On Tue, 9 May 2017 13:29:21 +0100, Stian Soiland-Reyes <st...@apache.org> wrote:
> I can only see this "value()" style make sense if there is also a common
> interface, perhaps DoubleFunction<Double>?
> https://docs.oracle.com/javase/8/docs/api/java/util/function/DoubleFunction.html
DoubleUnaryOperator would be better - double applyDouble(double) - then
Gamma can be used like this with a native DoubleStream:
double[] numbers = { -2.1, -2.0, -1.99, -1.95, -1.9, -1.8, -1.7, -1.6, -1.5,
-1.4, -1.3, -1.2, -1.1, -1.0,
-0.9 };
Arrays.stream(numbers).map(new Gamma())
.mapToObj(Double::toString)
.forEachOrdered(System.out::println);
Or even -- if you permit:
DoubleStream d = new Random().doubles().map(new Gamma());
https://docs.oracle.com/javase/8/docs/api/java/util/function/DoubleUnaryOperator.html
Not sure I like the function name "applyDouble(x)" though.. We could have a
static gamma() method (etc) as well.
===
One thought (which don't work too well with Streams without helper functions or
Gamma::new)):
If we are making instances of Gamma, then you could make it extend Number and
take the "x" argument in the constructor:
Number g = new Gamma(0.4);
System.out.println(g.floatValue());
Evaluation of the gamma function can be delayed until the first call on any of
the methods.
This is the style recommended by Elegant Objects:
http://www.yegor256.com/2014/05/05/oop-alternative-to-utility-classes.html
.. and would allow us to extend it to complex numbers in the future.
--
Stian Soiland-Reyes
The University of Manchester
http://www.esciencelab.org.uk/
http://orcid.org/0000-0001-9842-9718
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