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Questions tagged [immutability]

Immutability is the inability to modify data after it has been created. Modifications are instead made by copying the data. A property of immutable data is that it is *referentially transparent*.

Overview

Immutability is the inability to modify a variable after it is has been created.

It is a pattern found in many branches of programming; immutable objects are used widely within object oriented languages (such as Python's str type, Java's String and Integer type, .NET's System.String, etc.), functional programming (esp. Haskell and other pure languages), and other paradigms.

See also

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Immutable class?

How can one make a Java class immutable, what is the need of immutability and is there any advantage to using this?
JavaUser
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Immutable/Mutable Collections in Swift

I was referring to Apple's Swift programming guide for understanding creation of Mutable/ immutable objects(Array, Dictionary, Sets, Data) in Swift language. But I could't understand how to create a immutable collections in Swift. I would like to…
Pranav Jaiswal
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In Python, how can I make unassignable attributes (like ones marked with `final` in Java)?

Is there anything in Python that works like the final keyword in Java - i.e., to disallow assigning to a specific attribute of the instances of a class, after those instances have been created? I couldn't find anything like this in the…
Jason Coon
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How to create immutable objects in Java?

How to create immutable objects in Java? Which objects should be called immutable? If I have class with all static members is it immutable?
Neel Salpe
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In C#, why can't I modify the member of a value type instance in a foreach loop?

I know that value types should be immutable, but that's just a suggestion, not a rule, right? So why can't I do something like this: struct MyStruct { public string Name { get; set; } } public class Program { static void Main(string[]…
Cui Pengfei 崔鹏飞
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Set System.Drawing.Color values

Hi how to set R G B values in System.Drawing.Color.G ? which is like System.Drawing.Color.G=255; is not allowed because its read only Property or indexer 'System.Drawing.Color.G' cannot be assigned toit is read only i just need to create a Color…
Sudantha
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Converting mutable to immutable map

private[this]object MMMap extends HashMap[A, Set[B]] with MultiMap[A, B] How convert it to immutable?
Jeriho
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How do I create a Vec from a range and shuffle it?

I have the following code: extern crate rand; use rand::{thread_rng, Rng}; fn main() { let mut vec: Vec = (0..10).collect(); let mut slice: &[u32] = vec.as_mut_slice(); thread_rng().shuffle(slice); } and get the following…
le_me
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What's the use of System.String.Copy in .NET?

I'm afraid that this is a very silly question, but I must be missing something. Why might one want to use String.Copy(string)? The documentation says the method Creates a new instance of String with the same value as a specified String. Since…
Blair Conrad
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Are Elixir variables really immutable?

In Dave Thomas's book Programming Elixir he states "Elixir enforces immutable data" and goes on to say: In Elixir, once a variable references a list such as [1,2,3], you know it will always reference those same values (until you rebind the…
Odhran Roche
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Why shouldn't I use immutable POJOs instead of JavaBeans?

I have implemented a few Java applications now, only desktop applications so far. I prefer to use immutable objects for passing the data around in the application instead of using objects with mutators (setters and getters), also called…
Jonas
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How can I create a new instance of ImmutableDictionary?

I would like to write something like this: var d = new ImmutableDictionary { { "a", 1 }, { "b", 2 } }; (using ImmutableDictionary from System.Collections.Immutable). It seems like a straightforward usage as I am declaring all the…
Lukáš Lánský
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Is there a way to Object.freeze() a JavaScript Date?

According to MDN Object.freeze() documentation: The Object.freeze() method freezes an object: that is, prevents new properties from being added to it; prevents existing properties from being removed; and prevents existing properties, or their…
Andrew Eisenberg
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Immutable objects that reference each other?

Today I was trying to wrap my head around immutable objects that reference each other. I came to the conclusion that you can't possibly do that without using lazy evaluation but in the process I wrote this (in my opinion) interesting code. public…
Stilgar
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Why are strings immutable in many programming languages?

Possible Duplicate: Why can't strings be mutable in Java and .NET? Why .NET String is immutable? Several languages have chosen for this, such as C#, Java, and Python. If it is intended to save memory or gain efficiency for operations like…
snowfox
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