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