For an older version of this repository based on sedlex, refer to the sedlex branch.
Writing an OCaml parser with nice error messages should be easy - and now it is! Nice Parser comes in two parts:
- lib/: The
nice_parserlibrary (API) consolidates boilerplate code and wraps your auto-generated parser in a nice interface with beautiful error messages. In types:
Nice_parser.Make : functor(P : RAW_PARSER) -> NICE_PARSER.
- example/: The example parser lets you get started on your own parser in seconds. It is based on
nice_parserand standard tools:
Using the library and the skeleton, you can get started on your own parser in seconds:
opam install nice_parser # install the nice_parser library git clone https://github.com/smolkaj/nice-parser.git # clone this repository cd nice-parser && rm -r lib && mv example src # use example as starting point dune build src/example.a # try to build... dune exec src/bin/main.exe # ...and run your parser!
You should see the following output (the error message relies on OCaml >= 4.08's new source highlighting mechanism):
Trying to parse "(a b (c d) e)". -> (List ((Atom a) (Atom b) (List ((Atom c) (Atom d))) (Atom e))) Trying to parse "(long_atom_with_0123)". -> (List ((Atom long_atom_with_0123))) Trying to parse " ( so far so good but (this is)) illegal (isnt it?) (* parsing will fail ^^^^^^^ here *) ". Fatal error: exception Line 3, characters 25-32: 3 | but (this is)) illegal (isnt it?) ^^^^^^^ Error: [parser] unexpected token
How to build
Ideally, use OCaml 4.08 or higher (for beautiful error messages). The project can be built using dune. Consult the dune-project file for the necessary dependencies; all of them can be installed using the opam packet manager.
Suggestions and Improvements
Suggestions and changes are welcome. Please submit pull requests, or open issues.