fromString static method

Price fromString(String price)

Approximates price to a fraction. Please remember that this function can give unexpected results for values that cannot be represented as a fraction with 32-bit numerator and denominator. It's safer to create a Price object using the constructor.

Implementation

static Price fromString(String price) {

  List<String> two = price.split(".");
  BigInt number = BigInt.parse(two[0]);
  double f = 0.0;
  if (two.length == 2) {
    f = double.parse("0.${two[1]}");
  }
  BigInt maxInt = BigInt.from(Int32.MAX_VALUE.toInt());
  BigInt a;
  // List<List<BigInt>> fractions = List<List<BigInt>>();
  List<List<BigInt>> fractions = [];
  fractions.add([BigInt.zero, BigInt.one]);
  fractions.add([BigInt.one, BigInt.zero]);
  int i = 2;
  while (true) {
    if (number > maxInt) {
      break;
    }
    a = number;
    BigInt h = a * (fractions[i - 1][0]) + (fractions[i - 2][0]);
    BigInt k = a * (fractions[i - 1][1]) + (fractions[i - 2][1]);
    if (h > maxInt || k > maxInt) {
      break;
    }
    fractions.add([h, k]);
    if (f == 0.0) {
      break;
    }
    double point = 1 / f;
    number = BigInt.from(point);
    f = point - number.toDouble();
    i = i + 1;
  }
  BigInt n = fractions[fractions.length - 1][0];
  BigInt d = fractions[fractions.length - 1][1];
  return new Price(n.toInt(), d.toInt());
}