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This module defines signatures that are to be included in other signatures to ensure a consistent interface to invariant-style functions. There is a signature (S, S1, S2, S3) for each arity of type. Usage looks like:
type t
include Invariant.S with type t := t
or
type 'a t
include Invariant.S1 with type 'a t := 'a t
val invariant :
Base__.Import.Stdlib.Lexing.position ->'a->('a->Sexp.t)->(unit -> unit)->
unit
invariant here t sexp_of_t f runs f (), and if f raises, wraps the exception in an Error.t that states "invariant failed" and includes both the exception raised by f, as well as sexp_of_t t. Idiomatic usage looks like:
check_field is used when checking invariants using Fields.iter. It wraps an exception raised when checking a field with the field's name. Idiomatic usage looks like:
type t =
{ foo : Foo.t;
bar : Bar.t;
}
[@@deriving fields]
let invariant t : unit =
Invariant.invariant [%here] t [%sexp_of: t] (fun () ->
let check f = Invariant.check_field t f in
Fields.iter
~foo:(check Foo.invariant)
~bar:(check Bar.invariant))
;;