https://github.com/yallop/ocaml-reex

Staged regular expression library for MetaOCaml
https://github.com/yallop/ocaml-reex

metaocaml multi-stage-programming ocaml regex regular-expressions

Last synced: 12 days ago
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Staged regular expression library for MetaOCaml

• Host: GitHub
• URL: https://github.com/yallop/ocaml-reex
• Owner: yallop
• License: mit
• Created: 2022-04-02T13:55:39.000Z (almost 3 years ago)
• Default Branch: master
• Last Pushed: 2023-06-30T20:45:26.000Z (over 1 year ago)
• Last Synced: 2025-01-03T17:14:26.735Z (27 days ago)
• Topics: metaocaml, multi-stage-programming, ocaml, regex, regular-expressions
• Language: OCaml
• Homepage:
• Size: 25.4 KB
• Stars: 9
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
A staged regular expression library for MetaOCaml, based on ["Regular-expression derivatives reexamined"][reex-paper]

## Installing `reex`

1. Install the [BER MetaOCaml][ber-metaocaml] compiler using [OPAM][opam]:

   ```

   opam switch 4.14.1+BER

   eval $(opam env)

   ```

2. Add the [metaocaml-opam][metaocaml-opam] repository:

   ```

   opam remote add metaocaml git+https://github.com/metaocaml/metaocaml-opam.git

   ```

3. Install the `reex` and `reex_match` packages:

   ```

   opam pin add reex reex_match

   ```

## Using `reex`

The functions in the [`Reex`][reex] module construct regular expressions:

```ocaml

let letters = plus (range 'A' 'Z')   (* [A-Z]+ *)

let keyword = str "let" <|> str "and" <|> str "in"

```

Alternatively, the `Reex.regex` function builds a regular expression from a string:

```ocaml

let letters = regex "[A-Z]+"

let keyword = regex "let|and|in"

```

The [`Reex_match.match_`][reex_match] function generates OCaml code that matches one or more regular expressions.  For example, the following call

```ocaml

.

   .~(match_ ~options:{default_options with match_type=`ranges} .. ..

        [chr 'a'       , (fun _ _ -> .<"a">.);

         plus (chr 'b'), (fun _ _ -> .<"b">.)]) >.

```


generates the following OCaml code for matching "a" or "b+":

```ocaml

fun i s ->

  let rec f ~start ~index ~len s =

    match String.unsafe_get s index with

    | 'c'..'\255'|'\000'..'`' -> failwith "no match"

    | 'b' -> g ~start ~index:(index + 1) ~len s

    | 'a' -> h ~start ~index:(index + 1) ~len s

  and g ~start ~index ~len s =

    match String.unsafe_get s index with

    | 'c'..'\255'|'\000'..'a' -> "b"

    | 'b' -> g ~start ~index:(index + 1) ~len s

  and h ~start ~index ~len s = "a" in

  f ~start:i ~index:i ~len:(String.length s) s

```

[reex-paper]: https://www.ccs.neu.edu/home/turon/re-deriv.pdf

[metaocaml-opam]: https://github.com/metaocaml/metaocaml-opam

[ber-metaocaml]: https://okmij.org/ftp/ML/MetaOCaml.html

[opam]: https://opam.ocaml.org/

[reex]: https://github.com/yallop/reex/blob/master/lib/reex.mli

[reex_match]: https://github.com/yallop/reex/blob/master/lib/reex_match.mli