composable-indexes 0.9.0

In-memory collections with composable indexes
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
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

use crate::{
    ShallowClone,
    core::{Index, Insert, Remove, Seal, Update},
};

/// Implements an `Index` given state operations.
///
/// Example:
///
/// ```rust
/// use composable_indexes::{Collection, aggregation};
/// let sum_aggregate = aggregation::GenericAggregate::new(
///     // initial state
///     0,
///     // query function
///     |state: &i64| *state,
///     // insert function
///     |state: &mut i64, value: &i64| *state += *value,
///     // remove function
///     |state: &mut i64, value: &i64| *state -= *value,
/// );
/// let mut collection = Collection::new(sum_aggregate);
/// collection.insert(2);
/// collection.insert(3);
/// assert_eq!(collection.query(|ix| ix.get()), 5);
/// ```
#[derive(Clone)]
pub struct GenericAggregate<In, Query, State> {
    current_state: State,
    query: fn(st: &State) -> Query,
    insert: fn(&mut State, &In),
    remove: fn(&mut State, &In),
}

impl<In, Query, State> GenericAggregate<In, Query, State> {
    pub fn new(
        initial_state: State,
        query: fn(&State) -> Query,
        insert: fn(&mut State, &In),
        remove: fn(&mut State, &In),
    ) -> Self {
        Self {
            current_state: initial_state,
            query,
            insert,
            remove,
        }
    }
}

impl<In, Query, State> Index<In> for GenericAggregate<In, Query, State>
where
    State: 'static,
    Query: 'static,
    In: 'static,
{
    #[inline]
    fn insert(&mut self, _seal: Seal, op: &Insert<In>) {
        (self.insert)(&mut self.current_state, op.new);
    }

    #[inline]
    fn remove(&mut self, _seal: Seal, op: &Remove<In>) {
        (self.remove)(&mut self.current_state, op.existing);
    }
}

impl<In, Query: Clone, State> GenericAggregate<In, Query, State> {
    #[inline]
    pub fn get(&self) -> Query {
        (self.query)(&self.current_state)
    }
}

impl<In: Clone, Query: Clone, State: Clone> ShallowClone for GenericAggregate<In, Query, State> {}

/// Given an algebraic group, implement an [`Index`].
///
/// Example:
///
/// ```rust
/// use composable_indexes::{Collection, aggregation};
///
/// let number_of_a = aggregation::MonoidalAggregate::new(
//      // empty value
///     0,
///     // input function
///     |x: &String| x.chars().filter(|&c| c == 'a').count() as i64,
///     // combine function
///     |a: &i64, b: &i64| a + b,
///     // invert function
///     |a: &i64| -a,
///     // output function
///     |a: &i64| *a,
/// );
///
/// let mut collection = Collection::new(number_of_a);
/// collection.insert("apple".to_string());
/// collection.insert("banana".to_string());
/// assert_eq!(collection.query(|ix| ix.get()), 4);
/// ```
pub struct MonoidalAggregate<T, S, O> {
    state: S,
    input: fn(&T) -> S,
    combine: fn(&S, &S) -> S,
    invert: fn(&S) -> S,
    output: fn(&S) -> O,
}

impl<T, S, O> MonoidalAggregate<T, S, O> {
    pub fn new(
        empty: S,
        input: fn(&T) -> S,
        combine: fn(&S, &S) -> S,
        invert: fn(&S) -> S,
        output: fn(&S) -> O,
    ) -> Self {
        Self {
            state: empty,
            input,
            combine,
            invert,
            output,
        }
    }

    pub fn get(&self) -> O {
        (self.output)(&self.state)
    }
}

impl<T, S, O> Index<T> for MonoidalAggregate<T, S, O> {
    #[inline]
    fn insert(&mut self, _seal: Seal, op: &Insert<T>) {
        let inp = (self.input)(op.new);
        self.state = (self.combine)(&self.state, &inp);
    }

    #[inline]
    fn remove(&mut self, _seal: Seal, op: &Remove<T>) {
        let inp = (self.input)(op.existing);
        let inv = (self.invert)(&inp);
        self.state = (self.combine)(&self.state, &inv);
    }

    #[inline]
    fn update(&mut self, _seal: Seal, op: &Update<T>) {
        let old_ = (self.input)(op.existing);
        let new_ = (self.input)(op.new);
        let diff = (self.combine)(&(self.invert)(&old_), &new_);
        self.state = (self.combine)(&self.state, &diff);
    }
}

impl<T, S: Clone, O> Clone for MonoidalAggregate<T, S, O> {
    fn clone(&self) -> Self {
        MonoidalAggregate {
            state: self.state.clone(),
            input: self.input,
            combine: self.combine,
            invert: self.invert,
            output: self.output,
        }
    }
}

impl<T, S: Clone, O> ShallowClone for MonoidalAggregate<T, S, O> {}