tanh$m (2) --- calculate hyperbolic tangent              04/27/83


          | _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

          |      longreal function tanh$m (x)
          |      real x

          |      Library: vswtmath (Subsystem mathematical library)


          | _F_u_n_c_t_i_o_n

          |      This  routine  calculates  the  hyperbolic  tangent  of  its
          |      argument, defined as tanh(x) = 2/[exp(2x) + 1].   The  func-
          |      tion  never  signals  an error and returns valid results for
          |      all inputs.

          |      This function is intended to serve  as  a  single  precision
          |      function although it returns a double precision result.  The
          |      function  has been coded so that any value returned will not
          |      overflow or underflow  a  single  precision  floating  point
          |      value.   The  double  precision register overlaps the single
          |      precision register so it is possible to declare and use this
          |      function as simply a "real" function.


          | _I_m_p_l_e_m_e_n_t_a_t_i_o_n

          |      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

          |      dexp$m


          | _S_e_e _A_l_s_o

          |      dexp$m (2), dtnh$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


















            tanh$m (2)                    - 1 -                    tanh$m (2)