Expected unqualified-id before 'if' beginner in need of help

Projects Programming
1

Hi everyone,
For a college project, I have written this code however on the if statements it is giving me an expected unqualified-id before 'if' error when compiling the code and i have read through other topic posts with this problem but I just can't seem to fix it. could anyone help me out?

int LED1 = 2;
int LED2 = 3;
int LED3 = 4;
int potValue = 0;
int dutyCycle = map(potValue, 0, 1023, 100, 255);
void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
}

void loop() {
  potValue = analogRead(A0);
}

void Forward(int dutyCycle) {
  analogWrite(LED1, 10);
  analogWrite(LED2, 200);
  analogWrite(LED3, 10);
}
void left(int dutyCycle) {
  analogWrite(LED1, dutyCycle);
  analogWrite(LED2, 50);
  analogWrite(LED3, 10);
}
void right(int dutyCycle) {
  analogWrite(LED1, 10);
  analogWrite(LED2, 50);
  analogWrite(LED3, dutyCycle);
}
if (potValue == 512); {
  forward();}
else if (potValue > 512); {
  left();}
else (potValue < 512); {
  right();
  }
2

You have code outside of a function

Where does the right() function end ?

3

okay so i should place all my if statements inside another function?
and the right function end after the } before the if statement

4

You also want to lose a semicolon. What you wrote is the same as

  if (potValue == 512)
    ;

  forward();

A complete if statement that does nothing.

And unconditional execution of the forward() function.

a7

5

okay, so both semicolons should be deleted?
and what i am trying to achieve is that the code in "void forward" is executed when that value is reached.

6

No, just the one that inadvertently completes the if statement.

So like

  if (potValue == 512) {
    forward();
  }

I should point out that potValue will probably not be exactly 512 very dependably. Please put your finger on this does the same thing a bit differently:

  if (potValue > 544) {
    left();
  }
  else if (potValue < 480) {
     right();
  }
  else {
    forward();
  }

I used constants and made a little area around 512 for meaning forward. You could use a manifest constant, viz:

// up top for everyone to see and change
const int DEADBAND = 32;


// then later on

  if (potValue > 512 + DEADBAND) {
    left();
  }
  else if (potValue < 512 - DEADBAND) {
     right();
  }
  else {
    forward();
  }

HTH

a7

7

The basic rule is that you put all program statements that depend on a test returning true into a pair of braces. It is that simple.

White space, blank lines and tabs do not influence what code is executed, only the presence of the braces surrounding the code block

1 Like
8

yes i do get that potValue using an actual setup won't work like this but in this case we are asked to make it to be 512 so that is not something i can change, but other than removing the semicolons everything should be good

9

ah okay thanks

10

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