On to_enum and object identity

ruby-talk
1

Good Evening,

I was wondering about the following:

5 == 5.to_i # => true
"Str" == "Str".to_s # => true
enum = (1..3).to_enum
enum == enum.to_enum # => false
enum.object_id == enum.to_enum.object_id # => false

How come Enumerator#to_enum without any arguments doesn't just return self?

Thank you,
Paul

2

Probably because the contract for the returned instance is broken.
There are methods that are not present in all Enumerable, e.g.

irb(main):009:0> .to_enum.class.public_instance_methods(false).sort
=> [:each, :each_with_index, :each_with_object, :feed, :inspect,
:next, :next_values, :peek, :peek_values, :rewind, :size, :with_index,
:with_object]
irb(main):010:0> Array.instance_method :peek
NameError: undefined method `peek' for class `Array'
        from (irb):10:in `instance_method'
        from (irb):10
        from /usr/bin/irb:11:in `<main>'
irb(main):011:0> Array.instance_method :rewind
NameError: undefined method `rewind' for class `Array'
        from (irb):11:in `instance_method'
        from (irb):11
        from /usr/bin/irb:11:in `<main>'

Kind regards

robert

ยทยทยท

On Thu, Sep 22, 2016 at 4:56 PM, Paul Martensen <paul.martensen@gmx.de> wrote:

I was wondering about the following:

5 == 5.to_i # => true
"Str" == "Str".to_s # => true
enum = (1..3).to_enum
enum == enum.to_enum # => false
enum.object_id == enum.to_enum.object_id # => false

How come Enumerator#to_enum without any arguments doesn't just return self?

--
[guy, jim, charlie].each {|him| remember.him do |as, often| as.you_can
- without end}
http://blog.rubybestpractices.com/