A modern programming language that makes developers happier.

kotlinlang

Is it possible to have immutable parameters for functions in Kotlin?

Not sure I understand the question. You can’t reassign parameters in Kotlin. If the type of the parameter is immutable (like `String`) then you won’t be able to mutate the value it references, if it’s mutable (like `MutableList`) then you will.

I meant whether it's possible to have a function like below or not:

`fun foo(val a:Int) = a + 2;`

I get: _error: 'val' on function parameter is prohibited._

Perhaps try it? <https://play.kotlinlang.org/>

(The answer is yes and no - you can't use that syntax, it has to be `fun foo(a: Int) = a + 2`  but `a` will not be reassignable, which is all that using `val` when defining a variable does)

Ah, so function parameters are const by default.

One thing to look out for is that Kotlin _does_ allow name shadowing:
```fun foo(a: Int): Int {
    var a = a
    a = a + 2
    return a
}```


&gt; Ah, so function parameters are const by default.
Not just by default. They are _always_ non-reassignable. (I wouldn't use the term "const" as that is a keyword that can only be used in certain contexts.) Unlike C, C++ and C#, you can _never_ reassign a parameter inside a function.