Mach-O Linker Error Help

[PatrickD]

Hi guys. I'm having trouble trying to do an assignment for my c++ class. I have to design a program about a Peg that can hold disks on it. Each disk has to have a diameter smaller than the disk below it. Every time I try to compile my code, I get a linker error. I can compile in terminal using the -c command, but not by creating an a.out file.

Our professor also gave us a sample program from the book to help. However, this program won't compile for me either! Here is the code from our book:

// FILE: bag1.h
// CLASS PROVIDED: bag (part of the namespace main_savitch_3)
//
// TYPEDEF and MEMBER CONSTANTS for the bag class:
//   typedef ____ value_type
//     bag::value_type is the data type of the items in the bag. It may be any of
//     the C++ built-in types (int, char, etc.), or a class with a default
//     constructor, an assignment operator, and operators to
//     test for equality (x == y) and non-equality (x != y).
//
//   typedef ____ size_type
//     bag::size_type is the data type of any variable that keeps track of how many items
//     are in a bag.
//
//   static const size_type CAPACITY = _____
//     bag::CAPACITY is the maximum number of items that a bag can hold.
//
// CONSTRUCTOR for the bag class:
//   bag( )
//     Postcondition: The bag has been initialized as an empty bag.
//
// MODIFICATION MEMBER FUNCTIONS for the bag class:
//   size_type erase(const value_type& target);
//     Postcondition: All copies of target have been removed from the bag.
//     The return value is the number of copies removed (which could be zero).
//
//   void erase_one(const value_type& target)
//     Postcondition: If target was in the bag, then one copy has been removed;
//     otherwise the bag is unchanged. A true return value indicates that one
//     copy was removed; false indicates that nothing was removed.
//
//   void insert(const value_type& entry)
//     Precondition:  size( ) < CAPACITY.
//     Postcondition: A new copy of entry has been added to the bag.
//
//   void operator +=(const bag& addend)
//     Precondition:  size( ) + addend.size( ) <= CAPACITY.
//     Postcondition: Each item in addend has been added to this bag.
//
// CONSTANT MEMBER FUNCTIONS for the bag class:
//   size_type size( ) const
//     Postcondition: The return value is the total number of items in the bag.
//
//   size_type count(const value_type& target) const
//     Postcondition: The return value is number of times target is in the bag.
//
// NONMEMBER FUNCTIONS for the bag class:
//   bag operator +(const bag& b1, const bag& b2)
//     Precondition:  b1.size( ) + b2.size( ) <= bag::CAPACITY.
//     Postcondition: The bag returned is the union of b1 and b2.
//
// VALUE SEMANTICS for the bag class:
//    Assignments and the copy constructor may be used with bag objects.

#ifndef MAIN_SAVITCH_BAG1_H
#define MAIN_SAVITCH_BAG1_H
#include <cstdlib>  // Provides size_t

namespace main_savitch_3
{
    class bag
    { 
    public:
        // TYPEDEFS and MEMBER CONSTANTS
        typedef int value_type;
        typedef std::size_t size_type;
        static const size_type CAPACITY = 30;
        // CONSTRUCTOR
        bag( ) { used = 0; } 
        // MODIFICATION MEMBER FUNCTIONS
        size_type erase(const value_type& target);
        bool erase_one(const value_type& target);
        void insert(const value_type& entry);
        void operator +=(const bag& addend);
        // CONSTANT MEMBER FUNCTIONS
        size_type size( ) const { return used; }
        size_type count(const value_type& target) const;
    private:
        value_type data[CAPACITY];  // The array to store items
        size_type used;             // How much of array is used
    };

    // NONMEMBER FUNCTIONS for the bag class
    bag operator +(const bag& b1, const bag& b2);
}

#endif 

// FILE: bag1.cxx
// CLASS IMPLEMENTED: bag (see bag1.h for documentation)
// INVARIANT for the bag class:
//   1. The number of items in the bag is in the member variable used;
//   2. For an empty bag, we do not care what is stored in any of data; for a
//      non-empty bag the items in the bag are stored in data[0] through
//      data[used-1], and we don't care what's in the rest of data.

#include <algorithm> // Provides copy function
#include <cassert>   // Provides assert function
#include "bag1.h"
using namespace std;

namespace main_savitch_3
{
    const bag::size_type bag::CAPACITY;
    
    bag::size_type bag::erase(const value_type& target)
    {
	size_type index = 0;
	size_type many_removed = 0;

	while (index < used)
	{
	    if (data[index] == target)
	    {
		--used;
		data[index] = data[used];
		++many_removed;
	    }
	    else
		++index;
	}

	return many_removed;
    }

    bool bag::erase_one(const value_type& target)
    {
	size_type index; // The location of target in the data array    

	// First, set index to the location of target in the data array,
	// which could be as small as 0 or as large as used-1. If target is not
	// in the array, then index will be set equal to used.
	index = 0; 
	while ((index < used) && (data[index] != target))
	    ++index;

	if (index == used)
	    return false; // target isn’t in the bag, so no work to do.

	// When execution reaches here, target is in the bag at data[index].
	// So, reduce used by 1 and copy the last item onto data[index].
	--used;
	data[index] = data[used];    
	return true;
    }

    void bag::insert(const value_type& entry)
    // Library facilities used: cassert
    {   
        assert(size( ) < CAPACITY);

        data[used] = entry;
	++used;
    }

    void bag::operator +=(const bag& addend)
    // Library facilities used: algorithm, cassert
    {
	assert(size( ) + addend.size( ) <= CAPACITY);
	
	copy(addend.data, addend.data + addend.used, data + used);
	used += addend.used;
    }

    bag::size_type bag::count(const value_type& target) const
    {
        size_type answer;
        size_type i;

        answer = 0;
        for (i = 0; i < used; ++i)
            if (target == data[i])
                ++answer;
        return answer;
    }

    bag operator +(const bag& b1, const bag& b2)
    // Library facilities used: cassert
    {
        bag answer;

        assert(b1.size( ) + b2.size( ) <= bag::CAPACITY);

        answer += b1; 
        answer += b2;
        return answer;
    }
}

I don't understand why I can't get anything to compile. Any help would be greatly appreciated.

Thanks

[vin]

These two files aren't a program. Just a class definition and it's implementation.

You need to create another cpp file and include bag1.h in it and then write code in a main function that uses the class.

[AbstractionAnon]

Please post the exact error message you're getting.

Your code compiled for me with only one warning related to your use of algorithim's copy function.

>d:\program files\microsoft visual studio 10.0\vc\include\xutility(2227): warning C4996: 'std::_Copy_impl': Function call with parameters that may be unsafe - this call relies on the caller to check that the passed values are correct. To disable this warning, use -D_SCL_SECURE_NO_WARNINGS. See documentation on how to use Visual C++ 'Checked Iterators'
1>          d:\program files\microsoft visual studio 10.0\vc\include\xutility(2212) : see declaration of 'std::_Copy_impl'
1>          e:\warren\visual studio 2010\projects\junk\junk\bag1.cpp(73) : see reference to function template instantiation '_OutIt std::copy<const main_savitch_3::bag::value_type*,main_savitch_3::bag::value_type*>(_InIt,_InIt,_OutIt)' being compiled

P.S. This should really be a templated class (unless you haven't gotten to templates yet).