Struct NonEmpty

pub struct NonEmpty<T> {
    pub head: T,
    pub tail: Vec<T>,
}

Non-empty vector.

Fields

head: T

tail: Vec<T>

Implementations

impl<T> NonEmpty<T>

pub const fn new(e: T) -> Self

Alias for NonEmpty::singleton.

pub fn as_ref(&self) -> NonEmpty<&T>

Converts from &NonEmpty<T> to NonEmpty<&T>.

pub fn collect<I>(iter: I) -> Option<NonEmpty<T>>

where I: IntoIterator<Item = T>,

Attempt to convert an iterator into a NonEmpty vector. Returns None if the iterator was empty.

pub const fn singleton(head: T) -> Self

Create a new non-empty list with an initial element.

pub const fn is_empty(&self) -> bool

Always returns false.

pub const fn first(&self) -> &T

Get the first element. Never fails.

pub fn first_mut(&mut self) -> &mut T

Get the mutable reference to the first element. Never fails.

Examples

use nonempty::NonEmpty;

let mut non_empty = NonEmpty::new(42);
let head = non_empty.first_mut();
*head += 1;
assert_eq!(non_empty.first(), &43);

let mut non_empty = NonEmpty::from((1, vec![4, 2, 3]));
let head = non_empty.first_mut();
*head *= 42;
assert_eq!(non_empty.first(), &42);

pub fn tail(&self) -> &[T]

Get the possibly-empty tail of the list.

use nonempty::NonEmpty;

let non_empty = NonEmpty::new(42);
assert_eq!(non_empty.tail(), &[]);

let non_empty = NonEmpty::from((1, vec![4, 2, 3]));
assert_eq!(non_empty.tail(), &[4, 2, 3]);

pub fn push(&mut self, e: T)

Push an element to the end of the list.

pub fn pop(&mut self) -> Option<T>

Pop an element from the end of the list.

pub fn insert(&mut self, index: usize, element: T)

Inserts an element at position index within the vector, shifting all elements after it to the right.

Panics

Panics if index > len.

Examples

use nonempty::NonEmpty;

let mut non_empty = NonEmpty::from((1, vec![2, 3]));
non_empty.insert(1, 4);
assert_eq!(non_empty, NonEmpty::from((1, vec![4, 2, 3])));
non_empty.insert(4, 5);
assert_eq!(non_empty, NonEmpty::from((1, vec![4, 2, 3, 5])));
non_empty.insert(0, 42);
assert_eq!(non_empty, NonEmpty::from((42, vec![1, 4, 2, 3, 5])));

pub fn len(&self) -> usize

Get the length of the list.

pub fn len_nonzero(&self) -> NonZeroUsize

Gets the length of the list as a NonZeroUsize.

pub fn capacity(&self) -> usize

Get the capacity of the list.

pub fn last(&self) -> &T

Get the last element. Never fails.

pub fn last_mut(&mut self) -> &mut T

Get the last element mutably.

pub fn contains(&self, x: &T) -> bool

where T: PartialEq,

Check whether an element is contained in the list.

use nonempty::NonEmpty;

let mut l = NonEmpty::from((42, vec![36, 58]));

assert!(l.contains(&42));
assert!(!l.contains(&101));

pub fn get(&self, index: usize) -> Option<&T>

Get an element by index.

pub fn get_mut(&mut self, index: usize) -> Option<&mut T>

Get an element by index, mutably.

pub fn truncate(&mut self, len: usize)

Truncate the list to a certain size. Must be greater than 0.

pub fn iter(&self) -> Iter<'_, T>

use nonempty::NonEmpty;

let mut l = NonEmpty::from((42, vec![36, 58]));

let mut l_iter = l.iter();

assert_eq!(l_iter.len(), 3);
assert_eq!(l_iter.next(), Some(&42));
assert_eq!(l_iter.next(), Some(&36));
assert_eq!(l_iter.next(), Some(&58));
assert_eq!(l_iter.next(), None);

pub fn iter_mut(&mut self) -> impl DoubleEndedIterator<Item = &mut T> + '_

use nonempty::NonEmpty;

let mut l = NonEmpty::new(42);
l.push(36);
l.push(58);

for i in l.iter_mut() {
    *i *= 10;
}

let mut l_iter = l.iter();

assert_eq!(l_iter.next(), Some(&420));
assert_eq!(l_iter.next(), Some(&360));
assert_eq!(l_iter.next(), Some(&580));
assert_eq!(l_iter.next(), None);

pub fn from_slice(slice: &[T]) -> Option<NonEmpty<T>>

where T: Clone,

Often we have a Vec (or slice &[T]) but want to ensure that it is NonEmpty before proceeding with a computation. Using from_slice will give us a proof that we have a NonEmpty in the Some branch, otherwise it allows the caller to handle the None case.

