Is there any way to do something like the following in Vala ?
public int year {
get { return this.year; }
set requires (1500 < value && value < 2050) { this.year = value; }
}
No, but 'requires' is really just syntactic sugar for GLib.return_if_fail and GLib.return_val_if_fail, so you could just do:
public int year {
get { return this.year; }
set {
GLib.return_if_fail (1500 < value && value < 2050);
this.year = value;
}
}
Related
I have the below code that is creating the PriortyQueue structure using Dart. But since I cannot use heapify function inside the Constructor or factory constructor I cannot initialize PQ with an existing set of List. Can somebody guide me and show me how I can use heapify while creating PQ instance so I can initialize it with an existing List? Also If you have any other suggestions against doing something like this please also help me as well. thank you
class PriorityQueue<T extends Comparable<T>> {
List<T?> _tree;
PriorityQueue._(List<T?> tree) : _tree = tree;
factory PriorityQueue([List<T>? array]) {
List<T?> newArray = [null, ...array ?? []];
// ignore: todo
//TODO: missing heapify
return PriorityQueue._(newArray);
}
void insert(T node) {
_tree.add(node);
_swim(_tree.length - 1);
}
T getTop() {
_swap(1, _tree.length - 1);
T top = _tree.removeLast() as T;
_sink(1);
return top;
}
List<T> _heapify(List<T> array) {
int sinkNodeIndex = (array.length - 1) ~/ 2;
while (sinkNodeIndex >= 1) {
_sink(sinkNodeIndex);
sinkNodeIndex--;
}
}
void _sink(int nodeIndex) {
int leftChildIndex = nodeIndex * 2;
int rightChildIndex = leftChildIndex + 1;
int minNodeIndex = leftChildIndex;
// index can be unreachable
T? leftChild =
leftChildIndex >= _tree.length ? null : _tree[leftChildIndex];
T? rightChild =
rightChildIndex >= _tree.length ? null : _tree[rightChildIndex];
if (leftChild == null) {
return;
}
if (rightChild != null && leftChild.compareTo(rightChild) > 0) {
minNodeIndex = rightChildIndex;
}
if ((_tree[minNodeIndex] as T).compareTo(_tree[nodeIndex] as T) < 0) {
_swap(nodeIndex, minNodeIndex);
_sink(minNodeIndex);
}
}
void _swim(int nodeIndex) {
if (nodeIndex <= 1) return;
int parentIndex = nodeIndex ~/ 2;
if ((_tree[nodeIndex] as T).compareTo(_tree[parentIndex] as T) < 0) {
_swap(nodeIndex, parentIndex);
_swim(parentIndex);
}
}
void _swap(int i, int j) {
T temp = _tree[i] as T;
_tree[i] = _tree[j];
_tree[j] = temp;
}
#override
String toString() {
return _tree.toString();
}
}
I would make all the helper functions. _heapify, _sink/_swim, even _swap, be static functions which take the list as argument.
Then you can use them from anywhere, including inside the factory constructor.
Alternatively, you can change the constructor to returning:
return PriorityQueue._(newArray).._heapify();
This creates the PriorityQueue object, and then calls the _heapify method on it, before returning the value.
(I'd also make _tree have type List<T> and not insert the extra null at the beginning. It's more efficient to add/subtract 1 from indices than it is to cast to T.)
I ended up doing like Irn's first suggestion. But when I do functions static they lost Type of the class so I needed to specify for each function. Also, making List<T?> instead of List ended up with me fighting against the compiler.
