diff --git a/src/field/field_types.rs b/src/field/field_types.rs
index 481d87ba..f5d06fdb 100644
--- a/src/field/field_types.rs
+++ b/src/field/field_types.rs
@@ -206,6 +206,7 @@ pub trait Field:
         subgroup.into_iter().map(|x| x * shift).collect()
     }
 
+    // TODO: move these to a new `PrimeField` trait (for all prime fields, not just 64-bit ones)
     fn from_biguint(n: BigUint) -> Self;
 
     fn to_biguint(&self) -> BigUint;
diff --git a/src/gadgets/biguint.rs b/src/gadgets/biguint.rs
index a524a79b..8369bfc4 100644
--- a/src/gadgets/biguint.rs
+++ b/src/gadgets/biguint.rs
@@ -28,12 +28,10 @@ impl BigUintTarget {
 impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
     pub fn constant_biguint(&mut self, value: &BigUint) -> BigUintTarget {
         let limb_values = value.to_u32_digits();
-        let mut limbs = Vec::new();
-        for i in 0..limb_values.len() {
-            limbs.push(U32Target(
-                self.constant(F::from_canonical_u32(limb_values[i])),
-            ));
-        }
+        let limbs = limb_values
+            .iter()
+            .map(|l| self.constant(F::from_canonical_u32(l)))
+            .collect();
 
         BigUintTarget { limbs }
     }
diff --git a/src/gates/assert_le.rs b/src/gates/assert_le.rs
index 46432c03..98411ef2 100644
--- a/src/gates/assert_le.rs
+++ b/src/gates/assert_le.rs
@@ -13,6 +13,8 @@ use crate::plonk::plonk_common::{reduce_with_powers, reduce_with_powers_ext_recu
 use crate::plonk::vars::{EvaluationTargets, EvaluationVars, EvaluationVarsBase};
 use crate::util::{bits_u64, ceil_div_usize};
 
+// TODO: replace/merge this gate with `ComparisonGate`.
+
 /// A gate for checking that one value is less than or equal to another.
 #[derive(Clone, Debug)]
 pub struct AssertLessThanGate<F: PrimeField + Extendable<D>, const D: usize> {