decimal4d 0.0.2

A decimal library for Dart, which is full tested and supports infinite repeating decimals.

Decimal for Dart

A comprehensive decimal library for Dart that provides precise decimal arithmetic with support for infinite repeating decimals. Built for high-precision calculations without floating-point errors.

Features

• Precise Decimal Arithmetic: Exact arithmetic operations without floating-point precision loss
• Infinite Repeating Decimals: Automatic detection and representation of repeating decimals using rational numbers
• Multiple Rounding Modes: 8 different rounding strategies (up, down, ceiling, floor, halfUp, halfDown, halfEven, unnecessary)
• Flexible Parsing: Parse decimals from strings with various formats
• Rational Number Support: Seamlessly work with both terminating and non-terminating decimals
• Full Test Coverage: Comprehensive test suite ensuring reliability

Installation

Add this to your pubspec.yaml:

dependencies:
  decimal4d: [latestVersion]

Then run:

flutter pub get
# or
dart pub get

Quick Start

Basic Operations

import 'package:decimal4d/decimal.dart';

void main() {
  // Create decimals
  var a = Decimal.parse("12.34");           // 12.34
  var b = Decimal.fromInt(5);               // 5
  var c = Decimal.intFraction(10, 20);      // 0.5
  var d = 0.123.toDecimal();                // 0.123
  // Create rationals
  var e = Rational.intFraction(1, 3);       // 1/3
  var f = Rational.intFraction(1, 2);       // 1/2,  Not decimal 0.5

  // Arithmetic operations
  var sum = a + b;          // 17.34
  var diff = a - b;         // 7.34
  var product = a * b;      // 61.70
  var division = a / c;     // 12.34 / 0.5 = 1234 / 50 = 617/25

  // Arithmetic operations among rationals
  sum = a + e;              // 1234/100 + 1/3 = (1234*3+100*1)/(3*100) = 1901/150
  diff = e - f;             // 1/3 - 1/2 = -1/6
  product = b * f;          // 5 * 1/2 = 5/2 = 2.5

  // Comparison
  var g = Decimal.parse("1.2");
  var gg = Decimal.parse("1.200");
  var h = Rational.intFraction(6, 5);
  var hh = Rational.intFraction(24, 20);
  g == gg;                  // True
  g.strictEquals(gg);       // false
  g == h;                   // True
  
  // Convert to other types
  int intValue = a.toInt();             // 12 (truncates decimal part)
  double doubleValue = a.toDouble();    // 12.34
}

Rounding Operations

import 'package:decimal4d/decimal.dart';

void main() {
  var value = Decimal.parse("2.5");

  // Using halfUp rounding (default)
  var rounded = value.halfUp(0);  // 3

  // Using different rounding modes
  var result = value.withScale(0, RoundingMode.halfUp);     // 3
  var down = value.withScale(0, RoundingMode.down);         // 2
  var ceiling = value.withScale(0, RoundingMode.ceiling);   // 3
  var floor = value.withScale(0, RoundingMode.floor);       // 2

  // Rational
  var rational = Decimal.intFraction(4, 3);                 // 4/3
  rational.withScale(0, RoundingMode.down);                 // 1
  rational.withScale(1, RoundingMode.floor);                // 1.3
  rational.withScale(2, RoundingMode.ceiling);              // 1.34
}

API Reference

Decimal Class

Main class for decimal arithmetic. Represents fixed-scale decimals with unlimited precision.

Static Properties

• Decimal.zero - Returns a Decimal with value 0
• Decimal.one - Returns a Decimal with value 1

Constructors

• Decimal(BigInt value, int scale) - Direct constructor with BigInt value and scale
• Decimal.fromInt(int value) - Create from integer
• Decimal.intFraction(int numerator, int denominator) - Create from integer fraction
• Decimal.fraction(BigInt numerator, BigInt denominator) - Create from BigInt fraction
• Decimal.parse(String value) - Parse from string

Parse Examples:

• "2" → 2
• "0.2" → 0.2
• "-0.2000" → -0.2000 (preserves scale)
• ".0" → 0.0
• "-.25" → -0.25
• "1." → 1
• "-0." → 0
• "+.230" → 0.230

Properties

• int scale - Number of decimal places
• bool operator ==(Object other) - Equality (ignores trailing zeros)
• int compareTo(Decimal other) - Comparison

Methods

• String toString() - Convert to plain string representation
• int toInt() - Convert to int (truncates decimal part)
• BigInt toBigInt() - Convert to BigInt (truncates decimal part)
• double toDouble() - Convert to double (may lose precision)
• Rational toRational() - Convert to Rational representation

Arithmetic Operations

• Decimal operator +(Decimal other) - Addition
• Decimal operator -(Decimal other) - Subtraction
• Decimal operator *(Decimal other) - Multiplication
• Decimal operator /(Decimal other) - Division (may return Rational)
• Decimal operator -() - Negation
• Decimal abs() - Absolute value

Division

• Decimal divide(Decimal other, {int? scale, RoundingMode? mode}) - Division with optional rounding

Division Examples:

• Decimal.parse("10") / Decimal.parse("4") → Decimal("2.5")
• Decimal.parse("1") / Decimal.parse("3") → Rational("1/3")
• Decimal.parse("1") / Decimal.parse("8") → Decimal("0.125")
• Decimal.parse("1") / Decimal.parse("0") → throws ArgumentError

Comparison Operators

• bool operator <(Decimal other) - Less than
• bool operator <=(Decimal other) - Less than or equal to
• bool operator >(Decimal other) - Greater than
• bool operator >=(Decimal other) - Greater than or equal to
• bool strictEquals(Decimal other) - Strict equality check including scale or infraction of rational

Rounding

• Decimal withScale(int scale, RoundingMode mode) - Convert to specified scale with rounding
• Decimal halfUp(int scale) - Rounds to specified scale using half-up rounding

Extensions

• Decimal toDecimal({int? scale, RoundingMode? mode}) - Extension on double to convert to Decimal

Rational Class

Represents rational numbers (fractions) with automatic simplification.

Constructors

• Rational.intFraction(int numerator, int denominator) - Create from integer fraction
• Rational.fraction(BigInt numerator, BigInt denominator, {bool reduce = true}) - Create from BigInt fraction

Methods

All methods from Decimal class, including:

• Arithmetic operations: +, -, *, /
• Comparison: compareTo, <, <=, >, >=
• Type conversion: toString(), toDouble(), withScale()
• Negation: operator -()

Testing

Run the test suite:

dart test
# or
flutter test

License

See LICENSE file for details.

Repository

https://github.com/sheepzh/decimal4d