template parameters default value

Question

I'm trying my very first template. the following code compiles :

template<class T,class C=int> class MyClass
{};

But not this :

#include <vector>

using namespace std;
template<class T,class C=vector<T>> class MyClass
{};

Yet i see the standard vector class template declared like this :

template < class T, class Alloc=allocator<T> > class vector
{};

The errors the compiler throws are :

*error: spurious '>>', use '>' to terminate a template argument list
*error: definition of 'class MyClass' inside template parameter list
*error: two or more data types in declaration of 'type name'
*error: expected '>' before ';' token
*error: expected unqualified-id before ';' token

Perhaps you'd get use out of a compiler with better error messages. error: a space is required between consecutive right angle brackets (use '> >') I also assume you knew about this one, but error: no template named 'vector'; did you mean 'std::vector'? — Qaz
– Qaz, Commented Jul 11, 2015 at 23:48
If you compile it as C++11, you should be able to use >> without the space. — Petr Skocik
– Petr Skocik, Commented Jul 11, 2015 at 23:51

CinchBlue · Accepted Answer · 2015-07-11 23:49:08Z

2

http://coliru.stacked-crooked.com/a/f93734d989e10446

No, it works. You just forgot the std namespace.

answered Jul 11, 2015 at 23:49

CinchBlue

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5 Comments

CinchBlue Over a year ago

@coucou8949 Don't do this. This causes headaches if library names collide.

CinchBlue Over a year ago

@coucou8949 Yes. You should use std::.

coucou8949 Over a year ago

i removed this "using namespace std;" and did as you said.still the same errors.

Petr Skocik Over a year ago

The linked site compiles it as C++14. If you're compiling as regular old C++98, you must write std::vector<T> > instead std::vector<T>>.

coucou8949 Over a year ago

error: a space is required between consecutive right angle brackets (use '> >'). i think that's the problem.that's what the compiler should have thrown.someone should post a proper answer so i can make it the correct one.

coucou8949 · Accepted Answer · 2015-07-13 00:14:23Z

1

the code was :

#include <vector>

using namespace std;
template<class T,class C=vector<T>> class MyClass
{};

but i should have written :

#include <vector>

template<class T,class C=std::vector<T> > class MyClass//with space between right angle brackets  : '> >'
{};

answered Jul 13, 2015 at 0:14

coucou8949

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1 Comment

M.M Over a year ago

The requirement for the space was removed in C++11 - consider using a more up-to-date compiler

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