This directory contains a single source file, `mlr.bnf`, which is the
lexical/semantic grammar file for the Miller `put`/`filter` DSL
(domain-specific language) using the GOCC framework. (In a classical Lex/Yacc
framework, there would be separate `mlr.l` and `mlr.y` files; using GOCC, there
is a single `mlr.bnf` file.)

All subdirectories of `pkg/parsing/` are autogen code created by GOCC's
processing of `mlr.bnf`. They are nonetheless committed to source control,
since running GOCC takes quite a bit longer than the `go build` does, and the
BNF file doesn't often change. (_BNF_ is for _Backus-Naur Form_ which is the
phrasing of the grammar file that GOCC support.) See the top-level `miller/go`
build scripts for how to rerun GOCC. As of this writing, it's

```
gocc -o pkg/parsing pkg/parsing/mlr.bnf
````

as invoked from the repo base directory -- however you should instead use

```
tools/build-dsl
```

Making changes to `mlr.bnf` requires several minutes to re-run GOCC. For
experimental changes, please see the
[experiments](../../../experiments/dsl-parser) directory.