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| 1 | +use core::ops::{Generator, GeneratorState}; |
| 2 | +use core::iter::{Iterator, FusedIterator}; |
| 3 | +use core::marker::Unpin; |
| 4 | +use core::pin::Pin; |
| 5 | + |
| 6 | +/// `GenIterReturn<G>` is a iterator for generator with return value. |
| 7 | +/// |
| 8 | +/// Differences with `GenIter<G>`: |
| 9 | +/// 1. able to get return value of a generator |
| 10 | +/// 2. safe to call `next()` after generator is done without panic |
| 11 | +/// 3. maybe less efficient than `GenIter<G>` |
| 12 | +#[derive(Copy, Clone, Debug)] |
| 13 | +pub struct GenIterReturn<G: Generator + Unpin>(Result<G::Return, G>); |
| 14 | + |
| 15 | +impl<G: Generator + Unpin> GenIterReturn<G> { |
| 16 | + #[inline] |
| 17 | + pub fn new(g: G) -> Self { |
| 18 | + GenIterReturn(Err(g)) |
| 19 | + } |
| 20 | + |
| 21 | + #[inline] |
| 22 | + pub fn is_done(&self) -> bool { |
| 23 | + self.0.is_ok() |
| 24 | + } |
| 25 | + |
| 26 | + #[inline] |
| 27 | + pub fn return_or_self(self) -> Result<G::Return, Self> { |
| 28 | + match self.0 { |
| 29 | + Ok(r) => Ok(r), |
| 30 | + Err(_) => Err(self), |
| 31 | + } |
| 32 | + } |
| 33 | +} |
| 34 | + |
| 35 | +impl<G: Generator + Unpin> Iterator for &mut GenIterReturn<G> { |
| 36 | + type Item = G::Yield; |
| 37 | + |
| 38 | + #[inline] |
| 39 | + fn next(&mut self) -> Option<Self::Item> { |
| 40 | + match self.0 { |
| 41 | + Ok(_) => None, |
| 42 | + Err(ref mut g) => match Pin::new(g).resume(()) { |
| 43 | + GeneratorState::Yielded(y) => Some(y), |
| 44 | + GeneratorState::Complete(r) => { |
| 45 | + self.0 = Ok(r); |
| 46 | + None |
| 47 | + }, |
| 48 | + } |
| 49 | + } |
| 50 | + } |
| 51 | +} |
| 52 | + |
| 53 | +impl<G: Generator + Unpin> FusedIterator for &mut GenIterReturn<G> {} |
| 54 | + |
| 55 | +impl<G: Generator + Unpin> From<G> for GenIterReturn<G> { |
| 56 | + #[inline] |
| 57 | + fn from(g: G) -> Self { |
| 58 | + GenIterReturn::new(g) |
| 59 | + } |
| 60 | +} |
| 61 | + |
| 62 | +/// macro to simplify iterator - via - generator with return value construction |
| 63 | +/// |
| 64 | +/// Examples: |
| 65 | +/// ``` |
| 66 | +/// #![feature(generators)] |
| 67 | +/// |
| 68 | +/// use gen_iter::gen_iter_return; |
| 69 | +/// |
| 70 | +/// let mut g = gen_iter_return!({ |
| 71 | +/// yield 1; |
| 72 | +/// yield 2; |
| 73 | +/// return "done"; |
| 74 | +/// }); |
| 75 | +/// |
| 76 | +/// assert_eq!((&mut g).collect::<Vec<_>>(), [1, 2]); // use `&mut g` as an iterator |
| 77 | +/// assert_eq!(g.is_done(), true); // check whether generator is done |
| 78 | +/// assert_eq!((&mut g).next(), None); // safe to call `next()` after done |
| 79 | +/// assert_eq!(g.return_or_self().ok(), Some("done")); // get return value of generator |
| 80 | +/// ``` |
| 81 | +/// We should use `&mut g` in `for` statement, to keep `g` be valid after `for`, so we can get the return value. |
| 82 | +/// ```compile_fail |
| 83 | +/// #![feature(generators)] |
| 84 | +/// |
| 85 | +/// use gen_iter::gen_iter_return; |
| 86 | +/// |
| 87 | +/// let mut g = gen_iter_return!({ |
| 88 | +/// yield 1; |
| 89 | +/// yield 2; |
| 90 | +/// return "done"; |
| 91 | +/// }); |
| 92 | +/// for v in g {} // compile failed, should use `&mut g` |
| 93 | +/// ``` |
| 94 | +#[macro_export] |
| 95 | +macro_rules! gen_iter_return { |
| 96 | + ($block: block) => { |
| 97 | + $crate::GenIterReturn::new(|| $block) |
| 98 | + }; |
| 99 | + (move $block: block) => { |
| 100 | + $crate::GenIterReturn::new(move || $block) |
| 101 | + } |
| 102 | +} |
| 103 | + |
| 104 | +#[cfg(test)] |
| 105 | +mod tests { |
| 106 | + use super::GenIterReturn; |
| 107 | + |
| 108 | + #[test] |
| 109 | + fn it_works() { |
| 110 | + let mut g = gen_iter_return!({ |
| 111 | + yield 1; |
| 112 | + yield 2; |
| 113 | + return "done"; |
| 114 | + }); |
| 115 | + |
| 116 | + assert_eq!((&mut g).next(), Some(1)); |
| 117 | + assert_eq!(g.is_done(), false); |
| 118 | + assert_eq!((&mut g).next(), Some(2)); |
| 119 | + assert_eq!(g.is_done(), false); |
| 120 | + assert_eq!((&mut g).next(), None); |
| 121 | + assert_eq!(g.is_done(), true); |
| 122 | + assert_eq!((&mut g).next(), None); |
| 123 | + assert_eq!(g.return_or_self().ok(), Some("done")); |
| 124 | + } |
| 125 | + |
| 126 | + #[test] |
| 127 | + fn gen_iter_return_from() { |
| 128 | + let mut g: GenIterReturn<_> = GenIterReturn::from(|| { |
| 129 | + yield 1; |
| 130 | + yield 2; |
| 131 | + return "done"; |
| 132 | + }); |
| 133 | + let mut gi = &mut g; |
| 134 | + |
| 135 | + assert_eq!(gi.next(), Some(1)); |
| 136 | + assert_eq!(gi.next(), Some(2)); |
| 137 | + assert_eq!(gi.next(), None); |
| 138 | + |
| 139 | + assert_eq!(g.is_done(), true); |
| 140 | + assert_eq!(g.return_or_self().ok(), Some("done")); |
| 141 | + } |
| 142 | + |
| 143 | + #[test] |
| 144 | + fn gen_iter_return_macro() { |
| 145 | + let mut g = gen_iter_return!({ |
| 146 | + yield 1; |
| 147 | + yield 2; |
| 148 | + return "done"; |
| 149 | + }); |
| 150 | + |
| 151 | + let mut sum = 0; |
| 152 | + let mut count = 0; |
| 153 | + for y in &mut g { |
| 154 | + sum += y; |
| 155 | + count += 1; |
| 156 | + } |
| 157 | + assert_eq!(sum, 3); |
| 158 | + assert_eq!(count, 2); |
| 159 | + |
| 160 | + assert_eq!(g.is_done(), true); |
| 161 | + assert_eq!(g.return_or_self().ok(), Some("done")); |
| 162 | + } |
| 163 | +} |
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