fn reader_error(input: &str) -> String {

    Reader::parse(input)

        .err()

        .map(|e| e.to_string())

        .unwrap_or_else(|| panic!("{input:?} must be a reader error"))

}

fn scheme_true_is_a_reader_error() {

    for input in ["#t", "#T", "(if #t 1 2)"] {

        let message = reader_error(input);

        assert!(

            message.contains("#t is not nomiscript syntax; use t"),

}

fn scheme_false_is_a_reader_error() {

    for input in ["#f", "#F", "'#f"] {

        let message = reader_error(input);

        assert!(

            message.contains("#f is not nomiscript syntax; use nil"),

}

fn empty_parens_read_as_nil() {

    assert_eq!(Reader::parse("()").unwrap().exprs, vec![Expr::Nil]);

    assert_eq!(Reader::parse("( )").unwrap().exprs, vec![Expr::Nil]);

    assert_eq!(Reader::parse("'()").unwrap().exprs, vec![Expr::Nil]);

    assert_eq!(Reader::parse("'t").unwrap().exprs, vec![Expr::T]);

}

fn a_symbol_that_starts_with_nil_is_one_symbol() {

    assert_eq!(

        Reader::parse("nilly nil-x").unwrap().exprs,

        vec![Expr::Symbol("NILLY".into()), Expr::Symbol("NIL-X".into())]

}