| /** |
| * This file has no copyright assigned and is placed in the Public Domain. |
| * This file is part of the w64 mingw-runtime package. |
| * No warranty is given; refer to the file DISCLAIMER.PD within this package. |
| */ |
| /* catan.c */ |
| |
| /* |
| Contributed by Danny Smith |
| 2003-10-17 |
| |
| FIXME: This needs some serious numerical analysis. |
| */ |
| |
| #include <math.h> |
| #include <complex.h> |
| #include <errno.h> |
| |
| /* catan (z) = -I/2 * clog ((I + z) / (I - z)) */ |
| |
| double complex |
| catan (double complex Z) |
| { |
| double complex Res; |
| double complex Tmp; |
| double x = __real__ Z; |
| double y = __imag__ Z; |
| |
| if ( x == 0.0 && (1.0 - fabs (y)) == 0.0) |
| { |
| errno = ERANGE; |
| __real__ Res = HUGE_VAL; |
| __imag__ Res = HUGE_VAL; |
| } |
| else if (isinf (_hypot (x, y))) |
| { |
| __real__ Res = (x > 0 ? M_PI_2 : -M_PI_2); |
| __imag__ Res = 0.0; |
| } |
| else |
| { |
| __real__ Tmp = - x; |
| __imag__ Tmp = 1.0 - y; |
| |
| __real__ Res = x; |
| __imag__ Res = y + 1.0; |
| |
| Tmp = clog (Res/Tmp); |
| __real__ Res = - 0.5 * __imag__ Tmp; |
| __imag__ Res = 0.5 * __real__ Tmp; |
| } |
| |
| return Res; |
| } |