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Re: Undefined Definition

Dick: I feel like Bork; does Pavel feel like Biden?

I think that I'm stating my opinions in my own words, so I guess I can't
feel like Biden ...


Dick: If a specification says that ``it is not permissible
      to do something'' or that ``one must not do something,''
      then I expect that it is not proper reasoning to turn that
      into ``it is permissible to do something'' or
      ``it's perfectly ok to do something.''

I think there's a confusion here between the specification of valid
programs and the specification of valid implementations.  I guess I
can't envision a case in which I actually want to forbid an
implementation to provide a useful semantics in one of these undefined
situations.  I have always interpreted the "is an error" cases as
breathing space for the implementations, since they don't have to detect
the situation or signal an error, and a warning to the programmer not to
count on any particular semantics or harmlessness.  

More concisely, can you give an example of a situation that you strongly
prefer to have in the undefined category rather than the "may be
extended" category?