1use super::{AllocatedMulResultVar, EmulatedFpVar};
 2use ark_ff::PrimeField;
 3use ark_relations::r1cs::Result as R1CSResult;
 4
 5/// An intermediate representation especially for the result of a
 6/// multiplication, containing more limbs. It is intended for advanced usage to
 7/// improve the efficiency.
 8///
 9/// That is, instead of calling `mul`, one can call `mul_without_reduce` to
10/// obtain this intermediate representation, which can still be added.
11/// Then, one can call `reduce` to reduce it back to `EmulatedFpVar`.
12/// This may help cut the number of reduce operations.
13#[derive(Debug)]
14#[must_use]
15pub enum MulResultVar<TargetF: PrimeField, BaseF: PrimeField> {
16    /// as a constant
17    Constant(TargetF),
18    /// as an allocated gadget
19    Var(AllocatedMulResultVar<TargetF, BaseF>),
20}
21
22impl<TargetF: PrimeField, BaseF: PrimeField> MulResultVar<TargetF, BaseF> {
23    /// Create a zero `MulResultVar` (used for additions)
24    pub fn zero() -> Self {
25        Self::Constant(TargetF::zero())
26    }
27
28    /// Create an `MulResultVar` from a constant
29    pub fn constant(v: TargetF) -> Self {
30        Self::Constant(v)
31    }
32
33    /// Reduce the `MulResultVar` back to EmulatedFpVar
34    #[tracing::instrument(target = "r1cs")]
35    pub fn reduce(&self) -> R1CSResult<EmulatedFpVar<TargetF, BaseF>> {
36        match self {
37            Self::Constant(c) => Ok(EmulatedFpVar::Constant(*c)),
38            Self::Var(v) => Ok(EmulatedFpVar::Var(v.reduce()?)),
39        }
40    }
41}
42
43impl<TargetF: PrimeField, BaseF: PrimeField> From<&EmulatedFpVar<TargetF, BaseF>>
44    for MulResultVar<TargetF, BaseF>
45{
46    fn from(src: &EmulatedFpVar<TargetF, BaseF>) -> Self {
47        match src {
48            EmulatedFpVar::Constant(c) => MulResultVar::Constant(*c),
49            EmulatedFpVar::Var(v) => {
50                MulResultVar::Var(AllocatedMulResultVar::<TargetF, BaseF>::from(v))
51            },
52        }
53    }
54}
55
56impl_bounded_ops!(
57    MulResultVar<TargetF, BaseF>,
58    TargetF,
59    Add,
60    add,
61    AddAssign,
62    add_assign,
63    |this: &'a MulResultVar<TargetF, BaseF>, other: &'a MulResultVar<TargetF, BaseF>| {
64        use MulResultVar::*;
65        match (this, other) {
66            (Constant(c1), Constant(c2)) => Constant(*c1 + c2),
67            (Constant(c), Var(v)) | (Var(v), Constant(c)) => Var(v.add_constant(c).unwrap()),
68            (Var(v1), Var(v2)) => Var(v1.add(v2).unwrap()),
69        }
70    },
71    |this: &'a MulResultVar<TargetF, BaseF>, other: TargetF| { this + &MulResultVar::Constant(other) },
72    (TargetF: PrimeField, BaseF: PrimeField),
73);