From 72eb7189be3f5530589c408f3e338a078207ee78 Mon Sep 17 00:00:00 2001
From: Corwin <corwin@kuiper.dev>
Date: Wed, 15 May 2024 18:30:03 +0100
Subject: [PATCH 1/3] add dot and cross product

---
 agb-fixnum/src/lib.rs | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/agb-fixnum/src/lib.rs b/agb-fixnum/src/lib.rs
index 6b75318f..e9f427b6 100644
--- a/agb-fixnum/src/lib.rs
+++ b/agb-fixnum/src/lib.rs
@@ -1113,6 +1113,48 @@ impl<T: Number> Vector2D<T> {
         }
     }
 
+    #[doc(alias = "scalar_product")]
+    /// Calculates the dot product / scalar product of two vectors
+    /// ```
+    /// use agb_fixnum::Vector2D;
+    ///
+    /// let v1 = Vector2D::new(3, 5);
+    /// let v2 = Vector2D::new(7, 11);
+    ///
+    /// let dot = v1.dot(v2);
+    /// assert_eq!(dot, 76);
+    /// ```
+    /// The dot product for vectors *A* and *B* is defined as
+    /// > *A*<sub>*x*</sub> × *B*<sub>*x*</sub> + *A*<sub>*y*</sub> × *B*<sub>*y*</sub>.
+    pub fn dot(self, b: Self) -> T {
+        self.x * b.x + self.y * b.y
+    }
+
+    #[doc(alias = "vector_product")]
+    /// Calculates the *z* component of the cross product / vector product of two
+    /// vectors
+    /// ```
+    /// use agb_fixnum::Vector2D;
+    ///
+    /// let v1 = Vector2D::new(3, 5);
+    /// let v2 = Vector2D::new(7, 11);
+    ///
+    /// let dot = v1.cross(v2);
+    /// assert_eq!(dot, -2);
+    /// ```
+    /// The cross product for vectors *A* and *B* is defined as
+    /// > *A*<sub>*x*</sub> × *B*<sub>*y*</sub> - *A*<sub>*y*</sub> × *B*<sub>*x*</sub>.
+    ///
+    ///
+    /// Normally the cross product / vector product is itself a vector. This is
+    /// in the 3D case where the cross product of two vectors is perpendicular
+    /// to both vectors. The only vector perpendicular to two 2D vectors is
+    /// purely in the *z* direction, hence why this method only returns that
+    /// component. The *x* and *y* components are always zero.
+    pub fn cross(self, b: Self) -> T {
+        self.x * b.y - self.y * b.x
+    }
+
     #[must_use]
     /// Swaps the x and y coordinate
     /// ```

From f99a564f897cdb4dd89847c15125ec539768e1ae Mon Sep 17 00:00:00 2001
From: Corwin <corwin@kuiper.dev>
Date: Wed, 15 May 2024 19:43:48 +0100
Subject: [PATCH 2/3] add changelog entry for dot/cross

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4fc7fb74..f2bdbf6b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Added `dot` and `cross` product methods for `Vector2D`.
+
 ### Fixed
 
 - Fixed an issue with agb tracker where XM files with linear frequencies were playing the wrong notes

From 2887791109e53beb0f05564ed0c76173aa3e6cd2 Mon Sep 17 00:00:00 2001
From: Corwin <corwin@kuiper.dev>
Date: Wed, 15 May 2024 22:32:28 +0100
Subject: [PATCH 3/3] clarify it's only the z component

---
 agb-fixnum/src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/agb-fixnum/src/lib.rs b/agb-fixnum/src/lib.rs
index e9f427b6..d61852ae 100644
--- a/agb-fixnum/src/lib.rs
+++ b/agb-fixnum/src/lib.rs
@@ -1142,7 +1142,7 @@ impl<T: Number> Vector2D<T> {
     /// let dot = v1.cross(v2);
     /// assert_eq!(dot, -2);
     /// ```
-    /// The cross product for vectors *A* and *B* is defined as
+    /// The *z* component cross product for vectors *A* and *B* is defined as
     /// > *A*<sub>*x*</sub> × *B*<sub>*y*</sub> - *A*<sub>*y*</sub> × *B*<sub>*x*</sub>.
     ///
     ///