Re: How to you access a nested template class?
You may want to ponder about the following:
#include <cassert>
#include <map>
template < typename T >
class typemap {
typedef void (*id) ( void );
template < typename A >
static
void type_identifier ( void ) {}
std::map< id, T > data;
public:
template < typename A >
T const & value ( void ) const {
return ( data[ &type_identifier<A> ] );
}
template < typename A >
T & value ( void ) {
return ( data[ &type_identifier<A> ] );
}
};
int main ( void ) {
typemap<int> table;
table.value<char>() = 2;
table.value<int>() = 1;
assert( table.value<char>() == 2 );
assert( table.value<int>() == 1 );
}
Hi Kai-Uwe,
I've just started implementing this design in my code, but I can't
figure out why it won't work inside a template.
For example, if I delete your main() function above and replace the code
with this:
template <typename X>
int m ( void ) {
typemap<int> table;
table.value<char>() = 2; // line 59 in the error below
table.value<int>() = 1;
assert( table.value<char>() == 2 );
assert( table.value<int>() == 1 );
}
int main ( void ) {
m<int>();
}
When I compile it I end up with this:
t4.cpp: In function `int m()':
t4.cpp:59: error: parse error before `>' token
t4.cpp:60: error: parse error before `>' token
t4.cpp:61: error: parse error before `>' token
t4.cpp:62: error: parse error before `>' token
I don't understand why this happens, as I didn't think it mattered
*where* you used the code. Is there something special you must do in
this situation?
Thanks again,
Adam.