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//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
/// Extension trait for `Iterator<Item = Result<O, E>>` to selectively transform and map Oks and Errors.
pub trait TryFilterMap<O, E>: Sized {
/// Equivalent to [Iterator::filter_map] on all `Ok` values.
/// The filter function can fail with a result and turn an
/// [Result::Ok] into a [Result::Err]
///
/// ```
/// use std::str::FromStr;
/// use resiter::try_filter_map::TryFilterMap;
///
/// let filter_mapped: Vec<_> = vec![
/// Ok("1"),
/// Err("2".to_owned()),
/// Ok("a"), // will become an error
/// Err("4".to_owned()),
/// Ok("5"), // will be filtered out
/// Err("b".to_owned()),
/// Err("8".to_owned()),
/// ]
/// .into_iter()
/// .try_filter_map_ok(|txt| {
/// match usize::from_str(txt).map_err(|e| e.to_string()) {
/// Err(e) => Some(Err(e)),
/// Ok(u) => {
/// if u < 3 {
/// Some(Ok(u))
/// } else {
/// None
/// }
/// }
/// }
/// })
/// .collect();
///
/// assert_eq!(
/// filter_mapped,
/// [
/// Ok(1),
/// Err("2".to_owned()),
/// Err("invalid digit found in string".to_owned()),
/// Err("4".to_owned()),
/// Err("b".to_owned()),
/// Err("8".to_owned())
/// ]
/// );
/// ```
fn try_filter_map_ok<F, O2>(self, _: F) -> TryFilterMapOk<Self, F>
where
F: FnMut(O) -> Option<Result<O2, E>>;
/// Equivalent to [Iterator::filter_map] on all `Err` values.
/// The filter function can fail with a result and turn a
/// [Result::Err] into a [Result::Ok]
///
/// ```
/// use std::str::FromStr;
/// use resiter::try_filter_map::TryFilterMap;
///
/// let filter_mapped: Vec<_> = vec![
/// Ok("1".to_owned()),
/// Err("2".to_owned()), // will become ok
/// Ok("a".to_owned()),
/// Err("4".to_owned()), // will be removed
/// Ok("5".to_owned()),
/// Err("b".to_owned()), // will be an error
/// Err("8".to_owned()), // will be removed
/// ]
/// .into_iter()
/// .try_filter_map_err(|txt| {
/// match usize::from_str(&txt).map_err(|e| e.to_string()) {
/// Err(e) => Some(Err(e)),
/// Ok(u) => {
/// if u < 3 {
/// Some(Ok(u.to_string()))
/// } else {
/// None
/// }
/// }
/// }
/// })
/// .collect();
///
/// assert_eq!(
/// filter_mapped,
/// [
/// Ok("1".to_owned()),
/// Ok("2".to_owned()),
/// Ok("a".to_owned()),
/// Ok("5".to_owned()),
/// Err("invalid digit found in string".to_owned()),
/// ]
/// );
/// ```
fn try_filter_map_err<F, E2>(self, _: F) -> TryFilterMapErr<Self, F>
where
F: FnMut(E) -> Option<Result<O, E2>>;
}
impl<I, O, E> TryFilterMap<O, E> for I
where
I: Iterator<Item = Result<O, E>> + Sized,
{
#[inline]
fn try_filter_map_ok<F, O2>(self, f: F) -> TryFilterMapOk<Self, F>
where
F: FnMut(O) -> Option<Result<O2, E>>,
{
TryFilterMapOk { iter: self, f }
}
#[inline]
fn try_filter_map_err<F, E2>(self, f: F) -> TryFilterMapErr<Self, F>
where
F: FnMut(E) -> Option<Result<O, E2>>,
{
TryFilterMapErr { iter: self, f }
}
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct TryFilterMapOk<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F, O2> Iterator for TryFilterMapOk<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(O) -> Option<Result<O2, E>>,
{
type Item = Result<O2, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
return match self.iter.next() {
Some(Ok(x)) => match (self.f)(x) {
Some(r) => Some(r),
None => continue,
},
Some(Err(e)) => Some(Err(e)),
None => None,
};
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct TryFilterMapErr<I, F> {
iter: I,
f: F,
}
impl<I, O, E, E2, F> Iterator for TryFilterMapErr<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(E) -> Option<Result<O, E2>>,
{
type Item = Result<O, E2>;
fn next(&mut self) -> Option<Self::Item> {
loop {
return match self.iter.next() {
Some(Err(x)) => match (self.f)(x) {
Some(r) => Some(r),
None => continue,
},
Some(Ok(x)) => Some(Ok(x)),
None => None,
};
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}