currency_type

currency_type

The Currency type is a large numeric type, with exactly four digit after the decimal point. Internally, Currency using integer calculation to minimizes rounding errors.

The Currency type is appropriate for financial calculations that require large numbers of significant integral, up to four fractional digits, and minimize error caused by floating point calculation.

Why Using Currency ?

Currency prevent rounding error from floating point calculation. Currency also make comparisan more accurate and predictable.

Using Double

func main() {
  var a = 0.7;
  var b = 0.49;
  var c = a * a;

  print('$a * $a = $c');

  if (c == b) {
    print("Equal");
  } else {
    print("Not Equal");
  }
}

0.7 * 0.7 = 0.48999999999999994
Not Equal

Using Currency

func main() {
  var a = Currency.parse('0.7');
  var b = Currency.parse('0.49');
  var c = a * a;

  print('$a * $a = $c');

  if (c == b) {
    print("Equal");
  } else {
    print("Not Equal");
  }
}

0.7000 * 0.7000 = 0.4900
Equal

How To Use

To use currency_type module, you have to add to your project by run following command:

$ dart pub add currency_type 

or add directly in pubspec.yaml

dependencies: 
  currency_type: ^1.0.0

and then import to your dart file

import 'package:currency_type/currency_type.dart';

Variable declaration

You can declare Currency variable in 3 ways:

1. Create zero value

   var a = Currency();
   

2. Convert from numbers variable or literal :

   var b = 1234;
   var c = 1234.56;
   
   var d = Currency.from(b);
   var e = Currency.from(c);
   
   var f = Currency.from(1234);
   var g = Currency.from(1234.56);
   

3. Parsing from string :

   var f = Currency.parse('1234567890');
   var g = Currency.parse('1234567890123456.1234');
   

Operations

You can do arithmetic operation on Currency like addition, subtraction, multiplication, or division.

var h = d + e; 
var i = g - h;
var j = d * e; 
var k = g / f; 

var l = (d + e) * g;

Currency can also be compared to other Currency

if (k == l) {
   ...
}


if (h > Currency.from(100)) {
   ...
}

Big Numbers

Unlike double, Currency can store very big number precisely.

func main() {
  var a = 12345678901234567.1234;
  print("Big Double   : $a");

  var b = Currency.parse('12345678901234567.1234');
  print("Big Currency : $b");
}

Big Double   : 12345678901234568.0
Big Currency : 12345678901234567.1234

Copyright (c) 2021-2025, Mohamad Tantowi Mustofa (tantowi.com)
Licensed under BSD 3-Clause license.