Re: Problem trying to implement generics.

["Ayende Rahien" <Dont@spam.me>]

"James Rogers" <jimmaureenrogers@worldnet.att.net> wrote in message
news:3AD915C2.321EB048@worldnet.att.net...
> Ayende Rahien wrote:
> >
> > "Dmitry A. Kazakov" <dmitry@elros.cbb-automation.de> wrote in message
> > news:3AD858A3.3070803@elros.cbb-automation.de...
> > > Well, but what I still cannot understand, what is the objection
against
> > > *procedures* returning a value:
> >
> > Because that is the difference between functions & procedures?
> > If you wanted it that way, you could do this:
> > function Foo(...) return nothing;
> >
> > But I agree that it would be nice to be able to ignore function's return
> > value.
>
> A procedure may modify parameters, but may not return a value.
>
> The practice in C, C++, and Java of ignoring return values from
> functions or methods may seem very convenient. In fact it is a
> fundamental violation of the contract defined for a function. This
> is the single greatest reason exceptions were added to C++, and
> included from the start in Java.

I thought that they added exceptions because of this type of functions:
int & Foo();
Where there is no return value that you can use for errors.
For the rest, I agree.


> A common C programming paradigm
> is to have a function return an indication of success or failure.
> That same function may also modify some or all parameter values.
> It is also very common in C to ignore the return value of a
> function. What is the obvious problem? If the return value
> indicates success or failure, and that value is ignored, then the
> programmer is ensuring erroneous execution. Whenever the function
> fails, the programmer using that function continues to use the
> modified parameter values as though the function succeeded. This
> usually leads to very difficult debugging sessions because the error
> may not become obvious in the program until some later code block.
> It also relies upon the sometimes lucky choice of test cases to
> generate the error condition. If your test cases do not generate
> the error, then you will release erroneous code to your
> customer, which they will find for you, usually at significant
> expense for your company.
>
> In Ada you have a very strong contract concerning procedures and
> functions. Functions always return a value. That value has significant
> meaning. It cannot be ignored. Procedures are the form of subprogram
> to use when no significant value is to be returned.
>
> Jim Rogers
> Colorado Springs, Colorado USA