Example Use

use nonempty::NonEmpty;

let non_empty_vec = NonEmpty::from_slice(&[1, 2, 3, 4, 5]);
assert_eq!(non_empty_vec, Some(NonEmpty::from((1, vec![2, 3, 4, 5]))));

let empty_vec: Option<NonEmpty<&u32>> = NonEmpty::from_slice(&[]);
assert!(empty_vec.is_none());

pub fn from_vec(vec: Vec<T>) -> Option<NonEmpty<T>>

Often we have a Vec (or slice &[T]) but want to ensure that it is NonEmpty before proceeding with a computation. Using from_vec will give us a proof that we have a NonEmpty in the Some branch, otherwise it allows the caller to handle the None case.

This version will consume the Vec you pass in. If you would rather pass the data as a slice then use NonEmpty::from_slice.

Example Use

use nonempty::NonEmpty;

let non_empty_vec = NonEmpty::from_vec(vec![1, 2, 3, 4, 5]);
assert_eq!(non_empty_vec, Some(NonEmpty::from((1, vec![2, 3, 4, 5]))));

let empty_vec: Option<NonEmpty<&u32>> = NonEmpty::from_vec(vec![]);
assert!(empty_vec.is_none());

pub fn split_first(&self) -> (&T, &[T])

Deconstruct a NonEmpty into its head and tail. This operation never fails since we are guaranteed to have a head element.

Example Use

use nonempty::NonEmpty;

let mut non_empty = NonEmpty::from((1, vec![2, 3, 4, 5]));

// Guaranteed to have the head and we also get the tail.
assert_eq!(non_empty.split_first(), (&1, &[2, 3, 4, 5][..]));

let non_empty = NonEmpty::new(1);

// Guaranteed to have the head element.
assert_eq!(non_empty.split_first(), (&1, &[][..]));

pub fn split(&self) -> (&T, &[T], Option<&T>)

Deconstruct a NonEmpty into its first, last, and middle elements, in that order.

If there is only one element then last is None.

Example Use

use nonempty::NonEmpty;

let mut non_empty = NonEmpty::from((1, vec![2, 3, 4, 5]));

// When there are two or more elements, the last element is represented
// as a `Some`. Elements preceding it, except for the first, are returned
// in the middle.
assert_eq!(non_empty.split(), (&1, &[2, 3, 4][..], Some(&5)));

let non_empty = NonEmpty::new(1);

// The last element is `None` when there's only one element.
assert_eq!(non_empty.split(), (&1, &[][..], None));

pub fn append(&mut self, other: &mut Vec<T>)

Append a Vec to the tail of the NonEmpty.

Example Use

use nonempty::NonEmpty;

let mut non_empty = NonEmpty::new(1);
let mut vec = vec![2, 3, 4, 5];
non_empty.append(&mut vec);

let mut expected = NonEmpty::from((1, vec![2, 3, 4, 5]));

assert_eq!(non_empty, expected);

pub fn map<U, F>(self, f: F) -> NonEmpty<U>

where F: FnMut(T) -> U,

A structure preserving map. This is useful for when we wish to keep the NonEmpty structure guaranteeing that there is at least one element. Otherwise, we can use nonempty.iter().map(f).

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((1, vec![2, 3, 4, 5]));

let squares = non_empty.map(|i| i * i);

let expected = NonEmpty::from((1, vec![4, 9, 16, 25]));

assert_eq!(squares, expected);

pub fn try_map<E, U, F>(self, f: F) -> Result<NonEmpty<U>, E>

where F: FnMut(T) -> Result<U, E>,

A structure preserving, fallible mapping function.

pub fn flat_map<U, F>(self, f: F) -> NonEmpty<U>

where F: FnMut(T) -> NonEmpty<U>,

When we have a function that goes from some T to a NonEmpty<U>, we may want to apply it to a NonEmpty<T> but keep the structure flat. This is where flat_map shines.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((1, vec![2, 3, 4, 5]));

let windows = non_empty.flat_map(|i| {
    let mut next = NonEmpty::new(i + 5);
    next.push(i + 6);
    next
});

let expected = NonEmpty::from((6, vec![7, 7, 8, 8, 9, 9, 10, 10, 11]));

assert_eq!(windows, expected);

pub fn flatten(full: NonEmpty<NonEmpty<T>>) -> Self

Flatten nested NonEmptys into a single one.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((
    NonEmpty::from((1, vec![2, 3])),
    vec![NonEmpty::from((4, vec![5]))],
));

let expected = NonEmpty::from((1, vec![2, 3, 4, 5]));

assert_eq!(NonEmpty::flatten(non_empty), expected);

pub fn binary_search(&self, x: &T) -> Result<usize, usize>

where T: Ord,

Binary searches this sorted non-empty vector for a given element.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned.

