(*:maxLineLen=78:*)
theory Scala
imports Base
begin
chapter \<open>Isabelle/Scala systems programming \label{sec:scala}\<close>
text \<open>
Isabelle/ML and Isabelle/Scala are the two main implementation languages of
the Isabelle environment:
\<^item> Isabelle/ML is for \<^emph>\<open>mathematics\<close>, to develop tools within the context
of symbolic logic, e.g.\ for constructing proofs or defining
domain-specific formal languages. See the \<^emph>\<open>Isabelle/Isar implementation
manual\<close> @{cite "isabelle-implementation"} for more details.
\<^item> Isabelle/Scala is for \<^emph>\<open>physics\<close>, to connect with the world of systems
and services, including editors and IDE frameworks.
There are various ways to access Isabelle/Scala modules and operations:
\<^item> Isabelle command-line tools (\secref{sec:scala-tools}) run in a separate
Java process.
\<^item> Isabelle/ML antiquotations access Isabelle/Scala functions
(\secref{sec:scala-functions}) via the PIDE protocol: execution happens
within the running Java process underlying Isabelle/Scala.
\<^item> The \<^verbatim>\<open>Console/Scala\<close> plugin of Isabelle/jEdit @{cite "isabelle-jedit"}
operates on the running Java application, using the Scala
read-eval-print-loop (REPL).
The main Isabelle/Scala functionality is provided by \<^verbatim>\<open>Pure.jar\<close>, but
further add-ons are bundled with Isabelle, e.g.\ to access SQLite or
PostgreSQL using JDBC (Java Database Connectivity).
Other components may augment the system environment by providing a suitable
\<^path>\<open>etc/settings\<close> shell script in the component directory. Some shell
functions are available to help with that:
\<^item> Function \<^bash_function>\<open>classpath\<close> adds \<^verbatim>\<open>jar\<close> files in Isabelle path
notation (POSIX). On Windows, this is converted to native path names
before invoking @{tool java} or @{tool scala} (\secref{sec:scala-tools}).
\<^item> Function \<^bash_function>\<open>isabelle_scala_service\<close> registers global
service providers as subclasses of
\<^scala_type>\<open>isabelle.Isabelle_System.Service\<close>, using the raw Java name
according to @{scala_method (in java.lang.Object) getClass} (it should be
enclosed in single quotes to avoid special characters like \<^verbatim>\<open>$\<close> to be
interpreted by the shell).
Particular Isabelle/Scala services require particular subclasses:
instances are filtered according to their dynamic type. For example, class
\<^scala_type>\<open>isabelle.Isabelle_Scala_Tools\<close> collects Scala command-line
tools, and class \<^scala_type>\<open>isabelle.Scala.Functions\<close>
collects Scala functions (\secref{sec:scala-functions}).
\<close>
section \<open>Command-line tools \label{sec:scala-tools}\<close>
subsection \<open>Java Runtime Environment \label{sec:tool-java}\<close>
text \<open>
The @{tool_def java} tool is a direct wrapper for the Java Runtime
Environment, within the regular Isabelle settings environment
(\secref{sec:settings}) and Isabelle classpath. The command line arguments
are that of the bundled Java distribution: see option \<^verbatim>\<open>-help\<close> in
particular.
The \<^verbatim>\<open>java\<close> executable is taken from @{setting ISABELLE_JDK_HOME}, according
to the standard directory layout for regular distributions of OpenJDK.
The shell function \<^bash_function>\<open>isabelle_jdk\<close> allows shell scripts to
invoke other Java tools robustly (e.g.\ \<^verbatim>\<open>isabelle_jdk jar\<close>), without
depending on accidental operating system installations.
\<close>
subsection \<open>Scala toplevel \label{sec:tool-scala}\<close>
text \<open>
The @{tool_def scala} tool is a direct wrapper for the Scala toplevel,
similar to @{tool java} above. The command line arguments are that of the
bundled Scala distribution: see option \<^verbatim>\<open>-help\<close> in particular. This allows
to interact with Isabelle/Scala interactively.
\<close>
subsubsection \<open>Example\<close>
text \<open>
Explore the Isabelle system environment in Scala:
@{verbatim [display, indent = 2] \<open>$ isabelle scala\<close>}
@{scala [display, indent = 2]
\<open>import isabelle._
val isabelle_home = Isabelle_System.getenv("ISABELLE_HOME")
val options = Options.init()
options.bool("browser_info")
options.string("document")\<close>}
\<close>
subsection \<open>Scala compiler \label{sec:tool-scalac}\<close>
text \<open>
The @{tool_def scalac} tool is a direct wrapper for the Scala compiler; see
also @{tool scala} above. The command line arguments are that of the
bundled Scala distribution.
