将两个双精度值相乘在颤振中给出负数

Question

I need to multiply two large numbers for example,

 double x = 318191400000;
 double result =x*x;

But i am getting negative value for this when building in flutter .

Please help me on this.

[1]: https://i.stack.imgur.com/eyxJ4.png

Answer 1

You're not actually multiplying two double s here, but two int s which is overflowing the 64-bit integer resulting in a negative number.

With doubles:

void main() {
  double x = 318191400000;
  print(x*x); // Result: 1.0124576703396e+23
}

With ints:

void main() {
  int x = 318191400000;
  print(x*x); // Result: -8411186631728820224
}

If you ever print a double to the console, you'll always see it displayed in either scientific notation (for extremely large or small values) or with a decimal point with at least one trailing digit.

Answer 2

Finally i have found solution and sharing here for anyone having these kind of issues,

xValues[index].toDouble() * yValues[index].toDouble()

This gives the expected result which is 1.0124576703396e+23