StrategoXT 0.9.4
StrategoXT 0.9.4 -- released January 22, 2004
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Redhat 8.0:
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License
StrategoXT is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This software is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
Summary of Changes
- External definitions for separate compilation
- Parsing programs with concrete syntax
- Improvements in the run-time system
- Injections in signatures
- Extend dynamic rules
- Drastic reduction of resources in run-time system
- Upgrading pretty-print tables
- Lots of improvements and fixes
Separate Compilation
The Stratego compiler is a whole program compiler. This entails that
all imported modules are included into a single program, which is then
compiled. The advantage is that the compiler has complete knowledge of
all definitions in the program. The disadvantage is that compilation
of library modules is repeated for each program, which makes
compilation slow. To improve on this situation this release introduces
an extension of Stratego with external definitions, which enables
separate compilation. The separate compilation scheme is not per
module; rather a module and all modules that it imports can be made
available as a library. It is up to the programmer to determine the
boundary between library and application. The feature is available
in this release, but is still experimental.
External Definitions
External definitions are definitions of the form 'external f(as1|as2)'
or 'external f(as1|as2) = s' and indicate a strategy that is
implemented externally. It can be compiled with the normal calling
convention for strategies and will be renamed in the same way to f_n_m
with n the number of strategy parameters and m the number of term
parameters. The second form allows the specification of a strategy
body for the definition. This can be used by the compiler to inline
some applications of the strategy operator, but no implementation is
generated for such definitions. External definitions cannot be
extended.
External definitions generalize 'prim'itive strategies and can be used
to implement separate compilation. That is, to implement an external
definition f(as1|as2), the program should be linked with an object
file which provides a function f_n_m with n = |as1| and m =
|as2|. Such an object file can be produced from a program written
directly in C, or can be generated from a Stratego program.
Library Generation
The Stratego Compiler strc can be used now to generate a library from
a module file.str with the command
strc -i mod.str -c -o libmod.c --library
This produces three files:
- libmod.c
- libmod.str
- libmod.rtree
The first is the C implementation of the closure of mod.str. It
provides C functions for all user-defined strategies, and static C
functions for strategies generated at compile-time. The last two are
the concrete syntax and abstract syntax files for a Stratego module
with
external definitions for all strategies defined in mod.str and
imported modules. It is now possible to import libmod in another
Stratego program, instead of mod. Note that libmod.str is produced
mainly for documentation, libmod.rtree should be used to import. This
is done automatically by the compiler as long as the file is present.
Note that no modules from the 'library' should be imported in the
program via another path. This will lead to doubly defined strategies;
it is not allowed to extend external definitions.
The C program libmod.c can be compiled to an object file libmod.o and
to a library liblibmod.a. This should be done in a makefile; strc does
not deal with C compilation of libraries. Also strc does not
find
imported object libraries; these should be declared explicitly to the
C compiler (for instance using the LDADD flag in a makefile). Static
linking of the libraries thus produced may actually lead to
larger
executables since no unused-function-removal is performed on the
library (for obvious reasons). Shared libraries are the solution here
to save diskspace. This can be achieved by proper use of libtool in
the buildenvironment; again strc does not provide support for this.
(Remark: the C compilation facility in strc is mainly intended for use
by novices; any serious application of strc should be embedded in a
proper build environment where C compilation is better left to that
environment.)
The current version of strc does not produce implementations of
definitions for inlining in the importing program. This is catered for
in the implementation, though. Some more experience is needed with
this feature before making it available.
Currently, no
overlays are exported to the library module.
(Eelco Visser)
Other Language Extensions / Changes
Injections
An injection is a constructor declaration without constructor
name. This can be useful for introducing shorter sort names.
For example,
signature
constructors
FunDec : Id * FunArgs * Type * Exp -> Dec
: String -> Id
: List(FunArg) -> FunArgs
Injections are accepted syntactically, but since no typechecking is
done (yet), they make no difference for compilation at the
moment. However, the quality of (generated) signatures becomes much
better by this feature.
