Grako++ is a packrat parser runtime for Grako, written in C++.
Project description
Work in progress!
Grako++
Grako++ is a packrat parser runtime for Grako, written in C++. The aim is to provide a Grako-compatible parser generator, but with improved performance over Python.
Differences to Grako
The output is always AST/JSON.
The semantics class can be implemented in C++ or Cython (pure Python through Cython is planned).
The regular expression syntax is ECMAScript, not Python.
Some features of Grako are missing, see below in the TODO section.
State types must implement operator< for std::map (for future flexibility, consider implementing the hash trait, too).
Build
The library is header-files only currently, so you can just copy the files in include/ to a convenient location, or build from there. More formally, you can use cmake.
Build with clang by invoking: cmake -DCMAKE_CXX_COMPILER=/path/to/clang++
Building with g++ < 4.9 requires linking with the boost_regex library, because the std::regex implementation is broken. You can rely on the exported cmake library file to configure the right settings.
Other useful option: -DCMAKE_INSTALL_PREFIX:PATH=/path/to/install
Usage
The grakopp program is used like grako to compile PEG files to source code. There are four different source code output formats that can be specified with the -f/–format option:
–format |
–output |
Purpose |
---|---|---|
hpp |
name.hpp |
C++ declaration |
cpp |
name.cpp |
C++ implementation |
pxd |
name.pxd |
Cython declaration |
pyx |
name.pyx |
Cython implementation |
For pure C++ parsers, generating the hpp and cpp files is sufficient. For Python integration, the pxd and pyx files are also needed. For “name” you should subsitute the actual name of the parser (either the base name of the PEG file or the argument to the –name option). The filenames are, for now, hard-coded into the source files (the underscore protects the C++ implementation from Cython-generated source files).
Here is an example how to build a parser:
$ ./grakopp -f hpp -o _basic.hpp tests/basic/basic.peg
$ ./grakopp --whitespace="" --no-nameguard -f cpp -o _basic.cpp tests/basic/basic.peg
$ g++ -DGRAKOPP_MAIN -std=c++11 -Iinclude -O4 -o basic _basic.cpp -lboost_regex
You can invoke the parser like a Python parser generated with grako (currently, no options are supported, though, except for an internal option –test that compares the AST with a text fixture file):
$ echo -n e1e2 | ./basic /dev/stdin sequence
[
"e1",
"e2"
]
C++ Interface
The following header files exist:
Header |
Purpose |
---|---|
grakopp/exception.hpp |
Parser exceptions |
grakopp/buffer.hpp |
Buffer for I/O |
grakopp/ast.hpp |
AST implementation |
grakopp/parser.hpp |
Parser base class |
grakopp/grakopp/hpp |
Include all above |
grakopp/ast-io.hpp |
Optional AST stream I/O |
Python Integration
Until the Python package is prepared properly, build the Cython extensions manually, for example like this:
$ cd python/grakopp
$ cython --cplus buffer.pyx
$ cython --cplus ast.pyx
$ g++ -std=c++11 -I../../include -shared -pthread -fPIC -fwrapv -O2 -Wall -fno-strict-aliasing -I/usr/include/python2.7 -o buffer.so buffer.cpp
$ g++ -std=c++11 -I../../include -shared -pthread -fPIC -fwrapv -O2 -Wall -fno-strict-aliasing -I/usr/include/python2.7 -o ast.so ast.cpp
$ cd ../..
To continue the above example:
$ ./grakopp -f pxd -o basic.pxd tests/basic/basic.peg
$ ./grakopp -f pyx -o basic.pyx tests/basic/basic.peg
$ cython -Ipython --cplus basic.pyx
$ g++ -std=c++11 -Iinclude -shared -pthread -fPIC -fwrapv -O2 -Wall -fno-strict-aliasing -I/usr/include/python2.7 -o basic.so basic.cpp _basic.cpp -l boost_regex
You can then use it from Python:
$ PYTHONPATH=python python >>> from grakopp import buffer >>> b = buffer.PyBuffer() >>> b.from_string("e1e2") >>> import basic >>> p = basic.basicPyParser() >>> p.set_buffer(b) >>> a = p._sequence_() >>> a.to_python() ['e1', 'e2'] >>> b.pos 4 >>> a = p._sequence_() >>> a.to_python() FailedToken('e1')
TODO
dynamic Ast objects (so you can pass through Python or XML objects)
python/distutils integration
automatic compilation a la pyximport
add namespace
unicode support?
more support and tests for stateful parsing
regex syntax tests (make sure generated C strings are always proper)
profile and optimize
Grako features missing:
ignorecase (buffer match, matchre)
comments skipping
buffer line parsing and trace output (also in exceptions)
ParseInfo
rules with arguments
left recursion
semantic action “_default”
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