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From: "Bob Allen" <ballen3@email.msn.com>
Subject: Re: Interresting thread in comp.lang.eiffel
Date: 2000/07/13
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Date: 2000-07-13T00:00:00+00:00
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Thanks for the response, but I think I threw you off by the example.
The gist of my question is how can you let a supplier off the hook if you
don't care about a particular aspect of the contract.
The method provides a means of doing the opposite, weakening the
pre-condition and strengthen the post-condition. But I don't know how to
allow a class to ignore the parts of the post-condition.

Say for example a restaurant has a breakfast special for $3.99 you get 2
eggs, bacon, hash browns, toast, and grits. I don't particularly like grits,
but the regular price for a breakfast with 3 eggs, bacon, hash browns and
toast costs $5.00. So I order the special. They run out of grits before they
fill my order. How can I let them off the hook for the grits? Remember I
don't run the restaurant and cannot change their contracts.
class POPs_PLACE
feature
breakfast(payment)
Require
payment = $5.00
Ensure
3 Eggs, 1 bacon, 1 hash browns, 1 toast
breakfast_special(payment)
Require
payment = $3.99
Ensure
2 Eggs, 1 bacon, 1 hash browns, 1 toast, 1 grits

Bob Allen
Bob's Weekend Wonders
Training and Consulting
Land O Lakes, FL