = true]]  wenzelm@39865  649 wenzelm@39866  650 ML_val {* @{assert} (Config.get @{context} my_flag = true) *}  wenzelm@39865  651 wenzelm@39865  652 example_proof  wenzelm@39866  653  {  wenzelm@39866  654  note [[my_flag = false]]  wenzelm@39866  655  ML_val {* @{assert} (Config.get @{context} my_flag = false) *}  wenzelm@39866  656  }  wenzelm@39866  657  ML_val {* @{assert} (Config.get @{context} my_flag = true) *}  wenzelm@39865  658 qed  wenzelm@39865  659 wenzelm@39865  660 wenzelm@26872  661 section {* Names \label{sec:names} *}  wenzelm@20451  662 wenzelm@34925  663 text {* In principle, a name is just a string, but there are various  wenzelm@34925  664  conventions for representing additional structure. For example,  wenzelm@34927  665  @{text "Foo.bar.baz"}'' is considered as a long name consisting of  wenzelm@34927  666  qualifier @{text "Foo.bar"} and base name @{text "baz"}. The  wenzelm@34927  667  individual constituents of a name may have further substructure,  wenzelm@34927  668  e.g.\ the string \verb,\,\verb,,'' encodes as a single  wenzelm@34927  669  symbol.  wenzelm@34927  670 wenzelm@34927  671  \medskip Subsequently, we shall introduce specific categories of  wenzelm@34927  672  names. Roughly speaking these correspond to logical entities as  wenzelm@34927  673  follows:  wenzelm@34927  674  \begin{itemize}  wenzelm@34927  675 wenzelm@34927  676  \item Basic names (\secref{sec:basic-name}): free and bound  wenzelm@34927  677  variables.  wenzelm@34927  678 wenzelm@34927  679  \item Indexed names (\secref{sec:indexname}): schematic variables.  wenzelm@34927  680 wenzelm@34927  681  \item Long names (\secref{sec:long-name}): constants of any kind  wenzelm@34927  682  (type constructors, term constants, other concepts defined in user  wenzelm@34927  683  space). Such entities are typically managed via name spaces  wenzelm@34927  684  (\secref{sec:name-space}).  wenzelm@34927  685 wenzelm@34927  686  \end{itemize}  wenzelm@20451  687 *}  wenzelm@20437  688 wenzelm@20437  689 wenzelm@39863  690 subsection {* Strings of symbols \label{sec:symbols} *}  wenzelm@20437  691 wenzelm@34925  692 text {* A \emph{symbol} constitutes the smallest textual unit in  wenzelm@34925  693  Isabelle --- raw ML characters are normally not encountered at all!  wenzelm@34925  694  Isabelle strings consist of a sequence of symbols, represented as a  wenzelm@34925  695  packed string or an exploded list of strings. Each symbol is in  wenzelm@34925  696  itself a small string, which has either one of the following forms:  wenzelm@20437  697 wenzelm@20451  698  \begin{enumerate}  wenzelm@20437  699 wenzelm@37533  700  \item a single ASCII character @{text "c"}'', for example  wenzelm@37533  701  \verb,a,'',  wenzelm@37533  702 wenzelm@37533  703  \item a codepoint according to UTF8 (non-ASCII byte sequence),  wenzelm@20437  704 wenzelm@20488  705  \item a regular symbol \verb,\,\verb,<,@{text "ident"}\verb,>,'',  wenzelm@20476  706  for example \verb,\,\verb,,'',  wenzelm@20437  707 wenzelm@20488  708  \item a control symbol \verb,\,\verb,<^,@{text "ident"}\verb,>,'',  wenzelm@20476  709  for example \verb,\,\verb,<^bold>,'',  wenzelm@20437  710 wenzelm@20488  711  \item a raw symbol \verb,\,\verb,<^raw:,@{text text}\verb,>,''  wenzelm@34925  712  where @{text text} consists of printable characters excluding  wenzelm@20476  713  \verb,.,'' and \verb,>,'', for example  wenzelm@20476  714  \verb,\,\verb,<^raw:$\sum_{i = 1}^n$>,'',  wenzelm@20437  715 wenzelm@20488  716  \item a numbered raw control symbol \verb,\,\verb,<^raw,@{text  wenzelm@20476  717  n}\verb,>, where @{text n} consists of digits, for example  wenzelm@20451  718  \verb,\,\verb,<^raw42>,''.  wenzelm@20437  719 wenzelm@20451  720  \end{enumerate}  wenzelm@20437  721 wenzelm@39861  722  The @{text "ident"} syntax for symbol names is @{text "letter  wenzelm@39861  723  (letter | digit)\<^sup>*"}, where @{text "letter = A..Za..z"} and @{text  wenzelm@39861  724  "digit = 0..9"}. There are infinitely many regular symbols and  wenzelm@39861  725  control symbols, but a fixed collection of standard symbols is  wenzelm@39861  726  treated specifically. For example, \verb,\,\verb,,'' is  wenzelm@39861  727  classified as a letter, which means it may occur within regular  wenzelm@39861  728  Isabelle identifiers.  