diff --git a/coeffs.hh b/coeffs.hh
index 9303483..403c9bc 100644
--- a/coeffs.hh
+++ b/coeffs.hh
@@ -8,24 +8,19 @@ Copyright 2018 Ahmet Inan <inan@aicodix.de>
 
 namespace DSP {
 
-template <typename TYPE>
-struct CoeffsFunc
-{
-	virtual TYPE operator () (int, int) = 0;
-	virtual ~CoeffsFunc() = default;
-};
-
 template <int TAPS, typename TYPE>
 class Coeffs
 {
 	TYPE w[TAPS];
 public:
-	Coeffs(CoeffsFunc<TYPE> *func)
+	template <typename FUNC>
+	Coeffs(FUNC *func)
 	{
 		for (int n = 0; n < TAPS; ++n)
 			w[n] = (*func)(n, TAPS);
 	}
-	Coeffs(CoeffsFunc<TYPE> *func0, CoeffsFunc<TYPE> *func1)
+	template <typename FUNC0, typename FUNC1>
+	Coeffs(FUNC0 *func0, FUNC1 *func1)
 	{
 		for (int n = 0; n < TAPS; ++n)
 			w[n] = (*func0)(n, TAPS) * (*func1)(n, TAPS);
diff --git a/filter.hh b/filter.hh
index dd1b1d3..c841f23 100644
--- a/filter.hh
+++ b/filter.hh
@@ -8,12 +8,11 @@ Copyright 2018 Ahmet Inan <inan@aicodix.de>
 
 #include "const.hh"
 #include "utils.hh"
-#include "coeffs.hh"
 
 namespace DSP {
 
 template <typename TYPE>
-class LowPass : public CoeffsFunc<TYPE>
+class LowPass
 {
 	TYPE f;
 public:
@@ -26,7 +25,7 @@ public:
 };
 
 template <typename TYPE>
-class HighPass : public CoeffsFunc<TYPE>
+class HighPass
 {
 	TYPE f;
 public:
@@ -41,7 +40,7 @@ public:
 };
 
 template <typename TYPE>
-class BandPass : public CoeffsFunc<TYPE>
+class BandPass
 {
 	TYPE f0, f1;
 public:
diff --git a/window.hh b/window.hh
index 7bffef7..bd9364c 100644
--- a/window.hh
+++ b/window.hh
@@ -10,18 +10,17 @@ Copyright 2018 Ahmet Inan <inan@aicodix.de>
 #include "kahan.hh"
 #include "utils.hh"
 #include "unit_circle.hh"
-#include "coeffs.hh"
 
 namespace DSP {
 
 template <typename TYPE>
-struct Rect : public CoeffsFunc<TYPE>
+struct Rect
 {
 	TYPE operator () (int n, int N) { return n >= 0 && n < N ? 1 : 0; }
 };
 
 template <typename TYPE>
-struct Hann : public CoeffsFunc<TYPE>
+struct Hann
 {
 	TYPE operator () (int n, int N)
 	{
@@ -30,7 +29,7 @@ struct Hann : public CoeffsFunc<TYPE>
 };
 
 template <typename TYPE>
-struct Hamming : public CoeffsFunc<TYPE>
+struct Hamming
 {
 	TYPE operator () (int n, int N)
 	{
@@ -39,7 +38,7 @@ struct Hamming : public CoeffsFunc<TYPE>
 };
 
 template <typename TYPE>
-struct Lanczos : public CoeffsFunc<TYPE>
+struct Lanczos
 {
 	TYPE operator () (int n, int N)
 	{
@@ -53,7 +52,7 @@ struct Lanczos : public CoeffsFunc<TYPE>
 };
 
 template <typename TYPE>
-class Blackman : public CoeffsFunc<TYPE>
+class Blackman
 {
 	TYPE a0, a1, a2;
 public:
@@ -68,7 +67,7 @@ public:
 };
 
 template <typename TYPE>
-class Gauss : public CoeffsFunc<TYPE>
+class Gauss
 {
 	TYPE o;
 public:
@@ -80,7 +79,7 @@ public:
 };
 
 template <typename TYPE>
-class Kaiser : public CoeffsFunc<TYPE>
+class Kaiser
 {
 	TYPE a;
 	/*