.
        In the event that there is no such named sub-expression then returns zero.
      </p>
<p>
        The template overloads of this function, allow the string and/or character
        type to be different from the character type of the underlying sequence and/or
        regular expression: in this case the characters will be widened to the underlying
        character type of the original regular expression. A compiler error will
        occur if the argument passes a wider character type than the un