foobar Wrote:
> I still haven't seen one example of generic code that uses a generic
> conversion. I remain unconvinced about this point and would appreciate an
> example.
> this is however a minor point in the discussion (stylistic issue) so let's
> move on to the more important parts.
Good point. I don't have one from experience. I can build on your example:
class Elderly : Person {
Elderly to(Person p) {
Adult adult = to!Adult(p);
return new Elderly(adult);
}
}
The above would throw an exception if p was a Kid. Note that your solution does
not provide compile time checking because you'd still need a dynamic cast to
retrieve an Adult from your person.
Providing a generic abstraction so when someone does find a use is a major
style of Phobos.
> That was just one example. Let's discuss another one from your list then:
> uint foo = -1; // remember that this can be a result of a long calculation
> should the above compile in your opinion?
No, I think int to uint should not be implicit. Maybe there is a reason other
than C inheritance, I'm sure bearophile has a feature request for it.
> http://ideone.com/ksQDV
I have an account so I get 15sec of runtime:
http://ideone.com/9ZvNL
Ok, I'm surprised this is successful. So I made another test that fails on my
local machine, but strangely enough, succeeds on ideone...
http://ideone.com/gOtYc
Any way this demonstration is showing an issue with overflow. I have already
stated that explicit casts do not solve this and got no disagreement from you.
> I understand what you mean about the confirmation dialog but as you said
> yourself above, I'm not asking for a confirmation dialog but rather using
> safer actions.
> I think we agree on this.
Yes, we do agree. What we don't agree on is the best way to make things safer.
I am saying that implicit casts are not bad when data is not being lost.
And to! is a good candidate for providing safe conversions (possible data lost
but qualifiers remain).
And that mixing conversions that loose data with ones that transform it (class
conversion) is not an issue.
