functionis_rulepureprivate

pure logical function is_rule(line)
    character(len=*), intent(in) :: line    !! the line
    integer :: first, k, marks
    character :: c

    is_rule = .false.
    first = verify(line, ' ')
    if (first == 0 .or. first > 4) return
    c = line(first:first)
    if (c /= '-' .and. c /= '_' .and. c /= '*') return
    marks = 0
    do k = first, len(line)
        if (line(k:k) == c) then
            marks = marks + 1
        else if (line(k:k) /= ' ') then
            return
        end if
    end do
    is_rule = marks >= 3
end function is_rule