1 //! Generate random data.
6 //! use generate_random::GenerateRandom;
8 //! #[derive(GenerateRandom)]
15 //! // Providing a weight allows changing the probabilities.
16 //! // This variant is now twice as likely to be generated as the others.
21 //! let mut rng = rand::thread_rng();
22 //! let my_value = MyEnum::generate_random(&mut rng);
25 /// This derive macro provides an implementation
26 /// of the [`trait@GenerateRandom`] trait.
28 /// Enum variants can be given a `weight` attribute
29 /// to change how often it is generated.
30 /// By default, the weight is `1`.
31 /// The probability of a variants is its weight
32 /// divided by the sum over all variants.
33 pub use generate_random_macro::GenerateRandom;
35 /// Enable randomly generating values of a type.
37 /// This trait can be implemented using the derive
38 /// macro of the same name: [`macro@GenerateRandom`].
39 pub trait GenerateRandom {
40 /// Create a new random value of this type.
41 fn generate_random<R: rand::Rng + ?Sized>(rng: &mut R) -> Self;
44 macro_rules! impl_generate_random {
47 impl GenerateRandom for $t {
48 fn generate_random<R: rand::Rng + ?Sized>(rng: &mut R) -> Self {
56 impl_generate_random! {
75 impl<T: GenerateRandom> GenerateRandom for Option<T> {
76 fn generate_random<R: rand::Rng + ?Sized>(rng: &mut R) -> Self {
77 if bool::generate_random(rng) {
78 Some(T::generate_random(rng))
85 macro_rules! impl_generate_random_tuple {
86 ( $t0:ident $( $t:ident )* ) => {
87 impl< $t0, $( $t, )* > GenerateRandom for ( $t0, $( $t, )* )
94 fn generate_random<R: rand::Rng + ?Sized>(rng: &mut R) -> Self {
96 $t0::generate_random(rng),
98 $t::generate_random(rng),
103 impl_generate_random_tuple!( $( $t )* );
106 impl GenerateRandom for () {
107 fn generate_random<R: rand::Rng + ?Sized>(_rng: &mut R) -> Self {
114 impl_generate_random_tuple!(A B C D E F G H I J K L);
120 fn rng() -> impl rand::Rng {
121 use rand::SeedableRng;
122 rand_chacha::ChaCha8Rng::from(rand_chacha::ChaCha8Core::from_seed([37; 32]))
128 assert_eq!(u8::generate_random(&mut rng), 55);