# Comparable<T> class

Interface used by types that have an intrinsic ordering.

The compareTo operation defines a total ordering of objects, which can be used for ordering and sorting.

The Comparable interface should be used for the natural ordering of a type. If a type can be ordered in more than one way, and none of them is the obvious natural ordering, then it might be better not to use the Comparable interface, and to provide separate Comparators instead.

It is recommended that the order of a Comparable agrees with its operator operator == equality (`a.compareTo(b) == 0` iff `a == b`), but this is not a requirement. For example, double and DateTime have `compareTo` methods that do not agree with operator operator ==. For doubles the compareTo method is more precise than the equality, and for DateTime it is less precise.

Examples:

     (0.0).compareTo(-0.0);  // => 1
     0.0 == -0.0;            // => true
     var dt = new DateTime.now();
     var dt2 = dt.toUtc();
     dt == dt2;              // => false
     dt.compareTo(dt2);      // => 0

The Comparable interface does not imply the existence of the comparison operators `<`, `<=`, `>` and `>=`. These should only be defined if the ordering is a less-than/greater-than ordering, that is, an ordering where you would naturally use the words "less than" about the order of two elements.

If the equality operator and compareTo disagree, the comparison operators should follow the equality operator, and will likely also disagree with compareTo. Otherwise they should match the compareTo method, so that `a < b` iff `a.compareTo(b) < 0`.

The double class defines comparison operators that are compatible with equality. The operators differ from `double.compareTo` on -0.0 and NaN.

The DateTime class has no comparison operators, instead it has the more precisely named DateTime.isBefore and DateTime.isAfter.

Implemented by
  - BigInt
  - DateTime
  - Duration
  - num
  - String

## Constructors

Comparable()

## Properties

hashCode → int
  The hash code for this object. [...]
  read-only, inherited
runtimeType → Type
  A representation of the runtime type of the object.
  read-only, inherited

## Methods

compareTo(T other) → int
  Compares this object to another Comparable [...]
noSuchMethod(Invocation invocation) → dynamic
  Invoked when a non-existent method or property is accessed. [...]
  inherited
toString() → String
  Returns a string representation of this object.
  inherited

## Operators

operator ==(dynamic other) → bool
  The equality operator. [...]
  inherited

## Static Methods

compare(Comparable a, Comparable b) → int
  A Comparator that compares one comparable to another. [...]