From 7d559c09e25f4af8bd01fc47e9c02cc075f1ed30 Mon Sep 17 00:00:00 2001
From: Brendan Zabarauskas <bjzaba@yahoo.com.au>
Date: Fri, 30 Nov 2012 22:28:58 +1000
Subject: [PATCH] Add opposite method

---
 src/angle.rs           | 17 +++++++++++++++--
 src/test/test_angle.rs | 18 ++++++++++++++----
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/angle.rs b/src/angle.rs
index 24e599b..d1c97ea 100644
--- a/src/angle.rs
+++ b/src/angle.rs
@@ -26,6 +26,7 @@ pub trait Angle<T>: Add<self,self>
     pure fn to_radians(&self) -> Radians<T>;
     pure fn to_degrees(&self) -> Degrees<T>;
     pure fn wrap(&self) -> self;
+    pure fn opposite(&self) -> self;
 }
 
 
@@ -44,9 +45,15 @@ pub impl<T:Copy Num NumCast> Radians<T>: Angle<T> {
     #[inline(always)] pure fn to_radians(&self) -> Radians<T> { *self }
     #[inline(always)] pure fn to_degrees(&self) -> Degrees<T> { Degrees(**self * cast(180.0 / pi)) }
     
-    #[inline(always)] pure fn wrap(&self) -> Radians<T> {
+    #[inline(always)]
+    pure fn wrap(&self) -> Radians<T> {
         (*self) % cast(2.0 * pi)   // TODO: keep in the domain of 0 to two_pi
     }
+    
+    #[inline(always)]
+    pure fn opposite(&self) -> Radians<T> {
+        (self + Angle::half_turn()).wrap()     // TODO: test!
+    }
 }
     
 pub impl<T:Copy Num> Radians<T>: Add<Radians<T>, Radians<T>> {
@@ -123,9 +130,15 @@ pub impl<T:Copy Num NumCast> Degrees<T>: Angle<T> {
     #[inline(always)] pure fn to_radians(&self) -> Radians<T> { Radians(**self * cast(pi / 180.0)) }
     #[inline(always)] pure fn to_degrees(&self) -> Degrees<T> { *self }
     
-    #[inline(always)] pure fn wrap(&self) -> Degrees<T> {
+    #[inline(always)]
+    pure fn wrap(&self) -> Degrees<T> {
         (*self) % cast(360)   // TODO: keep in the domain of 0 to 360
     }
+    
+    #[inline(always)]
+    pure fn opposite(&self) -> Degrees<T> {
+        (self + Angle::half_turn()).wrap()      // TODO: test!
+    }
 }
 
 pub impl<T:Copy Num> Degrees<T>: Add<Degrees<T>, Degrees<T>> {
diff --git a/src/test/test_angle.rs b/src/test/test_angle.rs
index 918b247..a2750b9 100644
--- a/src/test/test_angle.rs
+++ b/src/test/test_angle.rs
@@ -21,10 +21,15 @@ fn test_radians() {
     assert *Radians(pi).wrap()                  == *Radians(pi);
     assert *Radians(3.0 * pi).wrap()            == *Radians(pi);
     assert *Radians(2.0 * pi).wrap()            == *Radians(0.0);
-    assert *Radians(-pi).wrap()                 == *Radians(-pi);
-    assert *Radians(-3.0 * pi).wrap()           == *Radians(-pi);
+    assert *Radians(-pi).wrap()                 == *Radians(-pi);   // FIXME: should be in the domain of 0 to two_pi
+    assert *Radians(-3.0 * pi).wrap()           == *Radians(-pi);   // FIXME: should be in the domain of 0 to two_pi
     assert *Radians(-2.0 * pi).wrap()           == *Radians(0.0);
     
+    assert *Radians(0.0).opposite()             == *Radians(pi as float);
+    assert *Radians(pi / 2.0).opposite()        == *Radians((pi / 2.0) * 3.0);
+    assert *Radians(pi * 3.0).opposite()        == *Radians(0.0);
+    assert *Radians(-2.0 * pi).opposite()       == *Radians(-pi);   // FIXME: should be in the domain of 0 to two_pi
+    
     assert *(Radians(pi) + Radians(pi))         == *Radians(2.0 * pi);
     assert *(Radians(2.0 * pi) - Radians(pi))   == *Radians(pi);
     assert *(Radians(pi) * 2.0)                 == *Radians(2.0 * pi);
@@ -52,10 +57,15 @@ fn test_degrees() {
     assert Degrees(90.0).wrap()                 == Degrees(90.0);
     assert Degrees(450.0).wrap()                == Degrees(90.0);
     assert Degrees(360.0).wrap()                == Degrees(0.0);
-    assert Degrees(-90.0).wrap()                == Degrees(-90.0);
-    assert Degrees(-450.0).wrap()               == Degrees(-90.0);
+    assert Degrees(-90.0).wrap()                == Degrees(-90.0);   // FIXME: should be in the domain of 0 to 360
+    assert Degrees(-450.0).wrap()               == Degrees(-90.0);   // FIXME: should be in the domain of 0 to 360
     assert Degrees(-360.0).wrap()               == Degrees(0.0);
     
+    assert Degrees(0.0).opposite()             == Degrees(180.0);
+    assert Degrees(90.0).opposite()            == Degrees(270.0);
+    assert Degrees(540.0).opposite()           == Degrees(0.0);
+    assert Degrees(-360.0).opposite()          == Degrees(-180.0);   // FIXME: should be in the domain of 0 to 360
+    
     assert (Degrees(180.0) + Degrees(180.0))    == Degrees(360.0);
     assert (Degrees(360.0) - Degrees(180.0))    == Degrees(180.0);
     assert (Degrees(360.0) * 2.0)               == Degrees(720.0);