Turtle Graphics Program - c++

Question

#include <iostream>
#include <fstream>
using namespace std;
void printArray(void);
char grid[6][34] = {'0'}; // empty floor
void movement(int command);
int direction = 2; // 1 for north, 2 for east, 3 for south, 4 for west. Turtle starts facing east.
void turtleMovement(int, int);
int spacesMoved; // used after F command.
int yCoord = 0; // Y position assumed 0;
int xCoord = 0; // X position assumed 0;
bool pen = 0; // assume pen is up
void initialize(void);
char command; // U for pen up, D for pen Down, R for right turn, L for left turn, F for forward movement with spaces moved, P for array print, and Q for end.
int main(){
initialize();
ifstream infile;
infile.open("commands.txt");
infile >> command;
while(command != 'Q'){
if(command == 'U'){
pen = 0;
}
else if(command == 'D'){
pen = 1;
}
if(command == 'R' || command == 'L'){
movement(command);
}
if(command == 'F'){
infile >> spacesMoved;
turtleMovement(yCoord, xCoord);
}
else if(command == 'P')
printArray();
infile >> command;
}
}
//=====================================================================================================================================================
//
// Function Name: intialize
//
// Pre: none
//
// Post: sets every element of the array grid to all zeroes.
//
//======================================================================================================================================================
void initialize()
{
for(int i = 0; i < 6; i++){ //
for(int j = 0; j < 34; j++){ // Initialization of Array to all zeros.
grid[i][j] = '0'; //
}
}
}
//=====================================================================================================================================================
//
// Function Name: printArray
//
// Pre: none
//
// Post: prints out the array grid to the console
//
//======================================================================================================================================================
void printArray()
{
for(int i = 0; i < 6; i++)
for(int j = 0; j < 34; j++){
grid[i][j];
cout << grid[i][j] << (j == 33 ? "\n" : ""); // if the row gets to 33 characters a new line will be made.
}
}
void movement(int command)
{
if (direction == 2){ // direction is east
if (command == 'R')
direction = 3;// if you're facing east and you turn right you're now facing south
else if (command == 'L') // if you're facing east and you turn left you're now facing north.
direction = 1;
}
else if (direction == 3) // direction is south
{
if (command == 'R') // turn right to go west
direction = 4;
else if (command == 'L') // turn left to go east
direction = 2;
}
else if (direction == 4) // direction is west
{
if (command == 'R') // right for north
direction = 1;
else if (command == 'L') // left for south
direction = 3;
}
else if (direction == 1) // direction is north
{
if (command == 'R') // right for east
direction = 2;
else if (command == 'L') // left for west
direction = 4;
}
}
void turtleMovement(int y, int x){
if(direction == 2){
int i = y;
for(int j = x; j < x + spacesMoved; j++){
if(pen == 1)
grid[i][j] = '1';
else
grid[i][j] = '0';
}
xCoord += spacesMoved - 1; //updates the x coordinate
}
else if(direction == 3){
for(int i = y; i < y + spacesMoved; i++){
int j = x;
if(pen == 1)
grid[i][j] = '1';
else
grid[i][j] = '0';
}
yCoord += spacesMoved - 1; //updates the y coordinate
}
else if(direction == 4){
int i = y;
for(int j = x; j > x - spacesMoved; j++){
if(pen == 1)
grid[i][j] = '1';
else if (pen == 0)
grid[i][j] = '0';
}
xCoord -= spacesMoved - 1; //updates the x coordinate
}
else if(direction == 1){
for(int i = y; i > y- spacesMoved; i++){
int j = x;
if(pen == 1)
grid[i][j] = '1';
else
grid[i][j] = '0';
}
yCoord -=spacesMoved - 1; //updates the y coordinate
}
}
I'm having extreme frustration with my program, when I try and do a 180 turn, i.e. a R R or a L L the whole program just freezes. Is it something with my logic? or a syntax? because it doesn't give me any of those errors.

Answer 1

Sorry, but your program is annoying me and it is a little hard to read.
Try this:
struct Position
{
int x;
int y;
};
struct Direction_Vector : Position
{
unsigned int direction;
};
const unsigned int MAX_DIRS = 4u;
void movement(char command,
const Direction_Vector present_dir,
Direction_Vector& new_dir)
{
unsigned int dir = present_dir.direction;
switch (command)
{
case 'R': // rotate clockwise;
dir = (dir + 1) % MAX_DIRS;
break;
case 'L': // rotate counter clockwise
dir = (dir + (MAX_DIRS - 1)) % MAX_DIRS;
break;
case 'M': // Move one position in the given direction
switch (dir)
{
case 0: // Assume north, Y decreases
new_dir.y = present_dir.y - 1;
break;
case 1: // Assume east, X increases
new_dir.x = present_dir.x + 1;
break;
case 2: // Assume south, Y increases
new_dir.y = present_dir.y - 1;
break;
case 3: // Assume west, X decreases
new_dir.x = present_dir.x - 1;
break;
}
break;
default:
break;
}
new_dir.direction = dir;
}
You may be able to optimize the movement section by using algebra and realizing a relationship between the direction and the ordinate that gets adjusted.
Also, I have not put in any boundary checking.
Sorry if I ruined your day by simplifying a lot of your posted code.
Use a debugger and step through the above code and figure out if it handles the 180 degree turns correctly.
Edit 1: Truth Tables
Here are the truth tables for the movement and ordinate changes
Direction | Delta X | Delta Y| // "delta" means change
----------+---------+--------+
0 | 0 | -1 |
----------+---------+--------+
1 | +1 | 0 |
----------+---------+--------+
2 | 0 | +1 |
----------+---------+--------+
3 | -1 | 0 |
----------+---------+--------+
Can you come up with an algebraic equation for the ordinates based on the direction?