Base.Invariant
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
module type S = sig ... end
module type S1 = sig ... end
module type S2 = sig ... end
module type S3 = sig ... end
val invariant :
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:
invariant [%here] t [%sexp_of: t] (fun () ->
... check t's invariants ... )
For polymorphic types:
let invariant check_a t =
Invariant.invariant [%here] t [%sexp_of: _ t] (fun () -> ... )
It's okay to use [%sexp_of: _ t]
because the exceptions raised by check_a
will show the parts that are opaque at top-level.
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))
;;