[tester756]

>Js has const, C has const, Java final.

C# has readonly and const

>Imho it'd be awesome if mutability were not the default

If they decided one day that - "let's make immutable by default", then it'd be performance hit - wouldn't it?

[kroltan]

C# does not (as far as I know) have readonly or const for local variables, only to fields. You can even have consts inside method bodies, but they are only actual compile-time constants.

codeflo means to declare a local variable that cannot be reassigned later.

    void Foo() {
        // this is possible in C# today, but only for compile-time constants
        const int Bar = 42;

        // this is what codeflo wants: variables that cannot be changed after declaration, but can hold runtime values
        readonly string text = $"Blah: {Bar + System.Environment.ProcessorCount}";

        // with such a variable, you wouldn't be able to reassign it later:
        text = "Some other text";
        // the line above would be a compile-time error, just like trying to reassign to a readonly field.
    }

[awild]

> If they decided one day that - "let's make immutable by default", then it'd be performance hit - wouldn't it?

Not really. It's just a syntactic default, reassigning local variables should be discouraged from except for iterators etc. It just fosters bad habits.

For example, A list can still be mutated like usual, the reference however may not change. This usually allows compilers to do optimizations in multithreaded situations. But that's not why I code that way, it reduces the cognitive burden of keeping track which variables are actual moving parts as opposed to context/names etc.

> C# has readonly and const

Haven't written C# in a few years, GP was talking about variables as far as I can tell and their lack of immutability.