template return type

[SECMoG1T]

Hi, i need help here , av gotta snippet here and i need to identify what causes the error.

template<typename T>
using ret_tuple=std::tuple<std::vector<std::size_t>,std::vector<std::string>,std::vector<T>>;

template<typename ... CONT,typename T>
ret_tuple my_collection(const CONT&&... conts<T>)///error on return type
{
 ///.... code here
}

the error occur on the return type of my function {my_collection} i need to know how i can make ret_tuple use the template parameter T from this function

error! invalid use of template name ret_tuple without arg list

Error	2	error C3547: template parameter 'T' cannot be used because it follows a
 template parameter pack and cannot be deduced from the function parameters of 
'my_collection'	c:\users\orion\documents\visual studio 2013\projects\azure\azure.cpp	11	1	Azure

is it possible to pass T the template param from this function to ret_tuple?? i tried this ret_tuple<T> it failed with some other errors.

thanks in advance.

[Peter87]

I think you have placed the <T> in the wrong place. You need it at the return type instead of the parameter.

template<typename ... CONT,typename T>
ret_tuple<T> my_collection(const CONT&&... conts)
{
 ///.... code here
}

[SECMoG1T]

Thank you @Peter but i also need to specialize conts to be of type T only

they are containers

is it possible? thanks man.

[SECMoG1T]

#updated

Well this compiles but i need conts to be of type T is it possible

template<typename T>
using ret_tuple =std::tuple<std::vector<std::size_t>,std::vector<std::string>,std::vector<T>>;

template<typename T,typename... CONT>
ret_tuple<T> my_collection(const CONT&&... conts)
{
  ///code  here
}

[SECMoG1T]

Anyone please.

[Peter87]

Maybe you can use std::enable_if or something like that to enforce the types are correct, but for the time being you can just assume the types passed to the function are correct. What you should be worrying about instead is how to extract the containers from conts.

If you are not going to pass the whole template parameter pack (conts) to another function you will have to let the first container be its own parameter and then call the function recursively. You probably also need to create a my_collection version that takes less arguments to stop the recursion. Take a look at the definition of "func()" at http://en.wikipedia.org/wiki/Variadic_template

[SECMoG1T]

ooh thanks n yea av got yet another function evaluate but i could proceed with the error, maybe i'll just limit my usage to single integral types

Thank you man.