This allows to compile further Scala modules, depending on existing
Isabelle/Scala functionality. The resulting \<^verbatim>\<open>class\<close> or \<^verbatim>\<open>jar\<close> files can be
added to the Java classpath using the shell function
\<^bash_function>\<open>classpath\<close>. Thus add-on components can register themselves
in a modular manner, see also \secref{sec:components}.
Note that Isabelle/jEdit @{cite "isabelle-jedit"} has its own mechanisms for
adding plugin components. This needs special attention, since it overrides
the standard Java class loader.
\<close>
subsection \<open>Scala script wrapper\<close>
text \<open>
The executable @{executable "$ISABELLE_HOME/bin/isabelle_scala_script"}
allows to run Isabelle/Scala source files stand-alone programs, by using a
suitable ``hash-bang'' line and executable file permissions. For example:
@{verbatim [display, indent = 2] \<open>#!/usr/bin/env isabelle_scala_script\<close>}
@{scala [display, indent = 2]
\<open>val options = isabelle.Options.init()
Console.println("browser_info = " + options.bool("browser_info"))
Console.println("document = " + options.string("document"))\<close>}
This assumes that the executable may be found via the @{setting PATH} from
the process environment: this is the case when Isabelle settings are active,
e.g.\ in the context of the main Isabelle tool wrapper
\secref{sec:isabelle-tool}. Alternatively, the full
\<^file>\<open>$ISABELLE_HOME/bin/isabelle_scala_script\<close> may be specified in expanded
form.
\<close>
subsection \<open>Project setup for common Scala IDEs\<close>
text \<open>
The @{tool_def scala_project} tool creates a project configuration for
Isabelle/Scala/jEdit:
@{verbatim [display]
\<open>Usage: isabelle scala_project [OPTIONS] PROJECT_DIR
Options are:
-L make symlinks to original scala files
Setup Gradle project for Isabelle/Scala/jEdit --- to support Scala IDEs
such as IntelliJ IDEA.\<close>}
The generated configuration is for Gradle\<^footnote>\<open>\<^url>\<open>https://gradle.org\<close>\<close>, but the
main purpose is to import it into common Scala IDEs, such as IntelliJ
IDEA\<^footnote>\<open>\<^url>\<open>https://www.jetbrains.com/idea\<close>\<close>. This allows to explore the
sources with static analysis and other hints in real-time.
The specified project directory needs to be fresh. The generated files refer
to physical file-system locations, using the path notation of the underlying
OS platform. Thus the project needs to be recreated whenever the Isabelle
installation is changed or moved.
\<^medskip>
By default, Scala sources are \<^emph>\<open>copied\<close> from the Isabelle distribution and
editing them within the IDE has no permanent effect.
Option \<^verbatim>\<open>-L\<close> produces \<^emph>\<open>symlinks\<close> to the original files: this allows to
develop Isabelle/Scala/jEdit within an external Scala IDE. Note that
building the result always requires \<^verbatim>\<open>isabelle jedit -b\<close> on the
command-line.
\<close>
section \<open>Registered Isabelle/Scala functions \label{sec:scala-functions}\<close>
subsection \<open>Defining functions in Isabelle/Scala\<close>
text \<open>
A Scala functions of type \<^scala_type>\<open>String => String\<close> may be wrapped as
\<^scala_type>\<open>isabelle.Scala.Fun\<close> and collected via an instance of the
class \<^scala_type>\<open>isabelle.Scala.Functions\<close>. A system component
can then register that class via \<^bash_function>\<open>isabelle_scala_service\<close>
in \<^path>\<open>etc/settings\<close> (\secref{sec:components}). An example is the
predefined collection of \<^scala_type>\<open>isabelle.Scala.Functions\<close> in
Isabelle/\<^verbatim>\<open>Pure.jar\<close> with the following line in
\<^file>\<open>$ISABELLE_HOME/etc/settings\<close>:
@{verbatim [display, indent = 2] \<open>isabelle_scala_service 'isabelle.Functions'\<close>}
The overall list of registered functions is accessible in Isabelle/Scala as
\<^scala_object>\<open>isabelle.Scala.functions\<close>.
\<close>
subsection \<open>Invoking functions in Isabelle/ML\<close>
text \<open>
Isabelle/PIDE provides a protocol to invoke registered Scala functions in
ML: this works both within the Prover IDE and in batch builds.
The subsequent ML antiquotations refer to Scala functions in a
formally-checked manner.
\begin{matharray}{rcl}
@{ML_antiquotation_def "scala_function"} & : & \<open>ML_antiquotation\<close> \\
@{ML_antiquotation_def "scala"} & : & \<open>ML_antiquotation\<close> \\
@{ML_antiquotation_def "scala_thread"} & : & \<open>ML_antiquotation\<close> \\
\end{matharray}
\<^rail>\<open>
(@{ML_antiquotation scala_function} |
@{ML_antiquotation scala} |
@{ML_antiquotation scala_thread}) @{syntax embedded}
\<close>
\<^descr> \<open>@{scala_function name}\<close> inlines the checked function name as ML string
literal.
