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
169
170
171
172
173
174
175
//
// 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 TryMap<O, E>: Sized {
/// Equivalent to [Iterator::map] on all `Ok` values.
/// The map function can fail with a result and turn a
/// [Result::Ok] into a [Result::Err]
///
/// ```
/// use std::str::FromStr;
/// use resiter::try_map::TryMap;
///
/// let mapped: Vec<_> = vec![
/// Ok("1"),
/// Err("2".to_owned()),
/// Ok("a"), // will become an error
/// Err("4".to_owned()),
/// Ok("5"), // will be too high
/// Err("b".to_owned()),
/// Err("8".to_owned()),
/// ]
/// .into_iter()
/// .try_map_ok(|txt| {
/// let n = usize::from_str(txt).map_err(|e| e.to_string())?;
/// if n < 3 {
/// Ok(n)
/// }
/// else {
/// Err("Too high".to_string())
/// }
/// })
/// .collect();
///
/// assert_eq!(
/// mapped,
/// [
/// Ok(1),
/// Err("2".to_owned()),
/// Err("invalid digit found in string".to_owned()),
/// Err("4".to_owned()),
/// Err("Too high".to_owned()),
/// Err("b".to_owned()),
/// Err("8".to_owned())
/// ]
/// );
/// ```
fn try_map_ok<F, O2>(self, _: F) -> TryMapOk<Self, F>
where
F: FnMut(O) -> Result<O2, E>;
/// Equivalent to [Iterator::map] on all `Err` values.
/// The map function can fail with a result and turn a
/// [Result::Err] into a [Result::Ok] or another [Result::Err]
/// possibly changing it's error type
///
/// ```
/// use std::str::FromStr;
/// use resiter::try_map::TryMap;
///
/// let mapped: Vec<_> = vec![
/// Ok(1),
/// Err("2".to_owned()), // will become ok
/// Ok(3),
/// Err("4".to_owned()), // will be "Too high"
/// Ok(5),
/// Err("b".to_owned()), // will be an error
/// Err("8".to_owned()), // will be "Too high"
/// ]
/// .into_iter()
/// .try_map_err(|txt| {
/// let n = usize::from_str(&txt).map_err(|e| e.to_string())?;
/// if n < 4 {
/// Ok(n)
/// }
/// else {
/// Err("Too high".to_owned())
/// }
/// })
/// .collect();
///
/// assert_eq!(
/// mapped,
/// [
/// Ok(1),
/// Ok(2),
/// Ok(3),
/// Err("Too high".to_owned()),
/// Ok(5),
/// Err("invalid digit found in string".to_owned()),
/// Err("Too high".to_owned()),
/// ]
/// );
/// ```
fn try_map_err<F, E2>(self, _: F) -> TryMapErr<Self, F>
where
F: FnMut(E) -> Result<O, E2>;
}
impl<I, O, E> TryMap<O, E> for I
where
I: Iterator<Item = Result<O, E>> + Sized,
{
#[inline]
fn try_map_ok<F, O2>(self, f: F) -> TryMapOk<Self, F>
where
F: FnMut(O) -> Result<O2, E>,
{
TryMapOk { iter: self, f }
}
#[inline]
fn try_map_err<F, E2>(self, f: F) -> TryMapErr<Self, F>
where
F: FnMut(E) -> Result<O, E2>,
{
TryMapErr { iter: self, f }
}
}
pub struct TryMapOk<I, F> {
iter: I,
f: F,
}
impl<I, O, E, F, O2> Iterator for TryMapOk<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(O) -> Result<O2, E>,
{
type Item = Result<O2, E>;
fn next(&mut self) -> Option<Self::Item> {
match self.iter.next() {
Some(Ok(x)) => Some((self.f)(x)),
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 TryMapErr<I, F> {
iter: I,
f: F,
}
impl<I, O, E, E2, F> Iterator for TryMapErr<I, F>
where
I: Iterator<Item = Result<O, E>>,
F: FnMut(E) -> Result<O, E2>,
{
type Item = Result<O, E2>;
fn next(&mut self) -> Option<Self::Item> {
match self.iter.next() {
Some(Err(x)) => Some((self.f)(x)),
Some(Ok(x)) => Some(Ok(x)),
None => None,
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}