/// Parses a string into multiple exressions, and returns an array of any values calculated.
        /// Does not include null values in the array (ie. when define statements are interpreted).
        /// Environment defaults to standard library.
        public static TruVal[] InterpretAll(string code, Environment env = null)
        {
            env = env ?? TruLibrary.Library;
            TruStatement[] exprs = TruStatement.ParseAll(code);

            List <TruVal> rtrnVals = new List <TruVal>();

            foreach (TruStatement expr in exprs)
            {
                TruVal result = expr.Interpret(env);
                if (result != null)
                {
                    rtrnVals.Add(result);
                }
            }

            return(rtrnVals.ToArray());
        }
        /// Launches a REPL where you can evaluate Tru statements.
        static void Main(string[] args)
        {
            Console.WriteLine(shortHelpStr);

            Environment global = TruLibrary.Library;

            while (true)
            {
                Console.Write(">>> ");
                string input = Console.ReadLine();
                if (input == "quit" || input == "exit")
                {
                    return;
                }
                else if (input == "help")
                {
                    Console.WriteLine(helpStr);
                }
                else
                {
                    try {
                        TruStatement[] statements = TruStatement.ParseAll(input);
                        foreach (TruStatement statement in statements)
                        {
                            TruVal result = statement.Interpret(global);
                            if (result != null)
                            {
                                Console.WriteLine(result);
                            }
                        }
                    } catch (TruSyntaxError e) {
                        Console.WriteLine($"Syntax Error: {e.Message}");
                    } catch (TruRuntimeException e) {
                        Console.WriteLine($"Runtime Exception: {e.Message}");
                    }
                }
            }
        }