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One template question

Started by nlbs Dec 5, 2008 at 10:17 AM 5 replies 850+ views

Original Post

Dec 5, 2008 at 10:17 AM

template <typename T, typename CONT /*= std::vector*/ > 
struct Stack{
    CONT elem;
};

The above code compiles fine as it should be If I just uncomment the std::vector one it fires compilation errors saying

error: expected type-specifier
error: expected '>'

But I don't find any syntactic or symantic error in the above code. can anybody please point it out.

PKLoki

Dec 5, 2008 at 10:22 AM

It's because std::vector is a templated type too, so you need to specify something for it to template on. For example, template > will work because now the compiler knows 'a vector of what?'

SiCrane

Dec 5, 2008 at 10:23 AM

You probably wanted:

template <typename T, typename CONT = std::vector<T> > struct Stack{    CONT elem;};

Guthur

Dec 5, 2008 at 10:23 AM

For std::vector to be considered a complete type it needs its one parameter specified. You might want something like this

template <typename T, typename CONT = std::vector<T> > struct Stack{    CONT elem;};

And as they say... ninja'd... twice :p

Evil Steve

Dec 5, 2008 at 10:23 AM

Try:

template <typename T, typename CONT = std::vector<T> > struct Stack{    CONT elem;};

EDIT: Waaaaay too slow [smile]

asdfg__12

Dec 5, 2008 at 10:26 AM

You can do what you want by using template template parameters:

#include <vector>template<typename T, template<typename T, typename Alloc> class CONT = std::vector>struct Stack{    CONT<T, std::allocator<T> > elem;};int main(){    Stack<int, std::vector> s;    return 0;}

[Edited by - D_Tr on December 5, 2008 10:26:07 AM]

nlbs

Dec 5, 2008 at 10:29 AM

Thanks all understood
I forgot that std::vector does not name a type rather std::vector is a Typename

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