From: Sean O'Dell <sean@...>
Date: 2003-11-20T06:48:16+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types)

On Wednesday 19 November 2003 01:38 pm, Yukihiro Matsumoto wrote:
> Hi,
>
> In message "Re: "stereotyping" (was: Re: Strong Typing (Re: Managing
> metadata about attribute types)"
>
>     on 03/11/20, "Sean O'Dell" <sean@celsoft.com> writes:
> |> library is requiring Socket interface, but without that kind of
> |> interface check, no flexibility is lost, it's little bit hard to find
> |> out the semantics.
> |
> |When a method is written to use the methods of another object, and that
> | code is distributed as a library, the function of that method is fixed. 
> | You must pass it an object that has the methods it requires, and those
> | methods must take the exact parameters it expects.
> |
> |The flexibility to change the method of the object is lost.  You cannot
> | change the parameters to the "send" method of a Socket object and pass it
> | to a library that uses it.  You will get an error deep inside the
> | library.
>
> I don't understand "the flexibility to change the method of the
> object".  What is that?  I think it has never existed before.
> We cannot lose something that has never existed.

Right now, if I inherit the File object, I can re-define the #read method to 
do something other than just read (perhaps log the read action somewhere).  
If I don't change the parameters, I can pass the object to other the methods 
of other classes that want a File object, and they can call obj.read safely.

However, if I change the parameters that #read takes, I can no longer pass 
that object to those methods.  I don't have that flexibility.  If I want to 
pass my object, I must leave the parameters of #read the same

> |> |Reconsider, Matz.
> |>
> |> Reconsider what?  I didn't tell you any decision yet.  I'm still
> |> the level of seeking what you mean.
> |
> |You said the following:
> |> I admit type checking can gain you something, at the cost of
> |> flexibility, which I don't want to pay in Ruby.
> |
> |You don't want to pay the price of type checking in Ruby.  My version of
> | it is really "interface checking," but either way what you said sounds
> | like you've decided you don't want to pay the price for any of this.
>
> You've misunderstood me.  I don't want to pay "the cost of losing
> flexibility", that means I don't want to make any change hindersc
> "my" flexibility, which can be harmed by "type checking based on
> inheritance".  Since your "interface checking" do not affect
> "flexibility" in bad manner, I said nothing against it.

You don't lose flexibility at all.  Your flexibility is exactly the same.  
Here, I'm going to go write an RCR and let's talk about it, I have the 
feeling I'm not being understood at all.

	Sean O'Dell