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

use crate::plonk::Expression;
use halo2_middleware::ff::Field;
use std::fmt::{self, Debug};

/// Expressions involved in a shuffle argument, with a name as metadata.
#[derive(Clone)]
pub struct Argument<F: Field> {
    pub(crate) name: String,
    pub(crate) input_expressions: Vec<Expression<F>>,
    pub(crate) shuffle_expressions: Vec<Expression<F>>,
}

impl<F: Field> Debug for Argument<F> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Argument")
            .field("input_expressions", &self.input_expressions)
            .field("shuffle_expressions", &self.shuffle_expressions)
            .finish()
    }
}

impl<F: Field> Argument<F> {
    /// Constructs a new shuffle argument.
    ///
    /// `shuffle` is a sequence of `(input, shuffle)` tuples.
    pub fn new<S: AsRef<str>>(name: S, shuffle: Vec<(Expression<F>, Expression<F>)>) -> Self {
        let (input_expressions, shuffle_expressions) = shuffle.into_iter().unzip();
        Argument {
            name: name.as_ref().to_string(),
            input_expressions,
            shuffle_expressions,
        }
    }

    pub(crate) fn required_degree(&self) -> usize {
        assert_eq!(self.input_expressions.len(), self.shuffle_expressions.len());

        let mut input_degree = 1;
        for expr in self.input_expressions.iter() {
            input_degree = std::cmp::max(input_degree, expr.degree());
        }
        let mut shuffle_degree = 1;
        for expr in self.shuffle_expressions.iter() {
            shuffle_degree = std::cmp::max(shuffle_degree, expr.degree());
        }

        // (1 - (l_last + l_blind)) (z(\omega X) (s(X) + \gamma) - z(X) (a(X) + \gamma))
        std::cmp::max(2 + shuffle_degree, 2 + input_degree)
    }

    /// Returns input of this argument
    pub fn input_expressions(&self) -> &Vec<Expression<F>> {
        &self.input_expressions
    }

    /// Returns table of this argument
    pub fn shuffle_expressions(&self) -> &Vec<Expression<F>> {
        &self.shuffle_expressions
    }

    /// Returns name of this argument
    pub fn name(&self) -> &str {
        &self.name
    }
}