1.3 KiB
Hacking on datalog
Datalog uses the canopy PEG
parser generator, the grammar for which is src/datalog.peg.
The included Makefile contains appropriate rules to build a Python 3
virtual environment, install the canopy compiler locally, build the
grammar, install pytest and run the test suite. All you should have to
do is make test, and away it all goes.
The datalog.parser module is generated code emitted by canopy and
should not be edited. It will be rebuilt as needed.
The parser is tested in test/test_datalog_parser.py which attempts
to provide coverage for the basic cases of the grammar itself. As of
v0.0.3 (and earlier) this coverage is somewhat incomplete.
The datalog.core module contains pretty much everything besides the
codegen'd parser. Particularly, it contains an Actions class which
uses hooks in the datalog PEG grammar (noted by the %foo ends of
lines) to construct a database AST for every whole file read.
The datalog.core module also implements evaluation of queries
against databases. This comes in the evaluate function and its
mutually recursive helper join. join is an implementation detail,
whereas evaluate is an intentionally exposed entry point. Future
versions of datalog may hide join.