Return to exp.c CVS log

Up to [CSRG BSD Unix] / 43BSD / contrib / icon / rt

Annotation of 43BSD/contrib/icon/rt/exp.c, revision 1.1

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

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.