From 4752774bae35f50694038870b97ccf469ee25f15 Mon Sep 17 00:00:00 2001
From: fcarreiro <facundo@aztecprotocol.com>
Date: Fri, 29 Nov 2024 16:39:31 +0000
Subject: [PATCH] feat: define std::hash for field

---
 .../src/barretenberg/ecc/fields/field_declarations.hpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/barretenberg/cpp/src/barretenberg/ecc/fields/field_declarations.hpp b/barretenberg/cpp/src/barretenberg/ecc/fields/field_declarations.hpp
index af1643bdc1b..7ebfcb7d56e 100644
--- a/barretenberg/cpp/src/barretenberg/ecc/fields/field_declarations.hpp
+++ b/barretenberg/cpp/src/barretenberg/ecc/fields/field_declarations.hpp
@@ -707,3 +707,13 @@ template <typename B, typename Params> void write(B& buf, field<Params> const& v
 }
 
 } // namespace bb
+
+// Define hash function for field elements, e.g., so that it can be used in maps.
+// See https://en.cppreference.com/w/cpp/utility/hash .
+template <typename Params> struct std::hash<bb::field<Params>> {
+    std::size_t operator()(const bb::field<Params>& ff) const noexcept
+    {
+        return std::hash<uint64_t>()(ff.data[0]) ^ (std::hash<uint64_t>()(ff.data[1]) << 1) ^
+               (std::hash<uint64_t>()(ff.data[2]) << 2) ^ (std::hash<uint64_t>()(ff.data[3]) << 3);
+    }
+};
\ No newline at end of file