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From "RPost" <rp0...@pacbell.net>
Subject Re: Type system notes
Date Sat, 19 Feb 2005 22:37:53 GMT
Still researching type system issues with a view to testing some altered
'plus' operator code.
Found a code construct I haven't seen before.

The DataValueDescriptor interface has several methods that return a
BooleanDataValue object. Curiously, though, the BooleanDataValue interface
extends the DataValueDescriptor interface.

I've seen a lot of low-level code before but I haven't seen code where
lower-level interfaces have a built-in dependency on an extending interface.
Everything I've seen only goes in one direction.

Is this common?

Would anyone care to provide some expert insight into the whys and
wherefores (and pitfalls if any) of using such a construct?

The more I look into this code the more impressed I am with the level of
development that went into it.


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