From: David Masover <ninja@...>
Date: 2010-07-29T11:40:11+09:00
Subject: Re: Object#tap (was Nice algorithm for 'spreading' indexes across an array?)

On Wednesday, July 28, 2010 09:03:18 am Harry Kakueki wrote:
> Is there any problem using Object#tap in this way?
> I saw some examples, but in the examples the object was not modified
> in the block.

Oh, you mean modifying the array?

> class Array
>  def spread(n)
>    dup.tap{|a| (size-n).downto(1).map{|b| size*b/(size-n+1)}.each{|c|
> a.delete_at(c)}}
>  end
> end

Not particularly. The thing you have to be careful of is reassigning it -- for 
example, this wouldn't work:

1.tap {|x| x+=1}

You have to actually modify the object. For example, if we're talking about 
arrays, instead of this:

string.tap {|x| x + 'foo'}

Do this:

string.tap {|x| x << 'foo'}

It seems like << returns self, so that's completely unnecessary, you could 
just do this:

(string << 'foo')

...but hopefully it illustrates the point.

I have a feeling I'm overcomplicating things, though. Here's one possible 
implementation of Object#tap:

class Object
  def tap
    yield self
    self
  end
end

Nothing mysterious about it at all. (MRI might do it in C, I'm not sure, but 
the above works.)