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Questions tagged [shallow-copy]

A shallow copy of an object is a duplicate that may not be fully independent of the original, in the sense that any references / pointers it holds to other objects refer to the same objects that the original's do. Use this tag for questions regarding implementing or using shallow copying methods.

Shallow copying is a process by which an object is duplicated to create a copy that may not be wholly independent of the original. Also known as "field by field" copying, this differs from deep copying with respect to the treatment of references / pointers to other objects: shallow copying copies the references / pointers held by the original, whereas deep copying makes a deep copy of each referenced object, too. Shallow copying is "shallow" in the sense that it copies only the original object itself, not any appearing deeper in its reference graph.

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Can I write different copyCtor for const and non-const instances?

I have the following problem: I have a class which should do this: Obj o; Obj o1(o), o1=o; // deep-copies const Obj c(o), c=o; // deep-copies const Obj c1(c), c1=c; // shallow-copies Obj o2(c), o2=c; // deep-copies How can I do this preferably…
Barney Szabolcs
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What is actually moving a variable in Rust?

I have never experimented with languages like C, C++, Go, etc., and I decided to start with Rust, I already understand a little what the stack and the Heap are, but, what does it really mean by moving a variable, the documentation says that it is…
Grizzly
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VB.NET, Is Object Returned by Reference from Function

This should be a fairly common question, but I haven't found a straightforward answer anywhere. If I instantiate an object within a function in VB.NET and return it, does it return it by reference or by value. IE - should I be worried about…
Ian
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why should I make a *shallow* copy of a dataframe?

related to why should I make a copy of a data frame in pandas I noticed that in the popular backtesting library, def __init__(self, data: pd.DataFrame) data = data.copy(False) in row 631. What's the purpose of such a copy?
ihadanny
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Default copy constructor in cpp shallow or deep copy?

Does the default copy-constructor do a shallow or a deep copy in C++? I am really confused with default copy constructor in cpp, as it does shallow copy or deep copy, as when I did v2=v1; suppose v1={1,2,3}, now if I have done v2[0]=1; It does not…
Robin Khurana
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Does LINQ new up memory when creating returns

Does LINQ actually perform a deep copy of the results to a different list/array/etc, or does it simply give me a list/array/etc. composed of references to the original?
Joel B
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Returning a new structure with fields changed

I'm looking for a simple way to return a new structure which is a copy of an existing one with some fields changed, without modifying the original. I get that you can use setf to change the data in one of the fields, like so: [1]> (defstruct foo…
Electric Coffee
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Selective shallow copy from one array to another

Assuming I have 2 array of different size i.e int arr[] = {0,1,2,3,4,5,6,7,8,9}; int *arr2 = new int[5]; I want to shallow copy some of them, Deep copy equivalent would be int j =0; if(!(i%2)) { arr2[j]=arr[i]; j++; …
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Shallow copy for arrays, why can't simply do newArr = oldArr?

Let's say I have an array of integers, "orig" I want to shallow copy it, so can't I just do this: int[] shallow = orig; My professor said that for primitives, shallow and deep copy are essentially the same, in that we have to copy over each index…
onepiece
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Avoiding ConcurrentModificationException on List by making a shallow copy

I have a class like the following: class Test { private LinkedList persons = new LinkedList; public synchronized void remove(Person person) { persons.remove(person); } public List…
His
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How would you improve this shallow copying class?

I've written a class with a single static method that copies property values from one object to another. It doesn't care what type each object is, only that they have identical properties. It does what I need, so I'm not engineering it further,…
Neil Barnwell
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Make a shallow copy in data.table

I read in an SO topic an answer from Matt Dowle about a shallow function to make shallow copies in data.table. However, I can't find the topic again. data.table does not have any exported function called shallow. There is an internal one but not…
JRR
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AngularJS : copy vs extend

Explanation : we come across some situation in which we need to copy one object to another object. In that case, we probably have two solutions: angular.copy() or angular.extend(). Challenge i am facing : As we know angular.copy(source, destination)…
Debug Diva
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Why setting a dict shallow copy to itself?

I think it's a bit weird question to ask. The thing is that while I was studying some parts of django code I came across something I've never seen before. According to Copy Difference Question and It's usage in dictionary we can create two…
Heartagramir
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Intercept C++ implicit copy constructor, or invoke its functionality

Given: class Foo { private: static int cntFoos; //... stuff... public: Foo() { cntFoos++; } ~Foo() { cntFoos--; } }; ... where "stuff" may be any set of properties. (The idea is to have a counter of instances of that…
tru7
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