polymorphism: overloading vs. overriding

[Bruno Medeiros]

Mike Parker wrote:
> Markus Kranz wrote:
>> Following the rule of last surprise: wouldn't it be desirable if the 
>> output of
>> the following program would be:
>>
>> Bar.doIt()
>> Bar.doIt(Bar)
>>
>> The actual output
>>
>> Bar.doIt()
>> Foo.doIt(Foo)
>>
>> at least for me is a little bit surprising since the best matching 
>> function
>> seems to be Bar.doIt(Bar).
>> As overriding with covariant return types is supported it seems a bit 
>> unnatural
>> to me that overriding with covariant arguments does not work.
>>
>> Instead of doing overload resolution before virtual function 
>> resolution (what
>> seems to be done now) an implementation of 'covariant arguments' 
>> theoretically
>> could be as simple as reversing the order of resolution.
>>
>> What do you think?
> 
> This line is the key:
> 
> Foo foo = new Bar();
> 
> foo is an instance of Foo, not an instance of Bar, 

No, that is wrong, foo *is* an instance of Bar. (yet, it's type contract 
is only that it is a Foo)




-- 
Bruno Medeiros - CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D