(Martin Bravenboer)
Extend Rules
First implementation of 'extend rules' variant of dynamic
rules. Defining a dynamic rule as
extend rules(
A : lhs -> rhs where s
)
creates a dynamic rule A, which as usual returns the rhs of the rule
last created. In addition, a rule bagof-A is generated, which rewrites
lhs to all rhss in the current scope, i.e., produces a list of all
'values' of lhs.
(Eelco Visser and Arthur van Dam)
Concrete-Syntax
Parsing Programs with Concrete-Syntax
Stratego supports definition of rewrite rules and strategies with
concrete syntax of the object language. This feature is also useful
for other languages. In the paper 'Retrofitting the
AutoBayes Program
Synthesis System with Concrete Syntax' it is shown how concrete syntax
can be added to Prolog. (Implementation in prolog-tools package.)
Concrete-syntax is a new package in the
StrategoXT bundle. Its purpose
is to provide generic utilities for handling programs with concrete
syntax for
arbitrary meta-languages. So far it provides just the
program parse-cs, which is an implementation of the generic
architecture for parsing with concrete syntax outlined in the GPCE'02
paper 'Meta-Programming with Concrete Object Syntax'.
The program is parameterized with meta-data indicating components for
various aspects such as parsing, exploding, desugaring, and
pretty-printing. The meta data can be specified in a .meta file
specific for a program to be parsed, or it can be associated with an
extension and registered in an
XTC repository.
For example, the following is the content of pl.meta, the meta-data
for Prolog programs with embedded syntax. The assumption (in this
example) is that syntax embeddings use a standard (
ToTerm?) convention
for indicating the boundary between meta- and object-syntax.
Meta([
Syntax("Prolog"),
ParseTable("Prolog.tbl"),
Explode("prolog-explode"),
PrettyPrintTable("Prolog-pretty.pp.af")
])
This information can be overridden in a file specific .meta file with
the same extension. For example, the following indicates an embedding
of ABIR in Prolog and a specific desugaring tool for this format:
Meta([
Syntax("PrologABIR"),
PostExplodeDesugar("abir-in-prolog-implode")
])
It overrides the syntax component, and adds a desugaring component.
In order to define such meta-data for a whole class of programs, it
can be defined in a meta file associated with a new extension. For
example, the following is the contents plabir.meta, which defines all
meta-data for preprocessing Prolog with embedded ABIR in files with
extension .plabir.
Meta([
Syntax("PrologABIR"),
Explode("prolog-explode"),
PostExplodeDesugar("abir-in-prolog-implode"),
PrettyPrintTable("Prolog-pretty.pp.af")
])
(Eelco Visser)
Transforming AsFix
Parse trees produced by sglr are in the
AsFix format which contains
all details concerning layout and the structure of lexical syntax.
For some applications it is useful to apply transformations to this
AsFix format, rather than the imploded abstract syntax. While generic
AsFix transformations can be written quite compactly using abstract
syntax (constructors app, prod, sort, etc), transformations which are
specific for the object language become gruesome. The --asfix switch
of the implode-asfix algorithm now indicates that
AsFix trees which
occur within the concrete syntax quotes should not be imploded. Thus,
it becomes possible to write transformations on
AsFix using concrete
syntax. (Valentin David)
Run-Time System
Don't Reconstruct Identical Term on Traversal
Changed one-step traversal functions such that a new term is only
built if there was an actual change to at least one of the sub-terms,
thus avoiding unnecessary term construction. (Based on an idea by
Eelco Dolstra.) A one off test on one program suggests that it makes
no difference at all. But we should wait for results with more
programs.
(Eelco Visser)
Jumpbuffer
Improved setjmp() choice operator implementation. Instead of
allocating a gigantic fixed-length array of jmp_buf buffers in the
data segment, we now dynamically allocate the array on the heap. The
array starts at size 1 and is doubled on demand, for O(1) amortised
time complexity.
This should fix the problems with very large statically allocated data
observed on some platforms (cygwin,
SuSE? 8.1). The new implementation
should also be slightly more efficient due to inlining.