class PriorityQueue<T extends Comparable<T>> {
List<T?> _tree;
PriorityQueue._(List<T?> tree) : _tree = tree;
factory PriorityQueue([List<T>? array]) {
List<T?> newArray = [null, ...array ?? []];
_heapify(newArray);
return PriorityQueue._(newArray);
}
bool get isNotEmpty {
return _tree.isNotEmpty;
}
void insert(T node) {
_tree.add(node);
_swim(_tree, _tree.length - 1);
}
void insertMultiple(List<T> array) {
for (var element in array) {
insert(element);
}
}
T? removeTop() {
if (_tree.length == 1) return null;
_swap(_tree, 1, _tree.length - 1);
T top = _tree.removeLast() as T;
_sink(_tree, 1);
return top;
}
void removeAll() {
_tree = [null];
}
static void _heapify<T extends Comparable<T>>(List<T?> array) {
int sinkNodeIndex = (array.length - 1) ~/ 2;
while (sinkNodeIndex >= 1) {
_sink(array, sinkNodeIndex);
sinkNodeIndex--;
}
}
static void _sink<T extends Comparable<T>>(List<T?> tree, int nodeIndex) {
int leftChildIndex = nodeIndex * 2;
int rightChildIndex = leftChildIndex + 1;
int minNodeIndex = leftChildIndex;
T? leftChild = leftChildIndex >= tree.length ? null : tree[leftChildIndex];
T? rightChild =
rightChildIndex >= tree.length ? null : tree[rightChildIndex];
if (leftChild == null) {
return;
}
if (rightChild != null && leftChild.compareTo(rightChild) > 0) {
minNodeIndex = rightChildIndex;
}
if ((tree[minNodeIndex] as T).compareTo(tree[nodeIndex] as T) < 0) {
_swap(tree, nodeIndex, minNodeIndex);
_sink(tree, minNodeIndex);
}
}
static void _swim<T extends Comparable<T>>(List<T?> tree, int nodeIndex) {
if (nodeIndex <= 1) return;
int parentIndex = nodeIndex ~/ 2;
if ((tree[nodeIndex] as T).compareTo(tree[parentIndex] as T) < 0) {
_swap(tree, nodeIndex, parentIndex);
_swim(tree, parentIndex);
}
}
static void _swap<T extends Comparable<T>>(List<T?> tree, int i, int j) {
T temp = tree[i] as T;
tree[i] = tree[j];
tree[j] = temp;
}
#override
String toString() {
return _tree.toString();
}
}
/*
I know this keyword is used to refer to class members but i am unable to understand what does 'this'.isEmpty() referring to. Some class ? class method? Or some variable?
For example:
this.value = value;
I understand that here, this.value is referring to class variable value but not for previous occurence of 'this'.
*/
public class StackWithMin extends Stack< NodeWithMin > {
public void push(int value) {
int newMin = Math.min(value, min());
super.push(new NodeWithMin(value,newMin));
}
public int min() {
if(this.isEmpty()) {
return Integer.MAX_VALUE; // Error value
} else {
return peek().min;
}
}
}
class NodeWithMin {
public int value;
public int min;
public NodeWithMin(int value, int min) {
this.value = v;
this.min = min;
}
}
"this" here is object of the class StackWithMin which is extending Stack class from java.util. so StackWithMin is instance of Stack class.
this.isEmpty() which is method defined in Stack, here checks if the stack has any element or not. if it has zero element it returns true else false.
Hope it clears your doubt.
