From: Benoit Daloze <eregontp@...>
Date: 2010-03-01T22:33:51+09:00
Subject: Re: Array#join using to_a if defined

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On 1 March 2010 04:25, Josh Cheek <josh.cheek@gmail.com> wrote:

> On Sun, Feb 28, 2010 at 12:53 PM, Benoit Daloze <eregontp@gmail.com>
> wrote:
>
> > Hi,
> >
> > I got recently an unexpected result using Array#join.
> >
> > In my thoughts, Array#join is sth like adding the separator between every
> > element#to_s.
> >
> > That is what seems to happen when there is no any #to_a method defined in
> > an
> > element:
> >
> > For example,
> > class N < Struct.new(:n)
> >  def to_s
> >    'to_s'
> >  end
> > end
> >
> > [N.new(2), N.new(3)].join(' ') #=> "2 3" and not "to_s to_s"
> >
>
> I got "to_s to_s" in 1.8.6, 1.8.7, and 1.9.1
>

Me:
irb for ruby-1.9.2-r26764
> class N < Struct.new(:n)
>   def to_s
>     'to_s'
>     end
>   end
=> nil
> [N.new(2), N.new(3)].join(' ')
=> "2 3"

irb for ruby-1.8.7-p249
> class N < Struct.new(:n)
>   def to_s
>     'to_s'
>     end
>   end
=> nil
> [N.new(2), N.new(3)].join(' ')
=> "to_s to_s"

So this would be only 1.9.2 behavior, but why on world this changed? It has
such bad side-effect in this case.

---
Also, while playing with Array, using Array#&, I saw it look on #eql? and
#hash methods. These two methods are relative to Hash usually, I didn't
expect methods of Array to depends of them.
A surprising result to me:

irb for ruby-1.9.2-r26764
> [1,2]&[2]
=> [2]
> class N
>   def initialize(n)
>     @n = n
>     end
>   attr_reader :n
>   def == o
>     @n == o.n
>     end
>   end
=> nil
> [N.new(1),N.new(2)]&[N.new(2)]
=> [] # instead of [#<N:.. @n=2>]

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