From 7048d8231be79cdefe39585aaaa43cd02c9f396f Mon Sep 17 00:00:00 2001
From: Michael Bayne <mdb@samskivert.com>
Date: Mon, 30 Apr 2012 15:07:44 -0700
Subject: [PATCH] Added Vector.cross() & co.

Closes #10.
---
 src/main/java/pythagoras/f/AbstractVector.java | 11 +++++++++++
 src/main/java/pythagoras/f/IVector.java        |  9 +++++++++
 src/main/java/pythagoras/f/Vector.java         |  7 +++++++
 3 files changed, 27 insertions(+)

diff --git a/src/main/java/pythagoras/f/AbstractVector.java b/src/main/java/pythagoras/f/AbstractVector.java
index 0d048bb..7b7b76e 100644
--- a/src/main/java/pythagoras/f/AbstractVector.java
+++ b/src/main/java/pythagoras/f/AbstractVector.java
@@ -17,6 +17,17 @@ public abstract class AbstractVector implements IVector
         return x()*other.x() + y()*other.y();
     }
 
+    @Override // from interface IVector
+    public Vector cross (IVector other) {
+        return cross(other, new Vector());
+    }
+
+    @Override // from interface IVector
+    public Vector cross (IVector other, Vector result) {
+        float x = x(), y = y(), ox = other.x(), oy = other.y();
+        return result.set(y*ox - x*oy, x*oy - y*ox);
+    }
+
     @Override // from interface IVector
     public Vector negate () {
         return negate(new Vector());
diff --git a/src/main/java/pythagoras/f/IVector.java b/src/main/java/pythagoras/f/IVector.java
index 0dd4fac..a7147b8 100644
--- a/src/main/java/pythagoras/f/IVector.java
+++ b/src/main/java/pythagoras/f/IVector.java
@@ -18,6 +18,15 @@ public interface IVector
     /** Computes and returns the dot product of this and the specified other vector. */
     float dot (IVector other);
 
+    /** Computes the cross product of this and the specified other vector.
+     * @return a new vector containing the result. */
+    Vector cross (IVector other);
+
+    /** Computes the cross product of this and the specified other vector, placing the result in
+     * the object supplied.
+     * @return a reference to the result, for chaining. */
+    Vector cross (IVector other, Vector result);
+
     /** Negates this vector.
      * @return a new vector containing the result. */
     Vector negate ();
diff --git a/src/main/java/pythagoras/f/Vector.java b/src/main/java/pythagoras/f/Vector.java
index 09eec17..6b6d98d 100644
--- a/src/main/java/pythagoras/f/Vector.java
+++ b/src/main/java/pythagoras/f/Vector.java
@@ -29,6 +29,13 @@ public class Vector extends AbstractVector
     public Vector () {
     }
 
+    /** Computes the cross product of this and the specified other vector, storing the result in
+     * this vector.
+     * @return a reference to this vector, for chaining. */
+    public Vector crossLocal (IVector other) {
+        return cross(other, this);
+    }
+
     /** Negates this vector in-place.
      * @return a reference to this vector, for chaining. */
     public Vector negateLocal () {