Re: compile template question

[Jonathan Wakely]

N.B. This has already been answered on gcc-help, where it belongs.
Sorry for not updating this list to say so.

I've also now added this topic to the isocpp.org FAQ:
https://isocpp.org/wiki/faq/templates#dependent-name-lookup-types

On 2 December 2016 at 12:12, chenzero wrote:
> Hello,
>
> I have following code,
>
> in gcc 4.8.4, the code can NOT compile, because of an error:
> error: need ‘typename’ before ‘std::map::iterator’ because
> ‘std::map’ is a dependent scope
>
> however, I can compile the same code in other C++ compiler(borland c++),
>
> whether there are some differences between gcc template syntax?
>
> Thank you very much!
>
> c.z.
>
>
> // code
> //---
>
> #include 
>
> #include 
> #include 
> using namespace std;
>
> /**
>  * get all keys of the map into vector
>  */
> template
> static void getKeySet(std::map& m, std::vector& ks) {
> std::map::iterator iter = m.begin();
> for(iter=m.begin();iter!=m.end();iter++) {
> ks.push_back(iter->first);
> }
> }
>
> int main() {
> map m1;
> //m1[1] = 1;
> vector ks;
> getKeySet(m1, ks);
> printf("key size: %d\n", ks.size());
> return 0;
> }
>
>
>

Re: compile template question

[Nathan Sidwell]

On 12/02/2016 07:12 AM, chenzero wrote:

Hello,

I have following code,

in gcc 4.8.4, the code can NOT compile, because of an error:
error: need ‘typename’ before ‘std::map::iterator’ because
‘std::map’ is a dependent scope

however, I can compile the same code in other C++ compiler(borland c++),

whether there are some differences between gcc template syntax?


Your code requires the typename. See 14.6.2 of the std for reasons.

nathan

--
Nathan Sidwell

compile template question

[chenzero]

Hello,

I have following code,

in gcc 4.8.4, the code can NOT compile, because of an error:
error: need ‘typename’ before ‘std::map::iterator’ because 
‘std::map’ is a dependent scope


however, I can compile the same code in other C++ compiler(borland c++),

whether there are some differences between gcc template syntax?

Thank you very much!

c.z.


// code
//---

#include 

#include 
#include 
using namespace std;

/**
 * get all keys of the map into vector
 */
template
static void getKeySet(std::map& m, std::vector& ks) {
std::map::iterator iter = m.begin();
for(iter=m.begin();iter!=m.end();iter++) {
ks.push_back(iter->first);
}
}

int main() {
map m1;
//m1[1] = 1;
vector ks;
getKeySet(m1, ks);
printf("key size: %d\n", ks.size());
return 0;
}