From: "Hal E. Fulton" <hal9000@...>
Date: 2002-08-08T14:40:42+09:00
Subject: Re: A very small challenge

----- Original Message ----- 
From: "Dave Thomas" <Dave@PragmaticProgrammer.com>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Wednesday, August 07, 2002 10:19 PM
Subject: Re: A very small challenge


> I've played with the idea of recording the winner in a Round
> object. It seems fairly natural:
(some snips)
>        # return the better of this card and another
>        def best_of(other)
>          if @suit == other.suit
>            @rank > other.rank ? self : other
>          elsif other.suit == :spade
>            other
>          else
>            self
>          end
>        end
>      end

Yes! Thank you.

You've made a simplification here which is tricky enough
that I'll point it out. You may even have done it semi-
unconsciously.  :)

I was thinking in terms of a "comparison" -- compare the
value of this card with that one. But you'd need to know
what suit led. So I had confused myself. Not uncommon.

In a simple comparison, x and y have a relationship that's
fixed without regard to ordering. I'm not making sense, 
am I? :)

But as long as you compare the cards in order from *earliest*
to *latest*, you don't worry what suit led.

Why this might be considered odd can be seen by looking at
these two cases:

  D6.best_of(C8)  #  C8
  C8.best_of(D6)  #  D6 - different answers

In other words, the chronologically earlier one wins. 

Since it is past 12:30 am right now (a dangerous time for
me to try to think) this still confuses me.

It's as if the test "x > y" were true and "y > x" were also
true.

It's not like integers, in other words. Imagine a method
like 

  class Fixnum
    def best_of(other)
      self > other ? self : other
    end
  end

Unless I've done something stupid, this means

  6.best_of(4)  #  6
  4.best_of(6)  #  6 - same answer 

You're probably shaking your head at my stating the 
obvious, so I'll shut up now.

> Having said that, I'm not familiar with the game, so here are some
> testcases which capture my assumptions of what I thought you meant :)

(snip)

That's precisely what I meant. Your assumptions are correct.

Cheers,
Hal