complex function ccot (z) c march 1979 edition. w. fullerton, c3, los alamos scientific lab. complex z external r1mach c 1 sqrt, tanh data eps, xmax, ylarge, ybig, rmin, ymin / 5*0.0, 1.5 / c if (eps.ne.0.0) go to 10 eps = r1mach(4) xmax = 1.0/eps ylarge = -0.5*alog(0.5*r1mach(3)) ybig = -0.5*alog(0.5*sqrt(r1mach(3))) rmin = exp (amax1(alog(r1mach(1)), -alog(r1mach(2))) + 0.01) c 10 x = real (z) y = aimag (z) if (abs(y).gt.ylarge) go to 30 c x2 = 2.0*x y2 = 2.0*y if (abs(x2).gt.xmax) go to 20 if (cabs(z).lt.rmin) call seteru (55hccot cabs(z) is zero or so 1 small that ccot overflows, 55, 5, 2) c call entsrc (irold, 1) sn2x = sin(x2) call erroff den = cosh(y2) - cos(x2) call erroff call entsrc (irold2, irold) c if (den.lt.x*x2*eps*eps) call seteru (74hccot cot is nearly sin 1gular, x is near a multiple of pi and y is near 0, 74, 3, 2) if (den.lt.x*x2*eps .and. abs(x).gt.0.5) call seteru (65hccot a 1nswer is lt half precision, x is near pi and y is near 0, 65, 1,1) c ccot = cmplx (sn2x/den, -sinh(y2)/den) return c 20 if (abs(y).lt.ymin) call seteru (75hccot answer would have no p 1recision, abs(x) is very big and abs(y) small, 75, 4, 2) if (abs(y).lt.ybig) call seteru (69hccot answer lt half precisi 1on, abs(x) is very big and abs(y) small, 69, 2, 1) c ccot = cmplx (0.0, 1.0/tanh(y2)) return c 30 ccot = cmplx (0.0, sign (1.0, y)) return c end