If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((0, vec![1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]));
assert_eq!(non_empty.binary_search(&0),   Ok(0));
assert_eq!(non_empty.binary_search(&13),  Ok(9));
assert_eq!(non_empty.binary_search(&4),   Err(7));
assert_eq!(non_empty.binary_search(&100), Err(13));
let r = non_empty.binary_search(&1);
assert!(match r { Ok(1..=4) => true, _ => false, });

If you want to insert an item to a sorted non-empty vector, while maintaining sort order:

use nonempty::NonEmpty;

let mut non_empty = NonEmpty::from((0, vec![1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]));
let num = 42;
let idx = non_empty.binary_search(&num).unwrap_or_else(|x| x);
non_empty.insert(idx, num);
assert_eq!(non_empty, NonEmpty::from((0, vec![1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55])));

pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>

where F: FnMut(&'a T) -> Ordering,

Binary searches this sorted non-empty with a comparator function.

The comparator function should implement an order consistent with the sort order of the underlying slice, returning an order code that indicates whether its argument is Less, Equal or Greater the desired target.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

Looks up a series of four elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1,4].

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((0, vec![1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]));
let seek = 0;
assert_eq!(non_empty.binary_search_by(|probe| probe.cmp(&seek)), Ok(0));
let seek = 13;
assert_eq!(non_empty.binary_search_by(|probe| probe.cmp(&seek)), Ok(9));
let seek = 4;
assert_eq!(non_empty.binary_search_by(|probe| probe.cmp(&seek)), Err(7));
let seek = 100;
assert_eq!(non_empty.binary_search_by(|probe| probe.cmp(&seek)), Err(13));
let seek = 1;
let r = non_empty.binary_search_by(|probe| probe.cmp(&seek));
assert!(match r { Ok(1..=4) => true, _ => false, });

pub fn binary_search_by_key<'a, B, F>( &'a self, b: &B, f: F, ) -> Result<usize, usize>

where B: Ord, F: FnMut(&'a T) -> B,

Binary searches this sorted non-empty vector with a key extraction function.

Assumes that the vector is sorted by the key.

If the value is found then Result::Ok is returned, containing the index of the matching element. If there are multiple matches, then any one of the matches could be returned. If the value is not found then Result::Err is returned, containing the index where a matching element could be inserted while maintaining sorted order.

Examples

Looks up a series of four elements in a non-empty vector of pairs sorted by their second elements. The first is found, with a uniquely determined position; the second and third are not found; the fourth could match any position in [1, 4].

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((
    (0, 0),
    vec![(2, 1), (4, 1), (5, 1), (3, 1),
         (1, 2), (2, 3), (4, 5), (5, 8), (3, 13),
         (1, 21), (2, 34), (4, 55)]
));

assert_eq!(non_empty.binary_search_by_key(&0, |&(a,b)| b),  Ok(0));
assert_eq!(non_empty.binary_search_by_key(&13, |&(a,b)| b),  Ok(9));
assert_eq!(non_empty.binary_search_by_key(&4, |&(a,b)| b),   Err(7));
assert_eq!(non_empty.binary_search_by_key(&100, |&(a,b)| b), Err(13));
let r = non_empty.binary_search_by_key(&1, |&(a,b)| b);
assert!(match r { Ok(1..=4) => true, _ => false, });

pub fn maximum(&self) -> &T

where T: Ord,

Returns the maximum element in the non-empty vector.

This will return the first item in the vector if the tail is empty.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::new(42);
assert_eq!(non_empty.maximum(), &42);

let non_empty = NonEmpty::from((1, vec![-34, 42, 76, 4, 5]));
assert_eq!(non_empty.maximum(), &76);

pub fn minimum(&self) -> &T

where T: Ord,

Returns the minimum element in the non-empty vector.

This will return the first item in the vector if the tail is empty.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::new(42);
assert_eq!(non_empty.minimum(), &42);

let non_empty = NonEmpty::from((1, vec![-34, 42, 76, 4, 5]));
assert_eq!(non_empty.minimum(), &-34);

pub fn maximum_by<F>(&self, compare: F) -> &T

where F: FnMut(&T, &T) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function.

This will return the first item in the vector if the tail is empty.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::new((0, 42));
assert_eq!(non_empty.maximum_by(|(k, _), (l, _)| k.cmp(l)), &(0, 42));

let non_empty = NonEmpty::from(((2, 1), vec![(2, -34), (4, 42), (0, 76), (1, 4), (3, 5)]));
assert_eq!(non_empty.maximum_by(|(k, _), (l, _)| k.cmp(l)), &(4, 42));

pub fn minimum_by<F>(&self, compare: F) -> &T

where F: FnMut(&T, &T) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function.

