Thread: What's a link error?

deleted

You need to define your AminoAcidAnalyzer and Element constructors. Even if they're empty, the linker requires that they be defined somewhere, which they aren't as is.

-Prelude

Imperito, I followed what you said but now aminoacid_analyzer.cpp does not recognize the class from aminoacid_analyzer.h

Here is what I got now. The error is "unknowed identifier 'AminoAcidAnalyzer'

Also, I'm not sure if I need to pass a acidCount as a parameter in the constructor?

aminoacid_main.cpp

Code:

#include "aminoacid_analyzer.h"
//#include "element.h"

int main( void )
{
	char elementFile[] = "elements.dat";
	
	AminoAcidAnalyzer *aaa = new AminoAcidAnalyzer;
	
	aaa->populate(elementFile);
	
	return 0;
}

aminoacid_analyzer.cpp

Code:

//#include <iostream.h>
//#include "aminoacid_analyzer.h"

AminoAcidAnalyzer::AminoAcidAnalyzer()
{
	acidCount = 0;
}

void AminoAcidAnalyzer::populate(char *elementFile)
{
	cout<<"It's Working!";
}

aminoacid_analyzer.h

Code:

#ifndef _AMINO_ACID_ANALYZER_
#define _AMINO_ACID_ANALYZER_

#include <iostream.h>
#include "element.h"

class AminoAcidAnalyzer
{
	Element elements[5];
	int acidCount;
	
	public:
		AminoAcidAnalyzer();
		void populate(char * elementFile);		 
};

#include "aminoacid_analyzer.cpp"

#endif

element.h

Code:

#ifndef __ELEMENT_H__
#define __ELEMENT_H__

class Element
{
	char atomic_symbol;
	double atomic_mass;
};

#endif

element.h
still yet to be implemented

>That's compilant and it compiles for me
Really? What compiler do you use? I get 7 errors with the code that was posted. Also make sure that you try to run the program, if all you do is compile it will go through cleanly because the linker activates after the compiler.

>Prelude, any thoughts?
Hehe

Try this:

Code:

main.cpp:

#include <iostream.h>
#include "element.h"
#include "aminoacid_analyzer.h"
#include "aminoacid_analyzer_fleshy.h"

int main( void )
{
  char elementFile[] = "elements.dat";	
  AminoAcidAnalyzer *aaa = new AminoAcidAnalyzer;	
  aaa->populate(elementFile);	
  return 0;
}

Code:

aminoacid_analyzer.h:

#ifndef AMINO_ACID_ANALYZER__
#define AMINO_ACID_ANALYZER__

class AminoAcidAnalyzer
{
  Element elements[5];
  int acidCount;	
public:
  AminoAcidAnalyzer();
  void populate(char * elementFile);		 
};

#endif

Code:

aminoacid_analyzer_fleshy.h:

AminoAcidAnalyzer :: AminoAcidAnalyzer()
{
  acidCount = 0;
}

void AminoAcidAnalyzer :: populate(char *elementFile)
{
  cout<<"It's Working!";
}

Code:

element.h:

#ifndef ELEMENT_H__
#define ELEMENT_H__

class Element
{
  char atomic_symbol;
  double atomic_mass;
};

#endif

Notes: The double underscore prefix in your mangled names is reserved by the implementation, avoid using it. You want to avoid #include'ing headers and source files anywhere but your main driver files or you risk linkage problems due to the spaghetti effect.

Personally, I prefer to define my class methods in another header if the class is large or in the same header as the declaration if the class is small. This is mostly because I don't like to include source files as a matter of style, it keeps things simpler to follow.

-Prelude