Notes on implementing concise calls to constructors with type parameters

[Ulf Zibis]

+1

especially:

    List<String> ls = new ArrayList();


-Ulf



Am 14.05.2009 23:17, Howard Lovatt schrieb:
> Hi Neal,
>
> Comments in text below.
>
> On 15/05/2009, at 2:32 AM, Neal Gafter <neal at gafter.com> wrote:
>
>   
>> On Thu, May 14, 2009 at 5:43 AM, Howard Lovatt  
>> <howard.lovatt at iee.org> wrote:
>> Hopefully this is sufficiently detailed to enable you to comment.
>>
>> This proposal is completely non-orthogonal and ignores the  
>> relationship between the type parameters of the types on the right- 
>> hand-side (typically a class) and the left-hand side (typically an  
>> interface).  Assuming there is a one-to-one relationship is bad  
>> design, even though it is most frequently the case; the compiler  
>> knows the relationships between the types and should use it.
>>     
>
> The advantage of the proposed algorithm is that it is for both the  
> compiler and programmer. For example if someone writes:
>
> List l = new();
>
> Then this is equivalent too and will generate the same error message as:
>
> List l = new List();
>
> So I don't see a problem with this, it is identical to current Java.
>
> If you want an symmetric declaration then you need to specify the  
> asymmetry, e.g.:
>
> List<String> ls = new ArrayList();
>
> Becomes:
>
> List<String> ls = new ArrayList<String>();
>
> I will come back to this example below.
>
>   
>>   The proposal change the meaning of existing code (with respect to  
>> raw types).
>>     
>
> The change in the raw types is as given above for the ArrayList  
> example. I don't think that this change will be a bad thing because at  
> present:
>
> List<String> ls = new ArrayList();
>
> Is almost certainly a typo or a lazy bit of coding and therefore the  
> change will fix these problems rather than break code.
>
> Other uses of raw types, e.g.:
>
> List l = new ArrayList();
>
> Are unchanged.
>
>   
>> It isn't clear how to make this proposal orthogonal to be used  
>> elsewhere than a variable declaration.
>>     
>
> I don't see this. For example the type declaration of a method  
> parameter can be considered like the LHS of a declaration. If generic  
> parameters are infered then you might have to specify them as you do  
> at present - i.e. no change.
>
>   
>> I suspect specifying this approach would result in a more complex  
>> specification than either the approach I've been advocating or the  
>> approach Maurizio has been implementing.
>>     
>
> I think the great advantage of this approach is that it is easy to  
> describe and easy to understand - because it is sytax sugar only.
>
>   
>> ______________________________________________________________________
>> This email has been scanned by the MessageLabs Email Security System.
>> For more information please visit http://www.messagelabs.com/email
>> ______________________________________________________________________
>>     
>
>
>