Core: Linear interpolation (Lerp) templates and reference example for (numbers, Point Size and Rect) (#215)

reference/LinearInterpolation/LinearInterpolation.cpp

@@ -0,0 +1,19 @@
+#include <Core/Core.h>
+
+using namespace Upp;
+
+// Generic Lerp and specializations
+
+CONSOLE_APP_MAIN
+{
+	StdLogSetup(LOG_COUT);
+	
+    DUMP(Lerp(10, 20, 0.5));
+    DUMP(Lerp(10.0, 20.0, 0.25));
+    DUMP(Lerp(Point(10, 20), Point(30, 40), 0.5));
+    DUMP(Lerp(Size(100, 200), Size(300, 400), 0.5));
+    DUMP(Lerp(Rect(0, 0, 100, 100), Rect(100, 100, 200, 200), 0.5));
+}
+
+
+

reference/LinearInterpolation/LinearInterpolation.upp

@@ -0,0 +1,11 @@
+description "Demonstrates the linear interpolation templates.\377";
+
+uses
+	Core;
+
+file
+	LinearInterpolation.cpp;
+
+mainconfig
+	"" = "";
+

uppsrc/Core/Gtypes.h

@@ -720,6 +720,36 @@ Pointf Normalize(const Pointf& p);
 Pointf Polar(double a);
 Pointf Polar(const Pointf& p, double r, double a);
 
+// Linear interopolation templates
+
+template <typename T>
+inline T Lerp(T a, T b, double t)
+{
+    return a + t * (b - a);
+}
+
+template <typename T>
+inline Point_<T> Lerp(Point_<T> a, Point_<T> b, double t)
+{
+    return Point_<T>(Lerp(a.x, b.x, t), Lerp(a.y, b.y, t));
+}
+
+template <typename T>
+inline Size_<T> Lerp(Size_<T> a, Size_<T> b, double t)
+{
+    return Size_<T>(Lerp(a.cx, b.cx, t), Lerp(a.cy, b.cy, t));
+}
+
+template <typename T>
+inline Rect_<T> Lerp(Rect_<T> a, Rect_<T> b, double t)
+{
+    return Rect_<T>(
+        Lerp(a.left, b.left, t),
+        Lerp(a.top, b.top, t),
+        Lerp(a.right, b.right, t),
+        Lerp(a.bottom, b.bottom, t)
+    );
+}
 
 // deprecated because of confusing name: