non static member warning

[Popping mad]

I was making this mock code up to isolate a problem and it suprised me with this new compiler error that I really don't understand in the context of my program

#include <iostream>
#include <vector>

namespace vect{

/*
* =====================================================================================
* Class: Lvalue
* Description: testing vector access as an lvalue
* =====================================================================================
*/

template < class T >
class Lvalue
{
public:

// ==================== LIFECYCLE =======================================
Lvalue (){}; /* constructor */
Lvalue (std::vector<T> in): _ofthings{in}{}; /* constructor */
Lvalue ( const Lvalue &other ); /* copy constructor */
~Lvalue (){}; /* destructor */

/* ==================== ACCESSORS ======================================= */
T& ofthings(){
return _ofthings;
};

void ofthings(std::vector<T> const vec){
_ofthings = vec;
};
/* ==================== MUTATORS ======================================= */

/* ==================== OPERATORS ======================================= */

const Lvalue& operator = ( const Lvalue &other ); // assignment operator
const T& operator [] (int index)
{
return ofthings()[index];
};
friend std::ostream &operator << (std::ostream &os, const Lvalue)
{
for(int i = 0; i < _ofthings.size(); i++ ){
std::cout << i << "\t";
}
return os;
};

/* ==================== DATA MEMBERS ======================================= */
protected:
std::vector<T> _ofthings;

private:

}; /* ----- end of template class Lvalue ----- */

};


int main ( int argc, char *argv[] )
{

std::vector<int> test {0};
for(int i = 0; i<10; i++ ){
test[i] = i;
std::cout << test[i] << "\t";
}
std::cout << std::endl;

vect::Lvalue<int> test2 {test};
for(int j=0, i = 10; i>0; i--, j++){
test[j] = i;
std::cout << test[j] << "\t";
}
std::cout << std::endl;






return EXIT_SUCCESS;
} /* ---------- end of function main ---------- */

It returns:
|| g++ -Wall -ggdb -pg -M *.c >make.deps
|| g++ -Wall -ggdb -pg -pg -pthread -o lvalue.exe lvalue.c
|| lvalue.c: In function ‘std::ostream& vect::operator<<(std::ostream&, vect::Lvalue<T>)’:
lvalue.c|61 col 25| error: invalid use of non-static data member ‘vect::Lvalue<T>::_ofthings’
|| for(int i = 0; i < _ofthings.size(); i++ ){
|| ^~~~~~~~~
lvalue.c|69 col 20| note: declared here
|| std::vector<T> _ofthings;
|| ^~~~~~~~~


I'm not making any const variable or a static variable. The cases I see for this in an only search involve classes wrapped in classes.

[Alf P. Steinbach]

On 29.11.2016 06:43, Popping mad wrote:
>
> It returns:
> || g++ -Wall -ggdb -pg -M *.c >make.deps
> || g++ -Wall -ggdb -pg -pg -pthread -o lvalue.exe lvalue.c
> || lvalue.c: In function ‘std::ostream& vect::operator<<(std::ostream&, vect::Lvalue<T>)’:
> lvalue.c|61 col 25| error: invalid use of non-static data member ‘vect::Lvalue<T>::_ofthings’
> || for(int i = 0; i < _ofthings.size(); i++ ){
> || ^~~~~~~~~
> lvalue.c|69 col 20| note: declared here
> || std::vector<T> _ofthings;
> || ^~~~~~~~~
>
>
> I'm not making any const variable or a static variable.

The `friend` function is not a member function.

There is no `this` object.


Cheers & hth.,

- Alf

[ruben safir]

On 11/29/2016 12:55 AM, Alf P. Steinbach wrote:
>> lvalue.c|69 col 20| note: declared here
>> || std::vector<T> _ofthings;
>> || ^~~~~~~~~
>>
>>
>> I'm not making any const variable or a static variable.
>
> The `friend` function is not a member function.
>
> There is no `this` object.

yeah, I take it back. You can be right sometimes. I fixed that but it
came back with a different error. I'll post it later. This is supposed
to be the simplified test case of a larger program. And it is tripping
me up on many parts.