thautwarm / typed-bnf-ocaml-demo Goto Github PK

Typed-BNF helps you minimize the procedures of writing parsers.

1. OCaml dune build system
2. Typed-BNF compiler(Python 3.10 required)
3. Opam libraries:
   • menhirLib
   • sedlex
   • sedlex.ppx

Dune project:

(library
 (name <your project name>)
 (libraries menhirLib sedlex sedlex.ppx)
 (preprocess
  (pps sedlex.ppx)))

Writing a json parser library requires only 2 hand-written files:

1. the grammar json.tbnf; or grammar for your own language xxx.tbnf.
2. lib/json_require.ml(or your lib/xxx_require.ml), which provides the implementation of the external symbols you declared in json.tbnf(or your xxx.tbnf).

Then you build the project with tbnf and menhir with this bash script:

tbnf json.tbnf ocaml  --outdir lib/ --mod json
menhir lib/json_parser.mly --external-tokens Json_tokens

MLI_CONTENT="$(cat lib/json_parser.mli)"
echo "open Json_require;;" > lib/json_parser.mli
echo $MLI_CONTENT >> lib/json_parser.mli

Inserting open Json_require to the head of lib/json_parser.mli is a required patch for menhir codegen.

run dune utop ..

utop # Easyjson.Api.parse_json("{\"1\": 2,   \"3\": [1, 2]}");;
- : Json_require.json =
Easyjson.Json_require.Dict
 [([|<abstr>|], Easyjson.Json_require.Int 2);
  ([|<abstr>|],
   Easyjson.Json_require.List
    [Easyjson.Json_require.Int 1; Easyjson.Json_require.Int 2])]