wenzelm@20437  729 wenzelm@37533  730  The character set underlying Isabelle symbols is 7-bit ASCII, but  wenzelm@37533  731  8-bit character sequences are passed-through unchanged. Unicode/UCS  wenzelm@37533  732  data in UTF-8 encoding is processed in a non-strict fashion, such  wenzelm@37533  733  that well-formed code sequences are recognized  wenzelm@37533  734  accordingly.\footnote{Note that ISO-Latin-1 differs from UTF-8 only  wenzelm@37533  735  in some special punctuation characters that even have replacements  wenzelm@37533  736  within the standard collection of Isabelle symbols. Text consisting  wenzelm@37533  737  of ASCII plus accented letters can be processed in either encoding.}  wenzelm@37533  738  Unicode provides its own collection of mathematical symbols, but  wenzelm@37533  739  within the core Isabelle/ML world there is no link to the standard  wenzelm@37533  740  collection of Isabelle regular symbols.  wenzelm@20476  741 wenzelm@20476  742  \medskip Output of Isabelle symbols depends on the print mode  wenzelm@29758  743  (\secref{print-mode}). For example, the standard {\LaTeX} setup of  wenzelm@29758  744  the Isabelle document preparation system would present  wenzelm@20451  745  \verb,\,\verb,,'' as @{text "\"}, and  wenzelm@20451  746  \verb,\,\verb,<^bold>,\verb,\,\verb,,'' as @{text  wenzelm@34925  747  "\<^bold>\"}. On-screen rendering usually works by mapping a finite  wenzelm@34925  748  subset of Isabelle symbols to suitable Unicode characters.  wenzelm@20451  749 *}  wenzelm@20437  750 wenzelm@20437  751 text %mlref {*  wenzelm@20437  752  \begin{mldecls}  wenzelm@34921  753  @{index_ML_type "Symbol.symbol": string} \\  wenzelm@20437  754  @{index_ML Symbol.explode: "string -> Symbol.symbol list"} \\  wenzelm@20437  755  @{index_ML Symbol.is_letter: "Symbol.symbol -> bool"} \\  wenzelm@20437  756  @{index_ML Symbol.is_digit: "Symbol.symbol -> bool"} \\  wenzelm@20437  757  @{index_ML Symbol.is_quasi: "Symbol.symbol -> bool"} \\  wenzelm@20547  758  @{index_ML Symbol.is_blank: "Symbol.symbol -> bool"} \\  wenzelm@20547  759  \end{mldecls}  wenzelm@20547  760  \begin{mldecls}  wenzelm@20437  761  @{index_ML_type "Symbol.sym"} \\  wenzelm@20437  762  @{index_ML Symbol.decode: "Symbol.symbol -> Symbol.sym"} \\  wenzelm@20437  763  \end{mldecls}  wenzelm@20437  764 wenzelm@20437  765  \begin{description}  wenzelm@20437  766 wenzelm@39864  767  \item Type @{ML_type "Symbol.symbol"} represents individual Isabelle  wenzelm@34921  768  symbols.  wenzelm@20437  769 wenzelm@20476  770  \item @{ML "Symbol.explode"}~@{text "str"} produces a symbol list  wenzelm@39821  771  from the packed form. This function supersedes @{ML  wenzelm@20476  772  "String.explode"} for virtually all purposes of manipulating text in  wenzelm@34925  773  Isabelle!\footnote{The runtime overhead for exploded strings is  wenzelm@34925  774  mainly that of the list structure: individual symbols that happen to  wenzelm@39821  775  be a singleton string do not require extra memory in Poly/ML.}  wenzelm@20437  776 wenzelm@20437  777  \item @{ML "Symbol.is_letter"}, @{ML "Symbol.is_digit"}, @{ML  wenzelm@20476  778  "Symbol.is_quasi"}, @{ML "Symbol.is_blank"} classify standard  wenzelm@20476  779  symbols according to fixed syntactic conventions of Isabelle, cf.\  wenzelm@20476  780  \cite{isabelle-isar-ref}.  wenzelm@20437  781 wenzelm@39864  782  \item Type @{ML_type "Symbol.sym"} is a concrete datatype that  wenzelm@39864  783  represents the different kinds of symbols explicitly, with  wenzelm@39864  784  constructors @{ML "Symbol.Char"}, @{ML "Symbol.Sym"}, @{ML  wenzelm@39864  785  "Symbol.UTF8"}, @{ML "Symbol.Ctrl"}, @{ML "Symbol.Raw"}.  wenzelm@20437  786 wenzelm@20437  787  \item @{ML "Symbol.decode"} converts the string representation of a  wenzelm@20451  788  symbol into the datatype version.  wenzelm@20437  789 wenzelm@20437  790  \end{description}  wenzelm@34925  791 wenzelm@34925  792  \paragraph{Historical note.