[under construction --
EelcoVisser - 16 May 2003]
A full fledged Stratego application does more than transform an ATerm into another ATerm. To transform programs it is necessary to parse the input program, turn the
parse tree into a an
abstract syntax tree, apply several transformations, and
pretty print? the output program. These separate operations should also be glued together into a complete transformation system. The
StrategoXT
tools support the creation and composition of components for all aspects of transformation systems. Since the tool set is very flexible and programmable, there are many possibilities for using it.
This page provides a guideline for setting up a typical
Stratego application. The application is developed as a package under the control of
AutoMake? and
AutoConf? using the
AutoXT abstractions developed for
StrategoXT.
As an example we examine the
prolog-tools package, which provides
basic support for transforming Prolog programs.
Structure of the Package
A source-to-source transformation system consists of a parser, several transformation components,
and a pretty-printer. These components are specified in subdirectories of the package. The
following directories are standard in a package providing support for one or more languages:
- syn -- syntax definitions
- sig -- signatures describing abstract syntax trees
- pp -- pretty-print tables
- xtc -- tool compositions
- tests -- unit and integration tests
In addition a package can contain several directories for transformation componens.
Configuration
It is customary to develop Stratego packages using the
AutoMake? and
AutoConf? in order to make packages easiliy portable to many (Unix compatible) platforms. If you are not familiar with
these tools please check out their documentation.
Configure.in
From the
configure.in file, the build-time
configure script is generated. It takes
configuration parameters such as external packages and substitutes them in makefiles and
other source files. The
USE_XT_PACKAGES macro can be used in order to get parameterization of the
StrategoXT packages.
https://svn.strategoxt.org/repos/StrategoXT/prolog-tools/trunk/configure.in
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bootstrap
In order to generate the
configure script and instantiate the makefile templates several
tools from the autoX family should be applied. The
bootstrap script calls these tools in
the right order. One unusual tool is
autoxt, which installs
AutoMake? macros supporting
the use of
StrategoXT tools. The
bootstrap script assumes that
autoxt can be found in the
path.
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Makefile.am
Each directory in the package should have a
Makefile. These
Makefiles are generated by
automake and autoconf from a declarative
Makefile.am. The top-level Makefile just declares
its subdirectory such that navigation code can be generated. The
Makefile.xt is installed
by
autoxt and contains standard make rules for applying
StrategoXT tools. It should be
included in each makefile in the package.
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The
AC_CONFIG_FILES macro defines all files that should be created by
configure.
Other Required Files
Automake/conf require the following files to exist in the package:
- README -- name and purpose of the package
- AUTHORS
- ChangeLog -- fine grained log of changes
- NEWS -- course grained description of changes
Configuring the Package
Once the basic configuration is set up you can configure the package with the following sequence
of commands:
> ./bootstrap
> ./configure --prefix=/installation/directory --with-xt=/usr
Assuming that the
StrategoXT, ATerm, and
SDF distributions have been installed in
/usr. Now it should be possible to
make and
install the components in the package using the commands:
> make
> make install
Exported components are installed in subdirectories of the
/installation/directory.
Syntax Definition (syn)
The syntax definition of the language under consideration (Prolog in this case) is defined
in directory
syn/. The directory contains the following files:
The
Makefile.am defines which parse tables to make (
.tbl extension):
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Signature (sig)
The
algebraic signature defines the
abstract syntax of a language. The signature
of Prolog abstract syntax is defined in the
Prolog.str:
The signature can be derived automatically from a syntax definition using the tool
sdf-to-sig. The make rules
in
Makefile.xt invoke this tool based on the dependency of
.str files on
.def files. The
Prolog.def
file is made available via a symbolic link to the
../syn/ directory.
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Pretty-Printer (pp)
A pretty-printer renders an abstract syntax tree as text. The
GPP package in
StrategoXT provides tools for rendering ASTs as ascii text, html, and latex. The translation works by first translating an AST to a Box term, which declares formatting independently of the target device
and the source language. A Box can be formatted in different ways. The translation from AST to Box can be done in two ways.
GPP supports
pp-tables which define a mapping from AST constructors to Box terms. The
pp-gen? tool generates a default pp-table from a syntax definition. Alternatively one can program the translation from AST to Box in a Stratego program. Although the latter is more work, it may be necessary when more sophisticated formatting is required. The Prolog package uses both methods.
- Prolog.pp -- default pretty-print table for Prolog
- Prolog2abox.str -- Stratego transformation from Prolog abstract syntax to Box
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Tool Composition (xtc)
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Tests (tests)
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