From: Henning von Rosen <henning@...>
Date: 2002-01-09T21:13:23+09:00
Subject: "Visitor" should be "Iterator" in Programming Ruby?

"""The Visitor Pattern

It's the method each. """

I came to mention the above chapter in Programming Ruby, in a letter to
Thomas K�hne, the author of "A Functional Pattern System for Object-Oriented
Design". BTW, this is a very well written and interesting book, also from a
Ruby language design perspective. It also gives a brief presentation of the
FP resp OO concepts pros-and-cons in the beginning.
http://www-agce.informatik.uni-kl.de/~kuehne/fps/

>> Reading about the issue of less-lang-support->more-pattern-relevance, I
came
>> to think of a passage from one of the Ruby books. A chapter treats
>> implementations of some well-known patterns. The whole text of the
>> subchapter on The Visitior Pattern, is "It's the method each.".

[Thomas K�hne]>I find that hard to believe.
>With regard to the "Iterator Pattern" the answer would be "its the method
>each", but there is an element of double dispatch in visitor, which I don't
>think is supported by Ruby as a language mechanism and anyway it would >be
more than just the method "each".

Cheers,

Henning