Template instantiation syntax

[Sergey Gromov]

Fri, 10 Oct 2008 16:39:00 -0700,
Walter Bright wrote:
> Jason House wrote:
> > Is it ok to chain!nested!templates?  Gramatically, it's unambiguous.
> 
> No. The problem is, which is it?
> 
> a!b!c can be a!(b!c) or a!(b)!(c)
> 
> Andrei argued that it should be the former, as that is much more useful. 
> The problem is,
> 
> a!b!c
> 
> should be equivalent to:
> 
> a!(b)!(c)

Why is this necessary?  If a binary ! is right-associative and of a very 
high priority then a!b!c binds correctly:

TemplateInstance:
  TemplateIdentifer !( TemplateArgumentList )
  TemplateIdentifer ! Identifier
  TemplateIdentifer ! TemplateInstance

so that even a!b!c!(x,y) works as a!(b!(c!(x,y))), but a!(b)!(c) is not 
accepted.