Larry Evans <cppljevans@earthlink.net> writes:

> The ISO/IEC 14882 standard in 5.1 para 7 shows qualified-id may have
> ::template substring; however, para 7 doesn't say when this is
> useful.  Could someone please explain this to me?

It is needed on a lexical level to determine the meaning of
"<". Normally, given

  X::foo<a,b>::c

you look up X, then X::foo. If it is a template, the '<' starts the
template parameters, so this is an access to member c of X::foo<a,b>.
Otherwise, this is equivalent to (X::foo < a), (b > ::c).

Now, if X is a template parameter, foo is a dependent name, and you
can't tell whether X::foo is a template or not until instantiation
time. Unfortunately, that means you could not parse that expression.
So the rule is: If X is a template parameter, the '<' parses as
an operator. If you mean it as a template argument list, you write

  X::template foo<a,b>::c

This is similar to the typename escape.

Regards,
Martin

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The ISO/IEC 14882 standard in 5.1 para 7 shows qualified-id may have
::template
substring; however, para 7 doesn't say when this is useful.   Could
someone please
explain this to me?

TIA.

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