undefined reference to CLASS::function() - c++

Question

So when I try to simply compile my code using "g++ Asg5.cpp" I receive the following error
/tmp/cczhpSGO.o: In function 'main':
Asg5.cpp:(.text+0x2fb): undefined reference to 'BinomialTree::insert(int)'
collect2: ld returned 1 exit status
If anyone's wondering why I'm not using a makefile, my professor simply wants to type g++ <.cpp with main()> to compile..
Anyway here's my code I really appreciate the assistance!
Asg5.cpp
#include "BinomialTree.h"
#include "BinomialNode.h"
#include <iostream>
#include <vector>
#include <fstream>
#include <sstream>
#include <stdlib.h>
#include <string>
#include <stdio.h>
using namespace std;
int main(int argc, char* argv[])
{
//input handling
if(argc != 2)
{
cout << "Incorrect Usage. \n Example: ./a.out <filename>" << endl;
exit(1);
}
BinomialTree *tree = new BinomialTree();
char *buffer;
char *token;
//read file into buffer.**************************************
string input;
ifstream file;
file.open(argv[1]);
if(file.is_open())
{
string str;
while(file.good())
{
getline(file,str);
input += " " + str;
}
}
else{
cout << "File not found"<< endl;
return 1;
}
file.close();
int buf;
stringstream ss(input);
vector<int> tokens;
while(ss >> buf)
{
tokens.push_back(buf);
}
int i = 0;
for(i = 0; i < tokens.size(); i++)
tree->insert(tokens[i]);
//end file reading *******************************************
delete tree;
}
BinomialNode.h
#ifndef _BINOMIALNODE_H_
#define _BINOMIALNODE_H_
#include "BinomialTree.h"
class BinomialNode
{
public:
int k;
BinomialNode *children[20];
int data;
BinomialNode();
};
#endif
BinomialNode.cpp
class BinomialNode
{
BinomialNode::BinomialNode(int n)
{
this->k = 0;
this->data = n;
}
}
BinomialTree.h
#ifndef _MULTIMAP_H_
#define _MULTIMAP_H_
#include "BinomialNode.h"
class BinomialTree
{
public:
BinomialNode * BQ[20];
void insert(int n);
void merge(BinomialNode *queue, BinomialNode *in, int k);
void print(BinomialNode *root, int tab);
};
#endif
BinomialTree.cpp
#include "BinomialNode.h"
#include "BinomialTree.h"
#include <iostream>
#include <cstdlib>
class BinomialTree
{
void BinomialTree::insert(int n)
{
BinomialNode *in = new BinomialNode(n);
if(BQ[0] == NULL)
{
BQ[0] = in;
return;
}
else
merge(BQ[0], in, 0);
}
void BinomialTree::merge(BinomialNode *queue, BinomialNode *in, int k)
{
if(queue == NULL)
{
BQ[k] = in;
return;
}
if(n == NULL)
{
BQ[k] = queue;
return;
}
if(queue->data > in->data)
{
merge(in, queue);
return;
}
queue->k++;
BinomialNode* temp[queue->k];
int i;
for(i = 0; i < queue->k-1; i++)
temp[i] = queue->children[i];
temp[queue->k-1] = in;
for(i = 0; i < queue->k; i++)
queue->children[i] = temp[i];
if(BQ[queue->k] == NULL)
{
BQ[queue->k] = queue;
return;
}
else
merge(queue, BQ[queue->k]);
}
void BinomialTree::print(BinomialNode *root, int tab)
{
if(root == NULL)
return;
int i;
for(i = 0; i < tab*5; i++) cout << " ";
cout << root->data << endl;
for(i = 0; i < root->k; i++) print(root->children[i], tab+1);
}
}

Answer 1

You cpp files shouldn't have Class in them. They should look more like:
BinomialNode.cpp
#include "BinomialNode.h"
BinomialNode::BinomialNode(int n) :
k(0)
{
data = n;
}
And of course the corollary for the much longer BinomialTree.cpp. Also, you should compile it with something like:
g++ BinomialTree.cpp BinomialNode.cpp Asg5.cpp -o asg5
Also you're going to run into a lot of other problems with you code. For instance:
BinomialNode * BQ[20];
I don't see BQ being initialized anywhere, which means you're pretty much guaranteed a seg fault if you were to run this. You need to initialize this or allocate it. Seeing lines like:
if(BQ[0] == NULL)
Makes me think you really wanted:
BinomialNode BQ[20];
Though you would still need to initialize it to all NULLs since you aren't guaranteed that will be full of NULLs when you run the program. Also, this is recursive and infinite and can't possibly work (in BinomialNode.h):
BinomialNode *children[20];
There are likely more issues with this code, but that wasn't your question, so I'll stop now!

Answer 2

You need to compile all the .cpp files into one program. You're not using BinomialTree.cpp anywhere right now. If your project requires that you simply type g++ Asg5.cpp then you need to #include your .cpp files or move their contents to your .h files. But the normal solution would be to build all the .cpp files together, not just the one containing main().