From: Sean O'Dell <sean@...>
Date: 2003-11-21T07:15:20+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types) )

On Thursday 20 November 2003 02:04 pm, Yukihiro Matsumoto wrote:
>   * We have two challenges to implement interface checking.  The one
>     is proper design of interface.  Sean wrote a new proposal in
>     [ruby-talk:85888].  But I don't like its appearance (my personal
>     feeling).  I have no idea what is good interface design.

Do you mean the one titled "New Type Checking System Idea?"

>   * The other is implementation.  Considering Ruby's dynamic nature,
>     the interface check would be done at run-time.  Since all of us do
>     not want the serious performance degrade, interface checking must
>     be implemented efficiently.  But I have no idea how to do it.

Actually, the new proposal only checks at compile-time, when a class which 
implements an interface is loaded, and whenever methods are added to the 
class.  After that, there is as little overhead as I can possibly imagine.  
After that, you just check for a flag in the object.  The flag says "this 
object has in its ancestry a class which properly, and completely implemented 
this interface."  It's a very, very quick check.  You don't calculate 
anything, the flag is passed from the class after the class has fully 
implemented the last of all the interface requirements. I can't even imagine 
any other system being quicker.

> In summary, "interface checking" (not static type checking we had seen
> before) is a good thing.  But I'm not sure it's good enough to put in
> the future Ruby, where API document might help, and where we have two
> challenges above.

This is heartening to hear.  All I get nowadays is Ziegler in one ear buzzing 
in and telling me everything I say is nonsense.

If I didn't make myself very clear in my new proposal, please ask me 
questions.  The new proposal should put the burden mostly at compile-time, 
and run-time checks should be very quick.  The syntax, I think, is far from 
ugly as well; in fact, it's really just plain Ruby pretty much.

	Sean O'Dell