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/Crystal 0.31

module Comparable(T)

Overview

The Comparable mixin is used by classes whose objects may be ordered.

Including types must provide an #<=> method, which compares the receiver against another object, returning:

  • a negative number if self is less than the other object
  • a positive number if self is greater than the other object
  • 0 if self is equal to the other object
  • nil if self and the other object are not comparable

Comparable uses #<=> to implement the conventional comparison operators (#<, #<=, #==, #>=, and #>). All of these return false when #<=> returns nil.

Note that returning nil is only useful when defining a partial comparable relationship. One such example is float values: they are generally comparable, except for NaN. If none of the values of a type are comparable between each other, Comparable shouldn't be included.

NOTE When nil is returned from #<=>, Array#sort and related sorting methods will perform slightly slower.

Direct including types

Defined in:

comparable.cr

Instance Method Summary

  • #<(other : T)

    Compares this object to other based on the receiver’s #<=> method, returning true if it returns a negative number.

  • #<=(other : T)

    Compares this object to other based on the receiver’s #<=> method, returning true if it returns a value equal or less then 0.

  • #<=>(other : T)

    The comparison operator.

  • #==(other : T)

    Compares this object to other based on the receiver’s #<=> method, returning true if it returns 0.

  • #>(other : T)

    Compares this object to other based on the receiver’s #<=> method, returning true if it returns a value greater then 0.

  • #>=(other : T)

    Compares this object to other based on the receiver’s #<=> method, returning true if it returns a value equal or greater than 0.

Instance Method Detail

def <(other : T)Source

Compares this object to other based on the receiver’s #<=> method, returning true if it returns a negative number.

def <=(other : T)Source

Compares this object to other based on the receiver’s #<=> method, returning true if it returns a value equal or less then 0.

abstract def <=>(other : T)Source

The comparison operator. Returns 0 if the two objects are equal, a negative number if this object is considered less than other, a positive number if this object is considered greter than other, or nil if the two objects are not comparable.

Subclasses define this method to provide class-specific ordering.

The comparison operator is usually used to sort values:

# Sort in a descending way:
[3, 1, 2].sort { |x, y| y <=> x } # => [3, 2, 1]

# Sort in an ascending way:
[3, 1, 2].sort { |x, y| x <=> y } # => [1, 2, 3]

def ==(other : T)Source

Compares this object to other based on the receiver’s #<=> method, returning true if it returns 0.

Also returns true if this and other are the same object.

def >(other : T)Source

Compares this object to other based on the receiver’s #<=> method, returning true if it returns a value greater then 0.

def >=(other : T)Source

Compares this object to other based on the receiver’s #<=> method, returning true if it returns a value equal or greater than 0.

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Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.31.1/Comparable.html