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Module Type_equal.Id

module Id: sig .. end
Id provides identifiers for types, and the ability to test (via Id.same) at run-time 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.
type 'a t 
module Uid: Unique_id_intf.Id
Every Id.t contains a unique id that is distinct from the Uid.t in any other Id.t. 
val uid : 'a t -> Uid.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 pa_sexp).
val create : name:string -> ('a -> Sexplib.Sexp.t) -> 'a t
val hash : 'a t -> int
accessors
val name : 'a t -> string
val to_sexp : 'a t -> 'a -> Sexplib.Sexp.t
val same : 'a t -> 'b t -> bool
same_witness t1 t2 and same_witness_exn t1 t2 return a type equality proof iff the two identifiers are physically equal. This is a useful way to achieve a sort of dynamic typing.

The following two idioms are semantically equivalent; however, using same and same_witness_exn instead of matching on same_witness has better performance because same_witness would allocate an intermediate Or_error.t. 

        match same_witness ta tb with
        | None -> ...
        | Some e -> ...
      

        if not (same ta tb)
        then ...
        else
          let e = same_witness_exn ta tb in
          ...
      

val same_witness : 'a t ->
       'b t -> ('a, 'b) Type_equal.equal Or_error.t
val same_witness_exn : 'a t -> 'b t -> ('a, 'b) Type_equal.equal
val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.t

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

accessors

same_witness t1 t2 and same_witness_exn t1 t2 return a type equality proof iff the two identifiers are physically equal. This is a useful way to achieve a sort of dynamic typing.

The following two idioms are semantically equivalent; however, using same and same_witness_exn instead of matching on same_witness has better performance because same_witness would allocate an intermediate Or_error.t. 

        match same_witness ta tb with
        | None -> ...
        | Some e -> ...
      

        if not (same ta tb)
        then ...
        else
          let e = same_witness_exn ta tb in
          ...