From ef1f1f316f1d6e4f839292a032286e7c5724c34b Mon Sep 17 00:00:00 2001
From: nwolek <nw@nathanwolek.com>
Date: Wed, 30 Dec 2015 12:12:47 -0500
Subject: [PATCH] Interpolator: Cosine option is now overloaded and passing
 tests. issue #71

---
 include/core/JamomaInterpolator.h  | 16 ++++++++++++----
 test/Interpolator/Interpolator.cpp | 22 ++++++++++++++++++++--
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/include/core/JamomaInterpolator.h b/include/core/JamomaInterpolator.h
index 5d6953d..3c7dad8 100644
--- a/include/core/JamomaInterpolator.h
+++ b/include/core/JamomaInterpolator.h
@@ -111,8 +111,10 @@ namespace Jamoma {
 		
 
 		/** Cosine interpolation
-			@param x0		Sample value at prior integer index
-			@param x1		Sample value at next integer index
+            @param x0		Unused sample value
+            @param x1		Sample value at prior integer index
+			@param x2		Sample value at next integer index
+            @param x3		Unused sample value
 			@param delta 	Fractional location between x0 (delta=0) and x1 (delta=1)
 			@return			The interpolated value
 		 */
@@ -121,10 +123,16 @@ namespace Jamoma {
 		public:
 			static const int 	delay = 1;
 			
-			constexpr T operator()(T x0, T x1, double delta) noexcept {
+			constexpr T operator()(T x1, T x2, double delta) noexcept {
 				T a = 0.5 * (1.0 - cos(delta * kPi));
-				return x0 + a * (x1-x0);
+				return x1 + a * (x2-x1);
 			}
+            
+            constexpr T operator()(T x0, T x1, T x2, T x3, double delta) noexcept {
+                // NW: ideally we would call the operator above to remain DRY, but I could not get syntax right
+                T a = 0.5 * (1.0 - cos(delta * kPi));
+                return x1 + a * (x2-x1);
+            }
 		};
 
 		
diff --git a/test/Interpolator/Interpolator.cpp b/test/Interpolator/Interpolator.cpp
index 803f8f1..fec42b3 100644
--- a/test/Interpolator/Interpolator.cpp
+++ b/test/Interpolator/Interpolator.cpp
@@ -216,10 +216,10 @@ class InterpolatorTest {
         int		badSampleCount = 0;
         Jamoma::Interpolator::Cosine<Jamoma::Sample> my_interp;
         
-        //auto 	x0 = -1.0;
+        auto 	x0 = -1.0;
         auto	x1 =  2.0;
         auto    x2 =  1.0;
-        //auto    x3 =  4.0;
+        auto    x3 =  4.0;
         
         // The following output was generated using the Octave code
         // in InterpolatorTargetOutput.m by NW
@@ -305,6 +305,24 @@ class InterpolatorTest {
         }
 		
 		mTest->TEST_ASSERT("testCosine produced correct interpolation output", badSampleCount == 0);
+        
+        // reset varaiables
+        badSampleCount = 0;
+        temp = 0.0;
+        tempExpected = 0.0;
+        delta = 0.0;
+        
+        for (int i = 0; i < expectedOutputCosine.size(); i++) {
+            delta = (i + 1.0) / 64.0;
+            temp = my_interp(x0,x1,x2,x3,delta);
+            tempExpected = expectedOutputCosine[i];
+            if (! mTest->compare(temp, tempExpected, true, 8) ) {
+                badSampleCount++;
+                std::cout << "sample " << i << " had a difference of " << std::fabs(temp - tempExpected) << std::endl;
+            }
+        }
+        
+        mTest->TEST_ASSERT("testCosine overloaded operator produced consistent output", badSampleCount == 0);
 	}