chfmt Subroutine

        subroutine chfmt(d, e, f)
            !< Change format specifier for reals
            !-----------------------------------------------------------
            ! Change format specifier for reals
            !
            ! Inputs:
            !   d -> integer, optional
            !       digits after decimal
            !   e -> integer, optional
            !       digits in exponent
            !       When this is set to -1, the exponent part is dropped
            !   f -> character, optional
            !       form
            !       Valid options: 'F' (decimal), 'E' (exponential),
            !           'S' (scientific), 'N' (engineering)
            !       If 'F' is specified, then the value for e is 
            !           overridden and set to -1.
            !
            ! If no arguments are passed, this function resets all the 
            ! parameters to their default values (as provided in the 
            ! following table. Else, only the passed arguments will be
            ! updated (the others will be left unchanged). 
            !
            ! This function is sticky; a format once set will continue 
            ! to apply till either it is changed or the program ends.
            !
            ! Default values: 
            !   d (digits after decimal) --> 6
            !   e (digits in exponent) --> -1
            !   f (form) --> 'F' (decimal)
            !
            !TODO: Add support for width also?
            !http://www.cs.mtu.edu/~shene/COURSES/cs201/NOTES/chap05/format.html
            !-----------------------------------------------------------

            implicit none
            integer, intent(in), optional :: d
            integer, intent(in), optional :: e
            character, intent(in), optional :: f

            if (.not. (present(d) .or. present(e) .or. present(f))) then
                dec_ = 6
                exp_ = 0
                form_ = 'F'
            else
                if (present(d)) dec_ = d
                if (present(e)) exp_ = e
                if (present(f)) then
                    if (.not. (f .eq. 'F' .or. f .eq. 'E' .or. &
                            f .eq. 'S' .or. f .eq. 'N')) then
                        print *, 'Error: Unknown kind specified.'
                        stop
                    end if
                    form_ = f
                    if (form_ .eq. 'F') exp_ = -1
                end if
            end if

        end subroutine chfmt