return o;
}
+Real
+Bezier::slope_at_point (Real t) const
+{
+ Offset second_order[3];
+ Offset third_order[2];
+
+ for (vsize i = 0; i < 3; i++)
+ second_order[i] = ((control_[i + 1] - control_[i]) * t) + control_[i];
+
+ for (vsize i = 0; i < 2; i++)
+ third_order[i] = ((second_order[i + 1] - second_order[i]) * t) + second_order[i];
+
+ if (third_order[1][X_AXIS] - third_order[0][X_AXIS] == 0)
+ return infinity_f;
+
+ return (third_order[1][Y_AXIS] - third_order[0][Y_AXIS]) / (third_order[1][X_AXIS] - third_order[0][X_AXIS]);
+}
+
/*
Cache binom (3, j) t^j (1-t)^{3-j}
*/