double parabola(double x, double y) { return integrate(0.0, x, delegate double(double x) { return y * x; } ) } double integrate(double x1, double x2, double delegate(double dx) f) { double sum = 0; double dx = 0.0001; for (double x = x1; x < x2; x += dx) sum += f(x) * dx; return sum; }