diff --git a/src/main/scala/org/lemon/advent/lib/collections.scala b/src/main/scala/org/lemon/advent/lib/collections.scala
index 5fcd983..66d88d0 100644
--- a/src/main/scala/org/lemon/advent/lib/collections.scala
+++ b/src/main/scala/org/lemon/advent/lib/collections.scala
@@ -1,5 +1,17 @@
 package org.lemon.advent.lib
 
 extension [A](it: Iterator[A])
+  /** Returns the nth element of the iterator.
+    *
+    * @param n the index of the element to return
+    * @throws NoSuchElementException if there is no nth element
+    * @return the nth element of the iterator
+    */
   def nth(n: Int): A = it.drop(n).next
+
+  /** Returns the nth element of the iterator, or None if there is no nth element.
+    *
+    * @param n the index of the element to return
+    * @return the nth element of the iterator, or None if there is no nth element
+    */
   def nthOption(n: Int): Option[A] = it.drop(n).nextOption
diff --git a/src/main/scala/org/lemon/advent/lib/combinations.scala b/src/main/scala/org/lemon/advent/lib/combinations.scala
index d5b8b0c..e95942c 100644
--- a/src/main/scala/org/lemon/advent/lib/combinations.scala
+++ b/src/main/scala/org/lemon/advent/lib/combinations.scala
@@ -1,7 +1,11 @@
 package org.lemon.advent.lib
 
 extension [T](xs: Iterable[T])
-
+  /** Returns an iterator of all unordered pairs of elements in the iterable.
+    * If the collection contains duplicates, the pairs will not be unique.
+    *
+    * @return iterator of all unordered pairs
+    */
   def pairs: Iterator[(T, T)] =
     for
       (x, i) <- xs.iterator.zipWithIndex
@@ -9,6 +13,11 @@ extension [T](xs: Iterable[T])
       if i < j
     yield (x, y)
 
+  /** Returns an iterator of all unordered triples of elements in the iterable.
+    * If the collection contains duplicates, the triples will not be unique.
+    *
+    * @return iterator of all unordered triples
+    */
   def triples: Iterator[(T, T, T)] =
     for
       (x, i) <- xs.iterator.zipWithIndex
diff --git a/src/main/scala/org/lemon/advent/lib/math.scala b/src/main/scala/org/lemon/advent/lib/math.scala
index c3731fe..1890a25 100644
--- a/src/main/scala/org/lemon/advent/lib/math.scala
+++ b/src/main/scala/org/lemon/advent/lib/math.scala
@@ -4,13 +4,29 @@ import scala.math.Integral.Implicits._
 import scala.math.Ordering.Implicits._
 
 extension [N: Integral](a: N)
+  /** Returns the positive modulo of this mod `n`. If the regular modulo is negative, this
+    * will shift it back into the positive ranges.
+    *
+    * @param n the modulus
+    * @return the positive modulo of this mod `n`
+    */
   def +%(n: N): N =
     val mod = a % n
     if mod < Integral[N].zero then mod + n else mod
 
+  /** Returns the greatest common divisor of this and `b`.
+    *
+    * @param b the other number
+    * @return the greatest common divisor of this and `b`
+    */
   def gcd(b: N): N =
     @annotation.tailrec
     def loop(a: N, b: N): N = if b == Integral[N].zero then a else loop(b, a % b)
     loop(a, b)
 
+  /** Returns the least common multiple of this and `b`.
+    *
+    * @param b the other number
+    * @return the least common multiple of this and `b`
+    */
   def lcm(b: N): N = a * b / a.gcd(b)
diff --git a/src/main/scala/org/lemon/advent/lib/memoize.scala b/src/main/scala/org/lemon/advent/lib/memoize.scala
index e17b6d7..d88428f 100644
--- a/src/main/scala/org/lemon/advent/lib/memoize.scala
+++ b/src/main/scala/org/lemon/advent/lib/memoize.scala
@@ -2,6 +2,20 @@ package org.lemon.advent.lib
 
 import scala.collection.mutable
 
+/** Memoizes a function, caching the results of previous calls.
+  * Use as:
+  * ```scala
+  * lazy val fib: BigInt => BigInt = memoize {
+  *  case 0 => 0
+  *  case 1 => 1
+  *  case n => fib(n - 1) + fib(n - 2)
+  * }
+  * fib(100) shouldBe BigInt("354224848179261915075")
+  * ```
+  *
+  * @param f the function to memoize
+  * @return a memoized version of the function
+  */
 def memoize[T, R](f: T => R): T => R =
   val cache = mutable.Map.empty[T, R]
   (t: T) => cache.getOrElseUpdate(t, f(t))