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package bjc.utils.gen;
import java.util.Random;
import bjc.utils.funcdata.FunctionalList;
import bjc.utils.data.GenHolder;
import bjc.utils.data.IHolder;
import bjc.utils.data.Pair;
/**
* Represents a random number generator where certain results are weighted
* more heavily than others.
*
* @author ben
*
* @param <E>
* The type of values that are randomly selected.
*/
public class WeightedRandom<E> {
/**
* The list of probabilities for each result
*/
private FunctionalList<Integer> probs;
/**
* The list of possible results to pick from
*/
private FunctionalList<E> results;
/**
* The source for any needed random numbers
*/
private Random src;
private int totalChance;
/**
* Create a new weighted random generator with the specified source of
* randomness
*
* @param sr
* The source of randomness to use.
*/
public WeightedRandom(Random sr) {
probs = new FunctionalList<>();
results = new FunctionalList<>();
src = sr;
}
/**
* Add a probability for a specific result to be given.
*
* @param chance
* The chance to get this result.
* @param res
* The result to get when the chance comes up.
*/
public void addProb(int chance, E res) {
probs.add(chance);
results.add(res);
totalChance += chance;
}
/**
* Generate a weighted random value.
*
* @return A random value selected in a weighted fashion.
*/
public E genVal() {
GenHolder<Integer> v = new GenHolder<>(src.nextInt(totalChance));
IHolder<E> res = new GenHolder<E>();
GenHolder<Boolean> bl = new GenHolder<>(true);
probs.forEachIndexed((i, p) -> {
if (bl.unwrap(vl -> vl)) {
if (v.unwrap((vl) -> vl < p)) {
res.transform((vl) -> results.getByIndex(i));
bl.transform((vl) -> false);
} else {
v.transform((vl) -> vl - p);
}
}
});
return res.unwrap((vl) -> vl);
}
/**
* Return a list of values that can be generated by this generator
*
* @return A list of all the values that can be generated
*/
public FunctionalList<E> getResults() {
return results;
}
/**
* Return a list containing values that can be generated paired with
* the probability of those values being generated
*
* @return A list of pairs of values and value probabilities
*/
public FunctionalList<Pair<Integer, E>> getValues() {
return probs.pairWith(results);
}
}
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