C++ iterator, function not running

[qwewq149]

133:40: error: \u2018remove\u2019 declared as function returning a function
(typename vector <T>::iterator ix, T n)

this is the error i get and i can't seem to get it to run. any help would be appreciated.

#include <iostream>
#include <string>
#include <vector>
using namespace std;
template <typename T>
   class Mlist
   {
   public:
    Mlist();//creates the list 
    T front();//returns the front of the list 
    T last();//returns the end of the list
    bool in(T x);//returns true if x is in the list and false otherwise
    bool empty(); // returns true if the list is empty
    void addfront(T entry);//add entry to the back of the list
    void addend(T entry);//add entry to the back of the list
    void addorder(T entry);//add entry to an ordered list
    void removefront();//removes the front of the list
    void removeend();//removes the back of the list
    void remove(T n);//searches the list and removes the entry with value n
    private:
    vector<T> mlist;
    void remove(typename vector<T>::iterator ix, T n);//uses an iterator and recursion to remove value n
    void addorder(typename vector<T>::iterator ix, T n);//uses an iterator and recursion to add value n in an ordered list
    }; // mlist

template <typename T>
    Mlist<T>::Mlist()
    {

    }

template <typename T>
    T Mlist<T>::front()
	{
	    T x;
	    if(empty())
		{
		    return x;
		}
	    else
	    	{
		    return *mlist.begin();
		}
	}

template <typename T>
    T Mlist<T>::last()
	{
	    T x;
	    if(empty())
		{
		    return x;
		}
	    else
	    	{
		    return *(--mlist.end());
		}
	}

template <typename T>
   bool Mlist<T>::in (T x)
    {
	for(int i = 0; i < mlist.size();)
	    {
		if(mlist[i] ==x)
	    	    {
			return true;
		    }
	    }
    
	return false;
    }

template <typename T>
    bool Mlist<T>::empty()
    {
	if(mlist.size() == 0)
	    {
		return true;
	    }
	else
	    {
		return false;
	    }
    }

template <typename T>
    void Mlist<T>:: addfront(T x)
	{
	    if(this ->empty())
		{
		    mlist.push_back(x);
		}
	    else
		{
		    mlist.insert(mlist.begin(),x);
		}
	}

template <typename T>
    void Mlist<T>:: removefront()
	{
	    if(!this ->empty())
		{
		    mlist.erase(mlist.begin());
		}
	}

template <typename T>
    void Mlist<T>:: removeend()
	{
	    if(!this ->empty())
		{
		    (--mlist.end());
		}
	}

template <typename T>
    void Mlist<T>::addorder (T entry)
	{
	    if(this ->empty())
		{
		    addorder(mlist.begin(), entry);
		}
	    else
		{
		    mlist.push_back(entry);
		}
	}

template <typename T>
    void Mlist<T>::remove(T n)
	(typename vector <T>::iterator ix, T n)
	{
	    if(ix==mlist.end())
		{
		    return
		}
		if (*ix ==n)
		{
		    mlist.erase(ix, n);
		    remove(ix);
		}
		else
		{
		    remove(++ix, n);
		}
	}

int main()
{
 Mlist<int> test1=Mlist<int>() ;
 test1.addend(5);
 test1.addend(7);
 test1.addend(4);
 test1.remove(7);
 cout << test1.front()<< endl;
 cout << test1.last()<< endl;
 Mlist<string> test2= Mlist<string>() ;
 test2.addend("John");
 test2.addend("Paul");
 test2.addend("Mary");
 test2.addend("Kate");
 test2.remove("Paul");
 cout << test2.front()<< endl;
 cout << test2.last()<< endl;
}

[keskiverto]

What is on the line 133?

You have essentially:

void      // return type
foo       // name
( int n ) // arguments
( double y, int n ) // mysterious line 133
{}        // function body 

[qwewq149]

i guess i was suppose to move the line next to remove;

so now it looks like

template <typename T>
    void Mlist<T>::remove (typename vector <T>::iterator ix, T n)
	{
	    if(ix==mlist.end())
		{
		    return;
		}
		if (*ix ==n)
		{
		    mlist.erase(ix, n);
		    remove(ix);
		}
		else
		{
		    remove(++ix, n);
		}
	}

but now i get the error:
/tmp/cc54uecp.o: In function `main':
hw4.cpp:(.text+0x67): undefined reference to `Mlist<int>::remove(int)'
hw4.cpp:(.text+0x239): undefined reference to `Mlist<std::string>::remove(std::string)'
collect2: error: ld returned 1 exit status

[keskiverto]

Of course.

Within your class definition (lines 5-24) you do declare (on line 19) that Mlist has member void remove( T n )

However, there is no implementation for that member function anywhere, so linker cannot link them in and gives the error message.


On lines 131-~148 you do have a template implementation for (non-existent) member
void remove(typename vector <T>::iterator ix, T n)


If you had non-templates:

class Foo {
  void bar( int );
};

void Foo::bar( double ) { // compiler error
  // class Foo does not have member bar(double)
}