# Argument Passing Behavior

When arguments are passed to a function, they are copied. Therefore, values that are passed into a function are unchanged in the caller's scope when the function returns. This behavior is known as [call-by-value](https://en.wikipedia.org/w/index.php?title=Evaluation_strategy\&oldid=896280571#Call_by_value).

```
// Declare a function that changes the first two elements
// of an array of integers.
//
fun change(_ numbers: [Int]) {
    // Change the elements of the passed in array.
    // The changes are only local, as the array was copied.
    //
    numbers[0] = 1
    numbers[1] = 2
    // `numbers` is `[1, 2]`
}

let numbers = [0, 1]

change(numbers)
// `numbers` is still `[0, 1]`
```

Parameters are constant, i.e., it is not allowed to assign to them.

```
fun test(x: Int) {
    // Invalid: cannot assign to a parameter (constant)
    //
    x = 2
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://max-daunarovich.gitbook.io/flow-network/introduction/functions/argument-passing-behavior.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.