> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/r/runtime_evaluation/in_an_environment.md).

# In an environment

```ruby
func eval_with_x(code, x, y) {
    var f = eval(code)
    x = y
    eval(code) - f
}
 
say eval_with_x(x: 3, y: 5, code: '2 ** x')   # => 24
```