Why C++ Supports both Class and Typename for Type Parameters

re: Why C++ Supports both Class and Typename for Type Parameters

Nish — Thu, 12 Aug 2004 02:36:00 GMT

Cool - thanks for the info :-)

re: Why C++ Supports both Class and Typename for Type Parameters

Gavin Greig — Thu, 12 Aug 2004 08:37:00 GMT

So is there ever a good reason to use "class" rather than "typename" for a type parameter, or is it purely for backwards compatibility?

re: Why C++ Supports both Class and Typename for Type Parameters

stan lippman — Thu, 12 Aug 2004 14:48:00 GMT

is there ever a `good' reason? no, if you feel the need to converge on a single naming convention, typename is clearer, i believe, to those fresh to the language. however, if you analyze the necessary keystrokes, typename spans the entire keyboard and so is not just longer to type, but requires greater facility -- of course, that is said tongue-in-cheek.

re: Why C++ Supports both Class and Typename for Type Parameters

Gavin Greig — Fri, 13 Aug 2004 10:51:00 GMT

:-) Good answer. Thanks.

re: Why C++ Supports both Class and Typename for Type Parameters

Michael Kleber — Fri, 13 Aug 2004 19:13:00 GMT

I just had to use typename for the "unfortunate obsession with expressions" sense and I still don't understand why. Consider the following moronic way to find the length of a vector:

using namespace std;
template <class T> int vcount(vector<T> v) {
int i;
typename vector<T>::iterator vi;
for(i=0,vi=v.begin(); vi!=v.end(); i++,vi++)
;
return(i);
}

Much to my surprise, g++ 3.4.0 didn't like vector<T>::iterator until I put a typename before it. (Looks like older g++'s think it's just fine.)

I remain baffled, but at least typename was there for me!

T??? kh??a typename trong C++ « Vietnamese Developers’ Blog

T??? kh??a typename trong C++ « Vietnamese Developers’ Blog — Wed, 31 Oct 2007 19:47:21 GMT

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