[Info-vax] Rust as a HS language, was: Re: Quiet?

[Dave Froble]

On 4/7/2022 8:36 PM, Arne Vajhøj wrote:
> On 4/7/2022 2:58 PM, Dave Froble wrote:
>> On 4/7/2022 1:39 PM, Simon Clubley wrote:
>>> BTW, testing can only prove the presence of bugs and not the absence
>>> of them. Someone else can still come along and do testing in a different
>>> way that finds undiscovered issues. Look at the stuff about EVL that
>>> I posted recently as an example.
>>
>> Not if all possible outcomes are expected and handled.
>>
>> A good design will include handling all possible outcomes.  Anything else is
>> just when, not if, something unexpected occurs.
>
> True.
>
> But not particular relevant.
>
> Too many cases to test.
>
> If your program take 1 KB of input then there are
> 2**8192 possible inputs. That is a pretty big number.
>
> But it is what it takes to prove that this
> program is correct by test.
>
> Of course you can probably pick a couple of handful
> careful designed test cases and if they work, then you
> are somewhat optimistic that the program will work in
> general. But that is different from proving.

I was not discussing data or testing.  I was discussing program design.

As a simple example, I've seen code that invokes a system service and them maybe 
tests the service completion.  Never takes into consideration that there is a 
completion status of invoking the service.  Would it not be relevant to know 
that the QIO did not fail, it was the queuing of the QIO that failed.

Such stuff, including my favorite "that never happens".

-- 
David Froble                       Tel: 724-529-0450
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