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Date: | 2009-02-22 (20:59) |
From: | Dario Teixeira <darioteixeira@y...> |
Subject: | Unusual type declaration and Sexplib |
Hi, I'm having some trouble serialising via Sexplib a data structure defined recursively. Consider module M defined below; note how type foobar_t includes a "with sexp" declaration, telling the Sexplib syntax extension to create (de)serialisers automatically. However, type t cannot rely on that automatism, because type declarations with the "as" operator are not fully supported. Therefore, I need to create the (de)serialisers for this type manually. module M: sig type 'a foobar_t = [ `Foo of int | `Bar of 'a list ] with sexp type t = private [< 'a foobar_t ] as 'a val foo: int -> t val bar: t list -> t end = struct type 'a foobar_t = [ `Foo of int | `Bar of 'a list ] with sexp type t = 'a foobar_t as 'a let foo x = `Foo x let bar x = `Bar x end So basically the problem is creating the functions with the following signatures: val sexp_of_t: t -> Sexplib.Sexp.t val t_of_sexp: Sexplib.Sexp.t -> t Using as base the automatically created functions whose signatures are as follows: val sexp_of_foobar_t: ('a -> Sexplib.Sexp.t) -> 'a foobar_t -> Sexplib.Sexp.t val foobar_t_of_sexp: (Sexplib.Sexp.t -> 'a) -> Sexplib.Sexp.t -> 'a foobar_t But in practice, I'm having trouble seeing how these later functions can be used. The problem lies in their recursive definition: how would I break it? (And yes, I realise that the definition of type t is unusual, but it's extremely convenient for avoiding a lot of explicit annotations and coercions [1]). Thanks for your help! Best regards, Dario Teixeira [1] http://groups.google.com/group/fa.caml/browse_thread/thread/7552095ab859fb5f/9c4a6fd19812fbcc