narrow/
length.rs

1//! The length (number of elements) of a collection.
2
3use std::{collections::VecDeque, rc::Rc, sync::Arc};
4
5/// The length (or number of elements) of a collection.
6pub trait Length {
7    /// Returns the number of elements in the collection, also referred to as
8    /// its length.
9    fn len(&self) -> usize;
10
11    /// Returns `true` if there are no elements in the collection.
12    #[inline]
13    fn is_empty(&self) -> bool {
14        self.len() == 0
15    }
16}
17
18impl<const N: usize, T> Length for [T; N] {
19    fn len(&self) -> usize {
20        N
21    }
22}
23
24impl<T> Length for [T] {
25    #[inline]
26    fn len(&self) -> usize {
27        <[T]>::len(self)
28    }
29}
30
31impl<T> Length for &[T] {
32    #[inline]
33    fn len(&self) -> usize {
34        <[T]>::len(self)
35    }
36}
37
38impl<T> Length for &mut [T] {
39    #[inline]
40    fn len(&self) -> usize {
41        <[T]>::len(self)
42    }
43}
44
45impl<T> Length for Vec<T> {
46    #[inline]
47    fn len(&self) -> usize {
48        Vec::len(self)
49    }
50}
51
52impl<T> Length for Box<[T]> {
53    #[inline]
54    fn len(&self) -> usize {
55        <[T]>::len(self)
56    }
57}
58
59impl<T> Length for Rc<[T]> {
60    #[inline]
61    fn len(&self) -> usize {
62        <[T]>::len(self)
63    }
64}
65
66impl<T> Length for Arc<[T]> {
67    #[inline]
68    fn len(&self) -> usize {
69        <[T]>::len(self)
70    }
71}
72
73impl<T> Length for VecDeque<T> {
74    #[inline]
75    fn len(&self) -> usize {
76        VecDeque::len(self)
77    }
78}
79
80impl Length for &str {
81    fn len(&self) -> usize {
82        str::len(self)
83    }
84}
85
86impl Length for String {
87    fn len(&self) -> usize {
88        String::len(self)
89    }
90}
91
92impl<T: Length> Length for Option<T> {
93    fn len(&self) -> usize {
94        self.as_ref().map_or(0, Length::len)
95    }
96}
97
98impl<T> Length for std::vec::IntoIter<T> {
99    fn len(&self) -> usize {
100        ExactSizeIterator::len(self)
101    }
102}
103
104impl<T> Length for std::slice::Iter<'_, T> {
105    fn len(&self) -> usize {
106        ExactSizeIterator::len(self)
107    }
108}
narrow/length.rs

narrow/
length.rs
