X,Y coordinate cartesian plane code

Projects Programming
1

My code is printing some pretty wild results and im not sure what in my code is causing this.

An example for what my serial monitor reads is

"
Enter a value for x
Your x coordinate is 2
Enter a value for y
Your y coordinate is 3
2 is in quadrant 1
2 is in quadrant 3
2 is on the x-axis "

Why all the different outputs?

Thanks in advance

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600); //setup serial communication

}

void loop() {
  // put your main code here, to run repeatedly:
  int x, y;

  Serial.println("\nEnter a value for x");
  while (Serial.available() <= 0);
  x = Serial.parseInt();
  Serial.print("Your x coordinate is ");
  Serial.print(x);

  Serial.println("\nEnter a value for y");
  while (Serial.available() <= 0);
  y = Serial.parseInt();
  Serial.print("Your y coordinate is ");
  Serial.println(y);
 

   if (x != 0 && y != 0)
  {
    if (x > 0 && y > 0)
    {
    Serial.print(x,y);
    Serial.println(" is in quadrant 1");
  }
  else if (x > 0 && y < 0)
  {
    Serial.print(x,y);
    Serial.println(" is in quadrant 4");
  }
  else if (x < 0 && y > 0)
  {
    Serial.print(x,y);
    Serial.println(" is in quadrant 2");
  }
  else (x < 0 && y < 0);
  {
    Serial.print(x,y);
    Serial.println(" is in quadrant 3");
  }
  }
  
  if (x == 0 && y != 0)
  {
    Serial.print(x,y);
    Serial.println(" is on the y axis");
  }
  else if (x != 0 && y == 0);
  {
    Serial.print(x,y);
    Serial.println(" is on the x axis");
  }

}
2

The old "extraneous semicolon" trick :slight_smile:

  else (x < 0 && y < 0);

Pete

3 
while (Serial.available() <= 0);

This waits for just one character to be available. Is that what you intended?

4

No, i need to get an ordered pair from the user ,x and y value. do I need to change that command? what would that look like?

5

The lineSerial.print(x,y);does not print x and y, but x in the numerical system y.

6

Google "arduino parse serial" for lots of examples and discussion.

7

and here:

  else if (x != 0 && y == 0);

Pete

9

It's worse than that

Arghhh. I didn't see that. Maybe it's missing the 'if'.

Pete

10

Delta_G:

else (x < 0 && y < 0);

It's worse than that. An else shouldn't have a condition at all.

So the 'condition' gets parsed as an expression.

What is happening here is that he put the (unnecessary and syntactically incorrect) condition in, got a compile error, and found that adding a semicolon made the compile error go away.

11

I don't think the condition is unnecessary. He's missing "if" in front of it so that it is "else if(condition)".

Pete