Processing 1.0 - Processing Discourse - Returning a float from a function

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Returning a float from a function (Read 1050 times)

AkronMacon

Returning a float from a function
Sep 17^th, 2009, 4:31am

I'm just getting started with Processing and am having trouble creating a function to compute the haversine of an angle. The function needs to take the angle (float) and return the haversine (float).

I've created the following simple static program to test the function, but I receive "unexpected token: float" with the function declaration highlighted. Am I doing something daft, or just completely off base?

Code:

println(haversine(PI/2));


float haversine(float haverAngle) {
  float haverReturn=0;
  haverReturn=(0.5*(1-cos(haverAngle))); //Definition from Wolfram
  return(haverReturn);
}

blindfish

Re: Returning a float from a function
Reply #1 - Sep 17^th, 2009, 4:58am

Try:

Code:

void setup() {
  println(haversine(PI/2));
}


float haversine(float haverAngle) {
  float haverReturn=0;
  haverReturn=(0.5*(1-cos(haverAngle))); //Definition from Wolfram
  return(haverReturn);
}

Not including setup() makes Processing run slightly differently. This has been explained in the forums before; but I must admit I still haven't got my head round it entirely... Basically it's better to include it, even for very basic sketches. Also note that if you're setting 'size', the size statement should always be the first statement in setup()...

Where is the what if the what is in why?

blindfish God Member Offline Posts: 793	Re: Returning a float from a function Reply #2 - Sep 17^th, 2009, 5:08am P.S. I did some work with the Haversine formula recently in ActionScript and found this reference very useful and also this.
	Where is the what if the what is in why?

PhiLho

Re: Returning a float from a function
Reply #3 - Sep 17^th, 2009, 5:12am

blindfish wrote on Sep 17^th, 2009, 4:58am:

Not including setup() makes Processing run slightly differently. This has been explained in the forums before; but I must admit I still haven't got my head round it entirely...

Simple: if you don't have a setup(), the pre-processor will put all your code in an invisible, generated setup(). So if you declare functions, you will get illegal code, as Java doesn't support functions inside functions.
So code without setup() must be quite linear...

blindfish God Member Offline Posts: 793	Re: Returning a float from a function Reply #4 - Sep 17^th, 2009, 10:05am That was it! Actually pretty simple really - just that I had forgotten: My memory is pretty bad these days...
	Where is the what if the what is in why?

AkronMacon

Re: Returning a float from a function
Reply #5 - Sep 17^th, 2009, 7:00pm

Thanks, including the short setup() made all the difference!

The following code works:

Code:

void setup() {
println(haversine(PI/2));
}

float haversine(float haverAngle){
  float haverReturn=0;
  haverReturn=(0.5*(1-cos(haverAngle))); //Definition from Wolfram
  return(haverReturn);
}

Thanks for the links too; I'm finding that even the venerable navigation text Bowditch is a bit short on some of the details of calculation for this project.

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