2.9BSD - /usr/src/lib/m/exp.c

   1: /*
   2: 	exp returns the exponential function of its
   3: 	floating-point argument.
   4: 
   5: 	The coefficients are #1069 from Hart and Cheney. (22.35D)
   6: */
   7: 
   8: #include <errno.h>
   9: #include <math.h>
  10: 
  11: int errno;
  12: static double   p0  = .2080384346694663001443843411e7;
  13: static double   p1  = .3028697169744036299076048876e5;
  14: static double   p2  = .6061485330061080841615584556e2;
  15: static double   q0  = .6002720360238832528230907598e7;
  16: static double   q1  = .3277251518082914423057964422e6;
  17: static double   q2  = .1749287689093076403844945335e4;
  18: static double   log2e   = 1.4426950408889634073599247;
  19: static double   sqrt2   = 1.4142135623730950488016887;
  20: static double   maxf    = 10000;
  21: 
  22: double
  23: exp(arg)
  24: double arg;
  25: {
  26:     double fract;
  27:     double temp1, temp2, xsq;
  28:     int ent;
  29: 
  30:     if(arg == 0.)
  31:         return(1.);
  32:     if(arg < -maxf)
  33:         return(0.);
  34:     if(arg > maxf) {
  35:         errno = ERANGE;
  36:         return(HUGE);
  37:     }
  38:     arg *= log2e;
  39:     ent = floor(arg);
  40:     fract = (arg-ent) - 0.5;
  41:     xsq = fract*fract;
  42:     temp1 = ((p2*xsq+p1)*xsq+p0)*fract;
  43:     temp2 = ((1.0*xsq+q2)*xsq+q1)*xsq + q0;
  44:     return(ldexp(sqrt2*(temp2+temp1)/(temp2-temp1), ent));
  45: }

Defined functions

Defined variables