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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 Oks and Errors.
pub trait Map<O, E>: Sized {
/// Map all `Ok` items while leaving `Err` as is
///
/// ```
/// use resiter::map::Map;
/// use std::str::FromStr;
///
/// let mapped: Vec<_> = ["1", "2", "a", "4", "5"]
/// .iter()
/// .map(|txt| usize::from_str(txt))
/// .map_ok(|i| 2 * i)
/// .collect();
///
/// assert_eq!(mapped[0], Ok(2));
/// assert_eq!(mapped[1], Ok(4));
/// assert!(mapped[2].is_err());
/// assert_eq!(mapped[3], Ok(8));
/// assert_eq!(mapped[4], Ok(10));
/// ```
fn map_ok<F, O2>(self, _: F) -> MapOk<Self, F>
where
F: FnMut(O) -> O2;
/// Map all `Err` items while leaving `Ok` as is
///
/// ```
/// use resiter::map::Map;
/// use std::str::FromStr;
/// let mapped: Vec<_> = ["1", "2", "a", "4", "5"]
/// .iter()
/// .map(|txt| usize::from_str(txt))
/// .map_err(|e| format!("{:?}", e))
/// .collect();
///
/// assert_eq!(
/// mapped,
/// vec![
/// Ok(1),
/// Ok(2),
/// Err("ParseIntError { kind: InvalidDigit }".to_string()),
/// Ok(4),
/// Ok(5),
/// ]
/// );
/// ```
fn map_err<F, E2>(self, _: F) -> MapErr<Self, F>
where
F: FnMut(E) -> E2;
}
impl<I, O, E> Map<O, E> for I
where
I: Iterator<Item = Result<O, E>> + Sized,
{
#[inline]
fn map_ok<F, O2>(self, f: F) -> MapOk<Self, F>
where
F: FnMut(O) -> O2,
{
MapOk { iter: self, f }
}
#[inline]
fn map_err<F, E2>(self, f: F) -> MapErr<Self, F>
where
F: FnMut(E) -> E2,
{
MapErr { iter: self, f }
}
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct MapOk<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F, O2> Iterator for MapOk<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(O) -> O2,
{
type Item = Result<O2, E>;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().map(|r| r.map(&mut self.f))
}
#[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 MapErr<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F, E2> Iterator for MapErr<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(E) -> E2,
{
type Item = Result<O, E2>;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().map(|r| r.map_err(&mut self.f))
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_map_ok_hint() {
use std::str::FromStr;
let hint = ["1", "2", "a", "4", "5"]
.iter()
.map(|txt| usize::from_str(txt))
.map_ok(|i| 2 * i)
.size_hint();
assert_eq!(hint, (5, Some(5)));
}
#[test]
fn test_map_err_hint() {
use std::str::FromStr;
let hint = ["1", "2", "a", "4", "5"]
.iter()
.map(|txt| usize::from_str(txt))
.map_err(|e| format!("{:?}", e))
.size_hint();
assert_eq!(hint, (5, Some(5)));
}
}