My goal is to create a bunch of observables from a source observable, so that I can subscribe to them individually.
When I do that manually (that is, creating each subSource manually), things work as expected: the values added to the original source propagate adequately to the subSources.
But when I create them in a loop, adding them to a List<IObservable<T>>, the subscriptions to elements taken from that list don't seem to be working:
class Program
{
static void Main(string[] args)
{
// using Subject for the sake of example
var source = new Subject<int>();
// manually creating each subSource
var source0 = source.Where((t, i) => i % 3 == 0);
var source1 = source.Where((t, i) => i % 3 == 1);
var source2 = source.Where((t, i) => i % 3 == 2);
// creating a List of subsources
List<IObservable<int>> sources = new List<IObservable<int>>();
int count = 3;
for (int i = 0; i < count; i++)
{
sources.Add(source.Where((v, ix) => ix % 3 == i));
}
// subscribing to one subSource from each group
source0.Subscribe(Console.WriteLine); // this works
sources[1].Subscribe(Console.WriteLine); // this doesn't
// feeding data
Observable.Range(0, 20).Subscribe(source);
Console.ReadKey();
}
}
The predicate of your Where clause references the loop variable i.
However, the predicate is tested when a value is published from source - not when the loop is iterated. By the that time, i has reached it's final value 3.
To fix this, create a new variable inside the loop to store the current value of i, and reference that in your Where predicate:
for (int i = 0; i < count; i++)
{
var j = i;
sources.Add(source.Where((v, ix) => ix % 3 == j)); // note use of j here
}
for (int i = 0; i < count; i++)
{
**var j = i;**
sources.Add(source.Where((v, ix) => ix % 3 == j));
}
Closures.
Related
I have a 3x5 matrix that acts as a game reel. First, I search through the game symbols that I am interested in (let's call them wild clones) and then I search through their children (to locate the game object that has the animation) and then I activate those animations.
private IEnumerator EnableWilds(float delayBetweenWildsAppear)
{
WildSymbol[] wilds = FindObjectsOfType<WildSymbol>();
GameObject[] symbols = new GameObject[wilds.Length];
for (int i = 0; i < wilds.Length; i++)
{
symbols[i] = wilds[i].gameObject;
}
for (int i = 0; i < symbols.Length; i++)
{
if ( symbols[i].name.Contains("(Clone)") )
{
int reelIndex = symbols[i].GetComponentInParent<GameReel>().ReelIndex;
int indexOnReel = symbols[i].GetComponent<WildSymbol>().IndexOnReel;
// ??
for (int j = 0; j < symbols[i].transform.childCount; j++)
{
if ( symbols[i].transform.GetChild(j).gameObject.name.Contains("MM_wild") )
{
symbols[i].transform.GetChild(j).gameObject.SetActive(true);
yield return new WaitForSeconds(delayBetweenWildsAppear);
}
}
}
}
}
I started thinking about how I can activate those wilds starting from the top left corner, and coming down the reel and moving on to the next reel and animating the wilds from top to bottom, etc...
So, I realized I need to get each symbol's reel index (i.e. column number) and index on reel (i.e. position on the reel) so I go Reel1 and then wild clone 1 and 2 and 3, and then Reel2 followed by wild clone 1 and 2 and 3, and so on...
I am trying to do this where I have put a // ?? but at this point, I am a bit lost, conceptually. I cannot figure out how to perform tghis traversal.
Could someone please help me with this?
Here is how I solved it myself, and then simplified it:
private IEnumerator DisableWilds(float delayBetweenWildsDisappear)
{
WildSymbol[] wilds = FindObjectsOfType<WildSymbol>();
wilds = wilds.Where( (item, index) => item.name.Contains("(Clone)") )
.OrderBy( x => x.GetComponent<WildSymbol>().IndexOnReel )
.OrderBy( x => x.GetComponentInParent<GameReel>().ReelIndex )
.ToArray();
for (int i = 0; i < wilds.Length; i++)
{
for (int j = 0; j < wilds[i].transform.childCount; j++)
{
if (wilds[i].transform.GetChild(j).gameObject.name.Contains("MM_wild"))
{
wilds[i].transform.GetChild(j).gameObject.SetActive(false);
yield return new WaitForSeconds(delayBetweenWildsDisappear);
}
}
}
}
I'm trying to build a 2D sparse matrix class using std::map, which should be called in (for example) the following way:
SparseMatrix<double> M(2,2); // Create a new sparse matrix with 2 rows and 2 columns
M[{1,1}] = 3.1; // Sets element {1,1} to 3.1
The following class can perform these tasks:
template < typename T >
class SparseMatrix
{
std::map< array<int, 2>, T> data;
const array<int, 2> size;
public:
SparseMatrix(const int rows, const int cols)
: size({ rows, cols }) {}
// []-operator to set and get values from matrix
T& operator[](const array< int,2 > indices)
{
// Check if given indices are within the size of the matrix
if(indices[0] >= size[0] || indices[1] >= size[1])
throw invalid_argument("Indices out of bounds");
return data[indices];
}
};
Using this class it is possible to create a new object and set the element, however, the []-operator is also used to get elements, for example:
std::cout << M[{1,1}] << std::endl;
The problem with this is that if this is used to get an element that is not set already, it creates a new part in the map with the given indices and a value of 0, which is undesired for a sparse matrix class, as the map should only contain the non-zero elements.
