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Date: Wed, 23 Nov 2011 01:07:25 +0100
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Date: 2011-11-23T01:07:25+01:00
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On 22.11.11 22:26, Dmitry A. Kazakov wrote:

> Sure, I meant only dynamic checks of *program correctness*. Overflow or
> index are not such checks, they are here to enforce defined, contracted
> behavior.
>
> Pre-/post-conditions and accessibility checks pretend [only pretend] to be
> correctness checks, yielding true if the program is correct. As the result
> the user expects them not to raise exceptions

This will indeed be a wrong expectation; why would programmers
expect that there will be no exceptions if there are checks
all over the place?

> and is programming the rest
> correspondingly. That is a wrong idea, which makes programs less safe due
> to false expectations. It is same as reading file and expecting that
> End_Error is never raised. I want that exception expectations were
> contracted and checked statically. If impossible to prove, the program
> should only be legal if it is *visibly* annotated as potentially raising
> the corresponding exception.

DbC (TM) means: an objects primitive operation may raise an exception.
That's part of the business.

Thus if there is

    procedure ...
       with post => postcondition;

then, yes, it should probably be understood to mean

    procedure ...
       with post => raise when not postcondition;

is there substantial difference in behavior, regarding both that
of the program and that of the programmer?