// like an IP address.
		isNotNumber := false
		for i := range len(piece) {
			switch {
			case (piece[i] >= 'a' && piece[i] <= 'z' ||
				piece[i] == '-'):
				// Found a non-digit character, so
				// this piece is not a number.
				isNotNumber = true
			case piece[i] >= '0' && piece[i] <= '9':
				// Nothing to do.
			default:
				// Found invalid character.
				return false
			}

pkg unicode, const UpperLower ideal-char
pkg unicode, const Version ideal-string
pkg unicode, func Is(*RangeTable, int32) bool
pkg unicode, func IsControl(int32) bool
pkg unicode, func IsDigit(int32) bool
pkg unicode, func IsGraphic(int32) bool
pkg unicode, func IsLetter(int32) bool
pkg unicode, func IsLower(int32) bool
pkg unicode, func IsMark(int32) bool
pkg unicode, func IsNumber(int32) bool

are in <a href="#Rune_literals">rune literals</a> (except that <code>\'</code> is illegal and
<code>\"</code> is legal), with the same restrictions.
The three-digit octal (<code>\</code><i>nnn</i>)
and two-digit hexadecimal (<code>\x</code><i>nn</i>) escapes represent individual
<i>bytes</i> of the resulting string; all other escapes represent
the (possibly multi-byte) UTF-8 encoding of individual <i>characters</i>.

wanted to produce 2n-wide T, we would do // // for i := 0; i < n; i++ { // d := bLimbs[i] // T[n+i] = addMulVVW(T[i:n+i], aLimbs, d) // } // // where d is a digit of the multiplier, T[i:n+i] is the shifted // position of the product of that digit, and T[n+i] is the final carry. // Note that T[i] isn't modified after processing the i-th digit. // // Instead of running two loops, one for Step 1 and one for Steps 2–6, // the result of Step 1 is computed during the next loop. This is // possible because...