fingertrees 0.2.11

Immutable persisten finger trees
Documentation 
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

use std::ops::Add;

use crate::measure::Measured;
use crate::monoid::Monoid;
use crate::node::{Node, NodeInner};
use crate::reference::Refs;

#[derive(Clone)]
pub enum Digit<V> {
    One([V; 1]),
    Two([V; 2]),
    Three([V; 3]),
    Four([V; 4]),
}

impl<V> Digit<V>
where
    V: Measured,
{
    pub(crate) fn split<F>(&self, mut measure: V::Measure, pred: &mut F) -> (&[V], &V, &[V])
    where
        F: FnMut(&V::Measure) -> bool,
    {
        let slice = self.as_ref();
        if slice.len() == 1 {
            (&[], &slice[0], &[])
        } else {
            let slice = self.as_ref();
            for (index, item) in slice.iter().enumerate() {
                measure = measure.join(&item.measure());
                if pred(&measure) {
                    return (&slice[..index], &slice[index], &slice[index + 1..]);
                }
            }
            let index = slice.len() - 1;
            (&slice[..index], &slice[index], &[])
        }
    }

    pub(crate) fn find<F>(&self, mut measure: V::Measure, pred: &mut F) -> (V::Measure, &V)
    where
        F: FnMut(&V::Measure) -> bool,
    {
        let last = self.as_ref().len() - 1;
        for (index, value) in self.as_ref().iter().enumerate() {
            let next_measure = measure.join(&value.measure());
            if pred(&next_measure) || index == last {
                return (measure, value);
            }
            measure = next_measure;
        }
        unreachable!()
    }
}

impl<'a, V, R> Add<R> for &'a Digit<V>
where
    V: Clone,
    R: AsRef<[V]>,
{
    type Output = Digit<V>;

    fn add(self, other: R) -> Self::Output {
        match (self.as_ref(), other.as_ref()) {
            (_, []) => self.clone(),
            ([v0], [v1]) => Digit::Two([v0.clone(), v1.clone()]),
            ([v0], [v1, v2]) => Digit::Three([v0.clone(), v1.clone(), v2.clone()]),
            ([v0], [v1, v2, v3]) => Digit::Four([v0.clone(), v1.clone(), v2.clone(), v3.clone()]),
            ([v0, v1], [v2]) => Digit::Three([v0.clone(), v1.clone(), v2.clone()]),
            ([v0, v1], [v2, v3]) => Digit::Four([v0.clone(), v1.clone(), v2.clone(), v3.clone()]),
            ([v0, v1, v2], [v3]) => Digit::Four([v0.clone(), v1.clone(), v2.clone(), v3.clone()]),
            _ => panic!(
                "impossible to create digit of size: {}",
                self.as_ref().len() + other.as_ref().len(),
            ),
        }
    }
}

impl<V: Measured> Measured for Digit<V> {
    type Measure = V::Measure;

    fn measure(&self) -> Self::Measure {
        self.as_ref()
            .iter()
            .fold(Self::Measure::unit(), |measure, val| {
                measure.join(&val.measure())
            })
    }
}

impl<V> AsRef<[V]> for Digit<V> {
    fn as_ref(&self) -> &[V] {
        match self {
            Digit::One(v) => v,
            Digit::Two(v) => v,
            Digit::Three(v) => v,
            Digit::Four(v) => v,
        }
    }
}

impl<'a, V> From<&'a [V]> for Digit<V>
where
    V: Clone,
{
    fn from(slice: &'a [V]) -> Digit<V> {
        match slice {
            [v0] => Digit::One([v0.clone()]),
            [v0, v1] => Digit::Two([v0.clone(), v1.clone()]),
            [v0, v1, v2] => Digit::Three([v0.clone(), v1.clone(), v2.clone()]),
            [v0, v1, v2, v3] => Digit::Four([v0.clone(), v1.clone(), v2.clone(), v3.clone()]),
            _ => panic!("immposible to create digit from of size: {}", slice.len()),
        }
    }
}

impl<'a, R, V: Measured> From<&'a Node<R, V>> for Digit<Node<R, V>>
where
    R: Refs<V>,
    V: Measured,
{
    fn from(node: &'a Node<R, V>) -> Digit<Node<R, V>> {
        match node.as_ref() {
            NodeInner::Leaf(..) => Digit::One([node.clone()]),
            NodeInner::Node2 { left, right, .. } => Digit::Two([left.clone(), right.clone()]),
            NodeInner::Node3 {
                left,
                middle,
                right,
                ..
            } => Digit::Three([left.clone(), middle.clone(), right.clone()]),
        }
    }
}