From: Austin Ziegler <austin@...>
Date: 2003-11-20T09:21:25+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata  about attribute types)

On Thu, 20 Nov 2003 06:32:00 +0900, Sean O'Dell wrote:
> On Wednesday 19 November 2003 01:25 pm, Austin Ziegler wrote:
>> Since Bob is a smart programmer, he'll see in his error log:
>> 
>>  NoMethodError: undefined method `accept' for #<File:3> from ...
>> 
>> Well, this means that his File object doesn't know the method
>> #accept. Therefore, he can open the source to your HTTP library
>> and see "oh! this guy's expecting a Socket and has put accept in
>> the wrong place!" If Bob's a really smart programmer, he'd
>> already know that #accept is a Socket method.
> Wrong! There's no mention of the Socket object anywhere! The only
> way he would know that is by searching the source code of OTHER
> METHODS that call that method, then tracing back to where the
> object that is passed in was created. Then he can see Socket.new.

Not really. Since Ruby is open source, he can add a quick debug
print:

  def foo(arg)
    $STDERR.puts arg.inspect
    :
    :
  end

He runs the library normally and he'll see that the incoming
argument is a Socket. But there's also a neat 

The other point that I'll make is that I've had to deal with very
similar debugging mechanisms in C, C++, and PL/SQL.

> Also, don't make the assumption that the developer automatically
> knows #accept belongs to the Socket object. Your familiarity with
> Socket is causing you to discount the pain a developer feels when
> this sort of error occurs. A developer may know NOTHING about the
> Socket object and will not have a CLUE about #accept.

I'm actually not that familiar with Socket at all. I just did what
any Ruby developer can do in irb and discovered that Socket knows
about #accept.

-austin
--
austin ziegler    * austin@halostatue.ca * Toronto, ON, Canada
software designer * pragmatic programmer * 2003.11.19
                                         * 19.21.09