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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 for `Iterator<Item = Result<O, E>>` to filter the Ok(_) and leaving the Err(_) as
/// is, but allowing the filter to return a `Result<bool, E>` itself
pub trait TryFilter<O, E>: Sized {
/// Filters every `Ok`-value with a function that can return an Err.
/// Useful when the filter condition uses functions that can fail.
///
///```
/// use resiter::try_filter::TryFilter;
/// use std::str::FromStr;
///
/// let v = ["1", "2", "4", "a", "5"]
/// .iter()
/// .map(Ok)
/// .try_filter_ok(|e| usize::from_str(e).map(|n| n < 3))
/// .collect::<Vec<Result<_, _>>>();
///
/// assert_eq!(v.len(), 3);
/// assert_eq!(v.iter().filter(|x| x.is_ok()).count(), 2);
/// assert_eq!(v.iter().filter(|x| x.is_err()).count(), 1);
///```
fn try_filter_ok<F>(self, _: F) -> TryFilterOk<Self, F>
where
F: FnMut(&O) -> Result<bool, E>;
/// Filters every `Err`-value with a function that can return an Err.
/// Useful when the filter condition uses functions that can fail.
///
/// ```
/// use resiter::try_filter::TryFilter;
/// use std::num::ParseIntError;
/// use std::str::FromStr;
///
/// let v = ["1", "2", "4", "a", "5"]
/// .iter()
/// .map(|txt| usize::from_str(txt))
/// .try_filter_err(|_:&ParseIntError| Ok(false))
/// .collect::<Vec<Result<_, _>>>();
///
/// assert_eq!(v.iter().filter(|x| x.is_ok()).count(), 4);
/// assert_eq!(v.iter().filter(|x| x.is_err()).count(), 0);
/// ```
fn try_filter_err<F>(self, _: F) -> TryFilterErr<Self, F>
where
F: FnMut(&E) -> Result<bool, E>;
}
impl<I, O, E> TryFilter<O, E> for I
where
I: Iterator<Item = Result<O, E>> + Sized,
{
#[inline]
fn try_filter_ok<F>(self, f: F) -> TryFilterOk<Self, F>
where
F: FnMut(&O) -> Result<bool, E>,
{
TryFilterOk { iter: self, f }
}
#[inline]
fn try_filter_err<F>(self, f: F) -> TryFilterErr<Self, F>
where
F: FnMut(&E) -> Result<bool, E>,
{
TryFilterErr { iter: self, f }
}
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct TryFilterOk<I, F> {
iter: I,
f: F,
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct TryFilterErr<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F> Iterator for TryFilterOk<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(&O) -> Result<bool, E>,
{
type Item = Result<O, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
return match self.iter.next() {
Some(Ok(x)) => match (self.f)(&x) {
Ok(true) => Some(Ok(x)),
Ok(false) => continue,
Err(e) => Some(Err(e)),
},
other => other,
};
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let hint_sup = self.iter.size_hint().1;
(0, hint_sup)
}
}
impl<I, O, E, F> Iterator for TryFilterErr<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(&E) -> Result<bool, E>,
{
type Item = Result<O, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
return match self.iter.next() {
Some(Err(x)) => match (self.f)(&x) {
Ok(true) => Some(Err(x)),
Ok(false) => continue,
Err(e) => Some(Err(e)),
},
other => other,
};
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let hint_sup = self.iter.size_hint().1;
(0, hint_sup)
}
}