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package au.id.zancanaro.javacheck;
import java.util.*;
import java.util.function.Function;
@SuppressWarnings({"unused", "WeakerAccess"})
public final class Generators {
private Generators() {
}
/**
* Create a generator which explicitly depends on the current "size"
* parameter.
*
* @param makeGenerator A function from size to a generator
* @param <T> The static type of the returned generator
* @return The generator returned by makeGenerator
*/
public static <T> Generator<T> sized(Function<Integer, Generator<T>> makeGenerator) {
return (random, size) -> makeGenerator.apply(size).generate(random, size);
}
/**
* Remove a generator's shrink tree.
*
* @param gen The generator
* @param <T> The generator's static type
* @return A new generator which is the previous generator with shrink tree
* removed
*/
public static <T> Generator<T> noShrink(Generator<T> gen) {
return gen.withShrinkStrategy(value -> Iterators.emptyIterator());
}
@SafeVarargs
public static <T> Generator<T> oneOf(Generator<? extends T>... gens) {
return integer(0, gens.length).flatMap(index -> gens[index].map(x -> (T) x));
}
public static <T> Generator<T> elements(T[] elements) {
return elements(Arrays.asList(elements));
}
public static <T> Generator<T> elements(List<T> elements) {
return integer(0, elements.size()).map(elements::get);
}
public static Generator<Boolean> bool() {
return (random, size) ->
ShrinkTree.pure(random.nextBoolean())
.withShrinkStrategy(boolShrinkStrategy());
}
private static ShrinkStrategy<Boolean> boolShrinkStrategy() {
return value -> new Iterator<Boolean>() {
boolean hasMore = value;
@Override
public boolean hasNext() {
return hasMore;
}
@Override
public Boolean next() {
if (hasMore) {
return (hasMore = false);
} else {
throw new NoSuchElementException("Boolean shrink tree exhausted");
}
}
};
}
public static Generator<Long> longInteger(long lower, long upper) {
return (random, size) -> {
long value = random.longs(lower, upper).findFirst().getAsLong();
long bound = lower > 0 ? lower : (upper < 0 ? upper : 0);
return ShrinkTree.pure(value)
.withShrinkStrategy(longShrinkStrategy(bound));
};
}
public static Generator<Long> longInteger() {
return sized(size -> longInteger(-size, size));
}
private static ShrinkStrategy<Long> longShrinkStrategy(final long bound) {
return value -> new Iterator<Long>() {
long curr = value - bound;
@Override
public boolean hasNext() {
return curr != 0;
}
@Override
public Long next() {
long prevCurr = curr;
curr = curr / 2;
return value - prevCurr;
}
};
}
public static Generator<Integer> integer(int lower, int upper) {
return (random, size) -> {
int value = random.ints(lower, upper).findFirst().getAsInt();
int bound = lower > 0 ? lower : (upper < 0 ? upper : 0);
return ShrinkTree.pure(value)
.withShrinkStrategy(intShrinkStrategy(bound));
};
}
public static Generator<Integer> integer() {
return sized(size -> integer(-size, size));
}
public static Generator<Integer> natural() {
return sized(size -> integer(0, size));
}
public static ShrinkStrategy<Integer> intShrinkStrategy(int bound) {
return value -> new Iterator<Integer>() {
int curr = value - bound;
@Override
public boolean hasNext() {
return curr != 0;
}
@Override
public Integer next() {
int prevCurr = curr;
curr = curr / 2;
return value - prevCurr;
}
};
}
public static Generator<Double> doublePrecision(double lower, double upper) {
return (random, size) -> {
double value = random.doubles(lower, upper).findFirst().getAsDouble();
double bound = lower > 0 ? lower : (upper < 0 ? upper : 0);
return ShrinkTree.pure(value)
.withShrinkStrategy(doubleShrinkStrategy(bound, Double.MIN_NORMAL /* maybe pick a bigger epsilon? */));
};
}
public static Generator<Double> doublePrecision() {
return sized(size -> doublePrecision(-size, size));
}
public static ShrinkStrategy<Double> doubleShrinkStrategy(double bound, double epsilon) {
return value -> new Iterator<Double>() {
double curr = value - bound;
@Override
public boolean hasNext() {
return Math.abs(curr) > epsilon;
}
@Override
public Double next() {
double prevCurr = curr;
curr = curr / 2;
return value - prevCurr;
}
};
}
public static <T> Generator<List<T>> listOf(Generator<T> gen, int minElements, int maxElements) {
return (random, size) -> {
Generator<Integer> countGen = sized(s -> integer(minElements, maxElements));
int count = countGen.generate(random, size).getValue();
return Generator.list(count, gen)
.generate(random, size)
.filter(list -> minElements <= list.size() && list.size() < maxElements)
.map(Collections::unmodifiableList);
};
}
public static <T> Generator<List<T>> listOf(Generator<T> gen) {
return (random, size) -> {
Generator<Integer> countGen = sized(s -> integer(0, s));
int count = countGen.generate(random, size).getValue();
return Generator.list(count, gen)
.generate(random, size)
.map(Collections::unmodifiableList);
};
}
public static Generator<Character> character() {
return integer(0, 256).map(i -> (char) i.intValue());
}
public static Generator<Character> asciiCharacter() {
return integer(32, 127).map(i -> (char) i.intValue());
}
public static Generator<Character> alphaNumericCharacter() {
return oneOf(
integer(48, 58),
integer(65, 91),
integer(97, 123)).map(i -> (char) i.intValue());
}
public static Generator<Character> alphaCharacter() {
return oneOf(
integer(65, 91),
integer(97, 123)).map(i -> (char) i.intValue());
}
private static String makeString(Character[] arr) {
StringBuilder builder = new StringBuilder(arr.length);
for (Character c : arr) {
builder.append(c);
}
return builder.toString();
}
public static Generator<String> string() {
return stringOf(character());
}
public static Generator<String> stringOf(Generator<Character> charGen) {
return listOf(charGen).map(list -> {
char[] chars = new char[list.size()];
int i = 0;
for (Character c : list) {
chars[i++] = c;
}
return String.valueOf(chars);
});
}
}
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