lender/sources/
repeat_with.rs

1use core::marker::PhantomData;
2
3use crate::{prelude::*, FusedLender};
4
5/// Creates a new iterator that repeats elements of type `A` endlessly by
6/// applying the provided closure, the repeater, `F: FnMut() -> A`.
7///
8/// The `repeat_with()` function calls the repeater over and over again.
9///
10/// See [`iter::repeat_with()`](core::iter::repeat_with) for more information.
11/// # Examples
12/// ```rust
13/// # use lender::prelude::*;
14/// let mut lender = lender::repeat_with::<lend!(&'lend u8), _>(|| &0u8);
15/// assert_eq!(lender.next(), Some(&0));
16/// ```
17pub fn repeat_with<'a, L, F>(f: F) -> RepeatWith<'a, L, F>
18where
19    L: ?Sized + for<'all> Lending<'all> + 'a,
20    F: FnMut() -> Lend<'a, L>,
21{
22    RepeatWith { f, _marker: PhantomData }
23}
24
25/// A lender that repeats an element endlessly by applying a closure.
26///
27/// This `struct` is created by the [`repeat_with()`] function.
28pub struct RepeatWith<'a, L: ?Sized, F> {
29    f: F,
30    _marker: core::marker::PhantomData<&'a L>,
31}
32
33impl<'lend, 'a, L, F> Lending<'lend> for RepeatWith<'a, L, F>
34where
35    L: ?Sized + for<'all> Lending<'all> + 'a,
36    F: FnMut() -> Lend<'a, L>,
37{
38    type Lend = Lend<'lend, L>;
39}
40
41impl<'a, L, F> Lender for RepeatWith<'a, L, F>
42where
43    L: ?Sized + for<'all> Lending<'all> + 'a,
44    F: FnMut() -> Lend<'a, L>,
45{
46    #[inline]
47    fn next(&mut self) -> Option<Lend<'_, Self>> {
48        // SAFETY: 'a: 'lend
49        Some(unsafe { core::mem::transmute::<Lend<'a, L>, Lend<'_, L>>((self.f)()) })
50    }
51    #[inline]
52    fn advance_by(&mut self, _n: usize) -> Result<(), core::num::NonZeroUsize> {
53        Ok(())
54    }
55}
56
57impl<'a, L, F> FusedLender for RepeatWith<'a, L, F>
58where
59    L: ?Sized + for<'all> Lending<'all> + 'a,
60    F: FnMut() -> Lend<'a, L>,
61{
62}
63
64/// Creates a new fallible iterator that repeats elements of type `Result<A, E>`
65/// endlessly by applying the provided closure, the repeater,
66/// `F: FnMut() -> Result<A, E>`.
67///
68/// The `fallible_repeat_with()` function calls the repeater over and over again.
69///
70/// See [`iter::repeat_with()`](core::iter::repeat_with) for more information.
71pub fn fallible_repeat_with<'a, L, E, F>(f: F) -> FallibleRepeatWith<'a, L, E, F>
72where
73    L: ?Sized + for<'all> FallibleLending<'all> + 'a,
74    F: FnMut() -> Result<FallibleLend<'a, L>, E>,
75{
76    FallibleRepeatWith { f, _marker: PhantomData }
77}
78
79/// A fallible lender that repeats an element endlessly by applying a closure.
80///
81/// This `struct` is created by the [`fallible_repeat_with()`] function.
82pub struct FallibleRepeatWith<'a, L: ?Sized, E, F> {
83    f: F,
84    _marker: core::marker::PhantomData<(&'a L, E)>,
85}
86
87impl<'lend, 'a, L, E, F> FallibleLending<'lend> for FallibleRepeatWith<'a, L, E, F>
88where
89    L: ?Sized + for<'all> FallibleLending<'all> + 'a,
90    F: FnMut() -> Result<FallibleLend<'a, L>, E>,
91{
92    type Lend = FallibleLend<'lend, L>;
93}
94
95impl<'a, L, E, F> FallibleLender for FallibleRepeatWith<'a, L, E, F>
96where
97    L: ?Sized + for<'all> FallibleLending<'all> + 'a,
98    F: FnMut() -> Result<FallibleLend<'a, L>, E>,
99{
100    type Error = E;
101
102    #[inline]
103    fn next(&mut self) -> Result<Option<FallibleLend<'_, Self>>, Self::Error> {
104        (self.f)().map(|value| {
105            Some(
106                // SAFETY: 'a: 'lend
107                unsafe { core::mem::transmute::<FallibleLend<'a, L>, FallibleLend<'_, L>>(value) },
108            )
109        })
110    }
111    #[inline]
112    fn advance_by(&mut self, _n: usize) -> Result<Option<core::num::NonZeroUsize>, Self::Error> {
113        Ok(None)
114    }
115}
lender/sources/repeat_with.rs

lender/sources/
repeat_with.rs
