Module `QCheck.Gen`

Generate Random Values

type 'a t = Random.State.t -> 'a

A random generator for values of type 'a.

type 'a sized = int -> Random.State.t -> 'a

Random generator with a size bound.

val return : 'a -> 'a t

Create a constant generator.

val (>>=) : 'a t -> ('a -> 'b t) -> 'b t

Monadic bind for writing dependent generators. First generates an 'a and then passes it to the given function, to generate a 'b.

val (<*>) : ('a -> 'b) t -> 'a t -> 'b t

Infix operator for composing a function generator and an argument generator into a result generator.

val map : ('a -> 'b) -> 'a t -> 'b t

map f g transforms a generator g by applying f to each generated element.

val map2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t

map2 f g1 g2 transforms two generators g1 and g2 by applying f to each pair of generated elements.

val map3 : ('a -> 'b -> 'c -> 'd) -> 'a t -> 'b t -> 'c t -> 'd t

map3 f g1 g2 g3 transforms three generators g1, g2, and g3 by applying f to each triple of generated elements.

val map_keep_input : ('a -> 'b) -> 'a t -> ('a * 'b) t

map_keep_input f g transforms a generator g by applying f to each generated element. Returns both the generated element from g and the output from f.

val (>|=) : 'a t -> ('a -> 'b) -> 'b t

An infix synonym for map.

val oneof : 'a t list -> 'a t

Constructs a generator that selects among a given list of generators.

val oneofl : 'a list -> 'a t

Constructs a generator that selects among a given list of values.

val oneofa : 'a array -> 'a t

Constructs a generator that selects among a given array of values.

val frequency : (int * 'a t) list -> 'a t

Constructs a generator that selects among a given list of generators. Each of the given generators are chosen based on a positive integer weight.

val frequencyl : (int * 'a) list -> 'a t

Constructs a generator that selects among a given list of values. Each of the given values are chosen based on a positive integer weight.

val frequencya : (int * 'a) array -> 'a t

Constructs a generator that selects among a given array of values. Each of the array entries are chosen based on a positive integer weight.

val shuffle_a : 'a array -> unit t

Shuffles the array in place.

val shuffle_l : 'a list -> 'a list t

Creates a generator of shuffled lists.

val unit : unit t

The unit generator.

val bool : bool t

The boolean generator.

val float : float t

Generates floating point numbers.

val pfloat : float t

Generates positive floating point numbers.

val nfloat : float t

Generates negative floating point numbers.

val nat : int t

Generates small natural numbers.

val neg_int : int t

Generates negative integers.

val pint : int t

Generates positive integers uniformly.

val int : int t

Generates integers uniformly.

val small_nat : int t

Synonym to nat.

since 0.5.1

val small_int : int t

Small UNSIGNED integers, for retrocompatibility.

deprecated
use small_nat.

val small_signed_int : int t

Small SIGNED integers.

since 0.5.2

val int_bound : int -> int t

Uniform integer generator producing integers within 0... bound.

raises Invalid_argument
if the argument is negative.

val int_range : int -> int -> int t

Uniform integer generator producing integers within low,high.

raises Invalid_argument
if low > high or if the range is larger than max_int.

val graft_corners : 'a t -> 'a list -> unit -> 'a t

graft_corners gen l () makes a new generator that enumerates the corner cases in l and then behaves like g.

since 0.6

val int_pos_corners : int list

Non-negative corner cases for int.

since 0.6

val int_corners : int list

All corner cases for int.

since 0.6

val (--) : int -> int -> int t

Synonym to int_range.

val ui32 : int32 t

Generates (unsigned) int32 values.

val ui64 : int64 t

Generates (unsigned) int64 values.

val list : 'a t -> 'a list t

Builds a list generator from an element generator. List size is generated by nat.

val list_size : int t -> 'a t -> 'a list t

Builds a list generator from a (non-negative) size generator and an element generator.

val list_repeat : int -> 'a t -> 'a list t

list_repeat i g builds a list generator from exactly i elements generated by g.

val array : 'a t -> 'a array t

Builds an array generator from an element generator. Array size is generated by nat.

val array_size : int t -> 'a t -> 'a array t

Builds an array generator from a (non-negative) size generator and an element generator.

val array_repeat : int -> 'a t -> 'a array t

array_repeat i g builds an array generator from exactly i elements generated by g.

val opt : 'a t -> 'a option t

An option generator.

val pair : 'a t -> 'b t -> ('a * 'b) t

Generates pairs.

val triple : 'a t -> 'b t -> 'c t -> ('a * 'b * 'c) t

Generates triples.

val quad : 'a t -> 'b t -> 'c t -> 'd t -> ('a * 'b * 'c * 'd) t

Generates quadruples.

since 0.5.1

val char : char t

Generates characters upto character code 255.

val printable : char t

Generates printable characters.

val numeral : char t

Generates numeral characters.

val string_size : ?gen:char t -> int t -> string t

Builds a string generator from a (non-negative) size generator. Accepts an optional character generator (the default is char).

val string : ?gen:char t -> string t

Builds a string generator. String size is generated by nat. Accepts an optional character generator (the default is char).

val small_string : ?gen:char t -> string t

Builds a string generator. String size is in the range 0--10. Accepts an optional character generator (the default is char).

val small_list : 'a t -> 'a list t

Generates lists of small size (range 0 -- 10).

since 0.5.3

val join : 'a t t -> 'a t

Collapses a generator of generators to simply a generator.

since 0.5

val sized : 'a sized -> 'a t

Creates a generator from a size-bounded generator by first generating a size using nat and passing the result to the size-bounded generator.

val sized_size : int t -> 'a sized -> 'a t

Creates a generator from a size-bounded generator by first generating a size using the integer generator and passing the result to the size-bounded generator.

since 0.5

val fix : ('a sized -> 'a sized) -> 'a sized

Fixpoint combinator for generating recursive, size-bounded data types. The passed size-parameter should decrease to ensure termination.

Example:

type tree = Leaf of int | Node of tree * tree

let leaf x = Leaf x
let node x y = Node (x,y)

let g = QCheck.Gen.(sized @@ fix
  (fun self n -> match n with
    | 0 -> map leaf nat
    | n ->
      frequency
        [1, map leaf nat;
         2, map2 node (self (n/2)) (self (n/2))]
    ))

val generate : ?rand:Random.State.t -> n:int -> 'a t -> 'a list

generate ~n g generates n instances of g.

val generate1 : ?rand:Random.State.t -> 'a t -> 'a

generate1 g generates one instance of g.

package qcheck

Module QCheck.Gen

Generate Random Values

Module `QCheck.Gen`