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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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What is the fastest way to make a shallow copy of list in Python3.5+?

The are several alternatives to make a shallow copy of a list in Python 3.5+. The obvious ones are: some_list.copy() some_list[:] list(some_list) [*some_list] and others... Which method is the fastest? NOTE: While this question is related…
godaygo
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How to use both default and custom copy constructor in C++?

I have a long class with a lot of data members. I want to write a copy constructor for it. But, if I write my own copy constructor, I lose access to the default copy constructor. I just want to repair a few pointers in my own copy constructor. So I…
pablo
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Multiply operator applied to list(data structure)

I'm reading How to think like a computer scientist which is an introductory text for "Python Programming". I want to clarify the behaviour of multiply operator (*) when applied to lists. Consider the function make_matrix def make_matrix(rows,…
Aman Aggarwal
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What is the difference between being shallowly and deeply equal? How is this applied to caching?

Found the following in my notes, but I am unable to make sense of it: Primitive type wrapper classes implement caching for a limited number of values. This guarantees that a limited number of deeply equal wrapper objects are also shallowly…
Albatross32
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JS Recursive object assign

I learned that when using Object.assign() it extends only the top level object. How can I deeply extend the object? For example, let's say I have the following source object: const source = { id: 1, otherKey: {}, params: { page: { a:…
undefined
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In python, is a function return a shallow or deep copy?

In python, if I have x = y any modification to x will also modify y, and I can do x = deepcopy(y) if I want to avoid modifying y while working on x Say, instead, that I have: myFunc(): return y def main(): x = myFunc() Is it still the…
user
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How do I make a shallow copy of a Perl hash reference?

I want to push a reference to a hash. By that I mean I want to push a reference to a new hash that is a shallow copy of the hash I am given. How do I create the shallow copy?
Don
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Shallow copy of mpz_t

GMP provides methods for initializing and assigning an mpz_t. A call to mpz_init_set(a, b) will assign to a the content of b. However, I assume, this performs a deep copy on b. On my project I need to work with arrays of mpz_t that are as long as…
James
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Scala case class uses shallow copy or deep copy?

case class Person(var firstname: String, lastname: String) val p1 = Person("amit", "shah") val p2 = p1.copy() p1.firstname = "raghu" p1 p2 p1 == p2 As i went through some documentation which says scala copy method of case class uses shallow…
Navin Gelot
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Why are objects automatically passed by reference?

I have a general question about deep- and shallow-copy in the context of the pass-by-reference- and pass-by-value-concept of C#: In C# it is a requirement to explicitly create methods that accept pointers/references to be able to pass such to the…
Florian R. Klein
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How to make a separate copy of an object in Perl 6?

I don't fully understand the docs, so I've tried clone, and it seems if there is an attribute of a mutable class, it can be changed in the new object using the old one (and that's what I don't want). How to make them (i.e. the copy and the original)…
Eugene Barsky
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Java - Implement deep and shallow copy of an array

I am trying to understand the concept of shallow vs deep copy in Java. There is a lot of articles and Q&A about this subject, but whenever I try to implement these concepts in a real Java code, everything become unclear to me. One of the answers on…
Strider
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In c# does Array.ToArray() perform a DEEP copy?

This should be a pretty basic question, but I've been having a little trouble finding a definite answer. When you have an array of values and you use the .ToArray() method does it create a deep or shallow copy of the array?
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C++ compiler 'shallow' copies and assignments

I'm taking a class on object oriented programming using C++. In our text it says, If we do not declare a copy constructor, the compiler inserts code that implements a shallow copy. If we do not declare an assignment operator, the compiler inserts…
bigcodeszzer
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Shallow copy reference into variable in Perl

In Perl, you can assign to a variable a reference to another variable, like this: my @array = (1..10); my $ref = \@array; And, as it is a reference, you can do something like this and both variables will be affected: push @array, 11; push @$ref,…
Francisco Zarabozo
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