package yuujinchou

README.mkd

# Yuujinchou: Name Pattern Combinators

_Yuujinchou_ is an OCaml package of name patterns for implementing import statements. Please consult the [documentation](https://favonia.org/yuujinchou/yuujinchou/Yuujinchou).

## How to Use It

```ocaml
open Yuujinchou

type data = int

(** An environment is a mapping from paths to data. *)
type env = (Pattern.path, data) Hashtbl.t

(** [remap pattern env] uses the [pattern] to massage
    the environment [env]. *)
let remap pattern env =
  let compiled_pattern = Result.get_ok @@ Action.compile_ pattern in
  let new_env = Hashtbl.create @@ Hashtbl.length env in
  begin
    env |> Hashtbl.iter @@ fun path data ->
    match Action.run_ compiled_pattern path with
    | `NoMatch -> ()
    | `Matched l -> l |> List.iter @@ fun (path, ()) ->
      match Hashtbl.find_opt new_env path with
      | None -> Hashtbl.replace new_env path data
      | Some data' ->
        if data <> data' then
          failwith "Inconsistent data assigned to the same path."
  end;
  new_env

(** [import env pattern imported] imports the environment
    [imported] massaged by [pattern] into [env]. *)
let import env pattern imported =
  Hashtbl.replace_seq env @@ Hashtbl.to_seq @@ remap pattern imported
```

## Installation

You need OCaml 4.08.0 or newer. The package is available on the OPAM repository:
```
opam install yuujinchou
```

You could also check out the source repository and install the latest version in development:
```
git clone https://github.com/favonia/yuujinchou.git
opam install ./yuujinchou
```