logo
Tags down

shadow

Why doesn't JS provide a simple way to perform a deep copy on objects?


By : patty
Date : September 15 2020, 10:00 AM
fixed the issue. Will look into that further
a) In a language where all variables are anyway treated as objects, why does the = operator distinguish [...] ?
code :


Share : facebook icon twitter icon

Why doesn't the .NET framework provide a method to deep copy objects?


By : Gökhan Kurt
Date : March 29 2020, 07:55 AM
Hope that helps The problem is substantially harder than you seem to realize, at least in the general case.
For starters, a copy isn't just deep or shallow, it's a spectrum.

How to deep-copy closure objects (private objects) while Deep Copying


By : Tamara
Date : March 29 2020, 07:55 AM
Hope this helps It's not a good solution as all functions accessing your "private" cells variable have to declared as this.someFunction instead of Board.prototype so each Board instance will have their own funcions instead of sharing them.
Here is some sample code that would break prototype (c instanceof b is not true) but since you can't use prototype because you need to access closure variables in your functions that would not matter.
code :
function Test(privates) { 
    var msg = [];
    if(privates!==undefined){
      msg=deepCopy(privates.msg,[]);
    }
    this.Message = function(newMsg) {
        if (newMsg) {
            msg.push(newMsg);
        } else {
            return msg;
        }
    }
    this.clone=function(){
      var orgMsg=msg
      var ret = function(){
        Test.call(this,{msg:orgMsg});
      }
      return deepCopy(this,new ret());
    }
}
// this does not set prototype correctly
function deepCopy(from,to) {
    if(from == null || typeof(from) != 'object') {
        return from;
    }
    for(var key in from) {
      // this.Message has closure ref to msg
      // you can't copy it because we've set a new
      // closure ref
      if(typeof from[key]!=="function"){
        to[key] = deepCopy(from[key]);
      }
    }
    return to;  
}

var b = new Test();
b.Message("Before cloning");
console.log("b message before cloning:",b.Message());
var c = b.clone();
console.log("c message after cloning:",c.Message());
b.Message("From BB after Clone");
console.log("c message after pushing new item in b:",c.Message());
c.Message("From CC after Clone");
console.log("b message after pushing new item in c:",b.Message());
console.log("c message after pushing new item in b:",c.Message());
Test.prototype.Message(){
 //here the msg variable doesn't exist
}

Does Job(Configuration conf) perform shallow copy or deep copy?


By : Naveen Sagar
Date : March 29 2020, 07:55 AM
wish helps you Here is the link to the current Job.java source. A quick glance shows that constructor calls super(conf, null);, so we need to grab the super class (JobContext) for a peek. The relevant line in that constructor is here:
code :
this.conf = new org.apache.hadoop.mapred.JobConf(conf);

Provide simplest example where deep copy is needed in ruby


By : Simon C
Date : March 29 2020, 07:55 AM
it should still fix some issue The example you have shown does not describe the difference between a deep and a shallow copy. Instead, consider this example:
code :
class Klass
  attr_accessor :name
end

anna = Klass.new
anna.name = 'Anna'

anna_lisa = anna.dup
anna_lisa.name << ' Lisa'
# => "Anna Lisa"

anna.name
# => "Anna Lisa"
anna_lena = Marshal.load( Marshal.dump(anna))

How do you perform a deep copy on an object? How do you make a copy constructor?


