dropping parentheses on template instantiation

[Andrei Alexandrescu]

Denis Koroskin wrote:
> On Sun, 05 Oct 2008 22:18:26 +0400, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> wrote:
> 
>> I just realized something different. After making an informal review 
>> of some code, I saw that a large percentage of template instantiations 
>> only need ONE argument.
>>
>> This makes me think, with the old "!" notation, parentheses could be 
>> dropped entirely without prejudice:
>>
>> auto covariance = Matrix!real(n, n);
>> auto normalized = SparseVector!double(n);
>>
>> and so on.
>>
>> To the unbridled joy of the enemies of the Sad Pirate, the dot won't 
>> work for template instantiation because without the parentheses it 
>> DOES engender ambiguity.
>>
>> Now say we take the following route:
>>
>> 1) We find something different from shouting
>>
>> 2) We drop the parentheses for 1 argument
>>
>> That sounds like a possible winner. In this case the "#" becomes 
>> considerably more attractive, in fact very attractive exactly because 
>> it looks unlike any letter:
>>
>> auto covariance = Matrix#real(n, n);
>> auto normalized = SparseVector#double(n);
>>
>> Ideas?
>>
>>
>> Andrei
>>
>> P.S. The Sad Pirate is the emoticon
>>
>> .(
>>
>> It doesn't have an eye and is sad, too.
> 
> Just to clarify things: Do you propose moving the first template 
> argument outside of the parentheses *or* ditching them iff there is only 
> one parameter? I mean, what does the original code look like, because 
> there is ambiguaty in your statement (to me):

Ditch parens if there's only one argument. In that case the extra 
character becomes an enabling asset, not a liability.

> const int n = 42;
> auto covariance = Matrix!(real, n, n); <-> auto covariance = 
> Matrix#real(n,n);
> 
> *or*
> 
> auto covariance = Matrix!(real)(n, n); <-> auto covariance = 
> Matrix#real(n,n);

The latter.

> Other than that Vector at real or Vector#real both sound good!

I agree. In fact "Vector at real" sounds like a good way of talking 
about templates instead of "Vector instantiated with real". One reason 
for which I think "this" is a poor choice (as opposed to e.g. "self") is 
that it's very hard to talk about it.

> (BTW, don't start new thread by repling to some other one, please)

Just trying to keep various juice flavors separate. :o)


Andrei