Academic question: typename
- by Arman
Hi, recently I accounted with a "simple problem" of porting code from VC++ to gcc/intel.
The code is compiles w/o error on VC++:
#include <vector>
using std::vector;
template <class T>
void test_vec( std::vector<T> &vec)
{
typedef std::vector<T> M;
/*==> add here typename*/ M::iterator ib=vec.begin(),ie=vec.end();
};
int main()
{
vector<double> x(100, 10);
test_vec<double>(x);
return 0;
}
then with g++ we have some unclear errors:
g++ t.cpp
t.cpp: In function 'void test_vec(std::vector<T, std::allocator<_CharT> >&)':
t.cpp:13: error: expected `;' before 'ie'
t.cpp: In function 'void test_vec(std::vector<T, std::allocator<_CharT> >&) [with T = double]':
t.cpp:18: instantiated from here
t.cpp:12: error: dependent-name 'std::M::iterator' is parsed as a non-type, but instantiation yields a type
t.cpp:12: note: say 'typename std::M::iterator' if a type is meant
If we add typename before iterator the code will compile w/o pb.
If it is possible to make a compiler which can understand the code written in the more "natural way", then for me is unclear why we should add typename? Which rules of "C++ standards"(if there are some) will be broken if we allow all compilers to use without "typename"?
kind regards
Arman.