By : user3505793
Date : March 29 2020, 07:55 AM
it should still fix some issue You should implement copy constructors and copy assignment operators and take care when using new. You need one delete for each new - unless you surrender the pointer returned by new to a smart pointer. In C++03 you have std::auto_ptr that can be used to manage the memory resources for you.
Here's an example with comments inline:
code :
#include <iostream>
#include <memory>    // std::auto_ptr
#include <algorithm> // std::swap (<algorithm> in c++03, <utility> in >= c++11) 

class Piece {
public:
    // A virtual destructor to support deleting via base class pointer:
    virtual ~Piece() {}

    // You can't make constructors virtual, so add a clone()
    // function for copy constuction through a base class pointer
    virtual std::auto_ptr<Piece> clone() const = 0;

    // renamed get() into symbol()
    virtual char symbol() const = 0;
};

class One : public Piece {
public:
    // Use the implicit copy constructor for One and return a (smart) pointer
    // to the base class.
    std::auto_ptr<Piece> clone() const {
        return std::auto_ptr<Piece>(new One(*this));
    }
    char symbol() const { return '1'; }
};

class Two : public Piece {
public:
    std::auto_ptr<Piece> clone() const {
        return std::auto_ptr<Piece>(new Two(*this));
    }
    char symbol() const { return '2'; }
};

class Tile {
private:
    std::auto_ptr<Piece> occ;  // this now handles delete for you

public:
    Tile() : occ(NULL) {}      // default constructor
    Tile(Piece* p) : occ(p) {} // put pointer in auto_ptr

    // copy constructor, use the clone() function and conversion
    // to bool operator below. If "o" doesn't have a Piece, initialize occ
    // with an default constructed, empty, auto_ptr<Piece>.
    Tile(const Tile& o) : occ(o ? o.occ->clone() : std::auto_ptr<Piece>()) {}
    //                        ^
    //                        |
    //                        +--- conversion to bool in use

    // copy assignment operator
    Tile& operator=(const Tile& o) {
        Tile tmp(o);   // use the copy constructor above
        occ = tmp.occ; // steal pointer from tmp
        return *this;
    }

    // converting assignment operator
    Tile& operator=(Piece* p) {
        // delete the old pointer and replace it with p:
        occ.reset(p);
        return *this;
    }

    // Conversion to bool operator using std::auto_ptr's built in get()
    // to tell us if we have a Piece or not.
    operator bool() const { return occ.get() != NULL; }

    // Add a symbol() function to hide the logic to determine if this Tile
    // has a Piece or not.
    char symbol() const {
        // Check if there is a Piece in this Tile using the conversion
        // to bool operator here too:
        if(*this)
            return occ->symbol();
        else
            return '-'; // no Piece here
    }
};

// add support to stream a Tile to an ostream
std::ostream& operator<<(std::ostream& os, const Tile& t) {
    return os << t.symbol();
}

class Board {
private:
    Tile tiles[2][2];

public:
    Board() {
        // using the added operator() further down
        (*this)(0,0) = new One;
        (*this)(0,1) = new Two;
        (*this)(1,1) = new One;
    }

    // Note that cols and rows in arrays are usually seen as reversed.
    // tiles[2][2]               usually means:
    // tiles[<rows>=2][<cols>=2]

    // getTile() replacements - the interface here is still (col, row)
    // but it accesses the tiles[][] using the common form (row, col)
    Tile& operator()(int c, int r) { return tiles[r][c]; }
    Tile const& operator()(int c, int r) const { return tiles[r][c]; }

    // moving by swapping tiles
    void move(int c1, int r1, int c2, int r2) {
        // using operator() and the standard function std::swap
        std::swap((*this)(c1, r1), (*this)(c2, r2));
    }
};

// Add a stream operator to not have to call print() explicitly when streaming
std::ostream& operator<<(std::ostream& os, const Board& b) {
    for(int r = 0; r < 2; r++) {
        for(int c = 0; c < 2; c++) {
            // Use "Board::operator() const" and stream support for returned
            // Tile.
            os << b(c, r);
        }
        os << '\n';
    }
    os << '\n';
    return os;
}

int main() {
    // no need to "new" anything:

    Board oldBoard;
    Board newBoard(oldBoard); // use copy constructor

    // use streaming operators
    std::cout << "Old board: \n" << oldBoard;
    std::cout << "New board: \n" << newBoard;

