func flipCaseSingle(s string) (string, error) {
	rr := []rune(s)
	for i, r := range rr {
		if unicode.IsLetter(r) { // look for a letter  to flip
			if unicode.IsUpper(r) {
				rr[i] = unicode.ToLower(r)
				return string(rr), nil
			}
			rr[i] = unicode.ToUpper(r)
			return string(rr), nil
		}

	}
	return s, fmt.Errorf("could not case flip string %s", s)
}
// flipCaseSingle flips the case ( lower<->upper ) of a single char from the string s
// If the string cannot be flipped, the original string value and an error are returned
flipCaseSingle flips the case ( lower<->upper ) of a single char from the string s
If the string cannot be flipped, the original string value and an error are returned
// flipCaseSingle flips the case ( lower< - > upper ) of a single char from the string s // If the string cannot be flipped the original string value and an error are returned
func flipCaseSingle(s string) (string, error) {
	rr := []rune(s)
	for i, r := range rr {
		if unicode.IsLetter(r) { 
			if unicode.IsUpper(r) {
				rr[i] = unicode.ToLower(r)
				return string(rr), nil
			}
			rr[i] = unicode.ToUpper(r)
			return string(rr), nil
		}
	}
	return s, fmt.Errorf("could not case flip string %s", s)
}
func flipCaseSingle ( s string ) ( string , error ) { rr := [ ] rune ( s ) for i , r := range rr { if unicode . IsLetter ( r ) { if unicode . IsUpper ( r ) { rr [ i ] = unicode . ToLower ( r ) return string ( rr ) , nil } rr [ i ] = unicode . ToUpper ( r ) return string ( rr ) , nil } } return s , fmt . Errorf ( " " , s ) }
flipCaseSingle flips the case ( lower<->upper ) of a single char from the string s
If the string cannot be flipped, the original string value and an error are returned
flipCaseSingle flips the case ( lower< - > upper ) of a single char from the string s If the string cannot be flipped the original string value and an error are returned
// look for a letter  to flip