Processing 1.0 - Processing Discourse - How to add a double literal

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Index › Programming Questions & Help › Syntax Questions › How to add a double literal

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How to add a double literal (Read 619 times)

gskillas

How to add a double literal
Jan 13^th, 2009, 9:54pm

Hello,

to make an interactive plot of how light is scattered by dust I need to calculate spherical Bessel functions and for this I need a so called gamma function... which boils down to a LUT for factorials (n! = 1 * 2 * 3 * ... * n) up to 170! . Problem is I need to write something like:

static double factorial_list[171]={1.,1.,2.,6.,24.,120.,720.,5040.,40320.,
362880.,3.6288e6,3.99168e7,4.790016e8,6.2270208e9,
8.71782912e10,1.307674368e12,2.0922789888e13,

.
.
.

1.0333147966386145e40,3.7199332678990125e41,
.
.
.
};

(code from a C++ library developend by NIST), and I cannot get the literals into processing. It seems that there is an automatic addition of F to each of the numbers which is of course wrong for 1.0333147966386145e40 and every higher number (they go up to 7.257415615307999e306).

How can I write that? Alternatively is there any posibility to get a processing Version consistently using double as the basic floating point type?

Thanks in advance,

George

PhiLho

Re: How to add a double literal
Reply #1 - Jan 13^th, 2009, 10:24pm

It is hard, doubles are rarely needed in graphics (unless using scales or such), so they are apparently banned from Processing...

There is a possible workaround, a bit clumsy, perhaps somebody else will have a better idea:
Code:

double m = 1e38;
double x1 = 103.33147966386145 * m;
double x2 = 3719.9332678990125 * m;
println(x1 + " " + x2);

gskillas

Re: How to add a double literal
Reply #2 - Jan 14^th, 2009, 9:24am

Hello PhilHo

I considered the route you are describing, there is one real and one perceived problem with it. The real one first: for the power of 306 I will need eight multiplications with 1e38. Since each introduces a slight rounding error I will end up with a bit a different number than the one I wanted to have:

Code:

double m = 1e38;
double x1 = 7.257415615307999e2 *m *m *m *m *m *m *m *m;
println("7.257415615307999e306 " + x1);

Result:

7.257415615307999e306 7.257413915244855E306

The perceived one: I need to do this conversion for over 600 numbers which is at least cumbersome.

So are there any other suggestions out there?

Regards,

George

PS: If you want to do any sort of scientific visualisation then doubles are a must IMHO.

Stephen Williams YaBB Newbies Offline Posts: 39 Graz, Austria	Re: How to add a double literal Reply #3 - Jan 14^th, 2009, 10:05am How is this for an ugly hack double m = Double.valueOf("1e38").doubleValue(); double x1 = Double.valueOf("7.257415615307999e2").doubleValue() m m m m m m m m; println("7.257415615307999e306 " + x1);
	FLUID FORMS ~ Your Unique Design http://www.fluid-forms.com http://twitter.com/onato

PhiLho

Re: How to add a double literal
Reply #4 - Jan 14^th, 2009, 11:24am

Ah, good idea Stephen, but then you don't need the multiplication.
Code:

double x1 = Double.parseDouble("1.0333147966386145e40");
double x2 = Double.parseDouble("3.7199332678990125e41");
double x3 = Double.parseDouble("7.257415615307999e306");
println(x1 + " " + x2 + " " + x3);

gskillas, you can even write a one-letter function wrapping Double.parseDouble if you want to keep the code more readable.

Perhaps we could suggest another syntax sugar: if we append 'd' to a number, it is left as double, ie. the d is removed and no f is added. double x = 3.14d;
Not sure if it is easy/doable with Antlr.

gskillas YaBB Newbies Offline Posts: 3	Re: How to add a double literal Reply #5 - Jan 14^th, 2009, 11:56am Hello together, the syntax Double.parseDouble("1.0333147966386145e40"); is a bit ugly but marvelous Guess it will have to do for the time being. Thanks alot George

davbol Senior Member Offline Posts: 263	Re: How to add a double literal Reply #6 - Jan 14^th, 2009, 7:07pm or put your double stuff in a separate .java file (instead of a .pde) where the preprocessor won't affect it

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