} In the original SML90 standard the  wenzelm@34925  793  primitive ML type @{ML_type char} did not exists, and the basic @{ML  wenzelm@34925  794  "explode: string -> string list"} operation would produce a list of  wenzelm@34925  795  singleton strings as in Isabelle/ML today. When SML97 came out,  wenzelm@34927  796  Isabelle did not adopt its slightly anachronistic 8-bit characters,  wenzelm@34927  797  but the idea of exploding a string into a list of small strings was  wenzelm@34925  798  extended to symbols'' as explained above. Thus Isabelle sources  wenzelm@34925  799  can refer to an infinite store of user-defined symbols, without  wenzelm@34925  800  having to worry about the multitude of Unicode encodings.  wenzelm@20437  801 *}  wenzelm@20437  802 wenzelm@20437  803 wenzelm@34927  804 subsection {* Basic names \label{sec:basic-name} *}  wenzelm@20476  805 wenzelm@20476  806 text {*  wenzelm@20476  807  A \emph{basic name} essentially consists of a single Isabelle  wenzelm@20476  808  identifier. There are conventions to mark separate classes of basic  wenzelm@29761  809  names, by attaching a suffix of underscores: one underscore means  wenzelm@29761  810  \emph{internal name}, two underscores means \emph{Skolem name},  wenzelm@29761  811  three underscores means \emph{internal Skolem name}.  wenzelm@20476  812 wenzelm@20476  813  For example, the basic name @{text "foo"} has the internal version  wenzelm@20476  814  @{text "foo_"}, with Skolem versions @{text "foo__"} and @{text  wenzelm@20476  815  "foo___"}, respectively.  wenzelm@20476  816 wenzelm@20488  817  These special versions provide copies of the basic name space, apart  wenzelm@20488  818  from anything that normally appears in the user text. For example,  wenzelm@20488  819  system generated variables in Isar proof contexts are usually marked  wenzelm@34926  820  as internal, which prevents mysterious names like @{text "xaa"} to  wenzelm@34926  821  appear in human-readable text.  wenzelm@20476  822 wenzelm@20488  823  \medskip Manipulating binding scopes often requires on-the-fly  wenzelm@20488  824  renamings. A \emph{name context} contains a collection of already  wenzelm@20488  825  used names. The @{text "declare"} operation adds names to the  wenzelm@20488  826  context.  wenzelm@20476  827 wenzelm@20488  828  The @{text "invents"} operation derives a number of fresh names from  wenzelm@20488  829  a given starting point. For example, the first three names derived  wenzelm@20488  830  from @{text "a"} are @{text "a"}, @{text "b"}, @{text "c"}.  wenzelm@20476  831 wenzelm@20476  832  The @{text "variants"} operation produces fresh names by  wenzelm@20488  833  incrementing tentative names as base-26 numbers (with digits @{text  wenzelm@20488  834  "a..z"}) until all clashes are resolved. For example, name @{text  wenzelm@20488  835  "foo"} results in variants @{text "fooa"}, @{text "foob"}, @{text  wenzelm@20488  836  "fooc"}, \dots, @{text "fooaa"}, @{text "fooab"} etc.; each renaming  wenzelm@20488  837  step picks the next unused variant from this sequence.  wenzelm@20476  838 *}  wenzelm@20476  839 wenzelm@20476  840 text %mlref {*  wenzelm@20476  841  \begin{mldecls}  wenzelm@20476  842  @{index_ML Name.internal: "string -> string"} \\  wenzelm@20547  843  @{index_ML Name.skolem: "string -> string"} \\  wenzelm@20547  844  \end{mldecls}  wenzelm@20547  845  \begin{mldecls}  wenzelm@20476  846  @{index_ML_type Name.context} \\  wenzelm@20476  847  @{index_ML Name.context: Name.context} \\  wenzelm@20476  848  @{index_ML Name.declare: "string -> Name.context -> Name.context"} \\  wenzelm@20476  849  @{index_ML Name.invents: "Name.context -> string -> int -> string list"} \\  wenzelm@20476  850  @{index_ML Name.variants: "string list -> Name.context -> string list * Name.context"} \\  wenzelm@20476  851  \end{mldecls}  wenzelm@34926  852  \begin{mldecls}  wenzelm@34926  853  @{index_ML Variable.names_of: "Proof.context -> Name.context"} \\  wenzelm@34926  854  \end{mldecls}  wenzelm@20476  855 wenzelm@20476  856  \begin{description}  wenzelm@20476  857 wenzelm@20476  858  \item @{ML Name.internal}~@{text "name"} produces an internal name  wenzelm@20476  859  by adding one underscore.  wenzelm@20476  860 wenzelm@20476  861  \item @{ML Name.skolem}~@{text "name"} produces a Skolem name by  wenzelm@20476  862  adding two underscores.  