dtoc (2) --- convert double precision value to ASCII string  02/25/82


            _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

                 integer function dtoc (val, out, w, d)
                 long_real val
                 character out (ARB)
                 integer w, d

                 Library:  vswtlb (standard Subsystem library)


            _F_u_n_c_t_i_o_n

                 'Dtoc' converts the double precision floating point value in
                 'val'  to  a  character  string in 'out'.  The length of the
                 string is returned as the value of 'dtoc'.

                 The values of 'w' and 'd' control the  format  of  the  con-
                 verted  string.  Generally speaking, 'd' controls the number
                 of  decimal  positions  or  significant  digits,   and   'w'
                 specifies  the  maximum  length of the field.  The following
                 table explains the operation of 'dtoc'  for  different  com-
                 binations  of  'w'  and 'd'.  (Fortran and Basic programmers
                 take note:   d>12  corresponds  to  Basic  output,  12>=d>=0
                 corresponds  to Fortran 'F' format, and 0>d>=-12 corresponds
                 to Fortran 'E' format)

                 _'_d_'        _'_w_'    _R_e_s_u_l_t

                 d>12       w>16   If the value is in the range  1e7>v>=1e-2,
                                   it  is  converted into a BASIC-like fixed-
                                   point with no trailing  zeroes  after  the
                                   decimal point.  Otherwise, it is converted
                                   into  a BASIC-like exponential format with
                                   no  trailing  zeroes  after  the   decimal
                                   point.

                            w<=16  An error is returned.

                 12>=d>=0   -      If  possible,  the value is converted to a
                                   fixed-point  format  with  'd'   positions
                                   after the decimal point.  Otherwise, it is
                                   converted to an exponential format with as
                                   many  significant  digits as possible.  If
                                   'w' is less than 8, an exponential conver-
                                   sion is not possible and an error will  be
                                   returned.

                 0>d>-12    w>d+6  The  number is converted to an exponential
                                   format with 'd' significant digits.

                            w<=d+6 An error is returned.

                 To return an error, 'dtoc' places a string consisting  of  a
                 single question mark in 'out'.

                 It  should  be  noted  that 'w' is roughly equivalent to the


            dtoc (2)                      - 1 -                      dtoc (2)




            dtoc (2) --- convert double precision value to ASCII string  02/25/82


                 'size' parameter in other conversion routines such as 'itoc'
                 and 'ltoc'; 'w' specifies the maximum number of digits  that
                 may  be  produced.   Thus,  the maximum number of characters
                 returned in 'out' will never exceed 'w + 1'.


            _I_m_p_l_e_m_e_n_t_a_t_i_o_n

                 'Dtoc' first scales the number into the range 1 > v  >=  .1.
                 It  then  determines the format in which the number is to be
                 printed and rounds the value to the proper number of digits.
                 The digits are then extracted in  character  form.   One  of
                 several  conversion  routines  is  then  entered to take the
                 extracted  digits  and  add  decimal  points,   signs,   and
                 exponents as required by the 'd' and 'w' specifications.


            _A_r_g_u_m_e_n_t_s _M_o_d_i_f_i_e_d

                 out


            _C_a_l_l_s

                 itoc


            _B_u_g_s

                 Has  been thoroughly debugged, but has not stood the test of
                      time.


            _S_e_e _A_l_s_o

                 ctod (2), other conversion routines  ('cto?*'  and  '?*toc')
                 (2)





















            dtoc (2)                      - 2 -                      dtoc (2)