ext func __builtin_string_len(s: string) -> int;
ext func __builtin_string_concat(a: string, b: string) -> string;
ext func __builtin_string_is_empty(s: string) -> bool;
ext func __builtin_string_equals(lhs: string, rhs: string) -> bool;
ext func __fmt_string(to_fmt: string) -> string;

// FIXME: Remove `add_newline` parameter once strings with the \n character
// are handled correctly #323
ext func __builtin_string_display(s: string, add_newline: bool);
ext func __builtin_string_display_err(s: string, add_newline: bool);

/// Get the length of a given string
func len(s: string) -> int {
    s.__builtin_string_len()
}

/// Concatenate two strings together, returning a new one
func concat(lhs: string, rhs: string) -> string {
    lhs.__builtin_string_concat(rhs)
}

/// Display a string on stdout
func print(s: string) {
    s.__builtin_string_display(false)
}

/// Display a string and a newline on stdout
func println(s: string) {
    s.__builtin_string_display(true)
}

/// Display a string on stderr
func print_err(s: string) {
    s.__builtin_string_display_err(false)
}

/// Display a string and a newline on stderr
func println_err(s: string) {
    s.__builtin_string_display_err(true)
}

// FIXME: Once comparison operators are implemented, return `s.len() == 0`
func is_empty(s: string) -> bool {
    s.__builtin_string_is_empty()
}

// FIXME: This should maybe removed in favor of `==`
func equals(lhs: string, rhs: string) -> bool {
    lhs.__builtin_string_equals(rhs)
}