function in C++

With the semi-colon after the first line your loop will do nothing and therefore making the rest of the code void

This should read

void loop()

{

do my first thing;

if test 1 true, go to void thing2;

if test 2 true, go to void thing3;

}

The loop has no conditions so it will run forever

1 - does "first thing"

2 - test 1 (true) run thing2, then come back

3 - test 2 (true) run thing3, then come back

4 - start at top again

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

hi,

your problem seems simple.can you just give more actual code.

But an intermediate answer:

if void loop() is actually while(1) of for( ; ; ) then  "first thing " will always happen irrespective of any thing(any result or condition). but thing2 and thing3 will depend on their condition.

billpenner wrote:

 

When a function is finished, closed bracket}, where does the programming go?

My programming seems to fall through, that is the next function after the current function is complete seems to be running. Are incorrect brackets  causing my problem?

For example:

void loop() ;

{

do my first thing;

if test 1 true, go to void thing2

if test 2 true, go to void thing3

}

Where am I at this point? Am I back in the loop or do I fall through thing3 to what is after it in the program.

Please straighten me out a little. I am new to C++.

Thanks

Bill

 

 

Okay where are you after " } " ? if you can really reach at } then you will be sure at "first thing" . But the thing that you really reach at "}" depends on code above "}".ie first thing ,thing2 ,thing3.

Regards,

Parth

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.

Yes it does.  But you bring up another confusing thing.

When you say k = myMultiplyFunction(i, j); does that mean k  = a call to a function named " myMultiplyFunction")

and you are taking j and k to that function?

if so, why does all three variables ( myMultiplyFunction and I and j have to be declared as int again?

I think I understand why 'result' has to be created so the answer can be returned but  could you just make

k  = x * y

return ?

and is return necessary since the" } " ends the call function?

These questions and you guys response are like having an instructor at my side. I have understood more today than I have with many hours studying C++.

I can't thank you all enough.

Bill

In that example 'myMultiplyFunction' is called and 'i' and 'j' are passed in as parameters. The value returned from the function is then loaded into k, and it's the return keyword that does this.

If the function does not need to return data the keyword can be omitted.

Yes, there is a goto! But a wise person can avoid like this:

void loop() ; {

#define LAST = l;

#define FIRST = f;

char things = '-';

things = 'FIRST';

while ( things != 'LAST') {

     if test 1 true, thing2();

     if test 2 true, thing3();

     things = 'LAST';

     }

}

void thing2() ;

{

// Do whatever you need

printf(" thing2"):

}

void thing3() ;

{

// Do whatever you need

printf("thing3"):

}

Main:

     loop();

     printf("end of program");

This will invoke or call your function loop. The loop has been "fixed" to run once time until LAST is set.

I'm on my way again with a lot less frustration. Thanks to you all.

Bill

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