Trait Inverse

Source

pub trait Inverse<T>: Reduction<T> {
    // Required methods
    fn inverse(acc: Self::Total, x: T) -> (Self::Total, bool);
    fn undo(a: Self::Total, b: Self::Total) -> (Self::Total, bool);
    fn alternating(x: &[T]) -> (Self::Total, bool);

    // Provided method
    fn fits(_: Self::Total) -> bool { ... }
}

Expand description

A reduction whose step can be undone, as Alternated folds by it: Sum subtracts, and ScaledProduct and Product divide. An integer difference fits only within i64, a complex quotient only inside the normal range, and a float quotient only where no item, or product of the running mantissa and an item, leaves the normal floats. An alternated fold can then fail where the right fold taken item by item, or its exact result, would fit.

Required Methods§

Source

fn inverse(acc: Self::Total, x: T) -> (Self::Total, bool)

acc with the item x taken away, and whether it fits.

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fn undo(a: Self::Total, b: Self::Total) -> (Self::Total, bool)

The fold a with the fold b of the next run taken away, and whether it fits.

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fn alternating(x: &[T]) -> (Self::Total, bool)

The right fold of the slice x by the inverse, and whether it fits: for sums through a sum at each parity (alternated), and for products through the pairs’ quotients (pairwise).