devela/data/list/link/
const.rs

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1// devela::data::list::link:const
2//
3// This is a modified version of:
4// [`const_list`](https://crates.io/crates/const_list/0.1.0)
5
6use crate::ConstDefault;
7
8/// A linked list node in a `ConstList`.
9#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
10struct ConstListItem<'a, T: 'a> {
11    /// The item represented by this node.
12    first: T,
13    /// The rest of the list.
14    rest: &'a ConstList<'a, T>,
15}
16
17#[doc = crate::TAG_DATA_STRUCTURE!()]
18/// An immutable, append-only, linear, functional, non-contiguous, list.
19///
20/// A safe, predictable, and lightweight structure, suitable where immutability
21/// is an asset and compile-time guarantees matter more than list manipulation.
22///
23/// # Example
24/// ```
25/// # use devela::ConstList;
26/// const MY_LIST: ConstList<'static, i32> = ConstList::new()
27///     .push(2)
28///     .push(4)
29///     .push(8);
30///
31/// assert_eq!(8, *MY_LIST.pop().0.unwrap());
32/// ```
33#[doc = crate::doc_!(vendor: "const_list")]
34#[must_use]
35#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Hash)]
36pub struct ConstList<'a, T: 'a>(Option<ConstListItem<'a, T>>);
37
38impl<T> ConstDefault for ConstList<'_, T> {
39    const DEFAULT: Self = Self::new();
40}
41
42impl<'a, T: 'a> ConstList<'a, T> {
43    /// Creates a new, empty list.
44    pub const fn new() -> Self {
45        Self(None)
46    }
47
48    /// Gets a reference to the item at the provided index in this list, if any.
49    #[must_use]
50    pub const fn get(&self, index: usize) -> Option<&T> {
51        if let Some(value) = &self.0 {
52            if index == 0 {
53                Some(&value.first)
54            } else {
55                value.rest.get(index - 1)
56            }
57        } else {
58            None
59        }
60    }
61
62    /// Determines the length of this list.
63    #[must_use]
64    pub const fn len(&self) -> usize {
65        if let Some(value) = &self.0 {
66            value.rest.len() + 1
67        } else {
68            0
69        }
70    }
71
72    /// Whether the list is empty.
73    #[must_use]
74    pub const fn is_empty(&self) -> bool {
75        self.0.is_none()
76    }
77
78    /// Pushes a new item onto the beginning of this list,
79    /// producing a new list head.
80    pub const fn push(&'a self, value: T) -> Self {
81        ConstList(Some(ConstListItem { first: value, rest: self }))
82    }
83
84    /// Removes the first item (if any) from this list, and produces
85    /// the rest of the list.
86    pub const fn pop(&'a self) -> (Option<&'a T>, &'a Self) {
87        if let Some(value) = &self.0 {
88            (Some(&value.first), value.rest)
89        } else {
90            (None, self)
91        }
92    }
93
94    /// Creates an iterator over the contents of the list.
95    pub const fn iter(&self) -> ConstListIterator<T> {
96        ConstListIterator { target: self }
97    }
98}
99
100impl<'a, T> IntoIterator for &'a ConstList<'a, T> {
101    type Item = &'a T;
102    type IntoIter = ConstListIterator<'a, T>;
103
104    fn into_iter(self) -> Self::IntoIter {
105        ConstListIterator { target: self }
106    }
107}
108
109#[doc = crate::TAG_ITERATOR!()]
110/// Iterates over the contents of a [`ConstList`].
111#[must_use]
112#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
113pub struct ConstListIterator<'a, T> {
114    /// The current list head.
115    target: &'a ConstList<'a, T>,
116}
117impl<'a, T> Iterator for ConstListIterator<'a, T> {
118    type Item = &'a T;
119
120    fn next(&mut self) -> Option<Self::Item> {
121        let (first, rest) = self.target.pop();
122        self.target = rest;
123        first
124    }
125}
devela/data/list/link/const.rs

devela/data/list/link/
const.rs
