strip Function

    pure function strip(str, chars) result(newstr)

    character(len=*),intent(in) :: str  !! original string
    character(len=*),intent(in),optional :: chars !! characters to strip
    character(len=:),allocatable :: newstr !! new string

    integer :: i !! counter
    integer :: n !! length of str
    integer :: idx !! for using scan
    integer :: start_idx, end_idx  !! substring to keep

    if (present(chars)) then
        if (chars /= '') then
            ! have to step through manually from beginning and end
            n = len(str)
            start_idx = 1
            end_idx = n
            ! forward search
            do i = 1, n
                idx = scan(str(i:i), chars)
                if (idx > 0) then
                    start_idx = start_idx + 1
                else
                    exit
                end if
            end do
            ! backward search
            do i = n, 1, -1
                idx = scan(str(i:i), chars)
                if (idx > 0) then
                    end_idx = end_idx - 1
                else
                    exit
                end if
            end do
            if (end_idx <= start_idx) then
                newstr = ''  ! all stripped
            else
                newstr = str(start_idx:end_idx)  ! return substring
            end if
            return ! done
        end if
    end if

    ! in this case assuming it's a space, so use intrinsic functions
    newstr = trim(adjustl(str))

    end function strip