    // using the getTile() replacement, Board::operator():
    std::cout << "New board @ tile 1,0: " << newBoard(1, 0) << " before move\n";

    newBoard.move(0, 0, 1, 0);
    std::cout << "New board @ tile 1,0: " << newBoard(1, 0) << " after move\n\n";

    std::cout << "New board after move:\n" << newBoard;

    newBoard = oldBoard; // copy assignment operator
    std::cout << "New board after reinit:\n" << newBoard;
}
Related Posts Related Posts :
  • javascript addEventListener in react js component not working
  • Why does an alert box keep popping up with the word "undefined"
  • Should I use Jquery to click toggle instead of React?
  • Angular I don't call a function with (load)
  • Is there a way of making a javascript loop to repeatedly press a button?
  • How do I create a function that accepts multiple arguments to perform an arithmetic calculation in JavaScript?
  • Cancel Async/Await
  • How to rerender when refs change
  • Is there a more run-time efficient way to iterate through this array? (JavaScript)
  • Is there a more concise way to write this without a bunch of IF statements?
  • Filter Nested JSON based on the Object
  • Sankey-diagram PowerBI custom visual with color nodes and ordering
  • JavaScript anonymous function simulating arithmetic in lambda calculus, result returns `undefined`
  • How to uglify ES6 javascript with Flask?
  • How to fetch data from RESTAPI with react.js
  • Why does RETURN shows different output in javascript
  • How to correctly store an array of RegEx values in a JSON file and retrive it from Javascript?
  • How to solve slow loading page containing database information
  • React unwanted submit on every character inputed
  • Is it bad form to include <span> and <br> within <td> elements?
  • 'Product' s defined but never used in react?
  • "RNCSafeAreaView" was not found in the UIManager
  • Using Regex inside a textarea in Angular template driven form
  • Entering data directly into a table
  • How disable to select minutes in v-time-picker widget?
  • Rebind an event handler that was unbound with .off() method jQuery
  • In Angular 7 how to load CSS of Arabic language (RTL) from English language (LTR)
  • Unable to use a `Symbol` for a `Group` with paper.js
  • Can vuejs be used inside webcomponent?
  • Load "External" CSS (bootstrap) to specific DIV
  • How to make a checkbox show/hide text with onChange event
  • Is it ok to add meta tag in head using jQuery?
  • How to print to screen all array elements stored in local storage
  • React Native: How to pass params to parent component from child component prop
  • jQuery replace span contains comma with single comma
  • JavaScript function to convert unicode pseduo-alphabet to regular characters?
  • How can I pass parameter correctly?
  • How to create and render an app.json file for Heroku
  • Javascript - Is there a clearer way to express "if (a && b || !a && !b)"?
  • Date Validation in Javascript on Chrome
  • Cannot read a an object in Component, React
  • Can I use conditionals to render a grid widget?
  • How to minify index.html file with hundreds of scripts?
  • How to replace a string with another and with a different colour in ReactJS?
  • i need to give two clicks when the keyboard is open -- React native
  • CodeIgniter Update a row of two tables
  • Bootstrap CSS/Javascript For Carousel Only
  • Using Ionic (angular).Unable to access Hardware back button of mobile devices which have buttons inside the display/scre
  • should I use one component for edit and view with ngif or divided them to components?
  • Referential transparency in functional programming
  • Disable serviceWorker when online
  • How to get the coordinates of the pin/marker using ESRI and JavaScript?
  • Longest decrease subsequence subarray in Javascript
  • Update value from database with the hashed content from another column
  • eror 404 in react-routing
  • Youtube video in <object> tag
  • Is there a way to check null or undefined in a series of object of objects in lodash
  • .save() does not change the value of a field , django
  • Highcharts drilldown doesn't work for 3+ levels
  • How do I load an external JS library in Svelte/Sapper?
  • shadow
    Privacy Policy - Terms - Contact Us © 35dp-dentalpractice.co.uk