i'm relative new to this, so i want to implement dependency injection using typescript (is the first time I use this pattern), I'm more that using language programming like java or c# for OOP, so there is more easy to apply this pattern,
I found an example on internet and I can use it without problems on eclipse and visual studio, but when i use it on typescript the IDE raise an error like this:
Supplied parameters do not match any signature of call target
and is just at the end of implement it when this error appears
my base class:
class Motor {
Acelerar(): void {
}
GetRevoluciones(): number {
let currentRPM: number = 0;
return currentRPM;
}
}
export {Motor};
my class that uses motor
import { Motor } from "./1";
class Vehiculo {
private m: Motor;
public Vehiculo(motorVehiculo: Motor) {
this.m = motorVehiculo;
}
public GetRevolucionesMotor(): number {
if (this.m != null) {
return this.m.GetRevoluciones();
}
else {
return -1;
}
}
}
export { Vehiculo };
my interface and the type of motor
interface IMotor {
Acelerar(): void;
GetRevoluciones(): number;
}
class MotorGasoline implements IMotor {
private DoAdmission() { }
private DoCompression() { }
private DoExplosion() { }
private DoEscape() { }
Acelerar() {
this.DoAdmission();
this.DoCompression();
this.DoExplosion();
this.DoEscape();
}
GetRevoluciones() {
let currentRPM: number = 0;
return currentRPM;
}
}
class MotorDiesel implements IMotor {
Acelerar() {
this.DoAdmission();
this.DoCompression();
this.DoCombustion();
this.DoEscape();
}
GetRevoluciones() {
let currentRPM: number = 0;
return currentRPM;
}
DoAdmission() { }
DoCompression() { }
DoCombustion() { }
DoEscape() { }
}
and here is where the error appears:
import { Vehiculo } from "./2";
enum TypeMotor {
MOTOR_GASOLINE = 0,
MOTOR_DIESEL = 1
}
class VehiculoFactory {
public static VehiculoCreate(tipo: TypeMotor) {
let v: Vehiculo = null;
switch (tipo) {
case TypeMotor.MOTOR_DIESEL:
v = new Vehiculo(new MotorDiesel()); break;
case TypeMotor.MOTOR_GASOLINE:
v = new Vehiculo(new MotorGasoline()); break;
default: break;
}
return v;
}
}
I don't wanna use any library or module like SIMPLE-DIJS or D4js or any other for the moment, I just wanna know how to implement without them
You have this error because you don't specify a constructor on the Vehiculo type.
To declare a constructor you should use use the constructor keyword and not the name of the class.
class Vehiculo {
private m: Motor;
constructor(motorVehiculo: Motor) {
this.m = motorVehiculo;
}
public GetRevolucionesMotor(): number {
if (this.m != null) {
return this.m.GetRevoluciones();
}
else {
return -1;
}
}
}
I am new to the dependency injection pattern and I am having issues getting a new instance of a class from container.Resolve in tinyioc it just keeps returning the same instance rather than a new instance. Now for the code
public abstract class HObjectBase : Object
{
private string _name = String.Empty;
public string Name
{
get
{
return this._name;
}
set
{
if (this._name == string.Empty && value.Length > 0 && value != String.Empty)
this._name = value;
else if (value.Length < 1 && value == String.Empty)
throw new FieldAccessException("Objects names cannot be blank");
else
throw new FieldAccessException("Once the internal name of an object has been set it cannot be changed");
}
}
private Guid _id = new Guid();
public Guid Id
{
get
{
return this._id;
}
set
{
if (this._id == new Guid())
this._id = value;
else
throw new FieldAccessException("Once the internal id of an object has been set it cannot be changed");
}
}
private HObjectBase _parent = null;
public HObjectBase Parent
{
get
{
return this._parent;
}
set
{
if (this._parent == null)
this._parent = value;
else
throw new FieldAccessException("Once the parent of an object has been set it cannot be changed");
}
}
}
public abstract class HZoneBase : HObjectBase
{
public new HObjectBase Parent
{
get
{
return base.Parent;
}
set
{
if (value == null || value.GetType() == typeof(HZoneBase))
{
base.Parent = value;
}
else
{
throw new FieldAccessException("Zones may only have other zones as parents");
}
}
}
private IHMetaDataStore _store;
public HZoneBase(IHMetaDataStore store)
{
this._store = store;
}
public void Save()
{
this._store.SaveZone(this);
}
}
And the derived class is a dummy at the moment but here it is
public class HZone : HZoneBase
{
public HZone(IHMetaDataStore store)
: base(store)
{
}
}
Now since this is meant to be an external library I have a faced class for accessing
everything
public class Hadrian
{
private TinyIoCContainer _container;
public Hadrian(IHMetaDataStore store)
{
this._container = new TinyIoCContainer();
this._container.Register(store);
this._container.AutoRegister();
}
public HZoneBase NewZone()
{
return _container.Resolve<HZoneBase>();
}
public HZoneBase GetZone(Guid id)
{
var metadataStore = this._container.Resolve<IHMetaDataStore>();
return metadataStore.GetZone(id);
}
public List<HZoneBase> ListRootZones()
{
var metadataStore = this._container.Resolve<IHMetaDataStore>();
return metadataStore.ListRootZones();
}
}
However the test is failing because the GetNewZone() method on the Hadrian class keeps returning the same instance.