(Eelco Dolstra)
Stratego Standard Library
Posix Error Codes
The SSL has been extended with the module posix-error. This module
provides strategies to report errors that have occurred in POSIX
system functions. These strategies can be used to improve the error
reporting of for example IO related strategies. The posix-module
provides access to the errno variable and makes the strerror and
perror POSIX functions available to Stratego programs. The perror
strategy takes a String and produces an error message on the standard
error output describing the last error encountered during a call to a
system function.
The strategy
chdir is for example implemented as:
?pathname; prim("SSL_chdir", pathname) => 0
<+ < conc-strings
; perror
; fail
> ("SSL/chdir: Cannot change current working directory to ", <id>)
chdir output the following message if the pathname does not exist:
SSL/chdir: Cannot change current working directory to /tddmp: No
such file or directory
(Martin Bravenboer)
String Manipulation
The new module string-misc implements miscellaneous strategies on
strings. The module provides strategies for indenting, applying an s
to all lines, trim trailing characters, and some more.
(Arthur van Dam)
Misc
- set-random-seed, next-random, get-random-max: generate random
numbers.
- execv: execute a file without searching the PATH like execvp
does.
- chdir, getcwd: Change or get the working directory.
- rename-file: in cause of external devices the file is now copied.
- split-last: Splits a list into a tuple of its init list and last
element
- abspath, is-abspath, is-relpath, base-filename: posix compatible
strategies for the manipulation of pathnames.
XTC is now using
mkstemp for the creation of temporary. This means
that that temporary files of
XTC are from now created in the default
directory for temporary files (usually /tmp).
(Martin Bravenboer)
Utilities
Pretty-Printing: Difference of Pretty-Print Tables
The pretty-print tables generated by ppgen have to be edited manually
to achieve 'pretty' formatting of trees. However, when the syntax
definition is updated, the edited pretty-print table should be updated
as well. The new tool pptable-diff computes the differences between
two pretty-print tables and prunes and patches an old table to bring
it up to date with a new table. Thus, the pretty-print rules for the
parts of the language that were not changed are reused.
(Merijn de Jonge)
Pack-stratego
Added --slack flag to pack-stratego. Using this will let pack-stratego
continue even if a module isn't found, producing only a
warning. Pack-stratego has been extended to accept absolute pathnames
as input.
(Rob Vermaas)
Pack-sdf
Pack-sdf supports multiple output formats using the -of (or
--output-format) flag. By default pack-sdf from now returns an
SDF
definition in concrete syntax (-of txt). Other supported output
formats are asfix and ast. Pack-sdf from this release fails if a
module is not found.
Configuration
The package name 'strategoxt' is now also reflected in the location
of the
XTC repository, which is in
$prefix/share/strategoxt/XTC.
(Eelco Visser)
The following changes were prompted by Automake that now does check
that the names of macros being defined are properly quoted. While I
was at it, I have updated a couple of stylistic issues:
- properly quote where expected
- don't shell-quote where not needed
- use the weak versioning conventions (#serial)
This is the resulting autoxt.m4, still valid for both Autoconf 2.1x
and 2.5x, thanks!
(Valentin David)
Download and Installation
The release page contains the source distributions, binary RPMs, and
detailed instructions on how to install the distributions:
Bugs and Known Problems
NOT all the bugs and known problems for StrategoXT distributions have
been solved in this release. See the stratego-bugs list for reports
about (open) bugs:
For a more detailed overview of problems and missing features please
visit:
Please report any problems with installation or bugs in the
implementation to the
stratego-bugs@cs.uu.nl mailing list. Please
check the archive of the list to see if a report about the problem was
already submitted.
Contributions
Developments, beta tests, and bug fixes were carried out by
- Martin Bravenboer
- Arthur van Dam
- Valentin David
- Eelco Dolstra
- Armijn Hemel
- Rob Vermaas
- Eelco Visser
Special thanks to the students of the Program Transformation course.
