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When I try to compile (g++, ver=4.4.5) this code:

#include <map>
using namespace std;

template<typename T> void fun()
{
map<int, int>::iterator b; //OK
map<T, int>::iterator a; //NOK, error: expected ‘;’ before ‘a’
}

,I get follow compiller error:

error: expected ‘;’ before ‘a’

Can you explain me why I can't define iterator in this way ?

On Feb 13, 6:45*pm, zdun777 <zdu...@gmail.com> wrote:
> When I try to compile (g++, ver=4.4.5) this code:
>
> #include <map>
> using namespace std;
>
> template<typename T> void fun()
> {
> * * * * map<int, int>::iterator b; * * *//OK
> * * * * map<T, int>::iterator a; * * * //NOK, error: expected ‘;’ before ‘a’
>
> }
>
> ,I get follow compiller error:
>
> error: expected ‘;’ before ‘a’
>
> Can you explain me why I can't define iterator in this way ?

Hi
Under g++ 4.5.0, in addition to above
error message, the compiler issues another message, which describes
and gives hint, what you have to do:
error: need 'typename' before std::map<T, int>::iterator' because
'std::map<T, int>'
is a dependent scope.

HTH
-- Saeed Amrollahi

zdun777 <> writes:

> #include <map>
> using namespace std;
>
> template<typename T> void fun()
> {
> map<int, int>::iterator b; //OK
> map<T, int>::iterator a; //NOK, error: expected ‘;’ before ‘a’
> }
>
> ,I get follow compiller error:
>
> error: expected ‘;’ before ‘a’
>
> Can you explain me why I can't define iterator in this way ?

The compiler can't guess that "iterator" is a type inside map<T,int>
(you could have a specialization of map for some T where "iterator" is a
static member---and actually that's what the compiler assumes). You have
to say:

typename map<T,int>::iterator a;

-- Alain.

Thanks for explanation.
On 13 Lut, 16:56, Alain Ketterlin <al...@dpt-info.u-strasbg.fr> wrote:
> zdun777 <zdu...@gmail.com> writes:
> > #include <map>
> > using namespace std;
>
> > template<typename T> void fun()
> > {
> > * *map<int, int>::iterator b; * * *//OK
> > * *map<T, int>::iterator a; * * * //NOK, error: expected ‘;’ before ‘a’
> > }
>
> > ,I get follow compiller error:
>
> > error: expected ‘;’ before ‘a’
>
> > Can you explain me why I can't define iterator in this way ?
>
> The compiler can't guess that "iterator" is a type inside map<T,int>
> (you could have a specialization of map for some T where "iterator" is a
> static member---and actually that's what the compiler assumes). You have
> to say:
>
> * * typename map<T,int>::iterator a;
>
> -- Alain.