111 lines
3.0 KiB
Rust
111 lines
3.0 KiB
Rust
#[cfg(feature = "use_std")]
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use std::error::Error;
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use std::fmt::{Debug, Display, Formatter, Result as FmtResult};
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use std::iter::ExactSizeIterator;
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use either::Either;
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use crate::size_hint;
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/// Iterator returned for the error case of `IterTools::exactly_one()`
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/// This iterator yields exactly the same elements as the input iterator.
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///
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/// During the execution of exactly_one the iterator must be mutated. This wrapper
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/// effectively "restores" the state of the input iterator when it's handed back.
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///
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/// This is very similar to PutBackN except this iterator only supports 0-2 elements and does not
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/// use a `Vec`.
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#[derive(Clone)]
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pub struct ExactlyOneError<I>
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where
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I: Iterator,
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{
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first_two: Option<Either<[I::Item; 2], I::Item>>,
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inner: I,
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}
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impl<I> ExactlyOneError<I>
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where
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I: Iterator,
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{
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/// Creates a new `ExactlyOneErr` iterator.
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pub(crate) fn new(first_two: Option<Either<[I::Item; 2], I::Item>>, inner: I) -> Self {
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Self { first_two, inner }
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}
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fn additional_len(&self) -> usize {
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match self.first_two {
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Some(Either::Left(_)) => 2,
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Some(Either::Right(_)) => 1,
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None => 0,
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}
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}
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}
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impl<I> Iterator for ExactlyOneError<I>
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where
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I: Iterator,
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{
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type Item = I::Item;
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fn next(&mut self) -> Option<Self::Item> {
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match self.first_two.take() {
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Some(Either::Left([first, second])) => {
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self.first_two = Some(Either::Right(second));
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Some(first)
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},
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Some(Either::Right(second)) => {
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Some(second)
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}
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None => {
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self.inner.next()
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}
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}
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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size_hint::add_scalar(self.inner.size_hint(), self.additional_len())
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}
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}
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impl<I> ExactSizeIterator for ExactlyOneError<I> where I: ExactSizeIterator {}
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impl<I> Display for ExactlyOneError<I>
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where I: Iterator,
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{
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fn fmt(&self, f: &mut Formatter) -> FmtResult {
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let additional = self.additional_len();
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if additional > 0 {
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write!(f, "got at least 2 elements when exactly one was expected")
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} else {
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write!(f, "got zero elements when exactly one was expected")
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}
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}
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}
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impl<I> Debug for ExactlyOneError<I>
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where I: Iterator + Debug,
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I::Item: Debug,
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{
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fn fmt(&self, f: &mut Formatter) -> FmtResult {
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match &self.first_two {
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Some(Either::Left([first, second])) => {
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write!(f, "ExactlyOneError[First: {:?}, Second: {:?}, RemainingIter: {:?}]", first, second, self.inner)
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},
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Some(Either::Right(second)) => {
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write!(f, "ExactlyOneError[Second: {:?}, RemainingIter: {:?}]", second, self.inner)
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}
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None => {
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write!(f, "ExactlyOneError[RemainingIter: {:?}]", self.inner)
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}
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}
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}
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}
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#[cfg(feature = "use_std")]
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impl<I> Error for ExactlyOneError<I> where I: Iterator + Debug, I::Item: Debug, {}
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