Design by Contract in oz?
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How can you use [Design by Contract (DbC)](http://en.wikipedia.org/wiki/Design_by_contract) in [oz](http://www.mozart-oz.org/)? 

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<h3>In detail</h3>
I just came across oz via the book [Concepts, Techniques, and Models of Computer Programming](http://www.amazon.com/Concepts-Techniques-Models-Computer-Programming/dp/0262220695/ref=sr_1_1?ie=UTF8&qid=1343229613&sr=8-1&keywords=Concepts%2C+Techniques%2C+and+Models+of+Computer+Programming) and was disappointed that DbC was not covered. Is DbC somewhere implemented in oz or [mozart](http://www.mozart-oz.org/)? 

If not, how could you do it? This also interests me to see how well oz's [creative extension principle](http://www.info.ucl.ac.be/Enseignement/Cours/INGI1131/2007/Scripts/ircamTalk2006.pdf) really works...