Linker bug in code that was working

[ChemE]

Genetic algorithm program worked a few times, but the very same code stopped compiling a minute later. Only one constant value was changed in the code (from 50 to 250), and then it kept bugging when changed back (from 250 to 50).
System: Windows 7 x64 Enterprise
IDE: MS Visual Studio 2010 Premium

Mostly, I'm just asking for help on the compiling error. I've been bashing my head at it for a while trying to figure out what was repeated, but I don't see any degenercies. It looks like that the second error is pointing towards my random function in the header file, "iRandCust", but I can't seem to fix it. That function was "iRand" when I first got the error, and I had hoped that renaming it would fix the bug, but it hasn't.

Errors:
1: error LNK1169: one or more multiply defined symbols found
2: error LNK2005: "int __cdecl iRandCust(int,int)" (?iRandCust@@YAH@Z) already defined in FunctionsNSuch.obj

The program never compiles.

Code:

//main.cpp
// Genetic Algorithm CPP program 'n such.
// For the Math final project.
#include "FunctionsNSuch.h"

using namespace std;

int main(){
	cout << "Welcome to the Genetic Algorithm test lab.\n";

	cout << "Creating new set of chromosomes...\n";
	Chromosomes *mainSet = new Chromosomes();

	srand( (unsigned)time(NULL) );
	for (int i = 0; i < 100; i++){rand();}  //Did this because my first few rand() values kept coming back as the same thing every time.
	

	mainSet->PrintBest();
	mainSet->AdvanceWithPrint(50);
	cin.ignore();
	return 0;
}

//FunctionsNSuch.h
#include <iostream>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>


const int geneSize = 10;
const int chromosomeCount = 100;
const int keepCount = 5;
const int mutantRatio = 3;
const int mutantGeneCount = 4;
const double minLimits[] = {10, 1, 1, 1, 1, 1, 1, 1, 1, 1};
const double maxLimits[] = {100, 10, 10, 10, 10, 10, 10, 10, 10, 10};

static long nextFreeID = 1;

#include <iostream>

using namespace std;

struct Chromosome;
class Chromosomes;

int iRandCust(int lowerBound, int upperBound){
	return (lowerBound + rand() / RAND_MAX * (lowerBound + upperBound));
}

struct Chromosome{
	double g[geneSize];
	double result;
	bool hasResult, elite;
	long ID;
	Chromosome *next;
	void RandomizeGene(int geneIndex){
		g[geneIndex] = minLimits[geneIndex] + (double)rand() / RAND_MAX * (maxLimits[geneIndex] - minLimits[geneIndex]);
		return;
	}
	Chromosome(){
		next = NULL;
		hasResult = false;
		elite = false;
		ID = nextFreeID;
		nextFreeID++;
		for(int i = 0; i < geneSize; i++){
			RandomizeGene(i);
			//cout << "For gene #" << i << ", value: " << g[i] << ".\n";
		}
		//cout << "Made #" << ID << " (" << this << ").\n";
	}
	Chromosome(Chromosome *toDuplicate){
		next = NULL;
		hasResult = false;
		elite = false;
		ID = nextFreeID;
		nextFreeID++;
		for(int i = 0; i < geneSize; i++){
			g[i] = toDuplicate->g[i];
			//cout << "For gene #" << i << ", value: " << g[i] << ".\n";
		}
		//cout << "Made #" << ID << " (" << this << ").\n";
	}
	void Evaluate(){
		hasResult = true;
		result = (g[1] + g[2] * g[3] / g[4] - g[5] / g[6] + g[7] * g[8] * g[9]) / g[0];
	}
};

class Chromosomes{
	//Chromosome *first[2], *last[2], *toDelete;
	Chromosome *first, *last, *toDelete, *throwAway;
	int chromCount;
	//double maxFitness;
	Chromosome *elites[keepCount];
	int weakElite;
	long generationIndex;
	long deleteCount;
	int deletedList[1000];
	void DeleteChr(Chromosome *toDelete){
		/*cout << "Deleting #" << toDelete->ID << " (" << deleteCount << ").  (" << toDelete << ")\n";
		for(int i = 0; i < deleteCount; i++){
			if (toDelete->ID == deletedList[i]){
				cout << "Duplicate deletion: " << toDelete->ID << "!\n";
			}
		}
		deletedList[deleteCount] = toDelete->ID;
		deleteCount++;*/
		delete toDelete;
	}
	void UpdateWeakElite(){
		weakElite = 0;
		for (int i = 0; i < keepCount; ++i){
			if(elites[i]->result < elites[weakElite]->result){
				weakElite = i;
			}
		}
	}
	void AddNewChromosome(){
		if(first==NULL){
			throwAway = new Chromosome();
			DeleteChr(throwAway);
			first = new Chromosome();
			last = first;
		} else {
			last->next = new Chromosome();
			last = last->next;
		}
		chromCount++;
		return;
	}
	void AddDuplicantChromosome(Chromosome *parent){
		if(first==NULL){
			throwAway = new Chromosome();
			DeleteChr(throwAway);
			first = new Chromosome();
			last = first;
		} else {
			last->next = new Chromosome();
			last = last->next;
		}
		chromCount++;
		return;
	}
	void AddMutants(){
		Chromosome *current;
		int toMutate;
		
