Partition with two predicate

Question

I am looking for a way to partition a Vec with two predicate :

• One for the first partition point. For example x > 3
• One for the last element of the partition. For example x < 7

And so for example this vector :

[1, 2, 3, 4, 5, 6, 7, 8, 9]

having this slice :

[4, 5, 6]

I think I can use partition_point twice like the example on std. But is there another method (or crate) where I can pass directly two predicate and slice between the first match of the first predicate and the first match of the second predicate ?

Answer 1

This is pretty trivial to implement yourself. It's just a function that takes a slice and two predicates, and returns a subslice:

fn partition<T, P1, P2>(i: &[T], mut p1: P1, mut p2: P2) -> &[T]
    where P1: FnMut(&T) -> bool,
          P2: FnMut(&T) -> bool
{
    let mut start: usize = 0;

    while start < i.len() && !p1(&i[start]) {
        start += 1;
    }

    let mut end = start;

    while end < i.len() && p2(&i[end]) {
        end += 1;
    }

    &i[start..end]
}

(Playground)