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From "Eric Pugh" <>
Subject [chain] evaluating to use, contrast to pipeline?
Date Tue, 09 Nov 2004 09:13:06 GMT
Hi all,

Just checking out [chain], was thinking of replacing my own CoR
implementation.  The one thing that I have, that chain doesnt, is a visitor
object.  Now, I may be mixing up my GoF patterns here, but what I have are a
series of steps that are ordered.  I have a visitor who goes from one to the
other.  At each step, there is the option to continue or to stop.  The
visitor provides a place to collect up things like messages back to the

In [chain], instead of a visitor, I would have a well known context property
that would fulfill that role, correct?  I could even subclass Context to
have a typesafe .getVisitor() or .getMessagesHolder() to put my messages in

I was also looking at [pipeline] in sandbox, and was trying to grok the
difference.  What it seemed to boil down to is that in a pipeline you go
from A -> Z without ever stopping.  But, in [chain] you may go from A -> Z,
but if certain conditions occur, you may stop midway at J, correct?

Which brings me to my last question..  Why does returning false from a
command signify continue?  Why wasn't it return "true" means keep going?

Eric Pugh

PS, anyone mind if I update dependencies in the Maven build?

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