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authorCarlo Zancanaro <carlo@zancanaro.id.au>2015-06-04 11:41:19 +1000
committerCarlo Zancanaro <carlo@zancanaro.id.au>2015-06-04 11:41:19 +1000
commit0aa99a5f941b886597e7366be763dadc8c6db6dd (patch)
treee4baf24d169736b48d346835dc301945c73f89c9 /src
parente0fc94269698982d937b80ff5fd5b1ef8ef28cf4 (diff)
Clean up a bit of the ShrinkTree stuff, particularly for shrinking
Diffstat (limited to 'src')
-rw-r--r--src/main/java/au/id/zancanaro/javacheck/Generator.java25
-rw-r--r--src/main/java/au/id/zancanaro/javacheck/Generators.java3
-rw-r--r--src/main/java/au/id/zancanaro/javacheck/ShrinkTree.java65
3 files changed, 49 insertions, 44 deletions
diff --git a/src/main/java/au/id/zancanaro/javacheck/Generator.java b/src/main/java/au/id/zancanaro/javacheck/Generator.java
index 103bc69..0679f10 100644
--- a/src/main/java/au/id/zancanaro/javacheck/Generator.java
+++ b/src/main/java/au/id/zancanaro/javacheck/Generator.java
@@ -72,7 +72,7 @@ public interface Generator<T> {
for (Generator<? extends T> generator : generators) {
result[index++] = generator.generate(random, size).map(x -> (T) x);
}
- return ShrinkTree.zip(Function.identity(), result);
+ return ShrinkTree.combine(result, ShrinkTree::promoteChildren);
};
}
@@ -81,9 +81,7 @@ public interface Generator<T> {
* element taken from the provided generator.
*
* Shrinking for this type involves attempting to remove terms and shrink
- * each subtree in turn, recursively. (If the length must remain fixed then
- * the {@link ShrinkTree} produced by this generator should be filtered with
- * {@link ShrinkTree#filter(java.util.function.Predicate)}.
+ * each subtree in turn, recursively.
*
* @param count The length of the list to generate
* @param generator The generator to use for each term in the generated
@@ -98,7 +96,7 @@ public interface Generator<T> {
for (int i = 0; i < count; ++i) {
result[i] = generator.generate(random, size);
}
- return ShrinkTree.shrink(Function.identity(), result);
+ return ShrinkTree.combine(result, ShrinkTree::removeAndPromoteChildren);
};
}
@@ -128,7 +126,10 @@ public interface Generator<T> {
* result of this
*/
default <R> Generator<R> flatMap(Function<T, Generator<R>> action) {
- return (random, size) -> ShrinkTree.join(this.generate(random, size).map(action).map(g -> g.generate(random, size)));
+ return (random, size) -> ShrinkTree.join(
+ this.generate(random, size)
+ .map(action
+ .andThen(g -> g.generate(random, size))));
}
/**
@@ -156,6 +157,18 @@ public interface Generator<T> {
};
}
+ /**
+ * Create a new generator which generates values with a shrink tree
+ * determined by the provided {@link ShrinkStrategy}.
+ *
+ * @param strategy The shrink strategy by which to shrink generated values
+ * @return A new generator which will shrink values from this according to
+ * the provided strategy
+ */
+ default Generator<T> withShrinkStrategy(ShrinkStrategy<T> strategy) {
+ return (random, size) -> this.generate(random, size).withShrinkStrategy(strategy);
+ }
+
default Iterator<T> sample(Random random, int maxSize) {
return new GeneratorSampleIterator<>(this, random, maxSize);
}
diff --git a/src/main/java/au/id/zancanaro/javacheck/Generators.java b/src/main/java/au/id/zancanaro/javacheck/Generators.java
index e5699ac..9730bac 100644
--- a/src/main/java/au/id/zancanaro/javacheck/Generators.java
+++ b/src/main/java/au/id/zancanaro/javacheck/Generators.java
@@ -29,7 +29,7 @@ public final class Generators {
* removed
*/
public static <T> Generator<T> noShrink(Generator<T> gen) {
- return (random, size) -> ShrinkTree.pure(gen.generate(random, size).getValue());
+ return gen.withShrinkStrategy(value -> Iterators.emptyIterator());
