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A package that helps you working with fractions and mixed fractions.

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A package that helps you working with fractions and mixed fractions.

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https://pub.dev/packages/fraction


Working with fractions #

You can create an instance of Fraction using one of its constructors:

  • Default: it just requires the numerator and/or the denominator.

    Fraction(3, 5); // 3/5
    Fraction(3, 1); // 3
    
  • fromString: requires a String representing a fraction.

    Fraction.fromString("2/4"); // 2/4
    Fraction.fromString("-2/4"); // -2/4
    Fraction.fromString("2/-4"); // Throws an exception
    Fraction.fromString("-2"); // -2/1
    Fraction.fromString("/3"); // Error
    
  • fromDouble: converts a double into a fraction. Note that irrational numbers cannot be converted into fractions by definition; the constructor has the precision parameter which decides how precise the representation has to be.

    Fraction.fromDouble(1.5); // 3/2
    Fraction.fromDouble(-8.5); // -17/2
    Fraction.fromDouble(math.pi); // 208341/66317
    Fraction.fromDouble(math.pi, precision: 1.0e-4); // 333/106
    

    The constant pi cannot be represented as a fraction because it's an irrational number. The constructor considers only precison decimal digits to create a fraction.

Thanks to extension methods you can also create a Fraction object "on the fly" by calling the toFraction() method on a number or a string.

5.toFraction(); // 5/1
1.5.toFraction(); // 3/2
"6/5".toFraction(); // 6/5

Note that a Fraction object is immutable so methods that require changing the internal state of the object return a new instance. For example, the reduce() method reduces the fraction to the lowest terms and returns a new instance:

final fraction = Fraction.fromString("12/20"); // 12/20
final reduced = fraction.reduce(); // 3/5

Fraction strings can be converted from and to unicode glyphs when possible.

Fraction.fromGlyph("¼"); // Fraction(1, 4)
Fraction(1, 2).toStringAsGlyph(); // "½"

You can easily sum, subtract, multiply and divide fractions thanks to arithmetic operators:

final f1 = Fraction(5, 7);
final f2 = Fraction(1, 5);

final sum = f1 + f2; // -> 5/7 + 1/5
final sub = f1 - f2; // -> 5/7 - 1/5
final mul = f1 * f2; // -> 5/7 * 1/5
final div = f1 / f2; // -> 5/7 / 1/5

The Fraction type has a wide API with the most common operations you'd expect to make on a fraction:

Fraction(10, 2).toDouble();  // 5.0
Fraction(10, 2).inverse();   // 2/10
Fraction(1, 15).isWhole;     // false
Fraction(2, 3).negate();     // -2/3
Fraction(1, 15).isImproper;  // false
Fraction(1, 15).isProper;    // true

// Access numerator and denominator by index
final fraction = Fraction(-7, 12);

print('${fraction[0]}'); // -7
print('${fraction[1]}'); // 12

Any other index value different from 0 and 1 throws a FractionException exception. Two fractions are equal if their "cross product" is equal. For example 1/2 and 3/6 are said to be equivalent because 1*6 = 3*2 (and in fact 3/6 is the same as 1/2).

Working with mixed fractions #

A mixed fraction is made up of a whole part and a proper fraction (a fraction in which numerator <= denominator). Building a MixedFraction object is very easy:

MixedFraction(
  whole: 3, 
  numerator: 4, 
  denominator: 7
);

As it happens with fractions, you can use various named constructors as well:

MixedFraction.fromDouble(1.5);
MixedFraction.fromString("1 1/2");

There also is the possibility to initialize a MixedFraction using extension methods:

final mixed = "1 1/2".toMixedFraction();

Note that MixedFraction objects are immutable exactly like Fraction objects so you're guaranteed that the internal state of the instance won't change. Make sure to check the official documentation at pub.dev for a complete overview of the API.

Egyptian fractions #

An Egyptian fraction is a finite sum of distinct fractions where the numerator is always 1 and, the denominator is a positive number and all the denominators differ from each other. For example:

  • 5/8 = 1/2 + 1/8 (where "1/2 + 1/8" is the egyptian fraction)

In other words, egyptian fractions are a sum of fractions in the form 1/x that represent a proper or an improper fraction. Here's how they can be computed:

final egyptianFraction1 = Fraction(5, 8).toEgyptianFraction();
print("$egyptianFraction1"); // prints "1/2 + 1/8"

final egyptianFraction2 = MixedFraction(2, 4, 5).toEgyptianFraction();
print("$egyptianFraction2"); // prints "1 + 1 + 1/2 + 1/4 + 1/20"

The compute() method returns an iterable.

Notes #

Both Fraction and MixedFraction descend from the Rational type which allows parsing both kind of fractions with a single method call:

// This is a 'Fraction' object
Rational.tryParse('1/5'); // 1/5

// This is a 'MixedFraction' object
Rational.tryParse('2 4/7'); // 2 4/7

// This is 'null' because the string doesn't represent a fraction or a mixed fraction
Rational.tryParse(''); // null

Parsing integer values like Rational.tryParse('3') always returns a Fraction type but it can easily be converted into a mixed fraction using the Fraction.toMixedFraction method.

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A package that helps you working with fractions and mixed fractions.

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