Struct NonEmptyVec

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

Expand description

Non-empty vector.

Fields§

§head: T§tail: Vec<T>

Implementations§

§

impl<T> NonEmptyVec<T>

pub const fn new(e: T) -> NonEmptyVec<T>

Alias for NonEmptyVec::singleton.

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

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

pub fn collect(iter: I) -> Option<NonEmptyVec<T>>
where I: IntoIterator<Item = T>,

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

pub const fn singleton(head: T) -> NonEmptyVec<T>

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 rama_utils::collections::NonEmptyVec;

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

let mut non_empty = NonEmptyVec::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 rama_utils::collections::NonEmptyVec;

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

let non_empty = NonEmptyVec::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 rama_utils::collections::NonEmptyVec;

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

pub fn len(&self) -> usize

Get the length of the list.

pub fn len_nonzero(&self) -> NonZero<usize>

Gets the length of the list as a NonZeroUsize.

pub fn capacity(&self) -> NonZero<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 rama_utils::collections::NonEmptyVec;

let mut l = NonEmptyVec::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: NonZero<usize>)

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

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

use rama_utils::collections::NonEmptyVec;

let mut l = NonEmptyVec::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

use rama_utils::collections::NonEmptyVec;

let mut l = NonEmptyVec::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<NonEmptyVec<T>>
where T: Clone,

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

§Example Use

use rama_utils::collections::NonEmptyVec;

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

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

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

Often we have a Vec (or slice &[T]) but want to ensure that it is NonEmptyVec before proceeding with a computation. Using from_vec will give us a proof that we have a NonEmptyVec 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 NonEmptyVec::from_slice.

§Example Use

use rama_utils::collections::NonEmptyVec;

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

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

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

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

§Example Use

use rama_utils::collections::NonEmptyVec;

let mut non_empty = NonEmptyVec::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 = NonEmptyVec::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 NonEmptyVec into its first, last, and middle elements, in that order.

If there is only one element then last is None.

§Example Use

use rama_utils::collections::NonEmptyVec;

let mut non_empty = NonEmptyVec::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 = NonEmptyVec::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 NonEmptyVec.

§Example Use

use rama_utils::collections::NonEmptyVec;

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

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

assert_eq!(non_empty, expected);

pub fn map<U, F>(self, f: F) -> NonEmptyVec
where F: FnMut(T) -> U,

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

§Examples

use rama_utils::collections::NonEmptyVec;

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

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

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

assert_eq!(squares, expected);

pub fn try_map<E, U, F>(self, f: F) -> Result<NonEmptyVec, E>
where F: FnMut(T) -> Result<U, E>,

A structure preserving, fallible mapping function.

pub fn flat_map<U, F>(self, f: F) -> NonEmptyVec
where F: FnMut(T) -> NonEmptyVec,

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

§Examples

use rama_utils::collections::NonEmptyVec;

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

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

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

assert_eq!(windows, expected);

pub fn flatten(full: NonEmptyVec<NonEmptyVec<T>>) -> NonEmptyVec<T>

Flatten nested NonEmptyVecs into a single one.

§Examples

use rama_utils::collections::NonEmptyVec;

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

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

assert_eq!(NonEmptyVec::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 rama_utils::collections::NonEmptyVec;

let non_empty = NonEmptyVec::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 rama_utils::collections::NonEmptyVec;

let mut non_empty = NonEmptyVec::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, NonEmptyVec::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 rama_utils::collections::NonEmptyVec;

let non_empty = NonEmptyVec::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 rama_utils::collections::NonEmptyVec;

let non_empty = NonEmptyVec::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, });