From b7ae15576ffa41eee90f8072f7053760d6eeab6f Mon Sep 17 00:00:00 2001
From: ledwards2225 <l.edwards.d@gmail.com>
Date: Tue, 5 Sep 2023 19:26:03 +0000
Subject: [PATCH] update zero evaluation and comments

---
 .../cpp/src/barretenberg/honk/pcs/kzg/kzg.hpp            | 9 ++-------
 .../cpp/src/barretenberg/honk/pcs/shplonk/shplonk.hpp    | 6 +-----
 2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/kzg/kzg.hpp b/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/kzg/kzg.hpp
index 99bbda063bdc..ab2c8d8bb7a2 100644
--- a/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/kzg/kzg.hpp
+++ b/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/kzg/kzg.hpp
@@ -89,13 +89,8 @@ template <typename Curve, bool goblin_flag = false> class KZG {
             std::vector<GroupElement> commitments = { claim.commitment, quotient_commitment };
             std::vector<Fr> scalars = { one, claim.opening_pair.challenge };
             P_0 = GroupElement::template batch_mul<goblin_flag>(commitments, scalars);
-            // WORKTODO(luke): The evaluation is always zero due to the nature of shplonk. What is the proper way to
-            // handle this? Contraints to show scalar (evaluation) is zero? Or simply dont add anything and ensure this
-            // function is only used in the current context? 
-            // if (!claim.opening_pair.evaluation.get_value().is_zero()) {
-            //     auto ctx = verifier_transcript.builder;
-            //     lhs -= GroupElement::one(ctx) * claim.opening_pair.evaluation;
-            // }
+            // Note: This implementation assumes the evaluation is zero (as is the case for shplonk).
+            ASSERT(claim.opening_pair.evaluation.get_value() == 0);
         } else {
             P_0 = claim.commitment;
             P_0 += quotient_commitment * claim.opening_pair.challenge;
diff --git a/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/shplonk/shplonk.hpp b/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/shplonk/shplonk.hpp
index f53925af24e1..17c452471dcf 100644
--- a/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/shplonk/shplonk.hpp
+++ b/circuits/cpp/barretenberg/cpp/src/barretenberg/honk/pcs/shplonk/shplonk.hpp
@@ -173,7 +173,6 @@ template <typename Curve, bool goblin_flag = false> class ShplonkVerifier_ {
         auto Q_commitment = transcript.template receive_from_prover<Commitment>("Shplonk:Q");
 
         const Fr z_challenge = transcript.get_challenge("Shplonk:z");
-        Fr evaluation_zero; // 0 \in Fr
 
         // [G] = [Q] - ∑ⱼ ρʲ / ( r − xⱼ )⋅[fⱼ] + G₀⋅[1]
         //     = [Q] - [∑ⱼ ρʲ ⋅ ( fⱼ(X) − vⱼ) / ( r − xⱼ )]
@@ -192,7 +191,6 @@ template <typename Curve, bool goblin_flag = false> class ShplonkVerifier_ {
         // using a builder Simulator.
         if constexpr (Curve::is_stdlib_type) {
             auto builder = nu.get_context();
-            evaluation_zero = Fr(builder, 0);
 
             // Containers for the inputs to the final batch mul
             std::vector<Commitment> commitments;
@@ -236,8 +234,6 @@ template <typename Curve, bool goblin_flag = false> class ShplonkVerifier_ {
             G_commitment = GroupElement::template batch_mul<goblin_flag>(commitments, scalars);
 
         } else {
-            evaluation_zero = Fr(0);
-
             // [G] = [Q] - ∑ⱼ ρʲ / ( r − xⱼ )⋅[fⱼ] + G₀⋅[1]
             //     = [Q] - [∑ⱼ ρʲ ⋅ ( fⱼ(X) − vⱼ) / ( r − xⱼ )]
             G_commitment = Q_commitment;
@@ -272,7 +268,7 @@ template <typename Curve, bool goblin_flag = false> class ShplonkVerifier_ {
         }
 
         // Return opening pair (z, 0) and commitment [G]
-        return { { z_challenge, evaluation_zero }, G_commitment };
+        return { { z_challenge, Fr(0) }, G_commitment };
     };
 };
 } // namespace proof_system::honk::pcs::shplonk