1use rand::{distributions::Distribution, Rng};
 2use std::fmt::Debug;
 3use std::iter::Sum;
 4use std::ops::{Add, AddAssign, Mul, Neg, Sub, SubAssign};
 5
 6/// Represents a ring element. Currently implemented by ring_nq.rs#Rq and
 7/// ring_torus.rs#Tn. Is not a 'pure algebraic ring', but more a custom trait
 8/// definition which includes methods like `mod_switch`.
 9// assumed to be mod (X^N +1)
10pub trait Ring:
11    Sized
12    + Add<Output = Self>
13    + AddAssign
14    + Sum
15    + Sub<Output = Self>
16    + SubAssign
17    + Mul<Output = Self> // internal product
18    + Mul<u64, Output = Self> // scalar mul, external product
19    + Mul<Self::C, Output = Self>
20    + Neg<Output = Self>
21    + PartialEq
22    + Debug
23    + Clone
24    // + Copy
25    + Sum<<Self as Add>::Output>
26    + Sum<<Self as Mul>::Output>
27{
28    /// C defines the coefficient type
29    type C: Debug + Clone;
30    type Params: Debug+Clone+Copy;
31
32    // const Q: u64;
33    // const N: usize;
34
35    fn coeffs(&self) -> Vec<Self::C>;
36    fn zero(params: Self::Params) -> Self;
37    // note/wip/warning: dist (0,q) with f64, will output more '0=q' elements than other values
38    fn rand(rng: impl Rng, dist: impl Distribution<f64>, params: Self::Params) -> Self;
39
40    fn from_vec(params: Self::Params, coeffs: Vec<Self::C>) -> Self;
41
42    fn decompose(&self, beta: u32, l: u32) -> Vec<Self>;
43
44    fn remodule(&self, p:u64) -> impl Ring;
45    fn mod_switch(&self, p:u64) -> impl Ring;
46
47    /// returns [ [(num/den) * self].round() ] mod q
48    /// ie. performs the multiplication and division over f64, and then it
49    /// rounds the result, only applying the mod Q (if the ring is mod Q) at the
50    /// end.
51    fn mul_div_round(&self, num: u64, den: u64) -> Self;
52}