wenzelm@20476  863 wenzelm@39864  864  \item Type @{ML_type Name.context} represents the context of already  wenzelm@39864  865  used names; the initial value is @{ML "Name.context"}.  wenzelm@20476  866 wenzelm@20488  867  \item @{ML Name.declare}~@{text "name"} enters a used name into the  wenzelm@20488  868  context.  wenzelm@20437  869 wenzelm@20488  870  \item @{ML Name.invents}~@{text "context name n"} produces @{text  wenzelm@20488  871  "n"} fresh names derived from @{text "name"}.  wenzelm@20488  872 wenzelm@20488  873  \item @{ML Name.variants}~@{text "names context"} produces fresh  wenzelm@29761  874  variants of @{text "names"}; the result is entered into the context.  wenzelm@20476  875 wenzelm@34926  876  \item @{ML Variable.names_of}~@{text "ctxt"} retrieves the context  wenzelm@34926  877  of declared type and term variable names. Projecting a proof  wenzelm@34926  878  context down to a primitive name context is occasionally useful when  wenzelm@34926  879  invoking lower-level operations. Regular management of fresh  wenzelm@34926  880  variables'' is done by suitable operations of structure @{ML_struct  wenzelm@34926  881  Variable}, which is also able to provide an official status of  wenzelm@34926  882  locally fixed variable'' within the logical environment (cf.\  wenzelm@34926  883  \secref{sec:variables}).  wenzelm@34926  884 wenzelm@20476  885  \end{description}  wenzelm@20476  886 *}  wenzelm@20476  887 wenzelm@39857  888 text %mlex {* The following simple examples demonstrate how to produce  wenzelm@39857  889  fresh names from the initial @{ML Name.context}. *}  wenzelm@39857  890 wenzelm@39857  891 ML {*  wenzelm@39866  892  val list1 = Name.invents Name.context "a" 5;  wenzelm@39866  893  @{assert} (list1 = ["a", "b", "c", "d", "e"]);  wenzelm@39866  894 wenzelm@39866  895  val list2 =  wenzelm@39866  896  #1 (Name.variants ["x", "x", "a", "a", "'a", "'a"] Name.context);  wenzelm@39866  897  @{assert} (list2 = ["x", "xa", "a", "aa", "'a", "'aa"]);  wenzelm@39857  898 *}  wenzelm@39857  899 wenzelm@39857  900 text {* \medskip The same works reletively to the formal context as  wenzelm@39861  901  follows. *}  wenzelm@39857  902 wenzelm@39857  903 locale ex = fixes a b c :: 'a  wenzelm@39857  904 begin  wenzelm@39857  905 wenzelm@39857  906 ML {*  wenzelm@39857  907  val names = Variable.names_of @{context};  wenzelm@39866  908 wenzelm@39866  909  val list1 = Name.invents names "a" 5;  wenzelm@39866  910  @{assert} (list1 = ["d", "e", "f", "g", "h"]);  wenzelm@39866  911 wenzelm@39866  912  val list2 =  wenzelm@39866  913  #1 (Name.variants ["x", "x", "a", "a", "'a", "'a"] names);  wenzelm@39866  914  @{assert} (list2 = ["x", "xa", "aa", "ab", "'aa", "'ab"]);  wenzelm@39857  915 *}  wenzelm@39857  916 wenzelm@39857  917 end  wenzelm@39857  918 wenzelm@20476  919 wenzelm@34927  920 subsection {* Indexed names \label{sec:indexname} *}  wenzelm@20476  921 wenzelm@20476  922 text {*  wenzelm@20476  923  An \emph{indexed name} (or @{text "indexname"}) is a pair of a basic  wenzelm@20488  924  name and a natural number. This representation allows efficient  wenzelm@20488  925  renaming by incrementing the second component only. The canonical  wenzelm@20488  926  way to rename two collections of indexnames apart from each other is  wenzelm@20488  927  this: determine the maximum index @{text "maxidx"} of the first  wenzelm@20488  928  collection, then increment all indexes of the second collection by  wenzelm@20488  929  @{text "maxidx + 1"}; the maximum index of an empty collection is  wenzelm@20488  930  @{text "-1"}.  wenzelm@20476  931 wenzelm@34927  932  Occasionally, basic names are injected into the same pair type of  wenzelm@34927  933  indexed names: then @{text "(x, -1)"} is used to encode the basic  wenzelm@34927  934  name @{text "x"}.  wenzelm@20488  935 wenzelm@20488  936  \medskip Isabelle syntax observes the following rules for  wenzelm@20488  937  representing an indexname @{text "(x, i)"} as a packed string:  wenzelm@20476  938 wenzelm@20476  939  \begin{itemize}  wenzelm@20476  940 wenzelm@20479  941  \item @{text "?x"} if @{text "x"} does not end with a digit and @{text "i = 0"},  wenzelm@20476  942 wenzelm@20476  943  \item @{text "?xi"} if @{text "x"} does not end with a digit,  wenzelm@20476  944 wenzelm@20488  945  \item @{text "?x.i"} otherwise.  