ark-poly-commit 0.5.0

A library for constructing polynomial commitment schemes for use in zkSNARKs
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

//! Compute all combinations of values in a given list
//! Credit: https://github.com/meltinglava/uniquecombinations/
#[cfg(not(feature = "std"))]
use ark_std::vec::Vec;
/// Compute all combinations of values in a given list.
pub(crate) struct Combinations<T>
where
    T: Ord + Clone,
{
    original: Vec<T>,
    possition: Vec<usize>,
    len: usize,
    started: bool,
}

impl<T> Combinations<T>
where
    T: Ord + Clone,
{
    /// Initialize the permutations.
    pub(crate) fn new(mut original: Vec<T>, len: usize) -> Self {
        if original.len() > len && len >= 1 {
            original.sort_unstable();
            Self {
                original,
                possition: (0..len).collect(),
                len,
                started: false,
            }
        } else {
            panic!("the length has to be smaller then the datasets len");
        }
    }

    #[inline]
    fn insert(&self, col: &mut Vec<T>) {
        col.clear();
        self.possition
            .iter()
            .enumerate()
            .for_each(|(p, n)| col.insert(p, self.original[*n].clone()))
    }

    /// Clear the contents of the comb vector and insert the next combination.
    fn next_combination(&mut self, mut comb: &mut Vec<T>) -> bool {
        if !self.started {
            // first pass throught
            self.started = true;
            self.insert(&mut comb);
            true
        } else {
            let org_len = self.original.len();
            // check if we cant bump the back number
            if self.original[self.possition[self.len - 1]] == self.original[org_len - 1] {
                // locate the number closest behind that needs to be bumped
                for i in 2..=self.len {
                    if self.original[self.possition[self.len - i]] < self.original[org_len - i] {
                        //find the value of the
                        let lastpos = self.possition[self.len - i];
                        let val = &self.original[lastpos];
                        for j in lastpos + 1..org_len {
                            if *val < self.original[j] {
                                for k in 0..i {
                                    self.possition[self.len - i + k] = j + k;
                                }
                                self.insert(&mut comb);
                                return true;
                            }
                        }
                    }
                }
                false
            } else {
                let mut i = self.possition[self.len - 1];
                let current = &self.original[i];
                let mut next = current;
                while current == next {
                    i += 1;
                    next = &self.original[i];
                }
                self.possition[self.len - 1] = i;
                self.insert(&mut comb);
                true
            }
        }
    }
}

impl<T> Iterator for Combinations<T>
where
    T: Ord + Clone,
{
    type Item = Vec<T>;

    fn next(&mut self) -> Option<Self::Item> {
        let mut vals = Vec::with_capacity(self.len);
        if self.next_combination(&mut vals) {
            Some(vals)
        } else {
            None
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn equals() {
        assert!(Combinations::new(vec![2, 2, 2], 2).next().unwrap() == vec![2, 2])
    }

    #[test]
    fn t_123() {
        assert!(
            dbg!(Combinations::new(vec![1, 2, 3], 2)
                .take(10)
                .collect::<Vec<_>>())
                == vec![vec![1, 2], vec![1, 3], vec![2, 3]]
        )
    }

    #[test]
    fn complicated() {
        let actual: Vec<_> = Combinations::new(vec![1, 2, 2, 3, 4], 3).collect();
        let expected = vec![
            vec![1, 2, 2],
            vec![1, 2, 3],
            vec![1, 2, 4],
            vec![1, 3, 4],
            vec![2, 2, 3],
            vec![2, 2, 4],
            vec![2, 3, 4],
        ];
        assert!(actual == expected)
    }
}