Merge pull request #97 from zkcrypto/field-sum-prod

Add `core::iter::{Sum, Product}` bounds on `Field`

CHANGELOG.md

@@ -10,6 +10,7 @@ and this library adheres to Rust's notion of
 - `ff::Field::{ZERO, ONE}`
 - `ff::Field::pow`
 - `ff::Field::{sqrt_ratio, sqrt_alt}`
+- `core::iter::{Sum, Product}` bounds on `ff::Field`
 - `ff::PrimeField::{MULTIPLICATIVE_GENERATOR, ROOT_OF_UNITY}`
 - `ff::helpers`:
   - `sqrt_tonelli_shanks`

ff_derive/src/lib.rs

@@ -839,10 +839,7 @@ fn prime_field_impl(
 
     /// Generates an implementation of multiplicative inversion within the target prime
     /// field.
-    fn inv_impl(
-        a: proc_macro2::TokenStream,
-        modulus: &BigUint,
-    ) -> proc_macro2::TokenStream {
+    fn inv_impl(a: proc_macro2::TokenStream, modulus: &BigUint) -> proc_macro2::TokenStream {
         // Addition chain for p - 2
         let mod_minus_2 = pow_fixed::generate(&a, modulus - BigUint::from(2u64));
 
@@ -1155,6 +1152,22 @@ fn prime_field_impl(
             }
         }
 
+        impl<T: ::core::borrow::Borrow<#name>> ::core::iter::Sum<T> for #name {
+            fn sum<I: Iterator<Item = T>>(iter: I) -> Self {
+                use ::ff::Field;
+
+                iter.fold(Self::ZERO, |acc, item| acc + item.borrow())
+            }
+        }
+
+        impl<T: ::core::borrow::Borrow<#name>> ::core::iter::Product<T> for #name {
+            fn product<I: Iterator<Item = T>>(iter: I) -> Self {
+                use ::ff::Field;
+
+                iter.fold(Self::ONE, |acc, item| acc * item.borrow())
+            }
+        }
+
         impl ::ff::PrimeField for #name {
             type Repr = #repr;
 

src/lib.rs

@@ -24,8 +24,11 @@ pub use bitvec::view::BitViewSized;
 
 #[cfg(feature = "bits")]
 use bitvec::{array::BitArray, order::Lsb0};
+
 use core::fmt;
+use core::iter::{Product, Sum};
 use core::ops::{Add, AddAssign, Mul, MulAssign, Neg, Sub, SubAssign};
+
 use rand_core::RngCore;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
 
@@ -47,19 +50,23 @@ pub trait Field:
     + 'static
     + ConditionallySelectable
     + ConstantTimeEq
+    + Neg<Output = Self>
     + Add<Output = Self>
     + Sub<Output = Self>
     + Mul<Output = Self>
-    + Neg<Output = Self>
+    + Sum
+    + Product
     + for<'a> Add<&'a Self, Output = Self>
-    + for<'a> Mul<&'a Self, Output = Self>
     + for<'a> Sub<&'a Self, Output = Self>
-    + MulAssign
+    + for<'a> Mul<&'a Self, Output = Self>
+    + for<'a> Sum<&'a Self>
+    + for<'a> Product<&'a Self>
     + AddAssign
     + SubAssign
-    + for<'a> MulAssign<&'a Self>
+    + MulAssign
     + for<'a> AddAssign<&'a Self>
     + for<'a> SubAssign<&'a Self>
+    + for<'a> MulAssign<&'a Self>
 {
     /// The zero element of the field, the additive identity.
     const ZERO: Self;