Using "return" and its associated syntax

Projects Programming
1

I'm using a ds1307 chip to bring real time into my Ard Pro Mini and someone posted some code out here in 2008 that looks like what I want. However I don't exactly understand the syntax that's being used here. My problem is that I do need to change hex values from the ds1307 to dec values and I'm having a problem doing this so far. This is the code that I think I need to utilize but I don't exactly understand it's syntax:

int DS1305::bcdToDec(const byte bcd) {
return ((bcd / 16 * 10) + (bcd % 16));
}

This was posted by windmis in 2008. My questions are as follows:

On this code what's going on with the double colon, "::" ?
After byte there appears to be a function name and then a variable or vice versa, how does this work? ie, "byte DS1305::bcdToDec".
After the function name there are three variables in the parenthesis, "(const byte bcd)" . I guess this is a variable, datatype, variable ?
.
Your help would be appreciated. Thank you,
.
Tim

2

The :: indicates that you have a method bcdToDec of the class DS1305. If you have an object of this class, you can access this functions as:

 DS1305 foo;
...
int baz = foo.bcdToDec (35);

The "const byte bcd" just means there's one parameter called bcd of type byte which isn't expected to changed inside the function (the const part). The last const is mostly a hint for the optimiser so that it knows it can do nasty things without having to worry about restoring the original value.

Korman

3

On this code what's going on with the double colon, "::" ?

int DS1305::bcdToDec(const byte bcd)

This means this is a function with the name "bcdToDec"

  • which is part of the class named "DS1305"
  • needing a parameter named "bcd" of the type const byte
  • and this function retuns an int.

If you want to have three parameters you need to separate them with , e.g int max(int x, int y) ....

more see - http://www.arduino.cc/en/Reference/FunctionDeclaration

4

robtillaart and Korman thank you for your advice. This will certainly help. And the reference to the function syntax was a magic bullet. Thanks guys!
.
Tim