Struct Probability

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pub struct Probability { /* private fields */ }

Expand description

A validated probability value in the closed interval [0, 1].

Implementations§

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impl Probability

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pub const fn new(value: f64) -> Self

Creates a probability without validation.

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pub const fn try_new(value: f64) -> Result<Self, ProbabilityError>

Creates a probability from a finite value in [0, 1].

§Errors

Returns ProbabilityError::NonFiniteProbability when value is NaN or infinite, and ProbabilityError::ProbabilityOutOfRange when value is outside [0, 1].

§Examples

use use_probability::{Probability, ProbabilityError};

let probability = Probability::try_new(0.25)?;
assert_eq!(probability, Probability::new(0.25));

assert!(matches!(
    Probability::try_new(1.5),
    Err(ProbabilityError::ProbabilityOutOfRange(1.5))
));

Examples found in repository ?

examples/basic_usage.rs (line 5)

3fn main() -> Result<(), use_probability::ProbabilityError> {
4    let rain = Probability::from_fraction(1, 4)?;
5    let traffic = Probability::try_new(0.5)?;
6    let either_delay = independent_union(rain, traffic);
7    let commute = Bernoulli::new(rain);
8
9    assert!((either_delay.value() - 0.625).abs() < 1.0e-12);
10    assert_eq!(commute.failure_probability(), Probability::try_new(0.75)?);
11    assert!((commute.variance() - 0.1875).abs() < 1.0e-12);
12
13    Ok(())
14}

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pub fn from_fraction(part: u64, total: u64) -> Result<Self, ProbabilityError>

Creates a probability from part / total.

§Errors

Returns ProbabilityError::ZeroTotal when total == 0, and ProbabilityError::PartExceedsTotal when part > total.

§Examples

use use_probability::Probability;

let probability = Probability::from_fraction(1, 4)?;
assert!((probability.value() - 0.25).abs() < 1.0e-12);

Examples found in repository ?

examples/basic_usage.rs (line 4)

3fn main() -> Result<(), use_probability::ProbabilityError> {
4    let rain = Probability::from_fraction(1, 4)?;
5    let traffic = Probability::try_new(0.5)?;
6    let either_delay = independent_union(rain, traffic);
7    let commute = Bernoulli::new(rain);
8
9    assert!((either_delay.value() - 0.625).abs() < 1.0e-12);
10    assert_eq!(commute.failure_probability(), Probability::try_new(0.75)?);
11    assert!((commute.variance() - 0.1875).abs() < 1.0e-12);
12
13    Ok(())
14}

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pub const fn validate(self) -> Result<Self, ProbabilityError>

Validates that an existing probability remains normalized.

§Errors

Returns the same error variants as Self::try_new.

Source

pub const fn value(&self) -> f64

Returns the stored probability value.

Examples found in repository ?

examples/basic_usage.rs (line 9)

3fn main() -> Result<(), use_probability::ProbabilityError> {
4    let rain = Probability::from_fraction(1, 4)?;
5    let traffic = Probability::try_new(0.5)?;
6    let either_delay = independent_union(rain, traffic);
7    let commute = Bernoulli::new(rain);
8
9    assert!((either_delay.value() - 0.625).abs() < 1.0e-12);
10    assert_eq!(commute.failure_probability(), Probability::try_new(0.75)?);
11    assert!((commute.variance() - 0.1875).abs() < 1.0e-12);
12
13    Ok(())
14}