// Optional leading sign.
	l.accept("+-")
	// Is it hex?
	digits := "0123456789_"
	if l.accept("0") {
		// Note: Leading 0 does not mean octal in floats.
		if l.accept("xX") {
			digits = "0123456789abcdefABCDEF_"
		} else if l.accept("oO") {
			digits = "01234567_"
		} else if l.accept("bB") {
			digits = "01_"
		}
	}
	l.acceptRun(digits)
	if l.accept(".") {
		l.acceptRun(digits)
	}