dlog$m (2) --- calculate double precision logarithm to the base 10  04/27/83


          | _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

          |      longreal function dlog$m (x)
          |      longreal x

          |      Library: vswtmath (Subsystem mathematical library)


          | _F_u_n_c_t_i_o_n

          |      This  function  implements  the  common  logarithm (base 10)
          |      function.  Arguments should be greater than zero.  The  con-
          |      dition  SWT_MATH_ERROR$ is signalled if there is an argument
          |      error.  An on-unit can be  established  to  deal  with  this
          |      error; the SWT Math Library contains a default handler named
          |      'err$m'  which the user may utilize.  If an invalid argument
          |      is supplied to the function the default return is the log of
          |      the absolute value of the argument, or zero in the case of a
          |      zero argument.


          | _I_m_p_l_e_m_e_n_t_a_t_i_o_n

          |      The algorithm involved uses a minimax rational approximation
          |      on a reduction of the argument.  All  positive  inputs  will
          |      return  a  valid  result.   It is adapted from the algorithm
          |      given  in  the  book  _S_o_f_t_w_a_r_e  _M_a_n_u_a_l  _f_o_r  _t_h_e  _E_l_e_m_e_n_t_a_r_y
          |      _F_u_n_c_t_i_o_n_s by William Waite and William Cody, Jr.  (Prentice-
          |      Hall, 1980).


          | _C_a_l_l_s

          |      Primos signl$


          | _S_e_e _A_l_s_o

          |      err$m (2), log$m (2),
          |      _S_W_T _M_a_t_h _L_i_b_r_a_r_y _U_s_e_r_'_s _G_u_i_d_e


















            dlog$m (2)                    - 1 -                    dlog$m (2)