Is it possible to solve this problem with the []-operator by making a distinction between 'setting' and 'getting'? In case of 'getting' should the operator only return a 0 without adding it to the map.
You can differentiate between reading and writing by using a proxy instead of a T&. Only showing the relevant code:
template <typename T>
class SparseMatrixProxy {
public:
//for reading an element:
operator T() const {
// Check if given indices are within the size of the matrix
if (indices[0] >= matrix.size[0] || indices[1] >= matrix.size[1])
throw std::invalid_argument("Indices out of bounds");
auto map_it = matrix.data.find(indices);
if (map_it == matrix.data.end()) {
return T{};
}
return map_it->second;
}
//for writing an element:
auto operator=(const T &t) {
//optional: when setting a value to 0 erase it from the map
if (t == T{}) {
matrix.data.erase(indices);
} else {
matrix.data[indices] = t;
}
return *this;
}
};
to be used in SparseMatrix like this:
// []-operator to set and get values from matrix
SparseMatrixProxy<T> operator[](const std::array<int, 2> indices) {
return {*this, indices};
}
With usage:
SparseMatrix<double> M(2, 2); // Create a new sparse matrix with 2 rows and 2 columns
M[{{1, 1}}] = 3.1; // Sets element {1,1} to 3.1
std::cout << M[{{1, 1}}] << '\n';
assert(M.mapsize() == 1); //1 element for index {1,1}
std::cout << M[{{0, 0}}] << '\n';
assert(M.mapsize() == 1); //still 1 element because reading doesn't insert an element
M[{{1, 1}}] = 0;
assert(M.mapsize() == 0); //0 elements because we set the only non-0 element to 0
Complete example.
There is std::map::find method. It returns an iterator and if it equals to map.end() then it means that the element is absent in the map.
Yup, it's a pain in the backside. Luckily the clever C++11 bods realised this and gave us a new method: at.
Use the at method (available from the C++11 standard onwards), which does not do any insertion, although you still need a catch handler for a possible std::out_of_range exception.
See http://en.cppreference.com/w/cpp/container/map/at
It's cheaper from performance point of view to implement sparse matrix by creating own mapping, e.g via storing indices.
template<typename T>
class SparseMatrix
{
...
int m, n;
vector<T> values;
vector<int> cols;
vector<int> rows;
}
template<typename T>
T SparseMatrix<T>::get(int row, int col) const
{
this->validateCoordinates(row, col);
int currCol = 0;
for (int pos = rows.at(row - 1) - 1; pos < rows.at(row) - 1; pos++)
{
currCol = cols.at(pos);
if (currCol == col)
return vals.at(pos);
else if (currCol > col)
break;
}
return T();
}
template<typename T>
SparseMatrix<T> & SparseMatrix<T>::set(T val, int row, int col)
{
// Validate coordinates here?
int pos = rows.at(row - 1) - 1;
int currCol = 0;
for (; pos < rows.at(row) - 1; pos++) {
currCol = cols.at(pos);
if (currCol >= col) {
break;
}
}
if (currCol != col) {
if (!(val == T())) {
this->insert(pos, row, col, val);
}
} else if (val == T()) {
this->remove(pos, row);
} else {
vals.at(pos) = val;
}
return *this;
}
template<typename T>
void SparseMatrix<T>::insert(int index, int row, int col, T val)
{
vals.insert(vals.begin() + index, val);
cols.insert(cols.begin() + index, col);
for (int i = row; i <= this->m; i++)
rows.at(i) = rows.at(i) + 1;
}
And so on...
I'm creating a random number generator which then sorts the digits from largest to smallest. Initially it worked but then I changed a few things. As far as I'm aware I undid all the changes (ctrl + z) but now I have errors at the points where i try to call the methods. This is probably a very amateur problem but I haven't found an answer. The error i'm met with is "method in class cannot be applied to given types"
Here's my code:
public class RandomMath {
public static void main(String[] args) {
String bigger = bigger(); /*ERROR HERE*/
System.out.println(bigger);
}
//create method for generating random numbers
public static int generator(int n){
Random randomGen = new Random();
//set max int to 10000 as generator works between 0 and n-1
for(int i=0; i<1; i++){
n = randomGen.nextInt(10000);
// exclude 1111, 2222, 3333, 4444, 5555, 6666, 7777, 8888, 9999, 0000
if((n==1111 || n==2222 || n==3333 || n ==4444 || n==5555)
||(n==6666 || n==7777 || n==8888 || n==9999 || n==0000)){
i--;
}
}
return n;
}
//create method for denoting the bigger number
public static String bigger(int generated){
generated = generator(); /*ERROR HERE*/
System.out.println(generated);
int[] times = new int[10];
while (generated != 0) {
int val = generated % 10;
times[val]++;
generated /= 10;
}
String bigger = "";
for (int i = 9; i >= 0; i--) {
for (int j = 0; j < times[i]; j++) {
bigger += i;
}
}
return bigger;
}
}
You have not defined a method bigger(), only bigger(int generated). Therefore, you must call your bigger method with an integer parameter.
