C++ compiling problem; class methods - c++

Question

I have started writing a very simple class, and all kinds of class methods seem to give me problems. I hope the problem is me and the solution is simple.
The command g++ -o main main.cpp gives the folowing output:
/usr/bin/ld: Undefined symbols:
Lexer::ConsoleWriteTokens()
collect2: ld returned 1 exit status
main.cpp:
#include<iostream>
#include"lexer.h"
int main(){
Lexer lexhnd = Lexer();
std::cout << "RAWR\n";
lexhnd.ConsoleWriteTokens();
std::cout << "\n\n";
return 0;
}
lexer.h:
#ifndef __SCRIPTLEXER
#define __SCRIPTLEXER
#include <iostream>
#include <string>
#include <vector>
#define DEF_TOKEN_KEYWORD 0
struct token{
int flag;
std::string data;
};
class Lexer
{
public:
// bool IsTrue();
// bool AddLine(char * line);
void ConsoleWriteTokens(void);
private:
std::vector<token> TOK_list;
};
#endif
lexer.cpp:
bool Lexer::IsTrue(){
return true;
};
bool Lexer::AddLine(char * line){
token cool;
cool.data = line;
TOK_list.push_back(cool);
string = line;
return true;
};
void Lexer::ConsoleWriteTokens(void){
for (int i = 0; i < TOK_list.size(); i++){
std::cout << "TOKEN! " << i;
}
return 0;
};
I am using g++ in xcode btw.
Thankyou very much in advance, I have been on this problem for a few hours.
EDIT:
g++ -o main lexer.h main.cpp
or
g++ -o main lexer.cpp main.cpp
or
g++ -o main main.cpp lexer.cpp
do NOT work either.
-Hyperzap

Answer 1

Your not compiling the lexer.cpp code.
Try
g++ -o main main.cpp lexer.cpp
as your compilation command.
PROBLEMS IN THE lexer.cpp
You probably want to include the lexer header in the lexer.cpp file
#include "lexer.h"
Also, you don't want to return an integer from void functions.
void Lexer::ConsoleWriteTokens(void){
for (int i = 0; i < TOK_list.size(); i++){
std::cout << "TOKEN! " << i;
}
//This function is void - it shouldn't return something
//return 0;
};
Finally, you have some problems withs this function
bool Lexer::AddLine(char * line){
token cool;
cool.data = line;
TOK_list.push_back(cool);
//what is this next line trying to achieve?
//string = line;
return true;
};
I'm not sure what you are trying to achieve with the line I commented out,
it doesn't seem to do anything and string isn't defined (did you mean std::string mystring = line;)
Finally, don't forget to uncomment the functions declaired in lexer.h that you are defining in lexer.cpp.

Answer 2

Include all the .cpp files in the command line, like this:
g++ -o main main.cpp lexer.cpp
When your project grows, it becomes wise to manage your project in some automatic way: Makefiles, ant, or some IDE-integrated project file.

Answer 3

Well g++ -o main main.cpp lexer.cpp sould do the trick. However I suggest making makefile files. When having a multiple amount of file they come in handy.
I would also suggest adding some optimization to your compilation like -O3 or -O2 (O is a letter o not zero digit!). The difference in execution speed is very noticable. Also if you are goig to make libraries out of your files, why not using --shared option that will create a liked library. I find making shared libraries very useful.