Module `Base_quickcheck.Observer`

Observers create random functions. Generator.fn creates a random function using an observer for the input type and a generator for the output type.

type -'a t = 'a Base_quickcheck__.Observer0.t

Basic Observers

val opaque : _ t: Produces an observer that treats all values as equivalent. Random functions generated using this observer will be constant with respect to the value(s) it observes.

type 'a t

val unit : Base.unit t
val bool : Base.bool t
val char : Base.char t
val string : Base.string t
val int : Base.int t
val int32 : Base.int32 t
val int63 : Base.Int63.t t
val int64 : Base.int64 t
val nativeint : Base.nativeint t
val float : Base.float t
val sexp : Base.Sexp.t t
val option : 'a t -> 'a Base.option t
val list : 'a t -> 'a Base.list t
val both : 'a t -> 'b t -> ('a * 'b) t
val either : 'a t -> 'b t -> ('a, 'b) Base.Either.t t
val result : 'a t -> 'b t -> ('a, 'b) Base.Result.t t

val fn : 'a Generator.t -> 'b t -> ('a -> 'b) t: Produces an observer that generates random inputs for a given function, calls the function on them, then observes the corresponding outputs.

val map_t : 'key t -> 'data t -> ('key, 'data, 'cmp) Base.Map.t t
val set_t : 'elt t -> ('elt, 'cmp) Base.Set.t t
val map_tree : 'key t -> 'data t -> ('key, 'data, 'cmp) Base.Map.Using_comparator.Tree.t t
val set_tree : 'elt t -> ('elt, 'cmp) Base.Set.Using_comparator.Tree.t t

Observers Based on Hash Functions

val of_hash_fold : (Base.Hash.state -> 'a -> Base.Hash.state) -> 'a t: Creates an observer that just calls a hash function. This is a good default for most hashable types not covered by the basic observers above.

Modifying Observers

val unmap : 'a t -> f:('b -> 'a) -> 'b t

Observers for Recursive Types

val fixed_point : ('a t -> 'a t) -> 'a t

Ties the recursive knot to observe recursive types.

For example, here is an observer for binary trees:

let tree_observer leaf_observer =
  fixed_point (fun self ->
    either leaf_observer (both self self)
    |> unmap ~f:(function
      | `Leaf leaf -> First leaf
      | `Node (l, r) -> Second (l, r)))

Low-Level functions

Most users do not need to call these functions.

val create : ('a -> size:Base.int -> hash:Base.Hash.state -> Base.Hash.state) -> 'a t
val observe : 'a t -> 'a -> size:Base.int -> hash:Base.Hash.state -> Base.Hash.state