added notes to resolve undefined behavior of calculations in tweening

interpolators in future.

scene/animation/tween_interpolaters.cpp

@@ -285,18 +285,18 @@ namespace cubic {
 namespace circ {
 	static real_t in(real_t t, real_t b, real_t c, real_t d)
 	{
-		return -c * (sqrt(1 - (t /= d) * t) - 1) + b;
+		return -c * (sqrt(1 - (t /= d) * t) - 1) + b; // TODO: ehrich: operation with t is undefined
 	}
 
 	static real_t out(real_t t, real_t b, real_t c, real_t d)
 	{
-		return c * sqrt(1 - (t = t / d - 1) * t) + b;
+		return c * sqrt(1 - (t = t / d - 1) * t) + b; // TODO: ehrich: operation with t is undefined
 	}
 
 	static real_t in_out(real_t t, real_t b, real_t c, real_t d)
 	{
 		if ((t /= d / 2) < 1) return -c / 2 * (sqrt(1 - t * t) - 1) + b;
-		return c / 2 * (sqrt(1 - t * (t -= 2)) + 1) + b;
+		return c / 2 * (sqrt(1 - t * (t -= 2)) + 1) + b; // TODO: ehrich: operation with t is undefined
 	}
 
 	static real_t out_in(real_t t, real_t b, real_t c, real_t d)
@@ -364,15 +364,15 @@ namespace back {
 	static real_t out(real_t t, real_t b, real_t c, real_t d)
 	{
         float s = 1.70158f;
-        return c * ((t = t / d- 1) * t * ((s + 1) * t + s) + 1) + b;
+        return c * ((t = t / d- 1) * t * ((s + 1) * t + s) + 1) + b; // TODO: ehrich: operation with t is undefined
 	}
 
 	static real_t in_out(real_t t, real_t b, real_t c, real_t d)
 	{
 		float s = 1.70158f;
-		if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525f)) + 1) * t - s)) + b;
+		if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525f)) + 1) * t - s)) + b; // TODO: ehrich: operation with s is undefined
 		float postFix = t -= 2;
-		return c / 2 * ((postFix) * t * (((s *= (1.525f)) + 1) * t + s) + 2) + b;
+		return c / 2 * ((postFix) * t * (((s *= (1.525f)) + 1) * t + s) + 2) + b; // TODO: ehrich: operation with s is undefined
 	}
 
 	static real_t out_in(real_t t, real_t b, real_t c, real_t d)