wenzelm@20476  946 wenzelm@20476  947  \end{itemize}  wenzelm@20470  948 wenzelm@34927  949  Indexnames may acquire large index numbers after several maxidx  wenzelm@34927  950  shifts have been applied. Results are usually normalized towards  wenzelm@34927  951  @{text "0"} at certain checkpoints, notably at the end of a proof.  wenzelm@34927  952  This works by producing variants of the corresponding basic name  wenzelm@34927  953  components. For example, the collection @{text "?x1, ?x7, ?x42"}  wenzelm@34927  954  becomes @{text "?x, ?xa, ?xb"}.  wenzelm@20476  955 *}  wenzelm@20476  956 wenzelm@20476  957 text %mlref {*  wenzelm@20476  958  \begin{mldecls}  wenzelm@39861  959  @{index_ML_type indexname: "string * int"} \\  wenzelm@20476  960  \end{mldecls}  wenzelm@20476  961 wenzelm@20476  962  \begin{description}  wenzelm@20476  963 wenzelm@39864  964  \item Type @{ML_type indexname} represents indexed names. This is  wenzelm@39864  965  an abbreviation for @{ML_type "string * int"}. The second component  wenzelm@39864  966  is usually non-negative, except for situations where @{text "(x,  wenzelm@39864  967  -1)"} is used to inject basic names into this type. Other negative  wenzelm@34926  968  indexes should not be used.  wenzelm@20476  969 wenzelm@20476  970  \end{description}  wenzelm@20476  971 *}  wenzelm@20476  972 wenzelm@20476  973 wenzelm@34927  974 subsection {* Long names \label{sec:long-name} *}  wenzelm@20476  975 wenzelm@34927  976 text {* A \emph{long name} consists of a sequence of non-empty name  wenzelm@34927  977  components. The packed representation uses a dot as separator, as  wenzelm@34927  978  in @{text "A.b.c"}''. The last component is called \emph{base  wenzelm@34927  979  name}, the remaining prefix is called \emph{qualifier} (which may be  wenzelm@34927  980  empty). The qualifier can be understood as the access path to the  wenzelm@34927  981  named entity while passing through some nested block-structure,  wenzelm@34927  982  although our free-form long names do not really enforce any strict  wenzelm@34927  983  discipline.  wenzelm@34927  984 wenzelm@34927  985  For example, an item named @{text "A.b.c"}'' may be understood as  wenzelm@34927  986  a local entity @{text "c"}, within a local structure @{text "b"},  wenzelm@34927  987  within a global structure @{text "A"}. In practice, long names  wenzelm@34927  988  usually represent 1--3 levels of qualification. User ML code should  wenzelm@34927  989  not make any assumptions about the particular structure of long  wenzelm@34927  990  names!  wenzelm@20437  991 wenzelm@20476  992  The empty name is commonly used as an indication of unnamed  wenzelm@34927  993  entities, or entities that are not entered into the corresponding  wenzelm@34927  994  name space, whenever this makes any sense. The basic operations on  wenzelm@34927  995  long names map empty names again to empty names.  wenzelm@20437  996 *}  wenzelm@20437  997 wenzelm@20476  998 text %mlref {*  wenzelm@20476  999  \begin{mldecls}  wenzelm@30365  1000  @{index_ML Long_Name.base_name: "string -> string"} \\  wenzelm@30365  1001  @{index_ML Long_Name.qualifier: "string -> string"} \\  wenzelm@30365  1002  @{index_ML Long_Name.append: "string -> string -> string"} \\  wenzelm@30365  1003  @{index_ML Long_Name.implode: "string list -> string"} \\  wenzelm@30365  1004  @{index_ML Long_Name.explode: "string -> string list"} \\  wenzelm@20547  1005  \end{mldecls}  wenzelm@34927  1006 wenzelm@34927  1007  \begin{description}  wenzelm@34927  1008 wenzelm@34927  1009  \item @{ML Long_Name.base_name}~@{text "name"} returns the base name  wenzelm@34927  1010  of a long name.  wenzelm@34927  1011 wenzelm@34927  1012  \item @{ML Long_Name.qualifier}~@{text "name"} returns the qualifier  wenzelm@34927  1013  of a long name.  wenzelm@34927  1014 wenzelm@34927  1015  \item @{ML Long_Name.append}~@{text "name\<^isub>1 name\<^isub>2"} appends two long  wenzelm@34927  1016  names.  wenzelm@34927  1017 wenzelm@34927  1018  \item @{ML Long_Name.implode}~@{text "names"} and @{ML  wenzelm@34927  1019  Long_Name.explode}~@{text "name"} convert between the packed string  wenzelm@34927  1020  representation and the explicit list form of long names.  