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package au.id.zancanaro;
import java.util.Iterator;
import java.util.function.Predicate;
public class Generators {
public static <T> Generator<T> suchThat(Generator<T> gen, Predicate<T> pred) {
return (random, size) -> {
RoseTree<T> result = gen.generate(random, size);
if (pred.test(result.getValue())) {
return result.filter(pred);
} else {
return suchThat(gen, pred).generate(random, size);
}
};
}
public static Generator<Integer> integer() {
return (random, size) -> {
int value = random.nextInt(size);
return new RoseTree<>(value, intShrinkingIterable(value));
};
}
private static Iterable<RoseTree<Integer>> intShrinkingIterable(final int value) {
return () -> new Iterator<RoseTree<Integer>>() {
int curr = value;
@Override
public boolean hasNext() {
return curr > 0;
}
@Override
public RoseTree<Integer> next() {
int prevCurr = curr;
curr = curr / 2;
return new RoseTree<>(value - prevCurr, intShrinkingIterable(value - prevCurr));
}
};
}
}
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