funny template variable declaration

[Peter]

in boost spirit examples some code example is given:

rule<r = *anychar_p;
parse("hello world", r);

what does the empty template bracket mean?

[Salt_Peter]

Peter wrote:

in boost spirit examples some code example is given:

rule<r = *anychar_p;
parse("hello world", r);

what does the empty template bracket mean?

It means that its a template and that its using a default template
variable.
silly example:

#include <iostream>
#include <ostream>

template< typename T = int >
struct Test
{
T t;
Test() : t() { }
const T& get() const { return t; }
};

int main()
{
Test< test;
std::cout << test.get() << std::endl;
}

If you remove the empty < you'll get the something like the following
error:
"missing template arguements"

[Gianni Mariani]

Peter wrote:

in boost spirit examples some code example is given:

rule<r = *anychar_p;
parse("hello world", r);

what does the empty template bracket mean?

Use the deafualts.

i.e.

template <typename T = intclass X;

X<> * y;

[Noah Roberts]

Peter wrote:

in boost spirit examples some code example is given:

rule<r = *anychar_p;
parse("hello world", r);

what does the empty template bracket mean?

rule is a template that can take 3 parameters but provides defaults for
all 3. The above use uses the defaults for every parameter.

[Noah Roberts]

Peter wrote:

in boost spirit examples some code example is given:

rule<r = *anychar_p;
parse("hello world", r);

what does the empty template bracket mean?

rule is a template that can take 3 parameters but provides defaults for
all 3. The above use uses the defaults for every parameter.