slice-group-by

An implementation of the group_by Haskell function for slices only.

It provides tools for efficiently iterating over a slice by groups defined by a function that specifies if two elements are in the same group.

Differences with Itertools::group_by

The Itertools::group_by method use a key to compare elements, this library works like, say, slice::sort_by, it uses a comparison function. It works on every Iterator type, slice-group-by work only with mutable and immutable slices, which is the power of this library, it is fast thanks to data locality.

Also slice-group-by support multiple search algorithms (i.e. linear, binary and exponential search) and can return groups starting from the end.

Examples

Linear Searched Immutable Groups

You will only need to define a function that returns true if two elements are in the same group.

The LinearGroupBy iterator will always gives contiguous elements to the predicate function.

use slice_group_by::GroupBy;

let slice = &[1, 1, 1, 3, 3, 2, 2, 2];

let mut iter = slice.linear_group_by(|a, b| a == b);

assert_eq!(iter.next(), Some(&[1, 1, 1][..]));
assert_eq!(iter.next(), Some(&[3, 3][..]));
assert_eq!(iter.next(), Some(&[2, 2, 2][..]));
assert_eq!(iter.next(), None);

Binary Searched Mutable Groups

It is also possible to get mutable non overlapping groups of a slice.

The BinaryGroupBy/Mut and ExponentialGroupBy/Mut iterators will not necessarily gives contiguous elements to the predicate function. The predicate function should implement an order consistent with the sort order of the slice.

use slice_group_by::GroupByMut;

let slice = &mut [1, 1, 1, 2, 2, 2, 3, 3];

let mut iter = slice.binary_group_by_mut(|a, b| a == b);

assert_eq!(iter.next(), Some(&mut [1, 1, 1][..]));
assert_eq!(iter.next(), Some(&mut [2, 2, 2][..]));
assert_eq!(iter.next(), Some(&mut [3, 3][..]));
assert_eq!(iter.next(), None);

Exponential Searched Mutable Groups starting from the End

It is also possible to get mutable non overlapping groups of a slice even starting from end of it.

use slice_group_by::GroupByMut;

let slice = &mut [1, 1, 1, 2, 2, 2, 3, 3];

let mut iter = slice.exponential_group_by_mut(|a, b| a == b).rev();

assert_eq!(iter.next(), Some(&mut [3, 3][..]));
assert_eq!(iter.next(), Some(&mut [2, 2, 2][..]));
assert_eq!(iter.next(), Some(&mut [1, 1, 1][..]));
assert_eq!(iter.next(), None);