Module Type_equal.IdSource

Id provides identifiers for types, and the ability to test (via Id.same) at runtime if two identifiers are equal, and if so to get a proof of equality of their types. Unlike values of type Type_equal.t, values of type Id.t do have semantic content and must have a nontrivial runtime representation.

Sourcetype 'a t
Sourceval sexp_of_t : ('a -> Sexplib0.Sexp.t) -> 'a t -> Sexplib0.Sexp.t
Sourcemodule type Arg0 = sig ... end
Sourcemodule type Arg1 = sig ... end
Sourcemodule type Arg2 = sig ... end
Sourcemodule type Arg3 = sig ... end
Sourcemodule type S0 = sig ... end
Sourcemodule type S1 = sig ... end
Sourcemodule type S2 = sig ... end
Sourcemodule type S3 = sig ... end
Sourcemodule Uid : sig ... end

Every Id.t contains a unique id that is distinct from the Uid.t in any other Id.t.

Sourceval uid : _ t -> Uid.t
Sourceval create : name:string -> ('a -> Sexp.t) -> 'a t

create ~name defines a new type identity. Two calls to create will result in two distinct identifiers, even for the same arguments with the same type. If the type 'a doesn't support sexp conversion, then a good practice is to have the converter be [%sexp_of: _], (or sexp_of_opaque, if not using ppx_sexp_conv).

Accessors

Sourceval hash : _ t -> int
Sourceval name : _ t -> string
Sourceval to_sexp : 'a t -> 'a -> Sexp.t
Sourceval hash_fold_t : Hash.state -> _ t -> Hash.state

same_witness t1 t2 and same_witness_exn t1 t2 return a type equality proof iff the two identifiers are the same (i.e., physically equal, resulting from the same call to create). This is a useful way to achieve a sort of dynamic typing. same_witness does not allocate a Some every time it is called.

same t1 t2 = is_some (same_witness t1 t2).

Sourceval same : _ t -> _ t -> bool
Sourceval same_witness : 'a t -> 'b t -> ('a, 'b) equal option
Sourceval same_witness_exn : 'a t -> 'b t -> ('a, 'b) equal
Sourcemodule Create0 (T : Arg0) : S0 with type t := T.t
Sourcemodule Create1 (T : Arg1) : S1 with type 'a t := 'a T.t
Sourcemodule Create2 (T : Arg2) : S2 with type ('a, 'b) t := ('a, 'b) T.t
Sourcemodule Create3 (T : Arg3) : S3 with type ('a, 'b, 'c) t := ('a, 'b, 'c) T.t