Question

I’ve created some mathematical functions that will be used in main() and by member functions in multiple host classes. I was thinking it would be easiest to make these math functions global in scope, but I’m not sure how to do this.

I’ve currently put all the functions in a file called Rdraws.cpp, with the prototypes in Rdraws.h. Even with all the #includes and externs, I’m getting a “symbol not found” compiler error at the first function call in main().

Here’s what I have:

// Rdraws.cpp
#include <cstdlib>
using namespace std;
#include <cmath>

#include "Rdraws.h"
#include "rng.h"

extern RNG rgen // this is the PRNG used in the simulation; global scope

void rmultinom( double p_trans[], int numTrials, int numTrans, int numEachTrans[] )
{ // function 1 def 
}

void rmultinom( const double p_trans[], const int numTrials, int numTrans, int numEachTrans[]) 
{ // function 2 def
}

int rbinom( int nTrials, double pLeaving )
{ // function 3 def
}

// Rdraws.h

#ifndef RDRAWS
#define RDRAWS

void rmultinom( double[], int, int, int[] );
void rmultinom( const double[], const int, int, int[] );
int rbinom( int, double );

#endif

// main.cpp
...
#include "Rdraws.h"
...

extern void rmultinom(double p_trans[], int numTrials, int numTrans, int numEachTrans[]);
extern void rmultinom(const double p_trans[], const int numTrials, int numTrans, int numEachTrans[]);
extern int rbinom( int n, double p );

RNG rgen; // global PRNG object created for simulation

int main() { ... }

I’m pretty new to programming. If there’s a dramatically smarter way to do this, I’d love to know.

---

Update

I’m a moron and didn’t realize I still hadn’t included Rdraws.cpp in my compiler. As a poster noted, I also forgot a semicolon.

I would still appreciate suggestions if the method outlined here could be improved upon.

Answer 1

Which compiler are you using? You need to first compile all of the source files into object files and then link all of the object files together.

Example:

g++ -c -Wall -O2 main.cpp
g++ -c -Wall -O2 Rdraws.cpp

And then to get the executable…

g++ -s main.o Rdraws.o