wenzelm@34927  1021 wenzelm@34927  1022  \end{description}  wenzelm@34927  1023 *}  wenzelm@34927  1024 wenzelm@34927  1025 wenzelm@34927  1026 subsection {* Name spaces \label{sec:name-space} *}  wenzelm@34927  1027 wenzelm@34927  1028 text {* A @{text "name space"} manages a collection of long names,  wenzelm@34927  1029  together with a mapping between partially qualified external names  wenzelm@34927  1030  and fully qualified internal names (in both directions). Note that  wenzelm@34927  1031  the corresponding @{text "intern"} and @{text "extern"} operations  wenzelm@34927  1032  are mostly used for parsing and printing only! The @{text  wenzelm@34927  1033  "declare"} operation augments a name space according to the accesses  wenzelm@34927  1034  determined by a given binding, and a naming policy from the context.  wenzelm@34927  1035 wenzelm@34927  1036  \medskip A @{text "binding"} specifies details about the prospective  wenzelm@34927  1037  long name of a newly introduced formal entity. It consists of a  wenzelm@34927  1038  base name, prefixes for qualification (separate ones for system  wenzelm@34927  1039  infrastructure and user-space mechanisms), a slot for the original  wenzelm@34927  1040  source position, and some additional flags.  wenzelm@34927  1041 wenzelm@34927  1042  \medskip A @{text "naming"} provides some additional details for  wenzelm@34927  1043  producing a long name from a binding. Normally, the naming is  wenzelm@34927  1044  implicit in the theory or proof context. The @{text "full"}  wenzelm@34927  1045  operation (and its variants for different context types) produces a  wenzelm@34927  1046  fully qualified internal name to be entered into a name space. The  wenzelm@34927  1047  main equation of this chemical reaction'' when binding new  wenzelm@34927  1048  entities in a context is as follows:  wenzelm@34927  1049 wenzelm@39861  1050  \medskip  wenzelm@34927  1051  \begin{tabular}{l}  wenzelm@34927  1052  @{text "binding + naming \ long name + name space accesses"}  wenzelm@34927  1053  \end{tabular}  wenzelm@34927  1054 wenzelm@39861  1055  \bigskip As a general principle, there is a separate name space for  wenzelm@34927  1056  each kind of formal entity, e.g.\ fact, logical constant, type  wenzelm@34927  1057  constructor, type class. It is usually clear from the occurrence in  wenzelm@34927  1058  concrete syntax (or from the scope) which kind of entity a name  wenzelm@34927  1059  refers to. For example, the very same name @{text "c"} may be used  wenzelm@34927  1060  uniformly for a constant, type constructor, and type class.  wenzelm@34927  1061 wenzelm@34927  1062  There are common schemes to name derived entities systematically  wenzelm@34927  1063  according to the name of the main logical entity involved, e.g.\  wenzelm@34927  1064  fact @{text "c.intro"} for a canonical introduction rule related to  wenzelm@34927  1065  constant @{text "c"}. This technique of mapping names from one  wenzelm@34927  1066  space into another requires some care in order to avoid conflicts.  wenzelm@34927  1067  In particular, theorem names derived from a type constructor or type  wenzelm@39839  1068  class should get an additional suffix in addition to the usual  wenzelm@39839  1069  qualification. This leads to the following conventions for derived  wenzelm@39839  1070  names:  wenzelm@39839  1071 wenzelm@39839  1072  \medskip  wenzelm@39839  1073  \begin{tabular}{ll}  wenzelm@39839  1074  logical entity & fact name \\\hline  wenzelm@39839  1075  constant @{text "c"} & @{text "c.intro"} \\  wenzelm@39839  1076  type @{text "c"} & @{text "c_type.intro"} \\  wenzelm@39839  1077  class @{text "c"} & @{text "c_class.intro"} \\  wenzelm@39839  1078  \end{tabular}  wenzelm@34927  1079 *}  wenzelm@34927  1080 wenzelm@34927  1081 text %mlref {*  wenzelm@34927  1082  \begin{mldecls}  wenzelm@34927  1083  @{index_ML_type binding} \\  wenzelm@34927  1084  @{index_ML Binding.empty: binding} \\  wenzelm@34927  1085  @{index_ML Binding.name: "string -> binding"} \\  wenzelm@34927  1086  @{index_ML Binding.qualify: "bool -> string -> binding -> binding"} \\  wenzelm@34927  1087  @{index_ML Binding.prefix: "bool -> string -> binding -> binding"} \\  wenzelm@34927  1088  @{index_ML Binding.conceal: "binding -> binding"} \\  wenzelm@34927  1089  @{index_ML Binding.str_of: "binding -> string"} \\  wenzelm@34927  1090  \end{mldecls}  wenzelm@20547  1091  \begin{mldecls}  haftmann@33174  1092  @{index_ML_type Name_Space.naming} \\  haftmann@33174  1093  @{index_ML Name_Space.default_naming: Name_Space.naming} \\  haftmann@33174  1094  @{index_ML Name_Space.add_path: "string -> Name_Space.naming -> Name_Space.naming"} \\  haftmann@33174  1095  @{index_ML Name_Space.full_name: "Name_Space.naming -> binding -> string"} \\  wenzelm@20547  1096  \end{mldecls}  wenzelm@20547  1097  \begin{mldecls}  haftmann@33174  1098  @{index_ML_type Name_Space.T} \\  haftmann@33174  1099  @{index_ML Name_Space.empty: "string -> Name_Space.T"} \\  haftmann@33174  1100  @{index_ML Name_Space.merge: "Name_Space.T * Name_Space.T -> Name_Space.T"} \\  haftmann@33174  1101  @{index_ML Name_Space.declare: "bool -> Name_Space.naming -> binding -> Name_Space.T ->  haftmann@33174  1102  string * Name_Space.T"} \\  haftmann@33174  1103  @{index_ML Name_Space.intern: "Name_Space.T -> string -> string"} \\  haftmann@33174  1104  @{index_ML Name_Space.extern: "Name_Space.T -> string -> string"} \\  wenzelm@34927  1105  @{index_ML Name_Space.is_concealed: "Name_Space.T -> string -> bool"}  wenzelm@20476  1106  \end{mldecls}  wenzelm@20437  1107 wenzelm@20476  1108  \begin{description}  wenzelm@20476  1109 wenzelm@39864  1110  \item Type @{ML_type binding} represents the abstract concept of  wenzelm@39864  1111  name bindings.  wenzelm@34927  1112 wenzelm@34927  1113  \item @{ML Binding.empty} is the empty binding.  wenzelm@20476  1114 wenzelm@34927  1115  \item @{ML Binding.name}~@{text "name"} produces a binding with base  wenzelm@39832  1116  name @{text "name"}. Note that this lacks proper source position  wenzelm@39832  1117  information; see also the ML antiquotation @{ML_antiquotation  wenzelm@39832  1118  binding}.  wenzelm@34927  1119 wenzelm@34927  1120  \item @{ML Binding.qualify}~@{text "mandatory name binding"}  wenzelm@34927  1121  prefixes qualifier @{text "name"} to @{text "binding"}. The @{text  wenzelm@34927  1122  "mandatory"} flag tells if this name component always needs to be  wenzelm@34927  1123  given in name space accesses --- this is mostly @{text "false"} in  wenzelm@34927  1124  practice. Note that this part of qualification is typically used in  wenzelm@34927  1125  derived specification mechanisms.  wenzelm@20437  1126 wenzelm@34927  1127  \item @{ML Binding.prefix} is similar to @{ML Binding.qualify}, but  wenzelm@34927  1128  affects the system prefix. This part of extra qualification is  wenzelm@34927  1129  typically used in the infrastructure for modular specifications,  wenzelm@34927  1130  notably local theory targets'' (see also \chref{ch:local-theory}).  wenzelm@20437  1131 wenzelm@34927  1132  \item @{ML Binding.conceal}~@{text "binding"} indicates that the  wenzelm@34927  1133  binding shall refer to an entity that serves foundational purposes  wenzelm@34927  1134  only. This flag helps to mark implementation details of  wenzelm@34927  1135  specification mechanism etc. Other tools should not depend on the  wenzelm@34927  1136  particulars of concealed entities (cf.\ @{ML  wenzelm@34927  1137  Name_Space.is_concealed}).  wenzelm@34927  1138 wenzelm@34927  1139  \item @{ML Binding.str_of}~@{text "binding"} produces a string  wenzelm@34927  1140  representation for human-readable output, together with some formal  wenzelm@34927  1141  markup that might get used in GUI front-ends, for example.  wenzelm@20476  1142 wenzelm@39864  1143  \item Type @{ML_type Name_Space.naming} represents the abstract  wenzelm@39864  1144  concept of a naming policy.  wenzelm@20437  1145 haftmann@33174  1146  \item @{ML Name_Space.default_naming} is the default naming policy.  wenzelm@20476  1147  In a theory context, this is usually augmented by a path prefix  wenzelm@20476  1148  consisting of the theory name.  wenzelm@20476  1149 haftmann@33174  1150  \item @{ML Name_Space.add_path}~@{text "path naming"} augments the  wenzelm@20488  1151  naming policy by extending its path component.  