From: Josh Cheek <josh.cheek@...>
Date: 2010-12-02T00:01:28+09:00
Subject: Re: Object#each ?

--001636c596cbf4147504965a938f
Content-Type: text/plain; charset=ISO-8859-1

On Wed, Dec 1, 2010 at 8:30 AM, Andrew Wagner <wagner.andrew@gmail.com>wrote:

> > This is a method that either works on a collection or on single item. As
> > soon as a you make Object behave like Enumerable, this breaks and leads
> > to recursion.
> >
>
> Well, sure. The whole point is to write, instead of the above:
>
> def do_sth_on(this)
>   this.each do
>    #whatever
>  end
> end
>

I think he means that you remove the base case that recursive functions may
be relying on. Here is an example:


# a function, maybe in a lib you are using,
# silently doing its job, you don't even know its there
# to do its job it must recursively traverse enumerable objects
# in this example, it just prints them out
def print_nested(iteratable)
  iteratable.each do |*objects|
    if objects.size > 1
      print_nested(objects)
      next
    end
    object = objects.first
    if object.respond_to? :each
      print_nested object
    else
      puts object
    end
  end
end


# prints 1 through 16
print_nested [
  1,2,[3,4,[5]],
  { 6 => 7,
    8 => [ 9 , 10 , { 11 => 12..14 } ]
  },
  "15\n16",
]


# make everything respond to each
class Object
  def each
    yield self
  end
end


# stack overflow
print_nested [
  1,2,[3,4,[5]],
  { 6 => 7,
    8 => [ 9 , 10 , { 11 => 12..14 } ]
  },
  "15\n16",
]

--001636c596cbf4147504965a938f--