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
use slice_trait::Slice;
#[const_trait]
pub trait SliceArgReduce<T>: Slice<Item = T>
{
/// Performs an argument reduction, finding the final righthand operand for which the comparison yields true.
///
/// # Example
///
/// ```rust
/// use slice_ops::ops::*;
///
/// fn my_argmax<T>(slice: &[T]) -> Option<usize>
/// where
/// T: PartialOrd
/// {
/// slice.argreduce(PartialOrd::gt)
/// }
///
/// fn my_argmin<T>(slice: &[T]) -> Option<usize>
/// where
/// T: PartialOrd
/// {
/// slice.argreduce(PartialOrd::lt)
/// }
///
/// let x = [1, 5, 5, 6, 2, -1, 0, -4, -1, 6];
///
/// assert_eq!(my_argmax(&x), x.argmax());
/// assert_eq!(my_argmin(&x), x.argmin());
/// ```
fn argreduce<'a, F>(&'a self, reduction: F) -> Option<usize>
where
F: FnMut(&'a T, &'a T) -> bool /*+ ~const Destruct*/,
T: 'a;
/// Performs an argument reduction on the hashed values, finding the final righthand operand for which the comparison yields true.
///
/// # Example
///
/// ```rust
/// use slice_ops::ops::*;
///
/// fn hasher(str: &&str) -> i32
/// {
/// i32::from_str_radix(str, 10).unwrap()
/// }
///
/// fn my_argmax(slice: &[&str]) -> Option<usize>
/// {
/// slice.argreduce_key(PartialOrd::gt, hasher)
/// }
///
/// fn my_argmin(slice: &[&str]) -> Option<usize>
/// {
/// slice.argreduce_key(PartialOrd::lt, hasher)
/// }
///
/// let x = ["1", "5", "5", "6", "2", "-1", "0", "-4", "-1", "6"];
///
/// assert_eq!(my_argmax(&x), x.argmax_by_key(hasher));
/// assert_eq!(my_argmin(&x), x.argmin_by_key(hasher));
/// ```
fn argreduce_key<'a, B, FR, FB>(&'a self, reduction: FR, hasher: FB) -> Option<usize>
where
FR: FnMut(&B, &B) -> bool /*+ ~const Destruct*/,
FB: FnMut(&'a T) -> B /*+ ~const Destruct*/,
T: 'a;
}
impl<T> SliceArgReduce<T> for [T]
{
fn argreduce<'a, F>(&'a self, mut f: F) -> Option<usize>
where
F: FnMut(&'a T, &'a T) -> bool,
T: 'a
{
let l = self.len();
if l == 0
{
return None;
}
let mut i = 1;
let mut j = 0;
while i < l
{
if f(&self[i], &self[j])
{
j = i;
}
i += 1;
}
Some(j)
}
fn argreduce_key<'a, B, FR, FB>(&'a self, mut predicate: FR, mut hasher: FB) -> Option<usize>
where
FR: FnMut(&B, &B) -> bool,
FB: FnMut(&'a T) -> B,
T: 'a
{
let l = self.len();
if l == 0
{
return None;
}
let mut j = 0;
let mut i = 1;
let mut key = hasher(&self[j]);
while i < l
{
let next_key = hasher(&self[i]);
if predicate(&next_key, &key)
{
j = i;
key = next_key;
}
i += 1;
}
Some(j)
}
}
#[cfg(test)]
mod test
{
#[test]
fn it_works()
{
}
}