Dart Double Fun

doubles.dart

import 'dart:math';

double roundDouble(double value, double places) { 
   num mod = pow(10.0, places); 
   return ((value * mod).round().toDouble() / mod); 
}

extension BetterDoubles on num {
  num roundAsDoubleBetter(double places) {
    final num mod = pow(10.0, places); 
    return ((this * mod).round().toDouble() / mod);
  }
}

void main() {
  final num price = 19.99;
  
  // Just the price
  print(price);
  
  // * 100, * operator returns a num
  print(price * 100);
  
  // roundToDouble includes nearest integer, this won't work
  print(price.roundToDouble());
  
  // We need a custom method
  print(roundDouble(double.parse(price.toString()), 2));
  
  // multipying but retaining most significant digits
  print(roundDouble(double.parse((price * 100).toString()), 2));
  
  // easier way to express the above
  final num priceTimes100 = price * 100;
  print(roundDouble(double.parse(priceTimes100.toString()), 2));
  
  // even easier way!
  print((price * 100).roundAsDoubleBetter(2));
}