wenzelm@20437  1152 haftmann@33174  1153  \item @{ML Name_Space.full_name}~@{text "naming binding"} turns a  wenzelm@30281  1154  name binding (usually a basic name) into the fully qualified  haftmann@29008  1155  internal name, according to the given naming policy.  wenzelm@20476  1156 wenzelm@39864  1157  \item Type @{ML_type Name_Space.T} represents name spaces.  wenzelm@20476  1158 haftmann@33174  1159  \item @{ML Name_Space.empty}~@{text "kind"} and @{ML Name_Space.merge}~@{text  wenzelm@20488  1160  "(space\<^isub>1, space\<^isub>2)"} are the canonical operations for  wenzelm@20488  1161  maintaining name spaces according to theory data management  haftmann@33174  1162  (\secref{sec:context-data}); @{text "kind"} is a formal comment  haftmann@33174  1163  to characterize the purpose of a name space.  wenzelm@20437  1164 haftmann@33174  1165  \item @{ML Name_Space.declare}~@{text "strict naming bindings  haftmann@33174  1166  space"} enters a name binding as fully qualified internal name into  haftmann@33174  1167  the name space, with external accesses determined by the naming  haftmann@33174  1168  policy.  wenzelm@20476  1169 haftmann@33174  1170  \item @{ML Name_Space.intern}~@{text "space name"} internalizes a  wenzelm@20476  1171  (partially qualified) external name.  wenzelm@20437  1172 wenzelm@20488  1173  This operation is mostly for parsing! Note that fully qualified  wenzelm@20476  1174  names stemming from declarations are produced via @{ML  haftmann@33174  1175  "Name_Space.full_name"} and @{ML "Name_Space.declare"}  haftmann@29008  1176  (or their derivatives for @{ML_type theory} and  wenzelm@20488  1177  @{ML_type Proof.context}).  wenzelm@20437  1178 haftmann@33174  1179  \item @{ML Name_Space.extern}~@{text "space name"} externalizes a  wenzelm@20476  1180  (fully qualified) internal name.  wenzelm@20476  1181 wenzelm@30281  1182  This operation is mostly for printing! User code should not rely on  wenzelm@30281  1183  the precise result too much.  wenzelm@20476  1184 wenzelm@34927  1185  \item @{ML Name_Space.is_concealed}~@{text "space name"} indicates  wenzelm@34927  1186  whether @{text "name"} refers to a strictly private entity that  wenzelm@34927  1187  other tools are supposed to ignore!  wenzelm@34927  1188 wenzelm@20476  1189  \end{description}  wenzelm@20476  1190 *}  wenzelm@30272  1191 wenzelm@39832  1192 text %mlantiq {*  wenzelm@39832  1193  \begin{matharray}{rcl}  wenzelm@39832  1194  @{ML_antiquotation_def "binding"} & : & @{text ML_antiquotation} \\  wenzelm@39832  1195  \end{matharray}  wenzelm@39832  1196 wenzelm@39832  1197  \begin{rail}  wenzelm@39832  1198  'binding' name  wenzelm@39832  1199  ;  wenzelm@39832  1200  \end{rail}  wenzelm@39832  1201 wenzelm@39832  1202  \begin{description}  wenzelm@39832  1203 wenzelm@39832  1204  \item @{text "@{binding name}"} produces a binding with base name  wenzelm@39832  1205  @{text "name"} and the source position taken from the concrete  wenzelm@39832  1206  syntax of this antiquotation. In many situations this is more  wenzelm@39832  1207  appropriate than the more basic @{ML Binding.name} function.  wenzelm@39832  1208 wenzelm@39832  1209  \end{description}  wenzelm@39832  1210 *}  wenzelm@39832  1211 wenzelm@39833  1212 text %mlex {* The following example yields the source position of some  wenzelm@39833  1213  concrete binding inlined into the text.  wenzelm@39833  1214 *}  wenzelm@39833  1215 wenzelm@39833  1216 ML {* Binding.pos_of @{binding here} *}  wenzelm@39833  1217 wenzelm@39861  1218 text {* \medskip That position can be also printed in a message as  wenzelm@39861  1219  follows. *}  wenzelm@39833  1220 wenzelm@39833  1221 ML_command {*  wenzelm@39833  1222  writeln  wenzelm@39833  1223  ("Look here" ^ Position.str_of (Binding.pos_of @{binding here}))  wenzelm@39833  1224 *}  wenzelm@39833  1225 wenzelm@39861  1226 text {* This illustrates a key virtue of formalized bindings as  wenzelm@39861  1227  opposed to raw specifications of base names: the system can use this  wenzelm@39861  1228  additional information for advanced feedback given to the user. *}  wenzelm@39833  1229 wenzelm@18537  1230 end