logprob 0.4.0

A wrapper around floats to handle log probabilities
Documentation 
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use core::error::Error;
/// An error for when a [`LogProb`](super::LogProb) is passed a value that isn't negative.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct FloatIsNanOrPositive;

impl Error for FloatIsNanOrPositive {}

impl core::fmt::Display for FloatIsNanOrPositive {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "LogProb constructed with positive or NaN value")
    }
}

/// An error for when a [`LogProb`](super::LogProb)  is passed a value that isn't negative.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct ProbabilitiesSumToGreaterThanOne;

impl Error for ProbabilitiesSumToGreaterThanOne {}

impl core::fmt::Display for ProbabilitiesSumToGreaterThanOne {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "The sum is greater than 1.0 (improper distribution)")
    }
}

impl From<FloatIsNanOrPositive> for ProbabilitiesSumToGreaterThanOne {
    fn from(_value: FloatIsNanOrPositive) -> Self {
        ProbabilitiesSumToGreaterThanOne
    }
}

/// An error for when [`softmax`](super::softmax) is passed a value that is NaN or infinity.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct FloatIsNanOrPositiveInfinity;

impl Error for FloatIsNanOrPositiveInfinity {}

impl core::fmt::Display for FloatIsNanOrPositiveInfinity {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "LogProb constructed with positive or NaN value")
    }
}

/// Errors for when subtracting two log probabilities
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum LogProbSubtractionError {
    ///Can't divide by zero (or subtract negative infinity)
    DivideByZero,
    ///Can't divide a number by a smaller one, since it will lead to a value outside of \[0,1\] in
    ///prob space.
    NumeratorBiggerThanDenominator,
}

impl Error for LogProbSubtractionError {}

impl core::fmt::Display for LogProbSubtractionError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            LogProbSubtractionError::DivideByZero => write!(
                f,
                "Subtracting negative infinity is equivalent to dividing by zero"
            ),
            LogProbSubtractionError::NumeratorBiggerThanDenominator => write!(
                f,
                "Dividng when the numerator is bigger than the denominator leads to a value greater than 1"
            ),
        }
    }
}