Function visioncortex::disjoint_sets::group_by

pub fn group_by<T, F>(items: Vec<T>, should_group: F) -> Vec<Vec<T>> where
    F: Fn(&T, &T) -> bool, 

Groups items with a equivalence testing function.

The testing function should define a equivalence relation ~ on the set of elements and return true for elements a and b if-and-only-if a ~ b. This implies that the function is commutative, i.e. should_group(a, b) == should_group(b, a).

Example

use visioncortex::disjoint_sets::group_by;
let points = vec![1,1,7,9,24,1,4,7,3,8];
let groups = group_by(points, |&x, &y| {
    (x - y) * (x - y) < 2
});
// should be grouped as below:
// {1, 1, 1}, {3, 4}, {7, 7, 8, 9}, {24}
for mut group in groups {
    println!("{:?}", group);
    group.sort();
    if group.len() == 4 {
        assert_eq!(group, [7, 7, 8, 9]);
    } else if group.len() == 3 {
        assert_eq!(group, [1, 1, 1]);
    } else if group.len() == 2 {
        assert_eq!(group, [3, 4]);
    } else {
        assert_eq!(group, [24]);
    }
}