		current = first;
		for (int i = 0; i < keepCount; i++){
			for (int j = 0; j < mutantRatio; j++){
				AddDuplicantChromosome(current);
				for (int k = 0; k < mutantGeneCount; k++){
					toMutate = iRandCust(0, geneSize - 1);
					last->RandomizeGene(toMutate);
				}
			}
			current = current->next;
		}
	}
public:
	Chromosomes(){
		deleteCount = 0;
		first = NULL;
		last = NULL;
		chromCount = 0;
		while(chromCount < chromosomeCount){
			//cout << "Adding...\n";
			AddNewChromosome();
		}
		generationIndex = 1;
	}
	~Chromosomes(){
		Chromosome *current, *toDelete;
		current = first;
		while(current){
			toDelete = current;
			current = current->next;
			DeleteChr(toDelete);
		}
	}

	void EvaluateAll(){
		Chromosome *current;
		current = first;
		while(current){
			if(!current->hasResult){
				current->Evaluate();
			}
			current = current->next;
		}
	}
	void ToNextGeneration(){	//Move to the next generation
		generationIndex++;
		
		//Evaluate
		EvaluateAll();
		
		//First, ID and keep the best from the prior generation
		Chromosome *current = first;
		for(int i = 0; i < keepCount; i++){		//Count first few chromosomes as tenative elites
			elites[i] = current;
			//cout << "Temp elite, default:  " << current->result << endl;
			current = current->next;
		}
		UpdateWeakElite();						//Find the weak elite
		//cout << "Chromosome count = " << chromCount << ".\n";
		for (int i = keepCount; i < chromosomeCount; ++i){		//Go through keeping high values as the elites
			if (current->result > elites[weakElite]->result){
				//cout << "Better elite found:  " << current->result << " (higher than " << elites[weakElite]->result << ").\n";
				elites[weakElite] = current;
				UpdateWeakElite();
			}
			current = current->next;
		}
		for (int i = 0; i < keepCount; i++){		//Mark elites
			elites[i]->elite = true;
			//cout << "Mark elite loop iteration #" << i << endl;
		}
		current = first;
		while(!current->elite){		//Delete until the first elite
			toDelete = current;
			current = current->next;
			DeleteChr(toDelete);
		}
		first = current;
		last = first;
		first->elite = false;
		//cout << "Found elite (" << current->result << ").\n";
		current = current->next;
		while (current) {
			if (current->elite) {
				last->next = current;
				last = current;
				last->elite = false;
				//cout << "Found elite (" << current->result << ").\n";
				current = current->next;
			} else {
				toDelete = current;
				//cout << "Found non-elite (" << current->result << ").\n";
				current = current->next;
				DeleteChr(toDelete);
			}
		}
		chromCount = keepCount;
		// Now only the elite chromosomes are left.
		
		// Generate new chromosomes
		while (chromCount < chromosomeCount){
			AddNewChromosome();
		}
	};

	void Advance (int numberOfGenerations){
		for (int i = 0; i < numberOfGenerations; i++){
			ToNextGeneration();
		}
	};
	void AdvanceWithPrint (int numberOfGenerations){
		for (int i = 0; i < numberOfGenerations; i++){
			ToNextGeneration();
			PrintBest();
		}
	};
	void PrintBest(){
		EvaluateAll();

		Chromosome *current, *currentElite;
		
		currentElite = first;
		current = first->next;

		while(current){
			if(current->result > currentElite->result){
				currentElite = current;
			}
			current = current->next;
		}

		//cout << "\nOut of " << chromCount << " chromosomes, the current best value is " << currentElite->result << " from the genes:\n";
		cout << "\nBest value in generation #" << generationIndex << " is " << currentElite->result << " from the genes:\n";
		for (int i = 0; i < (geneSize - 1); i++){
			//cout << " Gene #" << (i + 1) << ":  " << currentElite->g[i] << ", \n";
			cout << currentElite->g[i] << ", ";
		}
		//cout << " Gene #" << geneSize << ":  " << currentElite->g[(geneSize - 1)] << ".\n";
		cout << currentElite->g[(geneSize - 1)] << ".\n";
	};
};

[ChemE]

Update:

I took out

int iRandCust(int lowerBound, int upperBound){
	return (lowerBound + rand() / RAND_MAX * (lowerBound + upperBound));
}

and just replaced the one place where I used this function with the plain code. The program works now, so I'm guessing that this was the issue.

Can anyone tell me why that function was messing it up?