// trail.cc/* ---------------------------------------------------------------The Artificial Ant ProblemAn example for how to use gpc++ - The Genetic Programming KernelThis program is free software; you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation; either version 1, or (at your option)any later version.This program is distributed in the hope that it will be useful, butWITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNUGeneral Public License for more details.You should have received a copy of the GNU General Public Licensealong with this program; if not, write to the Free SoftwareFoundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.Copyright 1993, 1994 Adam Fraser, 1996, 1997 Thomas WeinbrennerFor comments, improvements, additions (or even money) contact:Thomas WeinbrennerGrauensteinstr. 2635789 LaimbachGermanyE-mail: thomasw@emk.e-technik.th-darmstadt.deWWW:    http://www.emk.e-technik.th-darmstadt/~thomasw--------------------------------------------------------------- */// This module is responsible for moving the ant around the artificial// world and picking up all the food the ant moves onto#include <fstream.h>#include "gp.h"#include "ant.h"// Read trail from filevoid Ant::readTrail (char* fname){  int x=0, y=0;  ifstream ifs (fname);  if (!ifs)     GPExitSystem ("Ant::readTrail", 		  "There is no trail data file" );  else    {      char ch=NOTHING;      // Move to the correct position in the data file: The area below      // hash.  The double '!' looks a bit odd, but is needed here as      // one of it is an operator redefined by the stream class      while (!(!ifs) && ch!='#') 	ifs >> ch;	      while (y<worldVertical)	{	  // Read character and put it in the constant world member	  // variable	  ifs >> ch;	  if (ch!=NOTHING && ch!=FOOD && ch!=GAP)	    GPExitSystem ("Ant::readTrail", 			  "Wrong character in trail data file" );	  constantWorld[x][y]=ch;	    	  // Increase index	  x++;	  if (x==worldHorizontal) 	    {	      y++;	      x=0;	    }	}      if (!ifs) 	GPExitSystem ("Ant::readTrail", 		      "Error reading trail data file" );    }  // Count the number of available food.  Needed to evaluate the  // standardised fitness.  for (maxFood=0, x=0; x<worldHorizontal; x++)    for (y=0; y<worldVertical; y++)      maxFood+=constantWorld[x][y]==FOOD;}// Reset ant and trail.void Ant::reset (int energy_){  for (int x=0; x<worldHorizontal; x++)    for (int y=0; y<worldVertical; y++)      world[x][y]=constantWorld[x][y];  energy=energy_;  direction=0;     // East  pos.x=0; pos.y=0;}// Print the trailostream& operator << (ostream &os, Ant &ant){  for (int y=0; y<worldVertical; y++)    {      for (int x=0; x<worldHorizontal; x++)	{	  // Ant's current position?	  if (ant.pos.x==x && ant.pos.y==y)	    os << 'A';	  else	    os << ant.world[x][y];	}      os << '\n';    }  return os;}// Turn the ant leftvoid Ant::left (){  if (!energy)     return;  energy--;  direction = (direction+1) % 4;}// Turn the ant rightvoid Ant::right (){  if (!energy)     return;  energy--;  direction = (direction+3) % 4;}// Return the final position if the ant would move forwardposition Ant::forwardPosition (){  position p=pos;  switch (direction)    {    case 0:      // East      if (p.x<worldHorizontal-1)	p.x++;      break;    case 1:      // North      if (p.y>0) 	p.y--;      break;    case 2:      // West      if (p.x>0) 	p.x--;      break;    case 3:      // South      if (p.y<worldVertical-1)	p.y++;      break;    default:      GPExitSystem ("Ant::forwardPosition", "Wrong switch statement");    }  return p;}// Move the ant forward and return whether food was foundint Ant::forward (){  if (!energy)     return 0;  energy--;  // New position  pos=forwardPosition ();  // Eat food, if something is there  int food=world[pos.x][pos.y]==FOOD;  if (food)    world[pos.x][pos.y]=NOTHING;  return food;}// Return whether there is food aheadint Ant::isFoodAhead (){  position p=forwardPosition ();  return world[p.x][p.y]==FOOD;}