Why can't templates use tuples for for argument types?

[Bill Baxter]

Jarrett Billingsley wrote:
> "BCS" <ao at pathlink.com> wrote in message 
> news:ce0a3343bf268c99691d2e8b71a at news.digitalmars.com...
>> How did you hack my system!!!! I'm sure you copied that right off my hard 
>> drive }:-|
>>
>> <g>
>> All joking aside, I keep running into that so often that I want a cleaner 
>> way to do it. I want the proper usage documented in the code, not the 
>> comments and the asserts. I want to be able to talk about things by name 
>> without having to make aliases. It's a minor point but...
>>
> 
> The issue is that there's currently no way to specify that a template 
> parameter can be 'anything'.  T means it's a type, alias T means it's a 
> symbol, and <sometype> T means it's a value.  If you could specify that a 
> parameter could take anything, this would be trivial.  How about using .. - 
> it means it's kind of like a tuple, but shorter ;)
> 
> template Foo(A.., B...)
> {
> 
> }
> 
> Or, take a page from Erlang:
> 
> template Foo(A | B...)
> {
> 
> }
> 
> In this case, A can be anything, and not just a type, because it's on the 
> left of a bar.  An issue with this, however, is that you can't have a type 
> parameter. 

Walter resoundingly rejected some other proposal that involved '..' on 
the grounds that '..' looks far too much like '...' to bleary eyes.  So 
I think .. is out.

--bb