From: Howard Roberts <howardroberts@...>
Date: 2008-07-09T18:07:05+09:00
Subject: Re: type specific operator

Amitraj singh Chouhan wrote:

> These checkings will be done at run time. My question is if we have an 
> Idea about the type of x and y initially(at the time of writing the 
> program) can we eliminate these type checks.

Why would you want to? Are you trying to solve a specific problem, or 
understand conceptually? Are you assuming some sort of efficiency gain 
by doing as you would like?
> I mean is there any 
> operator or method call that will directly treat x and y as fixnum. i.e. 
> something like
>                        int+(x,y)    //specific function for adding two 
> integer
>                        string+(x,y) //specific function for appending 
> two strings
> or any thing like that which will directly treat x and y as variables 
> known types
Objects such as Fixnum and String have a + method that they respond to:
  >> x=1
  => 1
  >> x.respond_to?("+")
  => true
or not:
  >> h= {:a =>1}
  => {:a=>1}
  >> h2 = {:b => "foo"}
  => {:b=>"foo"}
  >> h.respond_to?("+")
  => false
  >> new_h = h+h2
  NoMethodError: undefined method `+' for {:a=>1}:Hash
  from (irb):3

This is the idea behind DuckTyping. It doesn't matter the type of the 
object, so long as it responds to a specific message, all is well. As 
you see above, you can investigate for yourself ahead of time if the 
receiver responds to a particular message with respond_to?, but that 
doesn't really accomplish what you are looking for, specifically, in 
terms of the Ruby interpreter doing it's job at runtime.

Howard
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