anchor.diff:  ----------------------------
   
    * A few words on the `SandboxBuilder` works:
  -    - The library is build on top of the [AppDomain Class][appdomain] which 
  +    - The library is built on top of the [AppDomain Class][appdomain] which 
         allows to [Run Partially Trusted Code in a Sandbox][sandbox]. The 
         `SandboxBuilder` is only allowed to execute code
         `(SecurityPermissionFlag.Execution)`, which is the minimum permission that
  
positive.code:       (`Delay : f:(unit -> 'a IOEffect) -> 'a IOEffect`), which tries to evaluate
        the function at the newly created domain (`AppDomain`) with the minimum
        granted permision instead of the executing `AppDomain.CurrentDomain`.
        If the function evaluation is succesful then an `IOSafe 'a` value is returned, 
        otherwise an `Unsafe` `Exception` is returned.
      - In order to ensure that `IOEffect` types are only instantiated from inside
        the computation expression, a few examples: `IOSafe "42"` or 
  
negative.code: The next example show how we try to get access to the current file directory,
  count the amount of files and add it to the final result. This action will try 
  to perform an `File IO` which is not allowed in the `sandbox`. Due to this, the
  whole function is evaluated to an `Unsafe` value, which contain the `Exception` 
  thrown at runtime: *)
  
  let addition' x y = sandbox{ 
    return (Directory.EnumerateFiles(".") |> Seq.length) + x + y }
  