}
@SafeVarargs
@@ -230,7 +230,6 @@ public final class Generators {
chars[i++] = c;
}
return String.valueOf(chars);
-// return new String(chars);
});
}
}
diff --git a/src/main/java/au/id/zancanaro/javacheck/ShrinkTree.java b/src/main/java/au/id/zancanaro/javacheck/ShrinkTree.java
index 7dff917..bdc7604 100644
--- a/src/main/java/au/id/zancanaro/javacheck/ShrinkTree.java
+++ b/src/main/java/au/id/zancanaro/javacheck/ShrinkTree.java
@@ -41,55 +41,50 @@ public class ShrinkTree<T> {
tree.getValue().children.iterator()));
}
- private static <T> Iterator<ShrinkTree<T>[]> permutations(ShrinkTree<T>[] trees) {
+ private static <T> List<T> makeHeadList(ShrinkTree<T>[] trees) {
+ List<T> heads = new ArrayList<>(trees.length);
+ for (ShrinkTree<T> tree : trees) {
+ heads.add(tree.getValue());
+ }
+ return heads;
+ }
+
+ public static <T> Iterator<ShrinkTree<T>[]> promoteChildren(ShrinkTree<T>[] trees) {
return flatten(
- rangeIterator(trees.length,
- index -> mappingIterator(child -> {
+ rangeIterator(trees.length, index ->
+ mappingIterator(child -> {
@SuppressWarnings("unchecked")
ShrinkTree<T>[] result = (ShrinkTree<T>[]) new ShrinkTree[trees.length];
for (int i = 0; i < trees.length; ++i) {
result[i] = (i == index ? child : trees[i]);
}
return result;
- }, trees[index].getChildren())
- ));
- }
-
- private static <T> List<T> makeHeadList(ShrinkTree<T>[] trees) {
- List<T> heads = new ArrayList<>(trees.length);
- for (ShrinkTree<T> tree : trees) {
- heads.add(tree.getValue());
- }
- return heads;
+ }, trees[index].getChildren())));
}
- public static <T, R> ShrinkTree<R> zip(Function<List<T>, R> fn, ShrinkTree<T>[] trees) {
- return new ShrinkTree<>(
- fn.apply(makeHeadList(trees)),
- () -> mappingIterator(
- shrinks -> ShrinkTree.zip(fn, shrinks),
- ShrinkTree.permutations(trees)));
+ public static <T> Iterator<ShrinkTree<T>[]> removeChildren(ShrinkTree<T>[] trees) {
+ return rangeIterator(trees.length, index -> {
+ @SuppressWarnings("unchecked")
+ ShrinkTree<T>[] result = (ShrinkTree<T>[]) new ShrinkTree[trees.length - 1];
+ for (int i = 0; i < trees.length - 1; ++i) {
+ result[i] = trees[(i >= index ? i + 1 : i)];
+ }
+ return result;
+ });
}
- private static <T> Iterator<ShrinkTree<T>[]> removeEach(ShrinkTree<T>[] trees) {
- return concat(
- rangeIterator(trees.length, index -> {
- @SuppressWarnings("unchecked")
- ShrinkTree<T>[] result = (ShrinkTree<T>[]) new ShrinkTree[trees.length - 1];
- for (int i = 0; i < trees.length - 1; ++i) {
- result[i] = trees[(i >= index ? i + 1 : i)];
- }
- return result;
- }),
- permutations(trees));
+ public static <T> Iterator<ShrinkTree<T>[]> removeAndPromoteChildren(ShrinkTree<T>[] trees) {
+ return concat(removeChildren(trees), promoteChildren(trees));
}
- public static <T, R> ShrinkTree<R> shrink(Function<List<T>, R> fn, ShrinkTree<T>[] trees) {
+ public static <T> ShrinkTree<List<T>> combine(
+ ShrinkTree<T>[] trees,
+ Function<ShrinkTree<T>[], Iterator<ShrinkTree<T>[]>> processChildren) {
return new ShrinkTree<>(
- fn.apply(makeHeadList(trees)),
+ makeHeadList(trees),
() -> mappingIterator(
- shrinks -> ShrinkTree.shrink(fn, shrinks),
- ShrinkTree.removeEach(trees)));
+ shrinks -> ShrinkTree.combine(shrinks, processChildren),
+ processChildren.apply(trees)));
}
public <R> ShrinkTree<R> map(Function<T, R> f) {
@@ -126,12 +121,10 @@ public class ShrinkTree<T> {
strategy.shrink(value));
}
- @SuppressWarnings("unused")
public void print(Writer output) throws IOException {
print(output, Object::toString);
}
- @SuppressWarnings("unused")
public void print(Writer output, Function<T, String> toString) throws IOException {
output.write(toString.apply(this.getValue()));
output.write('[');