/* log returns the natural logarithm of its floating point argument. The coefficients are #2705 from Hart & Cheney. (19.38D) It calls frexp. */ #include #include int errno; double frexp(); static double log2 = 0.693147180559945309e0; static double ln10 = 2.302585092994045684; static double sqrto2 = 0.707106781186547524e0; static double p0 = -.240139179559210510e2; static double p1 = 0.309572928215376501e2; static double p2 = -.963769093368686593e1; static double p3 = 0.421087371217979714e0; static double q0 = -.120069589779605255e2; static double q1 = 0.194809660700889731e2; static double q2 = -.891110902798312337e1; double log(arg) double arg; { double x,z, zsq, temp; int exp; if(arg <= 0.) { errno = EDOM; return(-HUGE); } x = frexp(arg,&exp); while(x<0.5) { x = x*2; exp = exp-1; } if(x