\<^descr> \<open>@{scala name}\<close> and \<open>@{scala_thread name}\<close> invoke the checked function via
the PIDE protocol. In Isabelle/ML this appears as a function of type
\<^ML_type>\<open>string -> string\<close>, which is subject to interrupts within the ML
runtime environment as usual. A \<^scala>\<open>null\<close> result in Scala raises an
exception \<^ML>\<open>Scala.Null\<close> in ML. The execution of \<open>@{scala}\<close> works via a
Scala future on a bounded thread farm, while \<open>@{scala_thread}\<close> always forks
a separate Java thread.
The standard approach of representing datatypes via strings works via XML in
YXML transfer syntax. See Isabelle/ML operations and modules @{ML
YXML.string_of_body}, @{ML YXML.parse_body}, @{ML_structure XML.Encode},
@{ML_structure XML.Decode}; similarly for Isabelle/Scala. Isabelle symbols
may have to be recoded via Scala operations
\<^scala_method>\<open>isabelle.Symbol.decode\<close> and
\<^scala_method>\<open>isabelle.Symbol.encode\<close>.
\<close>
subsubsection \<open>Examples\<close>
text \<open>
Invoke the predefined Scala function \<^scala_function>\<open>echo\<close>:
\<close>
ML \<open>
val s = "test";
val s' = \<^scala>\echo\ s;
\<^assert> (s = s')
\<close>
text \<open>
Let the Scala compiler process some toplevel declarations, producing a list
of errors:
\<close>
ML \<open>
val source = "class A(a: Int, b: Boolean)"
val errors =
\<^scala>\<open>scala_toplevel\<close> source
|> YXML.parse_body
|> let open XML.Decode in list string end;
\<^assert> (null errors)\<close>
text \<open>
The above is merely for demonstration. See \<^ML>\<open>Scala_Compiler.toplevel\<close>
for a more convenient version with builtin decoding and treatment of errors.
\<close>
section \<open>Documenting Isabelle/Scala entities\<close>
text \<open>
The subsequent document antiquotations help to document Isabelle/Scala
entities, with formal checking of names against the Isabelle classpath.
\begin{matharray}{rcl}
@{antiquotation_def "scala"} & : & \<open>antiquotation\<close> \\
@{antiquotation_def "scala_object"} & : & \<open>antiquotation\<close> \\
@{antiquotation_def "scala_type"} & : & \<open>antiquotation\<close> \\
@{antiquotation_def "scala_method"} & : & \<open>antiquotation\<close> \\
\end{matharray}
\<^rail>\<open>
(@@{antiquotation scala} | @@{antiquotation scala_object})
@{syntax embedded}
;
@@{antiquotation scala_type} @{syntax embedded} types
;
@@{antiquotation scala_method} class @{syntax embedded} types args
;
class: ('(' @'in' @{syntax name} types ')')?
;
types: ('[' (@{syntax name} ',' +) ']')?
;
args: ('(' (nat | (('_' | @{syntax name}) + ',')) ')')?
\<close>
\<^descr> \<open>@{scala s}\<close> is similar to \<open>@{verbatim s}\<close>, but the given source text is
checked by the Scala compiler as toplevel declaration (without evaluation).
This allows to write Isabelle/Scala examples that are statically checked.
\<^descr> \<open>@{scala_object x}\<close> checks the given Scala object name (simple value or
ground module) and prints the result verbatim.
\<^descr> \<open>@{scala_type T[A]}\<close> checks the given Scala type name (with optional type
parameters) and prints the result verbatim.
\<^descr> \<open>@{scala_method (in c[A]) m[B](n)}\<close> checks the given Scala method \<open>m\<close> in
the context of class \<open>c\<close>. The method argument slots are either specified by
a number \<open>n\<close> or by a list of (optional) argument types; this may refer to
type variables specified for the class or method: \<open>A\<close> or \<open>B\<close> above.
Everything except for the method name \<open>m\<close> is optional. The absence of the
class context means that this is a static method. The absence of arguments
with types means that the method can be determined uniquely as \<^verbatim>\<open>(\<close>\<open>m\<close>\<^verbatim>\<open> _)\<close>
in Scala (no overloading).
\<close>
subsubsection \<open>Examples\<close>
text \<open>
Miscellaneous Isabelle/Scala entities:
\<^item> object: \<^scala_object>\<open>isabelle.Isabelle_Process\<close>
\<^item> type without parameter: @{scala_type isabelle.Console_Progress}
\<^item> type with parameter: @{scala_type List[A]}
\<^item> static method: \<^scala_method>\<open>isabelle.Isabelle_System.bash\<close>
\<^item> class and method with type parameters:
@{scala_method (in List[A]) map[B]("A => B")}
\<^item> overloaded method with argument type: @{scala_method (in Int) "+" (Int)}
\<close>
end
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