Puppet::Parser::Functions::newfunction(
  :reverse_each,
  :type => :rvalue,
  :arity => -1,
  :doc => <<-DOC
Reverses the order of the elements of something that is iterable and optionally runs a
[lambda](https://docs.puppetlabs.com/puppet/latest/reference/lang_lambdas.html) for each
element.

This function takes one to two arguments:

1. An `Iterable` that the function will iterate over.
2. An optional lambda, which the function calls for each element in the first argument. It must
   request one parameter.

**Example:** Using the `reverse_each` function

```puppet
$data.reverse_each |$parameter| { <PUPPET CODE BLOCK> }
```

or

```puppet
$reverse_data = $data.reverse_each
```

or

```puppet
reverse_each($data) |$parameter| { <PUPPET CODE BLOCK> }
```

or

```puppet
$reverse_data = reverse_each($data)
```

When no second argument is present, Puppet returns an `Iterable` that represents the reverse
order of its first argument. This allows methods on `Iterable` to be chained.

When a lamdba is given as the second argument, Puppet iterates the first argument in reverse
order and passes each value in turn to the lambda, then returns `undef`.

**Example:** Using the `reverse_each` function with an array and a one-parameter lambda

``` puppet
# Puppet will log a notice for each of the three items
# in $data in reverse order.
$data = [1,2,3]
$data.reverse_each |$item| { notice($item) }
```

When no second argument is present, Puppet returns a new `Iterable` which allows it to
be directly chained into another function that takes an `Iterable` as an argument.

**Example:** Using the `reverse_each` function chained with a `map` function.

```puppet
# For the array $data, return an array containing each
# value multiplied by 10 in reverse order
$data = [1,2,3]
$transformed_data = $data.reverse_each.map |$item| { $item * 10 }
# $transformed_data is set to [30,20,10]
```

**Example:** Using `reverse_each` function chained with a `map` in alternative syntax

```puppet
# For the array $data, return an array containing each
# value multiplied by 10 in reverse order
$data = [1,2,3]
$transformed_data = map(reverse_each($data)) |$item| { $item * 10 }
# $transformed_data is set to [30,20,10]
```

* Since 4.4.0

DOC
) do |args|
  Puppet::Parser::Functions::Error.is4x('reverse_each')
end