> For the complete Mojo documentation index, see [llms.txt](/llms.txt).
> Markdown versions of all pages are available by appending .md to any URL (e.g. /docs/manual/basics.md).

# @__parameter

:::caution Deprecated
The `@__parameter` decorator is deprecated and will be removed in a future
release. Use the current [closure](/docs/manual/functions/closures/) syntax
instead. The previous spelling `@parameter` is still accepted with a
deprecation warning.
:::

You can add `@__parameter` on a nested function to create a legacy
capturing closure. This means you can create a closure function that captures
values from the outer scope (regardless of whether they are variables or
parameters), and then use that closure as a parameter. For example:

```mojo
def use_closure[func: def(Int) capturing[_] -> Int](num: Int) -> Int:
    return func(num)

def create_closure():
    var x = 1

    @__parameter
    def add(i: Int) -> Int:
        return x + i

    var y = use_closure[add](https://mojolang.org/docs/reference/decorators/2.md)
    print(y)

def main():
    create_closure()
```

```output
3
```

Note the `[_]` in the function type:

```mojo
def use_closure[func: def(Int) capturing[_] -> Int](num: Int) -> Int:
```

This origin specifier represents the set of origins for the values that the
legacy closure captures. This allows the compiler to correctly extend the
lifetimes of those values. For more information on lifetimes and origins, see
[Lifetimes, origins and references](/docs/manual/values/lifetimes/).