Return Statement

Projects Programming
1

I am looking over some OneWire code and I do not totally understand the use of the return statements. Here is a example:

void loop(void) {
  byte i;
  byte present = 0;
  byte type_s;
  byte data[12];
  byte addr[8];
  float celsius, fahrenheit; 

  if ( !ds.search(addr)) {
    Serial.println("No more addresses.");
    Serial.println();
    ds.reset_search();
    delay(250);
    return;
  }

The program at the point it reaches the return statement is not in a subroutine other than loop(). So where does it return to? Does it gist restart the loop() code?

2

It causes an exit from loop(). Since loop() is called repeatedly, the effect is to re-start the loop() code from where it begins.

3

Thanks for clearing that up!

4

I never use that method. I would:

void loop(void) {
  byte i;
  byte present = 0;
  byte type_s;
  byte data[12];
  byte addr[8];
  float celsius, fahrenheit; 

  if ( !ds.search(addr)) {
    Serial.println("No more addresses.");
    Serial.println();
    ds.reset_search();
    delay(250);
  }
  else
  { do the rest of the code in loop... }
}
5

return there is to skip the code that follows that you failed to show.

6

I consider myself to be a descent C programmer but Arduino does things a little different. I'm not sure why they ditched the main() sub to replace it with setup() and loop(). Thanks for the help.

7

I'm also at a loss. :slight_smile:

It does save having to explain what 'while(1)' means.

8

When the Arduino was started decades ago it was intended as a simple way to use micro-controllers for non programmers. I thought of it as micros for artisans and poets. Since then it has grown like a cancer and become much more complex

9

There in fact is a main() function (they're not called subroutines in C / C++). It's just hidden from easy viewing (but you can find it) in the Arduino world. Its job is to initialize some hardware, call the setup() function where you do one-time stuff, and then call the loop() function inside an endless loop.

Now consider for a moment what your own main() function would do if this Arduino setup/loop paradigm didn't exist. It would initialize some hardware, do some one-time stuff, and then it would continually execute your main code in an endless loop. Sound familiar? So, the setup/loop paradigm works the way you'd write it yourself for 99.999% of the use cases.

10

Yeah, it's painless and does the same thing. I don't sweat it too much.

11

Don't leave us in the dark. How do you find the main function?

12

It depends on the details of your Arduino installation. I use Portable Installations. So, for v1.8.15 of the IDE, 'main.cpp' is in 'D:\Arduino-1.8.15\hardware\arduino\avr\cores\arduino'

13

You are free to define your own main(), it will run instead