CODEWITHSUNDEEP
ruby
Indyarocks
Indyarocks

Reputation: 653

equal? and eql? operator on Fixnum

As per definition, equal? checks if the two objects are same, where as eql? checks if the class are same and values are same.

x = 'hi'
y = 'hi'
x.equal? y # => false
x.eql? y # => true

x = 1
y = 1
x.equal? y # => true
x.eql? y # => true

Why is the second x.equal? y true? Aren't x and y two instances of Fixnum? Why doesn't it apply to Fixnum/Float as shown in the examples above?

Upvotes: 0

Views: 132

Answers (2)

Rivenfall
Rivenfall

Reputation: 1263

I know this question already has been answered but I'll add this about object_id's

my_string << 'something' and my_string.replace 'something' and bang methods like my_string.strip! don't change the object_id that's why you can change a constant's content like MyString = 'test'

But MyString.freeze will prevent you from the constant beeing mutable.

It's good to try things like this to learn the language :

irb(main):024:0> x = '1'
=> "1"
irb(main):025:0> y = x
=> "1"
irb(main):026:0> x.equal? y
=> true
irb(main):027:0> x << 'test'
=> "1test"
irb(main):028:0> y
=> "1test"
irb(main):029:0> nope = nope
=> nil

Upvotes: 0

Tim H.
Tim H.

Reputation: 76

Because x and y do actually refer to the exact same object. Unlike strings, each integer value has only one instance at any given time.

Reference: http://ruby-doc.org/core-2.2.1/Fixnum.html

There is effectively only one Fixnum object instance for any given integer value [...]

Edit: To make it a bit more clear, you might want to look at the object_id for these objects:

irb(main):001:0> x = 1
=> 1
irb(main):002:0> y = 1
=> 1
irb(main):003:0> x.object_id
=> 3
irb(main):004:0> y.object_id
=> 3 # Same ID as above
irb(main):005:0> x = 'hi'
=> "hi"
irb(main):006:0> y = 'hi'
=> "hi"
irb(main):007:0> x.object_id
=> 70287051883000
irb(main):008:0> y.object_id
=> 70287051869720 # Different ID than X

Upvotes: 5

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