Test Code
[Fact]
public void ListZones()
{
Hadrian instance = new Hadrian(new MemoryMetaDataStore());
Guid[] guids = { Guid.NewGuid(), Guid.NewGuid(), Guid.NewGuid() };
int cnt = 0;
foreach (Guid guid in guids)
{
HZone zone = (HZone)instance.NewZone();
zone.Id = guids[cnt];
zone.Name = "Testing" + cnt.ToString();
zone.Parent = null;
zone.Save();
cnt++;
}
cnt = 0;
foreach (HZone zone in instance.ListRootZones())
{
Assert.Equal(zone.Id, guids[cnt]);
Assert.Equal(zone.Name, "Testing" + cnt.ToString());
Assert.Equal(zone.Parent, null);
}
}
I know its probably something simple I'm missing with the pattern but I'm not sure, any help would be appreciated.
First, please always simplify the code to what is absolutely necessary to demonstrate the problem, but provide enough that it will actually run; I had to guess what MemoryMetaDataStore does and implement it myself to run the code.
Also, please say where and how stuff fails, to point others straight to the issue. I spent a few minues figuring out that the exception I was getting was your problem and you weren't even getting to the assertions.
That said, container.Resolve<HZoneBase>() will always return the same instance because that's how autoregistration in TinyIoC works - once an abstraction has been resolved, the same instance is always returned for subsequent calls.
To change this, add the following line to the Hadrian constructor:
this._container.Register<HZoneBase, HZone>().AsMultiInstance();
This will tell the container to create a new instance for each resolution request for HZoneBase.
Also, Bassetassen's answer about the Assert part is correct.
In general, if you want to learn DI, you should read Mark Seemann's excellent book "Dependency Injection in .NET" - not quite an easy read as the whole topic is inherently complex, but it's more than worth it and will let you get into it a few years faster than by learning it on your own.
In your assert stage you are not incrementing cnt. You are also using the actual value as the expected one in the assert. This will be confusing, becuase it says something is excpected when it actually is the actual value that is returned.
The assert part should be:
cnt = 0;
foreach (HZone zone in instance.ListRootZones())
{
Assert.Equal(guids[cnt], zone.Id);
Assert.Equal("Testing" + cnt.ToString(), zone.Name);
Assert.Equal(null, zone.Parent);
cnt++;
}
running this code:
public bool CheckTime(DateTime date, int UserID, int TotalTimeMin)
{
using (var context = new myDB())
{
var assginments = from c in context.Assignments.Where(x=>(x.AssignmentDateTime < date && x.AssignmentDateTime.Value.AddMinutes(TotalTimeMin) > date) ||
(x.AssignmentDateTime < date.AddMinutes(TotalTimeMin))) select c;
if(assginments != null) return false;
else return true;
}
}
I get this error.
LINQ to Entities does not recognize the method 'System.DateTime AddMinutes(Double)' method, and this method cannot be translated into a store expression.
TotalTimeMin is int. I am not sure what cause this:
AssignmentDateTime is DateTime? and maybe this is the problem ?
Use EntityFunctions.AddMinutes (requires EF 4):
public bool CheckTime(DateTime date, int UserID, int TotalTimeMin)
{
using (var context = new myDB())
{
var assginments = context.Assignments
.Where(x=>(x.AssignmentDateTime < date
&& EntityFunctions.AddMinutes(x.AssignmentDateTime,TotalTimeMin) > date)
|| (x.AssignmentDateTime < date.AddMinutes(TotalTimeMin)));
if(assginments != null) return false;
else return true;
}
}
Note that assignments will never be null (but it might be empty -- test assignments.Any()).