Function malachite_base::iterators::comparison::delta_directions

source · 
pub const fn delta_directions<I: Iterator>(xs: I) -> DeltaDirections<I> ⓘ
where
    I::Item: Ord,
Expand description

Returns an iterator that generates the Orderings of adjacent pairs of elements of a given iterator.

To put it another way (at least for types where subtraction is defined), the returned iterator produces the signs of the finite differences of the input iterator.

$f((x_k)_{k=0}^N) = (\operatorname{cmp}(x_k, x_{k-1}))_{k=1}^N$, where $N$ may be $\infty$.

The output length is infinite if xs is infinite, or $\max(n - 1, 0)$ otherwise, where $n$ is xs.count().

§Examples

use itertools::Itertools;
use malachite_base::iterators::comparison::delta_directions;
use std::cmp::Ordering::*;

assert_eq!(
    delta_directions([3, 1, 4, 1, 5, 9].into_iter()).collect_vec(),
    &[Less, Greater, Less, Greater, Greater]
)