94 lines
2.2 KiB
Rust
94 lines
2.2 KiB
Rust
//! Iterator utilities.
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/// Extra methods for iterators.
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pub trait IteratorExtras: Iterator {
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/// Create an iterator that produces adjacent pairs of elements from the iterator.
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fn adjacent_pairs(mut self) -> AdjacentPairs<Self>
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where
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Self: Sized,
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Self::Item: Clone,
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{
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let elem = self.next();
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AdjacentPairs { iter: self, elem }
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}
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}
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impl<T> IteratorExtras for T where T: Iterator {}
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/// Adjacent pairs iterator returned by `adjacent_pairs()`.
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///
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/// This wraps another iterator and produces a sequence of adjacent pairs of elements.
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pub struct AdjacentPairs<I>
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where
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I: Iterator,
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I::Item: Clone,
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{
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iter: I,
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elem: Option<I::Item>,
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}
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impl<I> Iterator for AdjacentPairs<I>
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where
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I: Iterator,
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I::Item: Clone,
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{
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type Item = (I::Item, I::Item);
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fn next(&mut self) -> Option<Self::Item> {
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self.elem.take().and_then(|e| {
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self.elem = self.iter.next();
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self.elem.clone().map(|n| (e, n))
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})
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}
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}
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#[cfg(test)]
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mod tests {
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use std::vec::Vec;
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#[test]
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fn adjpairs() {
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use super::IteratorExtras;
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assert_eq!(
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[1, 2, 3, 4]
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.iter()
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.cloned()
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.adjacent_pairs()
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.collect::<Vec<_>>(),
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vec![(1, 2), (2, 3), (3, 4)]
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);
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assert_eq!(
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[2, 3, 4]
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.iter()
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.cloned()
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.adjacent_pairs()
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.collect::<Vec<_>>(),
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vec![(2, 3), (3, 4)]
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);
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assert_eq!(
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[2, 3, 4]
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.iter()
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.cloned()
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.adjacent_pairs()
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.collect::<Vec<_>>(),
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vec![(2, 3), (3, 4)]
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);
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assert_eq!(
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[3, 4].iter().cloned().adjacent_pairs().collect::<Vec<_>>(),
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vec![(3, 4)]
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);
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assert_eq!(
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[4].iter().cloned().adjacent_pairs().collect::<Vec<_>>(),
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vec![]
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);
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assert_eq!(
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[].iter()
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.cloned()
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.adjacent_pairs()
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.collect::<Vec<(i32, i32)>>(),
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vec![]
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);
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}
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}
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