Add a Decimal type to your Flutter and Dart projects to handle operations on decimal numbers.

Why

Operation on decimal numbers using the regular double type can lead to precision errors. This is a general issue with floating point numbers, but it can be particularly problematic when working with money. See https://stackoverflow.com/questions/588004/is-floating-point-math-broken for more information on this issue or https://stackoverflow.com/questions/70693686/double-multiplication-in-dart-gives-unusual-result for a specific example in Dart.

How does this package work

Internally this package uses the BigInt type to store the decimal number as an integer and a regular int to count the number of decimal digits. This way we can do all the computations using integers and only convert to a decimal number when needed in the toString() method.

Getting started

Add the package to your pubspec.yaml by typing this value using your terminal in the root of your project:

dart pub add decimal_type

Usage

Import the package in your Dart file:

import 'package:decimal_type/decimal_type.dart';

Create a new Decimal object:

final value1 = Decimal.fromString('10.5');
final value2 = Decimal.fromDouble(2.351, decimalPrecision: 3);

final sum = value1 + value2;
final difference = value1 - value2;
final product = value1 * value2;
final quotient = value1 / value2;

print(sum); // 12.851
print(difference); // 8.149
print(product); // 24.6855
print(quotient); // 4.46618460229689517860 (capped to 20 decimal digits)

Additional information

When using division or creating a Decimal object from a double, you can specify the number of decimal digits to keep using the decimalPrecision parameter. This parameter defaults to 20 and accepts values between 0 and 20.