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Plumbing Expression

The plumbing expression is an experimental form of object expression for giving programmers greater control of the semantics the objects they define, and the price of less convenience and support. It is an experimantal feature of E whose semantics aren't quite settled yet. Use at your own risk.

In response to an incoming message to a plumbing object (an instance of a plumbing expression) the message becomes the specimen the matcher's pattern is to be matched against, and the matcher is executed.

BNF:	["/**" docComment "*/"] "def" (String | "_") auditors matcher
XML DTD:	See Object Expression
Java:	A plumbing expression compiles into a Java class that "extends Plumbing", and the matcher turns into an implementation of the callAll() method.
Example:
in Kernel-E:
in XML:
in Java: