IF Statement Mystery << Solved >>

Projects Programming
1

I hope someone can tell me what is wrong with this line of code;

if((Mode_X ++) > 2) Mode_X = 1;

This is the do loop code

   do{

    Busy_LED_On;
//    while(digitalRead(CW_Home_Pin) == true){

    debug_IF_Delay(Pulse_Delay_Val[x][Mode_X][1]);

    Reset_Count;

    do{
      StepPinToggle;
      Delay_Check(Pulse_Delay_Val[x][Mode_X][1]);
//      }while(digitalRead(CW_Home_Pin) == true);
    }while((INC_Count) <= (Angle_180_Count));

    Busy_LED_Off;
    
    if((x += digitalRead(DIR_Out_Pin)) > 9){ 

      if((Mode_X ++) > 2) Mode_X = 1;
      
      x=0;
    }

    digitalWrite(DIR_Out_Pin,!digitalRead(DIR_Out_Pin));

    debugF("\tMode_X >> ");
    debugln(Mode_X);
    debugF("\tx >> ");
    debugln(x);
    debuglnF("*****************");

    delay(2500);
//    while(digitalRead(CW_Home_Pin) == false){
//    while(INC_Count < false){
//        StepPinToggle;
//        Delay_Check(Delay);
//    }
      debug_SerialWait;

   }while(true);

I know the if statement works because Mode_X count increases from 2 to 3 instead of setting Mode_X to 1!!!!

2

I'm guessing it's because of the post increment of Mode_X. Maybe you need a pre increment here? Just a guess....

3

Try:

Mode_X++;
if(Mode_X > 2) 
{
   Mode_X = 1;
}
4

If Mode_X can only have values 1 and 2, then either use a conditional, or a modulus. Sorry, 82yo autistic mind shooting from the hip, might be useful or not.

5

Obviously not. You are saying "Increment Mode_X" and then the rest is a syntax error.

What it should be is

if((Mode_X ++) > 2) {
   Mode_X = 1;
   }
6

No syntax error.
The brackets are optional if there is only one statement to execute, and it is not necessary to put the statement on a separate line from the if statement.

Their is no problem with the line of code, just the posters understanding of what it does.

if((Mode_X ++) > 2) Mode_X = 1;

First the conditions (Mode_X > 2 ) is evaluated, then Mode_X is incremented.

7

Mode_X increments after the comparison to 2.

Compile this.

int Mode_X = 1;
void setup() {
  Serial.begin(115200);
  if ((Mode_X ++) > 2) Mode_X = 1;
  Serial.println(Mode_X);
}
void loop() {}
8

Check this out, run it and watch serial. I know it's 0,1 where you want 1,2 but that is left as an exerc ise for the reader.

int Mode_X = 1;
int BadMode = 1;
void setup() {
  Serial.begin(115200);
  
}
void loop() {

  Mode_X = (Mode_X + 1) % 2;
  BadMode = (BadMode++) % 2;
Serial.print("Mode_X="); Serial.println(Mode_X);
Serial.print("BadMode=");Serial.println(BadMode);
delay(2000);
}
9

I can't believe it, just change it to ++Mode_X so the incremented value is tested.

10

Did you notice you have Mode_X ++ instead of Mode_X++. But in reality it needs to be ++Mode_X increment then test.

11

Ok problem is fixed with this line of code

if( ++Mode_X > 2) Mode_X = 1;

Before I let you all go. May I be so bold as to ask one more question. What is the difference between Mode_X++ and +++ Mode_X?

Thanks everyone for sharing your great wisdom with me. :blush: :blush:

12

Don't forget to mark my post as Solved.

13

Tom.. :smiley: :+1: :coffee: :australia: