[
https://issues.apache.org/jira/browse/NUMBERS-167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17426761#comment-17426761
]
Alex Herbert commented on NUMBERS-167:
--------------------------------------
{quote}call either P or Q
{quote}
I think we need a functional interface that is not in java.util.function. The
alternative is to use ToDoubleBiFunction<RG, Double> which would require boxing
the argument of interest when calling this.
{code:java}
public final class RegularizedGamma {
// ...
@FunctionalInterface
public interface ObjDoubleBiFunction<T> {
double applyAsDouble(T t, double value);
}
public enum RG {
P,
Q
}
public static ObjDoubleBiFunction<RG> withArgumentA(double a) {
final ArgumentA argA = ArgumentA.of(a);
return (rg, x) -> {
switch (rg) {
case P:
return P.value(argA, x, DEFAULT_EPSILON, DEFAULT_ITERATIONS);
case Q:
return Q.value(argA, x, DEFAULT_EPSILON, DEFAULT_ITERATIONS);
default:
throw new IllegalStateException(); // Should never happen.
}
};
}
public static void call() {
double a = 0.5;
double x = 33;
ObjDoubleBiFunction<RG> f = RegularizedGamma.withArgumentA(a);
double v = f.applyAsDouble(RG.P, x);
}
// ...
{code}
If we are to define a custom interface then I would suggest this:
{code:java}
public interface ComplementFunction {
double value(double x);
double complement(double x);
}
public static ComplementFunction withArgumentA(double a) {
return new ComplementFunction() {
final ArgumentA argA = ArgumentA.of(a);
@Override
public double value(double x) {
return P.value(argA, x, DEFAULT_EPSILON, DEFAULT_ITERATIONS);
}
@Override
public double complement(double x) {
return Q.value(argA, x, DEFAULT_EPSILON, DEFAULT_ITERATIONS);
}
};
}
public static void call() {
double a = 0.5;
double x = 33;
ComplementFunction f = RegularizedGamma.withArgumentA(a);
double v = f.value(x);
double c = f.complement(x);
}
{code}
> RegularizedGamma.P with precomputed LogGamma value
> --------------------------------------------------
>
> Key: NUMBERS-167
> URL: https://issues.apache.org/jira/browse/NUMBERS-167
> Project: Commons Numbers
> Issue Type: Wish
> Components: gamma
> Reporter: Gilles Sadowski
> Priority: Minor
> Fix For: 1.1
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> We have
> {code:java}
> double v = RegularizedGamma.P.value(a, x);
> {code}
> where method {{value}} internally calls {{LogGamma.value(a)}}.
> There is a use-case for
> {code:java}
> double logGammaA = LogGamma.value(a);
> double v = RegularizedGamma.P.value(a, x, logGammaA);
> {code}
> for when the user varies {{x}} but not {{a}}.
> Method name TBD: Another overload of {{value}} may be confusing (?).
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