any help please, so i already wrote the prog but my if statement in my for loop is not working. the prog need to generate 6 random nos,then apply bubble sort which i already did.then the user must enter 6 numbers and these numbers must be compared against the random numbers and must say whether numbers are found in the random numbers or not. here's the code. something is wrong with the if statement ` public static void main(String[] args) {
try {
int numbers[] = new int[6]; //random numbers will be stored in new array
//2 loop will be created to avoid duplication of numbers
System.out.println("Array before Bubble sort");
for (int i = 0; i < 6; i++) {
numbers[i] = (int) (Math.random() * 40);
if (i > 0) {
for (int b = 0; b < i; b++) { //
if (numbers[b] == numbers[i]) {
i--; //decrement to continue the for loop if the integer has been repeated
}
}
}
System.out.print(numbers[i] + ","); //random numbers will be printed before using sorting bubble sort
}
//sort an array using bubble sort
bubbleSort(numbers);
System.out.println(" \nArray after bubble sort");
for (int i = 0; i < 6; i++) {
System.out.print(numbers[i] + ",");
}
BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
System.out.println("\ninput 6 number between 1 and 40");
int inputNumber = Integer.parseInt(input.readLine());
for (int b = 0; b < 6; b++) {
System.out.println("number:");
int outcome=Integer.parseInt(input.readLine());
if(outcome==numbers){
System.out.println("found in random numbers");
}else{
System.out.println("not found in random numbers");
}
}
} catch (Exception e) {
System.out.println("error");
}
}
public static void bubbleSort(int[] numbers) {
int n = numbers.length;
int temp = 0;
for (int i = 0; i < n; i++) {
for (int j = 1; j < (n - i); j++) {
if (numbers[j - 1] > numbers[j]) { //swap the element
temp = numbers[j - 1];
numbers[j - 1] = numbers[j];
numbers[j] = temp;
}
}
}
}
}`
System.out.println("\ninput 6 number between 1 and 40");
//Scanner is specifically designed for getting an input purpose and introduced in Java 5,so better use it
Scanner s = new Scanner(System.in);
//you need to have nested loop here
//But the best way to search is use binary search,as you have already sorted the array
while (s.hasNextInt()) {
//one at a time from the input is put to outcome
int outcome = s.nextInt();
boolean found = false;
for (int b = 0; b < 6; b++) {
found = false;
if (outcome == numbers[b]) {
found = true;
//remember to break the inner loop if a match is found
break;
} else {
found = false;
}
}
if (found == true) {
System.out.println("found in random numbers");
} else {
System.out.println("not found in random numbers");
}
I'm spawning objects from a list and so-far i got them to find a parent object that's already live in the scene.The problem is Random.Range() isn't working like I want. I want the listed Objects to spawn to a random parent, instead, they're spawning to the they're parent relative to the order of the list.
Ex. 0,1,2,3,4,5,6,7,8,9 = Bad
Ex. 8,3,1,4,6,3,7,9,5,2 = Good
lol
var theRange = Random.Range(obj1.Length,obj1.Length);
for(var i: int = 0; i < theRange; i++){
var obj2 : GameObject = obj1[i];
if(obj2.transform.childCount == 0){
objfromList.transform.parent = obj2.transform;
objfromList.transform.localPosition = Vector3(0,-2,0);
}
}
Deeply thankful
Following up on my comment, it sounds like you just want a shuffle function. Here is a simple Fisher-Yates shuffle:
void shuffle(int[] a){
for(int i = a.Length-1; i>=0; i--){
int j = Random.Range(0,i);
int tmp = a[i];
a[i] = a[j];
a[j] = tmp;
}
}
void usage(){
int[] a = {0,1,2,3,4,5}; // assumes obj1.Length = 6
shuffle(a);
for(int i = 0; i < a.Length; i++){
GameObject obj2 = obj1[a[i]];
GameObject objFromList = GetNextObject(); // dummy method grabbing next list object
objFromList.transform.parent = obj2.transform;
objFromList.transform.localPosition = Vector3(0,-2,0);
}
}
This should get you part way to what you need. If the order of obj1 isn't important you can shuffle it directly instead of using a secondary array like a in my example.