/// <summary></summary>
/// <param name="shell"></param>
public static void SetShell(PpsShell shell)
{
if (currentShell != null)
{
throw new ArgumentException();
}
currentShell = shell;
} // proc SetShell
} // proc SetShell
/// <summary>Returns the current shell.</summary>
/// <param name="shell"></param>
/// <returns></returns>
public static bool TryGetShell(out PpsShell shell)
=> (shell = currentShell) != null;
