function in C++

Hi billpenner

The loop function will repeat indefinitely.

The go-to parts of your code could transfer the program flow to the associated labels, from which the code will continue, essentially skipping any code in

between.

eg:

for(byte r = 0; r < 255; r++){
  for(byte g = 255; g > -1; g--){
  for(byte b = 0; b < 255; b++){
  if (analogRead(0) > 250){ goto bailout;}
  // more statements ...
  }
  }
}
bailout:

A better approach may be to turn the goto's into function calls. in this case the program flow will move to the function you declared and then return back to the point immediately after the function call.

eg.

void setup(){
  Serial.begin(9600);
}

void loop() {
  int i = 2;
  int j = 3;
  int k;

  k = myMultiplyFunction(i, j); // k now contains 6
  Serial.println(k);
  delay(500);
}

int myMultiplyFunction(int x, int y){
  int result;
  result = x * y;
  return result;
}

More information can be found on the following pages:

Arduino - Goto

Arduino - FunctionDeclaration

Does this clarify the situation somewhat?

Paul

OK, Call out the censors, he used the GOTO word……..

Ok, more seriously, GOTO is a bad thing to use and can leave you with a mess from a memory and cpu resource perspective, most modern languages do not even have it

The loop function technically does not loop forever as it is a simple function call, the underlying runtime is where the loop really is and it calls the loop function repeatedly

This is an important distinction as any variables you initialize in this function will be initialized again and again if your not careful and therefor mess with your program or just simply waste resources

If you want to be able to break out of a loop, set a variable to help and then use it as part of the looping condition, when your ready to exit, set the variable to the condition that cause the loop to exit

The LOOP() function is not the loop, remember that

This is a forever loop

While (true == true)

{

//Do stuff

}

Changing this to

Boolean exitFlag = false;

While (exitFlag == false)

{

//Do stuff and at some point set exitFlag to true)

}

This is the same basic loop but now has the ability to exit under proper control without a goto statement

Yeah, I didn't even realise the Arduino supported the goto command. Thought I'd left that behind with BASIC.

GOTO is a bad thing to use and can leave you with a mess

I know its disliked by some programmers, but I've seen others say there is nothing wrong with its use....

I guess there will always be opposing sides of every argument.

Mark

IMHO, the valid case that I saw for using goto was within a loop where you wish to terminate early from the loop or skip over code to go to next item in a loop. That was solved with the "break" or "iterate" commands. The trouble can be too many goto's creating a spaghetti like code too hard to follow.

Clem

Yeah I prefer to use 'break;' in these circumstances. Much easier to follow.

Yeah I prefer to use 'break;' in these circumstances. Much easier to follow.