1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
//
// 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 filter one kind of result (and leaving the other as is)
pub trait Filter<O, E>: Sized {
/// Filter `Ok` items while keeping `Err`
///
/// ```
/// use resiter::filter::Filter;
/// use std::str::FromStr;
///
/// let mapped: Vec<_> = ["1", "2", "a", "4", "5"]
/// .iter()
/// .map(|txt| usize::from_str(txt))
/// .filter_ok(|i| i % 2 == 0)
/// .collect();
/// assert_eq!(mapped.len(), 3);
/// assert_eq!(mapped[0], Ok(2));
/// assert!(mapped[1].is_err());
/// assert_eq!(mapped[2], Ok(4))
/// ```
fn filter_ok<F>(self, _: F) -> FilterOk<Self, F>
where
F: FnMut(&O) -> bool;
/// Filter `Err` values while keeping `Ok`
///
/// ```
/// use resiter::filter::Filter;
/// use std::str::FromStr;
///
/// let mapped: Vec<_> = ["1", "2", "a", "4", "5"]
/// .iter()
/// .map(|txt| usize::from_str(txt))
/// .filter_err(|_| false)
/// .collect();
///
/// assert_eq!(mapped, vec![Ok(1), Ok(2), Ok(4), Ok(5)]);
/// ```
fn filter_err<F>(self, _: F) -> FilterErr<Self, F>
where
F: FnMut(&E) -> bool;
}
impl<I, O, E> Filter<O, E> for I
where
I: Iterator<Item = Result<O, E>> + Sized,
{
#[inline]
fn filter_ok<F>(self, f: F) -> FilterOk<Self, F>
where
F: FnMut(&O) -> bool,
{
FilterOk { iter: self, f }
}
#[inline]
fn filter_err<F>(self, f: F) -> FilterErr<Self, F>
where
F: FnMut(&E) -> bool,
{
FilterErr { iter: self, f }
}
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct FilterOk<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F> Iterator for FilterOk<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(&O) -> bool,
{
type Item = Result<O, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Ok(x)) => {
if (self.f)(&x) {
return Some(Ok(x));
}
}
other => {
return other;
}
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let hint_sup = self.iter.size_hint().1;
(0, hint_sup)
}
}
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct FilterErr<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F> Iterator for FilterErr<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(&E) -> bool,
{
type Item = Result<O, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Err(x)) => {
if (self.f)(&x) {
return Some(Err(x));
}
}
other => {
return other;
}
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let hint_sup = self.iter.size_hint().1;
(0, hint_sup)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_filter_ok_hint() {
use std::str::FromStr;
let hint = ["1", "2", "a", "4", "5"]
.iter()
.map(|txt| usize::from_str(txt))
.filter_ok(|i| i % 2 == 0)
.size_hint();
assert_eq!(hint, (0, Some(5)));
}
#[test]
fn test_filter_err_hint() {
use std::str::FromStr;
let hint = ["1", "2", "a", "4", "5"]
.iter()
.map(|txt| usize::from_str(txt))
.filter_err(|_| false)
.size_hint();
assert_eq!(hint, (0, Some(5)));
}
}