From ebbc90c88d07eddd40842b570fcd04d6b55b869b Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Mon, 18 May 2015 14:55:20 +1000
Subject: [PATCH] noise: templatise lerp functions

---
 noise/lerp.cpp | 88 ++++++++++++++++++++++++++++++++++++--------------
 noise/lerp.hpp | 12 +++----
 2 files changed, 70 insertions(+), 30 deletions(-)

diff --git a/noise/lerp.cpp b/noise/lerp.cpp
index a9a646ec..84b7b5d1 100644
--- a/noise/lerp.cpp
+++ b/noise/lerp.cpp
@@ -23,48 +23,88 @@
 
 
 //-----------------------------------------------------------------------------
-double
-util::lerp::sigmoid (double val) {
-    return -1.0 + 2.0 / (1.0 + exp (-2.0 * val));
+template <typename T>
+T
+util::lerp::sigmoid (T val)
+{
+    static_assert (std::is_floating_point<T>::value, "lerp is only defined for floating types");
+    return -1 + 2 / (1 + std::exp (-2 * val));
 }
 
+template float util::lerp::sigmoid (float);
+template double util::lerp::sigmoid (double);
+
 
 //-----------------------------------------------------------------------------
-double util::lerp::trunc (double a, double, double)
-    { return a; }
+template <typename T>
+T
+util::lerp::trunc (T a, T, T)
+{
+    static_assert (std::is_floating_point<T>::value, "lerp is only defined for floating types");
+    return a;
+}
+
+template float util::lerp::trunc (float, float, float);
+template double util::lerp::trunc (double, double, double);
 
 
 //-----------------------------------------------------------------------------
-double
-util::lerp::linear (double a, double b, double weight) {
-    CHECK (weight >= 0.0 && weight <= 1.0);
-    return a * (1.0 - weight) + b * weight;
+template <typename T>
+T
+util::lerp::linear (T a, T b, T weight)
+{
+    static_assert (std::is_floating_point<T>::value, "lerp is only defined for floating types");
+    CHECK (weight >= 0 && weight <= 1);
+    return a * (1 - weight) + b * weight;
 }
 
+template float util::lerp::linear (float, float, float);
+template double util::lerp::linear (double, double, double);
+
 
 //-----------------------------------------------------------------------------
-double
-util::lerp::cosine (double a, double b, double weight) {
-    CHECK (weight >= 0.0 && weight <= 1.0);
-    double t  = (1.0 - cos (weight * PI<double>)) * 0.5;
+template <typename T>
+T
+util::lerp::cosine (T a, T b, T weight)
+{
+    static_assert (std::is_floating_point<T>::value, "lerp is only defined for floating types");
+    CHECK (weight >= 0 && weight <= 1);
+    T t  = (1 - std::cos (weight * PI<T>)) * T(0.5);
 
-    return a * (1.0 - t) + b * t;
+    return a * (1 - t) + b * t;
 }
 
+template float util::lerp::cosine (float, float, float);
+template double util::lerp::cosine (double, double, double);
+
 
 //-----------------------------------------------------------------------------
-double
-util::lerp::cubic (double a, double b, double weight) {
-    CHECK (weight >= 0.0 && weight <= 1.0);
-    double t = weight * weight * (3.0 - 2.0 * weight);
-    return a * (1.0 - t) + b * t;
+template <typename T>
+T
+util::lerp::cubic (T a, T b, T weight)
+{
+    static_assert (std::is_floating_point<T>::value, "lerp is only defined for floating types");
+    CHECK (weight >= 0 && weight <= 1);
+    T t = weight * weight * (3 - 2 * weight);
+    return a * (1 - t) + b * t;
 }
 
+template float util::lerp::cubic (float, float, float);
+template double util::lerp::cubic (double, double, double);
+
 
 //-----------------------------------------------------------------------------
-double
-util::lerp::quintic (double a, double b, double weight) {
-    CHECK (weight >= 0.0 && weight <= 1.0);
-    double t = weight * weight * weight * (weight * (weight * 6.0 - 15.0) + 10.0);
-    return a * (1.0 - t) + b * t;
+template <typename T>
+T
+util::lerp::quintic (T a, T b, T weight)
+{
+    static_assert (std::is_floating_point<T>::value, "lerp is only defined for floating types");
+
+    CHECK (weight >= 0 && weight <= 1);
+    T t = weight * weight * weight * (weight * (weight * 6 - 15) + 10);
+    return a * (1 - t) + b * t;
 }
+
+
+template float util::lerp::quintic (float, float, float);
+template double util::lerp::quintic (double, double, double);
diff --git a/noise/lerp.hpp b/noise/lerp.hpp
index 48d01b5a..618f6711 100644
--- a/noise/lerp.hpp
+++ b/noise/lerp.hpp
@@ -18,13 +18,13 @@
 #define __UTIL_NOISE_LERP_HPP
 
 namespace util { namespace lerp {
-    double sigmoid (double val);
+    template <typename T> T sigmoid (T val);
 
-    double linear  (double a, double b, double weight);
-    double cosine  (double a, double b, double weight);
-    double cubic   (double a, double b, double weight);
-    double quintic (double a, double b, double weight);
-    double trunc   (double a, double b, double weight);
+    template <typename T> T linear  (T a, T b, T weight);
+    template <typename T> T cosine  (T a, T b, T weight);
+    template <typename T> T cubic   (T a, T b, T weight);
+    template <typename T> T quintic (T a, T b, T weight);
+    template <typename T> T trunc   (T a, T b, T weight);
 } }
 
 #endif