JSON setFloat issue?

LiveElectronics

Hi. Does anybody already get this problem? I'm trying to put a float in a Json with

  JSONObject item;
  item=new JSONObject();
  float tmp=95.7;
  item.setFloat("j9T3", tmp) ;
  println(item);

And for output, i got "items": [{ "alb7r": 1, "name": "", "code": "", "j9T3": 95.69999694824219 }],

??? What's up?

How to write 96.7 in my Json???

Thanks for reading and answers...

GoToLoop

https://Processing.org/reference/float.html

blindfish

@GoToLoop: must admit I was also initially surprised that setFloat() results in numerical inaccuracy...

@LiveElectonics: the cause is that internally Processing first converts the float to a double:

public JSONObject setFloat(String key, float value) {
    this.put(key, new Double(value));
    return this;
  }

This is what creates the 'inaccuracy' - run this sketch and you'll see:

float tmp=95.7;
Double foo = new Double(tmp);
println(tmp);
println(foo);

Like all such inaccuracies this generally isn't a major problem; since internally all your code is subject to them. Having said that if you're writing the JSON file to a server to then be served to web clients and you have a lot of floats in there I'd also be frustrated by this; as it will increase the file size unnecessarily :/

In that case:

957/10 = 95.7

GoToLoop

Here's a wishful fix. But the evil side of private members are showing their ugly faces once more: X(

https://Processing.org/reference/private.html

//forum.Processing.org/two/discussion/13787/json-setfloat-issue

JSONObject item = new JSONObject() {
  public JSONObject setDouble(String key, double value) {
    put(key, new Double(value)); // not visible!!!
    return this;
  }
};

double val = 95.7d;
println(val);

item.setDouble("j9T3", val);
println(item);

exit();

That's why for a project such as Processing, classes shouldn't use private but rather protected.
So it allows those who needs to tweak or introduce new functionalities into existing APIs. :-B

LiveElectronics

Thanks for your answers and solutions. Cheers

LiveElectronics

@goToLoop : I'm confused about your solution. How to use the put method if it's not visible ? must i tweak environement files?

LiveElectronics

also, it's said that all classes are public in processing... Sorry for these noob questions but i'm starting java and processing language

LiveElectronics

Ok the method already exist... :) just need to use it with a correct double value. Cheers

GoToLoop

Ok the method already exist...

My! I didn't know setDouble() existed already. It wasn't in the reference and I didn't care to look for it straight from the source! #-o

Above was just my attempt to create setDouble() unbeknownst it was already there! X_X

I believe you've already realized that. But for precaution I'm gonna reiterate it below:
In order for setDouble() to work, either pass a double variable to it or suffix all literal values w/ d.
Like this 1 for example: 95.7d or 957e-1d. :-B