ctan.f
1.35 KB
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complex function ctan (z)
c march 1979 edition. w. fullerton, c3, los alamos scientific lab.
complex z
external r1mach
data eps, xmax, ylarge, ybig, ymin / 4*0.0, 1.50 /
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)))
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
c
call entsrc (irold, 1)
sn2x = sin(x2)
call erroff
den = cos(x2) + cosh(y2)
call erroff
call entsrc (irold2, irold)
c
if (den.lt.x*x2*eps*eps) call seteru ( 72hctan tan is nearly si
1ngular, x is near pi/2 or 3*pi/2 and y is near 0, 72, 3, 2)
if (den.lt.x*x2*eps) call seteru (74hctan answer lt half precis
1ion, x is near pi/2 or 3*pi/2 and y is near 0, 74, 1, 1)
c
ctan = cmplx (sn2x/den, sinh(y2)/den)
return
c
20 if (abs(y).lt.ymin) call seteru (75hctan 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 (69hctan answer lt half precisi
1on, abs(x) is very big and abs(y) small, 69, 2, 1)
c
ctan = cmplx (0.0, tanh(y2))
return
c
30 ctan = cmplx (0.0, -sign(1.0, y))
return
c
end