package tablecloth-base

Comparator provide a way for custom data structures to be used with Maps and Sets

Say we have a module Book which we want to be able to create a Set of

module Book = struct
  type t = {
    isbn: string;
    title: string;
  }

  let compare book_a book_b =
    String.compare book_a.isbn book_b.isbn
end

First we need to make our module conform to the S signature.

This can be done by using the Make functor.

module Book = struct
  type t = {
    isbn: string;
    title: string;
  }

  let compare book_a book_b =
    String.compare book_a.isbn book_b.isbn

  include Comparator.Make(struct
    type nonrec t = t

    let compare = compare
  end)
end

Now we can create a Set of books:

Set.from_list (module Book) [
  { isbn="9788460767923"; title="Moby Dick or The Whale" }
]