Struct rand::distributions::uniform::UniformInt

pub struct UniformInt<X> { /* fields omitted */ }

The back-end implementing [UniformSampler] for integer types.

Unless you are implementing [UniformSampler] for your own type, this type should not be used directly, use [Uniform] instead.

Implementation notes

For simplicity, we use the same generic struct UniformInt<X> for all integer types X. This gives us only one field type, X; to store unsigned values of this size, we take use the fact that these conversions are no-ops.

For a closed range, the number of possible numbers we should generate is range = (high - low + 1). To avoid bias, we must ensure that the size of our sample space, zone, is a multiple of range; other values must be rejected (by replacing with a new random sample).

As a special case, we use range = 0 to represent the full range of the result type (i.e. for new_inclusive($ty::MIN, $ty::MAX)).

The optimum zone is the largest product of range which fits in our (unsigned) target type. We calculate this by calculating how many numbers we must reject: reject = (MAX + 1) % range = (MAX - range + 1) % range. Any (large) product of range will suffice, thus in sample_single we multiply by a power of 2 via bit-shifting (faster but may cause more rejections).

The smallest integer PRNGs generate is u32. For 8- and 16-bit outputs we use u32 for our zone and samples (because it's not slower and because it reduces the chance of having to reject a sample). In this case we cannot store zone in the target type since it is too large, however we know ints_to_reject < range <= $unsigned::MAX.

An alternative to using a modulus is widening multiply: After a widening multiply by range, the result is in the high word. Then comparing the low word against zone makes sure our distribution is uniform.

Trait Implementations

impl UniformSampler for UniformInt<i8>

type X = i8

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<i16>

type X = i16

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<i32>

type X = i32

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<i64>

type X = i64

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<i128>

type X = i128

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<isize>

type X = isize

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<u8>

type X = u8

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<u16>

type X = u16

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<u32>

type X = u32

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<u64>

type X = u64

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<usize>

type X = usize

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl UniformSampler for UniformInt<u128>

type X = u128

The type sampled by this implementation.

fn new<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive lower bound and exclusive upper bound [low, high).

fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Construct self, with inclusive bounds [low, high].

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X

Sample a value.

fn sample_single<R: Rng + ?Sized, B1, B2>(
    low_b: B1,
    high_b: B2,
    rng: &mut R
) -> Self::X where
    B1: SampleBorrow<Self::X> + Sized,
    B2: SampleBorrow<Self::X> + Sized, 

Sample a single value uniformly from a range with inclusive lower bound and exclusive upper bound [low, high).

impl<X: Clone> Clone for UniformInt<X>

fn clone(&self) -> UniformInt<X>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<X: Copy> Copy for UniformInt<X>

impl<X: Debug> Debug for UniformInt<X>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.