add interp()

stepmania/src/RageUtil.h

@@ -41,6 +41,13 @@ inline unsigned long max( unsigned long a, unsigned int b ) { return a > b? a:b;
 // Do the multiply before the divide to that integer scales have more precision.
 #define SCALE(x, l1, h1, l2, h2)	(((x) - (l1)) * ((h2) - (l2)) / ((h1) - (l1)) + (l2))
 
+// Like SCALE(x, 0, 1, L, H); interpolate between L and H.
+template<typename T, typename U>
+inline U interp( T x, U l, U h )
+{
+        return U(x * (h - l) + l);
+}
+
 inline bool CLAMP( int &x, int l, int h )
 {
 	if (x > h)		{ x = h; return true; }