[ruby-talk:16907] Re: Something strange with Ruby's inheritance mechanism

At 11:41 PM 6/26/01 +0900, Patrick Logan wrote:
>(2) Ruby objects do not have associated "types". How an object can be used
>      is dependent on the kinds of methods it has, not whether it is a
>      subclass of this or that superclass.
>
>      For example:
>
>class ObjectOne
>   def frobnicate
>     puts 1
>   end
>end
>
>class ObjectTwo
>   def frobnicate
>     puts "I am not a number. I am a Church numeral."
>   end
>end
>
>one = ObjectOne.new
>two = ObjectTwo.new
>
>def doit(something)
>   something.frobnicate
>end
>
>doit(one)
>doit(two)
>
>Results in:
>
>1
>I am not a number. I am a Church numeral.
>
>Even though the two objects are unrelated by class defiinition.

Surprisingly enough, this kind of weak typing can be done just as well in C++:

class ObjectOne {
   public:
     void frobnicate() {
         cout << 1 << endl;
     }
};

class ObjectTwo {
   public:
     void frobnicate() {
         cout << "I am not a number. I am a Church numeral." << endl;
     }
};

template <class T>
void doit(T something) {
   something.frobnicate();
}

int main() {
     ObjectOne one;
     ObjectTwo two;

     doit(one)
     doit(two)

     return 0;
}

Results in:

1
I am not a number. I am a Church numeral.

The point to me seems to be the nature of variables and bindings, rather 
than weak typing or the alleged absence of a type for Ruby objects - which 
by the way is contradicted by

class SomeObject; end
o = SomeObject.new
puts o.class            # => SomeObject

Bye,
         Luigi