Hi,

I have noticed that there is an entry for the ambiguity of > as
greater-than operator in default template-argument (=A714.2/13) but
there is none for >> as shift-right operator. While both cases
requires parentheses for template specialization (=A714.3/3).

Does it mean that >> is not ambiguous when used as default template
argument.
As in:
template< int i , class T = Bar< i>>2 >> Foo;

Or is it implicit. Is there a specific reason for that ?

--
Michael


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On 19 Mrz., 21:29, Michael Doubez <michael.dou...@free.fr> wrote:
> I have noticed that there is an entry for the ambiguity of > as
> greater-than operator in default template-argument (=A714.2/13) but
> there is none for >> as shift-right operator. While both cases
> requires parentheses for template specialization (=A714.3/3).
>
> Does it mean that >> is not ambiguous when used as default template
> argument.

It is ambiguous, see below.

> As in:
> template< int i , class T = Bar< i>>2 >> Foo;
>
> Or is it implicit. Is there a specific reason for that ?

It follows from 14.3/3, because name lookup is
used to detect whether Bar<i> is a template.

In fact the example given in that paragraph
applies to the default template parameter
as well:

Y<X<6>>1>> x4; // syntax error
Y<X<(6>>1)>> x5; // OK

Note that the special syntax rule of 14.2/13
is only relevant for non-type template parameters:

"When parsing a default template-argument for a
non-type template-parameter, the first non-nested >
is taken as the end of the template-parameter-list
rather than a greater-than operator."

but in your example the non-type template
parameter i is not affected, because it doesn't
have a default template argument.

HTH & Greetings from Bremen,

Daniel Kr   gler


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On 20 Mrz., 01:08, Daniel Kr   gler <daniel.krueg...@googlemail.com>
wrote:
> On 19 Mrz., 21:29, Michael Doubez <michael.dou...@free.fr> wrote:
>
> > I have noticed that there is an entry for the ambiguity of > as
> > greater-than operator in default template-argument (=A714.2/13) but
> > there is none for >> as shift-right operator. While both cases
> > requires parentheses for template specialization (=A714.3/3).
>
> > Does it mean that >> is not ambiguous when used as default template
> > argument.
>
> It is ambiguous, see below.

More precisely: The syntax is incorrect.

Greetings from Bremen,

Daniel Kr   gler


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