escaped := false
	quoted := false
	quote := '\x00'
	i := 0
	for _, r := range s {
		switch {
		case escaped:
			escaped = false
		case r == '\\':
			escaped = true
			continue
		case quote != 0:
			if r == quote {
				quote = 0
				continue
			}
		case r == '"' || r == '\'':
			quoted = true
			quote = r
			continue
		case unicode.IsSpace(r):

\f   U+000C form feed
\n   U+000A line feed or newline
\r   U+000D carriage return
\t   U+0009 horizontal tab
\v   U+000B vertical tab
\\   U+005C backslash
\'   U+0027 single quote  (valid escape only within rune literals)
\"   U+0022 double quote  (valid escape only within string literals)
</pre>

<p>
All other sequences starting with a backslash are illegal inside rune literals.
</p>
<pre class="ebnf">

	os.Exit(1)
}

// expectText is like Error but adds "got XXX" where XXX is a quoted representation of the most recent token.
func (in *Input) expectText(args ...interface{}) {
	in.Error(append(args, "; got", strconv.Quote(in.Stack.Text()))...)
}

// enabled reports whether the input is enabled by an ifdef, or is at the top level.
func (in *Input) enabled() bool {
	return len(in.ifdefStack) == 0 || in.ifdefStack[len(in.ifdefStack)-1]
}

	{"TrimLeft", "abba", "b", "abba"},
	{"TrimRight", "abba", "a", "abb"},
	{"TrimRight", "abba", "b", "abba"},
	{"Trim", "<tag>", "<>", "tag"},
	{"Trim", "* listitem", " *", "listitem"},
	{"Trim", `"quote"`, `"`, "quote"},
	{"Trim", "\u2C6F\u2C6F\u0250\u0250\u2C6F\u2C6F", "\u2C6F", "\u0250\u0250"},
	{"Trim", "\x80test\xff", "\xff", "test"},
	{"Trim", " Ġ ", " ", "Ġ"},
	{"Trim", " Ġİ0", "0 ", "Ġİ"},
	//empty string tests

\f   U+000C form feed
\n   U+000A line feed or newline
\r   U+000D carriage return
\t   U+0009 horizontal tab
\v   U+000B vertical tab
\\   U+005C backslash
\'   U+0027 single quote  (valid escape only within rune literals)
\"   U+0022 double quote  (valid escape only within string literals)
</pre>

<p>
An unrecognized character following a backslash in a rune literal is illegal.
</p>

<pre class="ebnf">

pkg strconv, func ParseFloat(string, int) (float64, error)
pkg strconv, func ParseInt(string, int, int) (int64, error)
pkg strconv, func ParseUint(string, int, int) (uint64, error)
pkg strconv, func Quote(string) string
pkg strconv, func QuoteRune(int32) string
pkg strconv, func QuoteRuneToASCII(int32) string
pkg strconv, func QuoteToASCII(string) string
pkg strconv, func Unquote(string) (string, error)