diff --git a/libs/riff/src/bitmask_iterators.rs b/libs/riff/src/bitmask_iterators.rs
index 8cd6bee0..35476380 100644
--- a/libs/riff/src/bitmask_iterators.rs
+++ b/libs/riff/src/bitmask_iterators.rs
@@ -1,74 +1,6 @@
-use std::fmt::Debug;
-use std::mem::size_of;
-use std::ops::Add;
-use std::ops::AddAssign;
-use std::ops::BitAnd;
-use std::ops::BitAndAssign;
-use std::ops::BitOr;
-use std::ops::BitOrAssign;
-use std::ops::BitXor;
-use std::ops::BitXorAssign;
-use std::ops::Div;
-use std::ops::DivAssign;
-use std::ops::Mul;
-use std::ops::MulAssign;
-use std::ops::Not;
-use std::ops::Shl;
-use std::ops::ShlAssign;
-use std::ops::Shr;
-use std::ops::ShrAssign;
-use std::ops::Sub;
-use std::ops::SubAssign;
+use super::numeric_traits::Unsigned;
 
-/// Adapter trait of this crate. Already implemented for all the unsigned integer types.
-pub trait Unsigned:
-    Sized
-    + PartialEq
-    + PartialOrd
-    + Debug
-    + Clone
-    + Copy
-    + Add<Output = Self>
-    + AddAssign
-    + Sub<Output = Self>
-    + SubAssign
-    + Mul<Output = Self>
-    + MulAssign
-    + Div<Output = Self>
-    + DivAssign
-    + BitAnd<Output = Self>
-    + BitAndAssign
-    + BitOr<Output = Self>
-    + BitOrAssign
-    + BitXor<Output = Self>
-    + BitXorAssign
-    + Shl<u32, Output = Self>
-    + ShlAssign<u32>
-    + Shr<u32, Output = Self>
-    + ShrAssign<u32>
-    + Not<Output = Self>
-{
-    fn zero() -> Self;
-    fn one() -> Self;
-    fn wrapping_neg(self) -> Self;
-    fn bit_length() -> u32 {
-        size_of::<Self>() as u32 * 8
-    }
-}
-
-macro_rules! impl_unsigned {
-    ($($T:ty),* $(,)?) => {$(
-        impl Unsigned for $T {
-            fn zero() -> Self { 0 }
-            fn one() -> Self { 1 }
-            fn wrapping_neg(self) -> Self { self.wrapping_neg() }
-        }
-    )*}
-}
-
-impl_unsigned! { usize, u8, u16, u32, u64, u128 }
-
-/// Returns an iterator over k-subsets of `(T::one() << n) - T::one()`.
+/// Generates all the $k$-subsets of $[0, N[$
 ///
 /// # Examples
 ///
@@ -76,7 +8,7 @@ impl_unsigned! { usize, u8, u16, u32, u64, u128 }
 /// ```
 /// use bitutils::combinations;
 ///
-/// assert_eq!(combinations::<u32>(3, 2).collect::<Vec<_>>(), vec![3, 5, 6],);
+/// assert_eq!(combinations::<u32>(3, 2).collect::<Vec<_>>(), vec![3, 5, 6]);
 /// ```
 pub fn bitmask_combinations<T: Unsigned>(n: u32, k: u32) -> BitmaskCombinations<T> {
     assert!(k < T::bit_length() && k < T::bit_length());
@@ -86,7 +18,6 @@ pub fn bitmask_combinations<T: Unsigned>(n: u32, k: u32) -> BitmaskCombinations<
     }
 }
 
-/// [See the document of `combinations`](combinations)
 #[derive(Clone, Debug, Default, Hash, PartialEq, Eq)]
 pub struct BitmaskCombinations<T> {
     n: u32,
@@ -111,7 +42,7 @@ impl<T: Unsigned> Iterator for BitmaskCombinations<T> {
     }
 }
 
