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
|
use std::cmp::Ordering;
use std::iter::Fuse;
use std::fmt;
use super::adaptors::{PutBack, put_back};
use crate::either_or_both::EitherOrBoth;
#[cfg(doc)]
use crate::Itertools;
/// Return an iterator adaptor that merge-joins items from the two base iterators in ascending order.
///
/// [`IntoIterator`] enabled version of [`Itertools::merge_join_by`].
pub fn merge_join_by<I, J, F>(left: I, right: J, cmp_fn: F)
-> MergeJoinBy<I::IntoIter, J::IntoIter, F>
where I: IntoIterator,
J: IntoIterator,
F: FnMut(&I::Item, &J::Item) -> Ordering
{
MergeJoinBy {
left: put_back(left.into_iter().fuse()),
right: put_back(right.into_iter().fuse()),
cmp_fn,
}
}
/// An iterator adaptor that merge-joins items from the two base iterators in ascending order.
///
/// See [`.merge_join_by()`](crate::Itertools::merge_join_by) for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct MergeJoinBy<I: Iterator, J: Iterator, F> {
left: PutBack<Fuse<I>>,
right: PutBack<Fuse<J>>,
cmp_fn: F
}
impl<I, J, F> Clone for MergeJoinBy<I, J, F>
where I: Iterator,
J: Iterator,
PutBack<Fuse<I>>: Clone,
PutBack<Fuse<J>>: Clone,
F: Clone,
{
clone_fields!(left, right, cmp_fn);
}
impl<I, J, F> fmt::Debug for MergeJoinBy<I, J, F>
where I: Iterator + fmt::Debug,
I::Item: fmt::Debug,
J: Iterator + fmt::Debug,
J::Item: fmt::Debug,
{
debug_fmt_fields!(MergeJoinBy, left, right);
}
impl<I, J, F> Iterator for MergeJoinBy<I, J, F>
where I: Iterator,
J: Iterator,
F: FnMut(&I::Item, &J::Item) -> Ordering
{
type Item = EitherOrBoth<I::Item, J::Item>;
fn next(&mut self) -> Option<Self::Item> {
match (self.left.next(), self.right.next()) {
(None, None) => None,
(Some(left), None) =>
Some(EitherOrBoth::Left(left)),
(None, Some(right)) =>
Some(EitherOrBoth::Right(right)),
(Some(left), Some(right)) => {
match (self.cmp_fn)(&left, &right) {
Ordering::Equal =>
Some(EitherOrBoth::Both(left, right)),
Ordering::Less => {
self.right.put_back(right);
Some(EitherOrBoth::Left(left))
},
Ordering::Greater => {
self.left.put_back(left);
Some(EitherOrBoth::Right(right))
}
}
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let (a_lower, a_upper) = self.left.size_hint();
let (b_lower, b_upper) = self.right.size_hint();
let lower = ::std::cmp::max(a_lower, b_lower);
let upper = match (a_upper, b_upper) {
(Some(x), Some(y)) => x.checked_add(y),
_ => None,
};
(lower, upper)
}
fn count(mut self) -> usize {
let mut count = 0;
loop {
match (self.left.next(), self.right.next()) {
(None, None) => break count,
(Some(_left), None) => break count + 1 + self.left.into_parts().1.count(),
(None, Some(_right)) => break count + 1 + self.right.into_parts().1.count(),
(Some(left), Some(right)) => {
count += 1;
match (self.cmp_fn)(&left, &right) {
Ordering::Equal => {}
Ordering::Less => self.right.put_back(right),
Ordering::Greater => self.left.put_back(left),
}
}
}
}
}
fn last(mut self) -> Option<Self::Item> {
let mut previous_element = None;
loop {
match (self.left.next(), self.right.next()) {
(None, None) => break previous_element,
(Some(left), None) => {
break Some(EitherOrBoth::Left(
self.left.into_parts().1.last().unwrap_or(left),
))
}
(None, Some(right)) => {
break Some(EitherOrBoth::Right(
self.right.into_parts().1.last().unwrap_or(right),
))
}
(Some(left), Some(right)) => {
previous_element = match (self.cmp_fn)(&left, &right) {
Ordering::Equal => Some(EitherOrBoth::Both(left, right)),
Ordering::Less => {
self.right.put_back(right);
Some(EitherOrBoth::Left(left))
}
Ordering::Greater => {
self.left.put_back(left);
Some(EitherOrBoth::Right(right))
}
}
}
}
}
}
fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
loop {
if n == 0 {
break self.next();
}
n -= 1;
match (self.left.next(), self.right.next()) {
(None, None) => break None,
(Some(_left), None) => break self.left.nth(n).map(EitherOrBoth::Left),
(None, Some(_right)) => break self.right.nth(n).map(EitherOrBoth::Right),
(Some(left), Some(right)) => match (self.cmp_fn)(&left, &right) {
Ordering::Equal => {}
Ordering::Less => self.right.put_back(right),
Ordering::Greater => self.left.put_back(left),
},
}
}
}
}
|
