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
use crate::{bits::Boolean, traits::bits::Xor};
use snarkvm_fields::Field;
use snarkvm_r1cs::{errors::SynthesisError, ConstraintSystem};
pub trait FullAdder<'a, F: Field>
where
Self: std::marker::Sized,
{
fn add<CS: ConstraintSystem<F>>(
cs: CS,
a: &'a Self,
b: &'a Self,
carry: &'a Self,
) -> Result<(Self, Self), SynthesisError>;
}
impl<'a, F: Field> FullAdder<'a, F> for Boolean {
fn add<CS: ConstraintSystem<F>>(
mut cs: CS,
a: &'a Self,
b: &'a Self,
carry: &'a Self,
) -> Result<(Self, Self), SynthesisError> {
let a_x_b = a.xor(cs.ns(|| "a XOR b"), b)?;
let sum = a_x_b.xor(cs.ns(|| "adder sum"), carry)?;
let c1 = Boolean::and(cs.ns(|| "a AND b"), a, b)?;
let c2 = Boolean::and(cs.ns(|| "carry AND (a XOR b)"), carry, &a_x_b)?;
let carry = Boolean::or(cs.ns(|| "c1 OR c2"), &c1, &c2)?;
Ok((sum, carry))
}
}