#include "cdflib.h"
double gam1(double *a)
/*
     ------------------------------------------------------------------
     COMPUTATION OF 1/GAMMA(A+1) - 1  FOR -0.5 .LE. A .LE. 1.5
     ------------------------------------------------------------------
*/
{
static double s1 = .273076135303957e+00;
static double s2 = .559398236957378e-01;
static double p[7] = {
    .577215664901533e+00,-.409078193005776e+00,-.230975380857675e+00,
    .597275330452234e-01,.766968181649490e-02,-.514889771323592e-02,
    .589597428611429e-03
};
static double q[5] = {
    .100000000000000e+01,.427569613095214e+00,.158451672430138e+00,
    .261132021441447e-01,.423244297896961e-02
};
static double r[9] = {
    -.422784335098468e+00,-.771330383816272e+00,-.244757765222226e+00,
    .118378989872749e+00,.930357293360349e-03,-.118290993445146e-01,
    .223047661158249e-02,.266505979058923e-03,-.132674909766242e-03
};
static double gam1,bot,d,t,top,w,T1;
/*
     ..
     .. Executable Statements ..
*/
    t = *a;
    d = *a-0.5e0;
    if(d > 0.0e0) t = d-0.5e0;
    T1 = t;
    if(T1 < 0) goto S40;
    else if(T1 == 0) goto S10;
    else  goto S20;
S10:
    gam1 = 0.0e0;
    return gam1;
S20:
    top = (((((p[6]*t+p[5])*t+p[4])*t+p[3])*t+p[2])*t+p[1])*t+p[0];
    bot = (((q[4]*t+q[3])*t+q[2])*t+q[1])*t+1.0e0;
    w = top/bot;
    if(d > 0.0e0) goto S30;
    gam1 = *a*w;
    return gam1;
S30:
    gam1 = t/ *a*(w-0.5e0-0.5e0);
    return gam1;
S40:
    top = (((((((r[8]*t+r[7])*t+r[6])*t+r[5])*t+r[4])*t+r[3])*t+r[2])*t+r[1])*t+
      r[0];
    bot = (s2*t+s1)*t+1.0e0;
    w = top/bot;
    if(d > 0.0e0) goto S50;
    gam1 = *a*(w+0.5e0+0.5e0);
    return gam1;
S50:
    gam1 = t*w/ *a;
    return gam1;
} /* END */