writing to a file (problem with file << )
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Thread: writing to a file (problem with file << )

  1. #1
    Join Date
    May 2009
    Posts
    44

    writing to a file (problem with file << )

    Code:
    #include <iostream> 
    #include <fstream> //allow writing to file instead of cout 
    #include <cstring>
    using namespace std;
    #include "date.h" 
    #include "person.h" 
    #include "student.h" 
    #include "Employee.h" 
    #include "setT.h"
    
    void main() {
    
    ofstream file ("test_output.txt"); //file for  test results
    
    file << "Program Output" << "\n"; //write title for test 
     
    
    Person *p1 = new Person("Lou", "lou@chat.ca", 20, 6, 1960);
    
    Set<Person> s,s2,s3; 
    Set<int> setints; 
    Set<Date> dates; 
    
    
    
    
    s.add(*p1); 
    
    if (p1 != &(s.someElement())) 
     cout << "OBJECTS ARE NOT THE SAME\n"; //should not happen
    
     
    s.add(*p1); //attempt to add a duplicate
    
    
    s.add(*(new Person("Frank", "f123@chat.ca", 20, 3, 1967))); 
    s.add(*(new Person("Dave", "f23@chat.ca", 21, 12, 1961)));
    
    
    s.add(*(new Student("Eric", "frank@chat.ca", Date(25, 4, 1958), "Carleton", 12345 ))); 
    s.add(*(new Student("Mary", "mary@chat.ca", Date(25, 4, 1955), "Carleton", 22234 ))); 
    s.add(*(new Employee("John", "johnchat.ca", Date(12, 12, 1970), "Nortel", 99912 )));
    
    int a = 5;
    int b = 12;
    int c = 12;
    int d = 42;
    
    setints.add(a).add(b).add(c).add(d).add(a); //note attempt to add a duplicate
    
    
    
    file << setints; //print the ints
    
    //file << "Printing the Set<int> \n"; //write comment to output file 
    //file << setints; //print the ints to file
    
    //print the names using the iterator.
    
    for (s.reset(); s.hasMore(); s.advance() ) 
          cout << s.element().getName() << "  ";
    
    //add some more people 
    s.add(*(new Person("Alan", "alan@chat.ca", 20, 3, 1967))); 
    s.add(*(new Person("Eric", "frank@chat.ca", 25, 4, 1958))); 
    s.add(*(new Person("Bruce", "bruce@chat.ca", 25, 4, 1955))); 
     
    
    //print out the three sets 
    //file << s << "\n" << s2 << "\n" << s3 << "\n";
    
    //Delete all the heap objects (they should all be in set s and dates 
    cout << endl;
    for (s.reset(); s.hasMore(); s.advance() ) 
    {
    	cout << "Deleting " << (s.element()) << endl;
    	delete &(s.element());
    
    }
    
    for (dates.reset(); dates.hasMore(); dates.advance() ) 
    {
        delete &(dates.element());
    	cout << "test2\n";
    }
    file.close(); //close output file 
    cin.get();
    
    } //end main
    I've had to comment out anything that has to do with file << in my assignment. I get an error saying:

    binary '<<' : no operator found which takes a right-hand operand of type 'Set<T>' (or there is no acceptable conversion).

    Can anybody tell me what's wrong with this...here is my set class

    Code:
    template <class T> 
    class Set { 
    public: 
    	Set(int initial_size = 4):index(0),numberOfElements(0)
    {
    capacity = initial_size;
    elements = new T*[capacity];
    for (int i = 0; i < capacity; i++) elements[i] = NULL;
    } 
    Set(const Set<T> & s)
    {
    capacity = s.capacity;
    elements = new T*[capacity];
    for (int = 0; i<capacity; i++)
    	elements[i] = s.elements[i];
    }
    ~Set(void){delete [] elements;} //destructor 
    Set<T> & operator=(const Set<T> & s)
    {
    	if (&s != this) {
    capacity = s.capacity;
    elements = new T*[capacity];
    for (int = 0; i<capacity; i++)
    	elements[i] = s.elements[i];
    	} return *this;
    }
    Set<T> & add(T & element)
    {
    	if ((index == capacity)) 
    	 {
    		 std::cout << endl << "Container is growing." << endl << endl;
    		 T ** temp = elements;
    		 elements = new T*[capacity*2];
    		 for(int i=0; i<index; i++) elements[i] = temp[i]; 
             capacity *= 2; 
             delete [] temp;
    	 }
    
      	 for(int i = 0; i < capacity; i++)
    	 if ((elements[i] != &element) && index < capacity)
    	 {elements[index] = &element; index++; numberOfElements++; cout << element << " added" << endl; break;}
    	 else {cout << endl << "Cannot add duplicate element." << endl << endl; break;}
    	 return *this;	 
    }  
    Set<T> & remove(const T & element)
    {
    	 if(size() < capacity/4) {  //Shrinks the container when 1/4 full 
    		 std::cout << "Container is shrinking.\n"; 
                elements = new t*[capacity/2]; 
                for(int i=0; i<index; i++) elements[i] = temp[i]; 
                capacity = capacity/2; 
                delete [] temp; 
    	 }
    } // remove object equal to element if it  exists 
    
    T & someElement() const 
    {
       index = 0;
       return  *elements[index++];
    }
    //answer some (any) element  of the set but don't remove it 
    //Iterator Methods 
    
    void reset() const {index = 0;}
    bool hasMore() const {return index < numberOfElements;} 
    void advance() const {index++;}
    T & element()const {return *elements[index];}
    
    int size()const {return numberOfElements;} //answer the number of elements in the set. 
    void printOn(ostream & ostr){ostr << "hey";} //print the elements of the set
    
    private: 
    T ** elements;  //to store elements (like assignment #1) 
    int numberOfElements; //number of elements in the set 
    int capacity; //max. no of elements the set can current memory can hold
    mutable int index; //private variable used for the iteration
    };

  2. #2
    Join Date
    Oct 2002
    Location
    Austria
    Posts
    1,284

    Re: writing to a file (problem with file << )

    Quote Originally Posted by heat89 View Post
    I get an error saying:

    binary '<<' : no operator found which takes a right-hand operand of type 'Set<T>' (or there is no acceptable conversion).

    Can anybody tell me what's wrong with this...
    As the compiler tries to tell you. There is no operator << for Set<T>
    try something like this

    Code:
    template <class T> 
    ostream & operator << ( ostream & o, const Set<T> & s ) {
        s.printOn(o);
        return o;
    }
    printOn is not const correct. It should be

    Code:
    void printOn(ostream & ostr) const {
        ostr << "hey";
    }
    Kurt

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