"Strong typing vs. strong testing"

TheFlyingDutchman zzbbaadd at aol.com
Thu Sep 30 10:55:39 CEST 2010


On Sep 30, 1:40 am, RG <rNOSPA... at flownet.com> wrote:
> In article
> <5bf24e59-1be0-4d31-9fa7-c03a8bf9b... at y12g2000prb.googlegroups.com>,
>
>
>
>
>
>  TheFlyingDutchman <zzbba... at aol.com> wrote:
> > > > Yes.  Nonetheless, the maximum() function does exactly what it is intended
> > > > to do *with the inputs it receives*.  The failure is outside the function;
> > > > it did the right thing with the data actually passed to it, the problem
> > > > was a user misunderstanding as to what data were being passed to it.
>
> > > > So there's a bug -- there's code which does not do what it was intended
> > > > to do.  However, that bug is in the caller, not in the maximum()
> > > > function.
>
> > > > This is an important distinction -- it means we can write a function
> > > > which performs that function reliably.  Now we just need to figure out
> > > > how to call it with valid data... :)
>
> > > We lost some important context somewhere along the line:
>
> > > > > > in C I can have a function maximum(int a, int b) that will always
> > > > > > work. Never blow up, and never give an invalid answer. If someone
> > > > > > tries to call it incorrectly it is a compile error.
>
> > > Please take note of the second sentence.
>
> > > One way or another, this claim is plainly false.  The point I was trying
> > > to make is not so much that the claim is false (someone else was already
> > > doing that), but that it can be demonstrated to be false without having
> > > to rely on any run-time input.
>
> > The second sentence is not disproved by a cast from one datatype to
> > another (which changes the value) that happens before maximum() is
> > called.
>
> You can't have it both ways.  Either I am calling it incorrectly, in
> which case I should get a compiler error, or I am calling it correctly,
> and I should get the right answer.  That I got neither does in fact
> falsify the claim.  The only way out of this is to say that
> maximum(8589934592, 1) returning 1 is in fact "correct", in which case
> we'll just have to agree to disagree.
>
1) long trying_to_break_maximum = 8589934592;
2) /* compiler adds */
   int created_to_allow_maximum_call = (int) trying_to_break_maximum;
3) maximum(created_to_allow_maximum_call, 1);

I think we have to agree to disagree, because I don't see the lack of
a compiler error at step 2 as a problem with the maximum() function.



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