From: Peter Zotov <whitequark@...>
Date: 2011-08-02T15:25:35+09:00
Subject: Re: how to make 1+a work if a is not a numeric  object?

On Tue, 2 Aug 2011 15:15:10 +0900, Zd Yu wrote:
> I defined a to_i method for a, but it seems not work.
>
> BTW, I do not want to override Fixnum's + method.

Numeric#coerce is your friend:
http://ruby-doc.org/core/classes/Numeric.html#M000959

For example:
ruby-1.9.2 :001 > class A
ruby-1.9.2 :002?>   def coerce(other)
ruby-1.9.2 :003?>     [other, 5]
ruby-1.9.2 :004?>     end
ruby-1.9.2 :005?>   end
  => nil
ruby-1.9.2 :006 > 1 + A.new
  => 6

-- 
   WBR, Peter Zotov.