From 0ffabf1419ab39a88eb7de35e8f34bdb185ddfbb Mon Sep 17 00:00:00 2001
From: Christoph Dietze <dietze@christophdietze.com>
Date: Tue, 12 Feb 2013 22:10:04 +0100
Subject: [PATCH] mirrorAngle(HALF_PI) should be -HALFPI rather than HALF_PI

---
 src/main/java/pythagoras/f/MathUtil.java     |  2 +-
 src/test/java/pythagoras/f/MathUtilTest.java | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 src/test/java/pythagoras/f/MathUtilTest.java

diff --git a/src/main/java/pythagoras/f/MathUtil.java b/src/main/java/pythagoras/f/MathUtil.java
index 3cf325e..133df38 100644
--- a/src/main/java/pythagoras/f/MathUtil.java
+++ b/src/main/java/pythagoras/f/MathUtil.java
@@ -169,7 +169,7 @@ public class MathUtil
      * Returns the mirror angle of the specified angle (assumed to be in [-pi, +pi]).
      */
     public static float mirrorAngle (float a) {
-        return (a > 0f ? FloatMath.PI : -FloatMath.PI) - a;
+        return a + (a > 0f ? -FloatMath.PI : FloatMath.PI);
     }
 
     /**
diff --git a/src/test/java/pythagoras/f/MathUtilTest.java b/src/test/java/pythagoras/f/MathUtilTest.java
new file mode 100644
index 0000000..5111d8a
--- /dev/null
+++ b/src/test/java/pythagoras/f/MathUtilTest.java
@@ -0,0 +1,19 @@
+//
+// Pythagoras - a collection of geometry classes
+// http://github.com/samskivert/pythagoras
+
+package pythagoras.f;
+
+import org.junit.*;
+import static org.junit.Assert.*;
+
+/**
+ * Tests parts of the {@link MathUtil} class.
+ */
+public class MathUtilTest
+{
+    @Test public void testMirrorAngle() {
+        assertEquals(-MathUtil.HALF_PI, MathUtil.mirrorAngle(MathUtil.HALF_PI), MathUtil.EPSILON);
+        assertEquals(MathUtil.HALF_PI, MathUtil.mirrorAngle(-MathUtil.HALF_PI), MathUtil.EPSILON);
+    }
+}