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Struct rand::distributions::uniform::UniformInt

source · [−]
pub struct UniformInt<X> { /* private fields */ }
Expand description

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

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

The type sampled by this implementation.

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

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

Sample a value.

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

Sample a single value uniformly from a range with inclusive lower bound and inclusive upper bound [low, high]. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.