public static Result<String> readFile2String(String path) {
try {
return Result.success(new String(Files.readAllBytes(Paths.get(path))));
} catch (IOException e) {
return Result.failure(String.format("IO error while reading file %s", path), e);
} catch (Exception e) {
return Result.failure(String.format("Unexpected error while reading file %s", path), e);
}
}
public class ListTest {
@Test
public void testFlattenResult() {
List<Integer> list = List.list(1, 2, 3, 4, 5, 0, 6, 7, 8, 9);
List<Double> list2 = List.flattenResult(list.map(inverse));
assertEquals(
"[1.0, 0.5, 0.3333333333333333, 0.25, 0.2, 0.16666666666666666, 0.14285714285714285, 0.125, 0.1111111111111111, NIL]",
list2.toString());
}
private Function<Integer, Result<Double>> inverse =
x -> x == 0 ? Result.failure("divide by 0") : Result.success((double) 1 / x);
}
private static Result<List<Element>> readDocument(String rootElementName, String stringDoc) {
final SAXBuilder builder = new SAXBuilder();
try {
final Document document = builder.build(new StringReader(stringDoc));
final Element rootElement = document.getRootElement();
return Result.success(List.fromCollection(rootElement.getChildren(rootElementName)));
} catch (IOException | JDOMException io) {
return Result.failure(
String.format(
"Invalid root element name '%s' or XML data %s", rootElementName, stringDoc),
io);
} catch (Exception e) {
return Result.failure(
String.format("Unexpected error while reading XML data %s", stringDoc), e);
}
}
public static Executable readXmlFile(
Supplier<Result<String>> sPath,
Supplier<Result<String>> sRootName,
Tuple<String, List<String>> format,
Effect<List<String>> e) {
final Result<String> path = sPath.get();
final Result<String> rDoc = path.flatMap(ReadXmlFile::readFile2String);
final Result<String> rRoot = sRootName.get();
final Result<List<String>> result =
rDoc.flatMap(
doc ->
rRoot
.flatMap(rootElementName -> readDocument(rootElementName, doc))
.map(list -> toStringList(list, format)));
return () -> result.forEachOrThrow(e);
}
public Result<A> lastOption() {
return foldLeft(Result.empty(), x -> Result::success);
}
public static <A, B> Result<List<B>> traverse(List<A> list, Function<A, Result<B>> f) {
return list.foldRight(
Result.success(List.list()), x -> y -> Result.map2(f.apply(x), y, a -> b -> b.cons(a)));
}
@Override
public Result<A> headOption() {
return Result.success(head);
}
@Override
public Result<A> headOption() {
return Result.empty();
}
public static <A> Result<List<A>> sequence_(List<Result<A>> list) {
return list.foldRight(
Result.success(List.list()), x -> y -> Result.map2(x, y, a -> b -> b.cons(a)));
}
