Why does the program increase the value of the x and the y even after they are bigger, then they should be?

Question

I'm making a program, that moves a dot, from the startx, starty to endx, endy. But it moves continuously, even after the x and the y are bigger than endx and endy. Here is the code:

int x, y;
            x = startx; y = starty;
            if(startx<goalx){
                if (starty < goaly) {
                    while (startx < goalx || starty < goaly) {
                        x += sqrt(2)*speedx;
                        y += sqrt(2)*speedy;
                    }
                }
                else {
                    while (startx < goalx || starty > goaly) {
                        x += sqrt(2)*speedx;
                        y -= sqrt(2)*speedy;
                    }
                }
            }
            else {
                if (starty < goaly) {
                    while (startx > goalx || starty < goaly) {
                        x -= sqrt(2)*speedx;
                        y += sqrt(2)*speedy;
                    }
                }
                else {
                    while (startx > goalx || starty > goaly) {
                        x -= sqrt(2)*speedx;
                        y -= sqrt(2)*speedy;
                    }
                }


            }
            cout << x << ", " << y << endl;

startx, starty, goalx and goaly are user inputs.

your else condition isn't working properly . The one containing loop — JAMSHAID, Dec 01 '19 at 11:25
So if startx = 12, starty = 23, goalx = 78 and goaly = 89, then it works. But when , fe : goaly = 22, then it doesn't — Gergő Szabó, Dec 01 '19 at 11:38
The conditions of the loops test values of `startx`, `goalx`, `starty`, and `goaly`. The bodies of the loops only change values of `x` and `y`, but never change the variables tested in the loop conditions. The loops are therefore infinite. — Peter, Dec 01 '19 at 12:24

score 1 · Accepted Answer · answered Dec 01 '19 at 11:25

1

The control structures depend on startx and starty but these are never changing. Supposedly x and y should be used instead.

answered Dec 01 '19 at 11:25

ldz

2,217
16
21

score 0 · Answer 2 · answered Dec 01 '19 at 11:39

0

try this

int x, y;
    x = startx; y = starty;
    int xInc = sqrt(2) * speedx;
    int yInc = sqrt(2) * speedy;
    if(x < goalx && y < goaly)
    {
        while(x < goalx || y < goaly)
        {
            x += xInc;
            y += yInc;
        }
    }
    else if(x < goalx && y > goaly)
    {
        while(x < goalx || y > goaly)
        {
            x += xInc;
            y -= yInc;
        }
    }
    else if(x > goalx && y < goaly)
    {
        while(x > goalx || y < goaly)
        {
            x -= xInc;
            y += yInc;
        }
    }
    else if(x > goalx && y > goaly)
    {
        while(x > goalx || y > goaly)
        {
            x -= xInc;
            y -= yInc;
        }
    }

answered Dec 01 '19 at 11:39

Shubham Agrawal

559
6
15

I have a 'cout << x << "," << y' at the end, and it doesn't give any output. It still stuck in the while loops. – Gergő Szabó Dec 01 '19 at 11:49
Yes add it bro, you have to intialize speedx, speedy, goalx, goaly, startx, starty....and if it doesn't work then share whole code instead of code-fragment. – Shubham Agrawal Dec 01 '19 at 11:51
The whole code is very very long... (starts and goals are user inputs) – Gergő Szabó Dec 01 '19 at 11:52
then do debugging.. use any debugger, or use cout statements in between to know, where it going wrong. – Shubham Agrawal Dec 01 '19 at 11:54

Why does the program increase the value of the x and the y even after they are bigger, then they should be?

2 Answers2