-/// Returns an iterator over subsets of `bs`.
+/// Generates all the subsets of `bs`.
 ///
 /// # Examples
 ///
@@ -119,7 +50,7 @@ impl<T: Unsigned> Iterator for BitmaskCombinations<T> {
 /// ```
 /// use bitutils::subsets;
 ///
-/// assert_eq!(subsets(10u32).collect::<Vec<_>>(), vec![0, 2, 8, 10],);
+/// assert_eq!(subsets(10u32).collect::<Vec<_>>(), vec![0, 2, 8, 10]);
 /// ```
 pub fn bitmask_subsets<T: Unsigned>(bs: T) -> BitmaskSubsets<T> {
     BitmaskSubsets {
@@ -129,7 +60,6 @@ pub fn bitmask_subsets<T: Unsigned>(bs: T) -> BitmaskSubsets<T> {
     }
 }
 
-/// [See the document of `subsets`](subsets)
 #[derive(Clone, Debug, Default, Hash, PartialEq, Eq)]
 pub struct BitmaskSubsets<T> {
     bs: T,
diff --git a/libs/riff/src/lib.rs b/libs/riff/src/lib.rs
index 0634a986..2c129752 100644
--- a/libs/riff/src/lib.rs
+++ b/libs/riff/src/lib.rs
@@ -3,10 +3,12 @@
 mod binary_search;
 mod bitmask_iterators;
 mod change_min_max;
+mod numeric_traits;
 mod pop_if;
 
 pub use binary_search::BinarySearch;
 pub use bitmask_iterators::bitmask_combinations;
 pub use bitmask_iterators::bitmask_subsets;
 pub use change_min_max::ChangeMinMax;
+pub use numeric_traits::Unsigned;
 pub use pop_if::PopIf;
diff --git a/libs/riff/src/numeric_traits.rs b/libs/riff/src/numeric_traits.rs
new file mode 100644
index 00000000..58843d81
--- /dev/null
+++ b/libs/riff/src/numeric_traits.rs
@@ -0,0 +1,69 @@
+use std::fmt::Debug;
+use std::mem::size_of;
+use std::ops::Add;
+use std::ops::AddAssign;
+use std::ops::BitAnd;
+use std::ops::BitAndAssign;
+use std::ops::BitOr;
+use std::ops::BitOrAssign;
+use std::ops::BitXor;
+use std::ops::BitXorAssign;
+use std::ops::Div;
+use std::ops::DivAssign;
+use std::ops::Mul;
+use std::ops::MulAssign;
+use std::ops::Not;
+use std::ops::Shl;
+use std::ops::ShlAssign;
+use std::ops::Shr;
+use std::ops::ShrAssign;
+use std::ops::Sub;
+use std::ops::SubAssign;
+
+/// Unsigned integer types.
+pub trait Unsigned:
+    Sized
+    + PartialEq
+    + PartialOrd
+    + Debug
+    + Clone
+    + Copy
+    + Add<Output = Self>
+    + AddAssign
+    + Sub<Output = Self>
+    + SubAssign
+    + Mul<Output = Self>
+    + MulAssign
+    + Div<Output = Self>
+    + DivAssign
+    + BitAnd<Output = Self>
+    + BitAndAssign
+    + BitOr<Output = Self>
+    + BitOrAssign
+    + BitXor<Output = Self>
+    + BitXorAssign
+    + Shl<u32, Output = Self>
+    + ShlAssign<u32>
+    + Shr<u32, Output = Self>
+    + ShrAssign<u32>
+    + Not<Output = Self>
+{
+    fn zero() -> Self;
+    fn one() -> Self;
+    fn wrapping_neg(self) -> Self;
+    fn bit_length() -> u32 {
+        size_of::<Self>() as u32 * 8
+    }
+}
+
+macro_rules! impl_unsigned {
+    ($($T:ty),* $(,)?) => {$(
+        impl Unsigned for $T {
+            fn zero() -> Self { 0 }
+            fn one() -> Self { 1 }
+            fn wrapping_neg(self) -> Self { self.wrapping_neg() }
+        }
+    )*}
+}
+
+impl_unsigned! { usize, u8, u16, u32, u64, u128 }