Re: How do I write directly to a memory address?

[Shark8 <onewingedshark@gmail.com>]

On Feb 9, 3:31 pm, Hyman Rosen <hyro...@mail.com> wrote:
> On 2/9/2011 5:23 PM, Shark8 wrote:
>
>
>
> > On Feb 9, 3:09 pm, Hyman Rosen<hyro...@mail.com>  wrote:
> >> On 2/9/2011 4:40 PM, Shark8 wrote:
>
> >>> What induction *CAN* do is tell you whether or not SumTo
> >>> is correctly constructed and that, barring exceptions, is
> >>> what guarantees the return-value to be correct.
>
> >>> IE It is a proof of correctness; not per se a returner of values.
>
> >> Oh. OK, then. But I need to know what my SumTo function is going to
> >> do with a given value of N. I'm trying to reason about the behavior
> >> of my code here, not abstract math.
>
> > ...Ah, so then does this mean that when you're coding something up
> > you don't care about "abstract logic"?
>
> > I hate to tell you {not really} but you JUST used "abstract math" when
> > you presented a subprogram which yields the same results for any
> > given input. IOW, you have shot your own argument down.
>
> Excuse me, but I really, truly do need to know what my
> subprogram is going to do. People have been telling me
> about "contracts" and "requirements" and "proofs of
> correctness" and that Ada is good for stuff. So I have
> this subprogram and I'd like to know what it will do
> for different values of its parameter so I'll know if
> I can use it or not.

And you answered yourself when I asked you to prove your example
would, in fact, return; that required you to justify usage of
Random().

That you "need to know what it's doing" indicates to me one of two
possibilities: either this function you have is not *really* yours but
instead someone else's that you've 'inherited' OR you are attempting
to use a tool {function/procedure} you do not fully understand for
a problem you might not fully understand.

Understanding a problem gives rise to the requirements and
possibilities-of-solutions; this is what helps guide the 'contract'
that *is* your subprogram's inputs and outputs.

The 'tool' in this case could be a "containers"-object/package, or
as it was in your example "Random()"... you were able to give
an answer (to proving it returned) PRECISELY because you *knew*
the details about that RNG.

In this context your "I really need to know what my subprogram
is going to do" seems very much like some college-kid whining
about how he "really needs to know what happens in book X,"
while decrying people telling him "read the book."

This is precisely to say that just as in reading the book the
answer to the question is answered, so to is your "I need to
know what happens" answered when a) contracts are made
and enforced AND b) proofs of completeness & correctness
are done.