Incorrect value of enum variable

Question

I just began a little fun project which is good ol' snake in CLI. What I'm currently figuring out is changing directions of a single dot inside a box (no snake yet!). I created an enum type with values up, down etc. and created a simple loop to update the position. What's curious is that no matter what value I assign to the direction variable, it is always 3 (DOWN). Here's working example:

#include <iostream> 
using namespace std;
bool gameOver;
const int width = 60;
const int height = 20;
int x, y, fruitX, fruitY, score;

enum eDirection {STOP, LEFT, RIGHT, UP, DOWN};
enum eDirection dir;

int modulo(int x,int N){
    return (x % N + N) %N;
}

void Setup(){
    gameOver = false;
    dir = LEFT;
    x = width / 2;
    y = height / 2;
    fruitX = rand() % width;
    fruitY = rand() % height;
    score = 0;
}

void Draw(){

    system("cls");

    for (int i = 0; i < width; i++){
        cout << "#";
    }
    cout << endl;

    for (int i = 0; i < height; i++){
        cout << "#";
        for (int j = 0; j < width; j++){

            if (j == x && i == y){
                cout << "O";
            }
            else{
            cout << " ";
            }
        }
        cout << "#";
        cout << endl;
    }

    for (int i = 0; i < width; i++){
        cout << "#";
    }
    cout << endl;

    if (dir = STOP){
        
    } else if (dir = UP){
        y = modulo((y - 1) , height);
    } else if (dir = DOWN){
        y = modulo((y + 1) , height);
    } else if (dir = LEFT){
        x = modulo((x - 1) , width);
    } else if (dir = RIGHT){
        x = modulo((x + 1) , width);
    }


}

void Input(){

}

void Logic(){

}

int main()
{
    Setup();
    while(!gameOver)
    {
        Draw();
        cout << endl;
        cout << "Direction value is: ";
        cout << dir;
        Input();
        Logic();
        //Sleep(10);
    }
}

Any ideas? I'm fairly new to C++ and it's still difficult for me to get my head around some of its concepts. Thanks in advance!

Answer 1

Change:

if (dir = STOP)

to:

if (dir == STOP)

since you want to compare those two, not assign UP to dir . Same change is required for your other conditions in the else-if statements.

Tip: Enable compiler warnings in order to get informed about those pesky logical errors. For example in GCC, you could use the useful all warnings flag (Wall), like this:

gcc -Wall snake.c -o snake

to get:

54:19: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
56:24: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
58:26: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
60:26: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
62:27: warning: suggest parentheses around assignment used as truth value [-Wparentheses]

where the the numbers at the start of each warning is in format line:column , allowing you to find the line of code that emits the warning, and also the column at that line.