
diff -r 12063e071d92 -r 97f8806c3ed6 doc-src/IsarImplementation/Thy/document/Syntax.tex
--- a/doc-src/IsarImplementation/Thy/document/Syntax.tex	Sun Oct 23 16:03:59 2011 +0200
+++ b/doc-src/IsarImplementation/Thy/document/Syntax.tex	Sun Oct 23 23:11:53 2011 +0200
@@ -23,7 +23,47 @@
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-FIXME%
+Pure \isa{{\isaliteral{5C3C6C616D6264613E}{\isasymlambda}}}-calculus as introduced in \chref{ch:logic} is
+  an adequate foundation for logical languages --- in the tradition of
+  \emph{higher-order abstract syntax} --- but end-users require
+  additional means for reading and printing of terms and types.  This
+  important add-on outside the logical core is called \emph{inner
+  syntax} in Isabelle jargon, as opposed to the \emph{outer syntax} of
+  the theory and proof language (cf.\ \chref{FIXME}).
+
+  For example, according to \cite{church40} quantifiers are
+  represented as higher-order constants \isa{All\ {\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}\ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{27}{\isacharprime}}a\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ bool{\isaliteral{29}{\isacharparenright}}\ {\isaliteral{5C3C52696768746172726F773E}{\isasymRightarrow}}\ bool} such that \isa{All\ {\isaliteral{28}{\isacharparenleft}}{\isaliteral{5C3C6C616D6264613E}{\isasymlambda}}x{\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}{\isaliteral{27}{\isacharprime}}a{\isaliteral{2E}{\isachardot}}\ B\ x{\isaliteral{29}{\isacharparenright}}} faithfully represents
+  the idea that is displayed as \isa{{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{3A}{\isacharcolon}}{\isaliteral{3A}{\isacharcolon}}{\isaliteral{27}{\isacharprime}}a{\isaliteral{2E}{\isachardot}}\ B\ x} via \hyperlink{keyword.binder}{\mbox{\isa{\isakeyword{binder}}}} notation.  Moreover, type-inference in the style of
+  Hindley-Milner \cite{hindleymilner} (and extensions) enables users
+  to write \isa{{\isaliteral{5C3C666F72616C6C3E}{\isasymforall}}x{\isaliteral{2E}{\isachardot}}\ B\ x} concisely, when the type \isa{{\isaliteral{27}{\isacharprime}}a} is
+  already clear from the context.\footnote{Type-inference taken to the
+  extreme can easily confuse users, though.  Beginners often stumble
+  over unexpectedly general types inferred by the system.}
+
+  \medskip The main inner syntax operations are \emph{read} for
+  parsing together with type-checking, and \emph{pretty} for formatted
+  output.  See also \secref{sec:read-print}.
+
+  Furthermore, the input and output syntax layers are sub-divided into
+  separate phases for \emph{concrete syntax} versus \emph{abstract
+  syntax}, see also \secref{sec:parse-unparse} and
+  \secref{sec:term-check}, respectively.  This results in the
+  following decomposition of the main operations:
+
+  \begin{itemize}
+
+  \item \isa{read\ {\isaliteral{3D}{\isacharequal}}\ parse{\isaliteral{3B}{\isacharsemicolon}}\ check}
+
+  \item \isa{pretty\ {\isaliteral{3D}{\isacharequal}}\ uncheck{\isaliteral{3B}{\isacharsemicolon}}\ unparse}
+
+  \end{itemize}
+
+  Some specification package might thus intercept syntax processing at
+  a well-defined stage after \isa{parse}, to a augment the
+  resulting pre-term before full type-reconstruction is performed by
+  \isa{check}, for example.  Note that the formal status of bound
+  variables, versus free variables, versus constants must not be
+  changed here!%
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@@ -32,7 +72,13 @@
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+Read and print operations are roughly dual to each other, such
+  that for the user \isa{s{\isaliteral{27}{\isacharprime}}\ {\isaliteral{3D}{\isacharequal}}\ pretty\ {\isaliteral{28}{\isacharparenleft}}read\ s{\isaliteral{29}{\isacharparenright}}} looks similar to
+  the original source text \isa{s}, but the details depend on many
+  side-conditions.  There are also explicit options to control
+  suppressing of type information in the output.  The default
+  configuration routinely looses information, so \isa{t{\isaliteral{27}{\isacharprime}}\ {\isaliteral{3D}{\isacharequal}}\ read\ {\isaliteral{28}{\isacharparenleft}}pretty\ t{\isaliteral{29}{\isacharparenright}}} might fail, produce a differently typed term, or a
+  completely different term in the face of syntactic overloading!%
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@@ -71,7 +117,22 @@
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+Parsing and unparsing converts between actual source text and
+  a certain \emph{pre-term} format, where all bindings and scopes are
+  resolved faithfully.  Thus the names of free variables or constants
+  are already determined in the sense of the logical context, but type
+  information might is still missing.  Pre-terms support an explicit
+  language of \emph{type constraints} that may be augmented by user
+  code to guide the later \emph{check} phase, for example.
+
+  Actual parsing is based on traditional lexical analysis and Earley
+  parsing for arbitrary context-free grammars.  The user can specify
+  this via mixfix annotations.  Moreover, there are \emph{syntax
+  translations} that can be augmented by the user, either
+  declaratively via \hyperlink{command.translations}{\mbox{\isa{\isacommand{translations}}}} or programmatically via
+  \hyperlink{command.parse-translation}{\mbox{\isa{\isacommand{parse{\isaliteral{5F}{\isacharunderscore}}translation}}}}, \hyperlink{command.print-translation}{\mbox{\isa{\isacommand{print{\isaliteral{5F}{\isacharunderscore}}translation}}}} etc.  The
+  final scope resolution is performed by the system, according to name
+  spaces for types, constants etc.\ determined by the context.%
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@@ -110,7 +171,30 @@
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+These operations define the transition from pre-terms and
+  fully-annotated terms in the sense of the logical core
+  (\chref{ch:logic}).
+
+  The \emph{check} phase is meant to subsume a variety of mechanisms
+  in the manner of ``type-inference'' or ``type-reconstruction'' or
+  ``type-improvement'', not just type-checking in the narrow sense.
+  The \emph{uncheck} phase is roughly dual, it prunes type-information
+  before pretty printing.
+
+  A typical add-on for the check/uncheck syntax layer is the \hyperlink{command.abbreviation}{\mbox{\isa{\isacommand{abbreviation}}}} mechanism.  Here the user specifies syntactic
+  definitions that are managed by the system as polymorphic \isa{let} bindings.  These are expanded during the \isa{check}
+  phase, and contracted during the \isa{uncheck} phase, without
+  affecting the type-assignment of the given terms.
+
+  \medskip The precise meaning of type checking depends on the context
+  --- additional check/unckeck plugins might be defined in user space!
+
+  For example, the \hyperlink{command.class}{\mbox{\isa{\isacommand{class}}}} command defines a context where
+  \isa{check} treats certain type instances of overloaded
+  constants according to the ``dictionary construction'' of its
+  logical foundation.  This involves ``type improvement''
+  (specialization of slightly too general types) and replacement by
+  certain locale parameters.  See also \cite{Haftmann-Wenzel:2009}.%
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