This will return the first item in the vector if the tail is empty.

use nonempty::NonEmpty;

let non_empty = NonEmpty::new((0, 42));
assert_eq!(non_empty.minimum_by(|(k, _), (l, _)| k.cmp(l)), &(0, 42));

let non_empty = NonEmpty::from(((2, 1), vec![(2, -34), (4, 42), (0, 76), (1, 4), (3, 5)]));
assert_eq!(non_empty.minimum_by(|(k, _), (l, _)| k.cmp(l)), &(0, 76));

pub fn maximum_by_key<U, F>(&self, f: F) -> &T

where U: Ord, F: FnMut(&T) -> U,

Returns the element that gives the maximum value with respect to the specified function.

This will return the first item in the vector if the tail is empty.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::new((0, 42));
assert_eq!(non_empty.maximum_by_key(|(k, _)| *k), &(0, 42));

let non_empty = NonEmpty::from(((2, 1), vec![(2, -34), (4, 42), (0, 76), (1, 4), (3, 5)]));
assert_eq!(non_empty.maximum_by_key(|(k, _)| *k), &(4, 42));
assert_eq!(non_empty.maximum_by_key(|(k, _)| -k), &(0, 76));

pub fn minimum_by_key<U, F>(&self, f: F) -> &T

where U: Ord, F: FnMut(&T) -> U,

Returns the element that gives the minimum value with respect to the specified function.

This will return the first item in the vector if the tail is empty.

Examples

use nonempty::NonEmpty;

let non_empty = NonEmpty::new((0, 42));
assert_eq!(non_empty.minimum_by_key(|(k, _)| *k), &(0, 42));

let non_empty = NonEmpty::from(((2, 1), vec![(2, -34), (4, 42), (0, 76), (1, 4), (3, 5)]));
assert_eq!(non_empty.minimum_by_key(|(k, _)| *k), &(0, 76));
assert_eq!(non_empty.minimum_by_key(|(k, _)| -k), &(4, 42));

pub fn sort(&mut self)

where T: Ord,

Sorts the nonempty.

The implementation uses slice::sort for the tail and then checks where the head belongs. If the head is already the smallest element, this should be as fast as sorting a slice. However, if the head needs to be inserted, then it incurs extra cost for removing the new head from the tail and adding the old head at the correct index.

Examples

use nonempty::nonempty;

let mut non_empty = nonempty![-5, 4, 1, -3, 2];

non_empty.sort();
assert!(non_empty == nonempty![-5, -3, 1, 2, 4]);

Trait Implementations

impl<T: Clone> Clone for NonEmpty<T>

fn clone(&self) -> NonEmpty<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for NonEmpty<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Default> Default for NonEmpty<T>

fn default() -> Self

Returns the “default value” for a type.

impl<A> Extend<A> for NonEmpty<A>

fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<T> From<(T, Vec<T>)> for NonEmpty<T>

fn from((head, tail): (T, Vec<T>)) -> Self

Turns a pair of an element and a Vec into a NonEmpty.

impl<T> From<NonEmpty<T>> for (T, Vec<T>)

fn from(nonempty: NonEmpty<T>) -> (T, Vec<T>)

Turns a non-empty list into a Vec.

impl<T> From<NonEmpty<T>> for NonEmpty<T>

fn from(other: NonEmpty<T>) -> NonEmpty<T>

Converts to this type from the input type.

impl<T> From<NonEmpty<T>> for Vec<T>

fn from(nonempty: NonEmpty<T>) -> Vec<T>

Turns a non-empty list into a Vec.

impl<T: Hash> Hash for NonEmpty<T>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T> Index<usize> for NonEmpty<T>

fn index(&self, index: usize) -> &T

use nonempty::NonEmpty;

let non_empty = NonEmpty::from((1, vec![2, 3, 4, 5]));

assert_eq!(non_empty[0], 1);
assert_eq!(non_empty[1], 2);
assert_eq!(non_empty[3], 4);

type Output = T

The returned type after indexing.

impl<T> IndexMut<usize> for NonEmpty<T>

fn index_mut(&mut self, index: usize) -> &mut T

Performs the mutable indexing (container[index]) operation.

impl<'a, T> IntoIterator for &'a NonEmpty<T>

type Item = &'a T

The type of the elements being iterated over.

type IntoIter = Chain<Once<&'a T>, Iter<'a, T>>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<T> IntoIterator for NonEmpty<T>

type Item = T

The type of the elements being iterated over.

type IntoIter = Chain<Once<T>, IntoIter<<NonEmpty<T> as IntoIterator>::Item>>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<T: Ord> Ord for NonEmpty<T>

fn cmp(&self, other: &NonEmpty<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T: PartialEq> PartialEq for NonEmpty<T>

fn eq(&self, other: &NonEmpty<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: PartialOrd> PartialOrd for NonEmpty<T>

fn partial_cmp(&self, other: &NonEmpty<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: Eq> Eq for NonEmpty<T>

impl<T> StructuralPartialEq for NonEmpty<T>