fixes to use references

src/field/extension_field/mod.rs

@@ -35,7 +35,7 @@ pub trait Frobenius<const D: usize>: OEF<D> {
         }
         let arr = self.to_basefield_array();
         let k = (Self::BaseField::order() - 1u32) / (D as u64);
-        let z0 = Self::W.exp_biguint(k * count as u64);
+        let z0 = Self::W.exp_biguint(&(k * count as u64));
         let mut res = [Self::BaseField::ZERO; D];
         for (i, z) in z0.powers().take(D).enumerate() {
             res[i] = arr[i] * z;

src/field/extension_field/quadratic.rs

@@ -261,7 +261,7 @@ mod tests {
         type F = QuadraticCrandallField;
         let x = F::rand();
         assert_eq!(
-            x.exp_biguint(<F as FieldExtension<2>>::BaseField::order()),
+            x.exp_biguint(&<F as FieldExtension<2>>::BaseField::order()),
             x.frobenius()
         );
     }

src/field/extension_field/quartic.rs

@@ -342,7 +342,7 @@ mod tests {
         const D: usize = 4;
         let x = F::rand();
         assert_eq!(
-            x.exp_biguint(<F as FieldExtension<D>>::BaseField::order()),
+            x.exp_biguint(&<F as FieldExtension<D>>::BaseField::order()),
             x.frobenius()
         );
         for count in 2..D {

src/field/extension_field/target.rs

@@ -32,7 +32,7 @@ impl<const D: usize> ExtensionTarget<D> {
         }
         let arr = self.to_target_array();
         let k = (F::order() - 1u32) / (D as u64);
-        let z0 = F::Extension::W.exp_biguint(k * count as u64);
+        let z0 = F::Extension::W.exp_biguint(&(k * count as u64));
         let zs = z0
             .powers()
             .take(D)

src/field/field.rs

@@ -220,7 +220,7 @@ pub trait Field:
         self.exp(power as u64)
     }
 
-    fn exp_biguint(&self, power: BigUint) -> Self {
+    fn exp_biguint(&self, power: &BigUint) -> Self {
         let digits = power.to_u32_digits();
         let radix = 1u64 << 32;
 
@@ -262,7 +262,7 @@ pub trait Field:
             let numerator = p.clone() + &p_minus_1 * n;
             if numerator.clone() % k == BigUint::zero() {
                 let power = (numerator / k) % p_minus_1;
-                return self.exp_biguint(power);
+                return self.exp_biguint(&power);
             }
         }
         panic!(

src/field/field_testing.rs

@@ -242,8 +242,8 @@ macro_rules! test_field_arithmetic {
                 let big_pow = &pow + &mul_group_order * cycles;
                 let big_pow_wrong = &pow + &mul_group_order * cycles + 1u32;
 
-                assert_eq!(base.exp_biguint(pow.clone()), base.exp_biguint(big_pow));
-                assert_ne!(base.exp_biguint(pow), base.exp_biguint(big_pow_wrong));
+                assert_eq!(base.exp_biguint(&pow), base.exp_biguint(&big_pow));
+                assert_ne!(base.exp_biguint(&pow), base.exp_biguint(&big_pow_wrong));
             }
 
             #[test]