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Diffstat (limited to 'math/s_csqrt.c')
| -rw-r--r-- | math/s_csqrt.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/math/s_csqrt.c b/math/s_csqrt.c new file mode 100644 index 0000000000..04ed410a16 --- /dev/null +++ b/math/s_csqrt.c @@ -0,0 +1,114 @@ +/* Complex square root of double value. + Copyright (C) 1997, 1998, 2005 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Based on an algorithm by Stephen L. Moshier <moshier@world.std.com>. + Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <complex.h> +#include <math.h> + +#include "math_private.h" + + +__complex__ double +__csqrt (__complex__ double x) +{ + __complex__ double res; + int rcls = fpclassify (__real__ x); + int icls = fpclassify (__imag__ x); + + if (rcls <= FP_INFINITE || icls <= FP_INFINITE) + { + if (icls == FP_INFINITE) + { + __real__ res = HUGE_VAL; + __imag__ res = __imag__ x; + } + else if (rcls == FP_INFINITE) + { + if (__real__ x < 0.0) + { + __real__ res = icls == FP_NAN ? __nan ("") : 0; + __imag__ res = __copysign (HUGE_VAL, __imag__ x); + } + else + { + __real__ res = __real__ x; + __imag__ res = (icls == FP_NAN + ? __nan ("") : __copysign (0.0, __imag__ x)); + } + } + else + { + __real__ res = __nan (""); + __imag__ res = __nan (""); + } + } + else + { + if (icls == FP_ZERO) + { + if (__real__ x < 0.0) + { + __real__ res = 0.0; + __imag__ res = __copysign (__ieee754_sqrt (-__real__ x), + __imag__ x); + } + else + { + __real__ res = fabs (__ieee754_sqrt (__real__ x)); + __imag__ res = __copysign (0.0, __imag__ x); + } + } + else if (rcls == FP_ZERO) + { + double r = __ieee754_sqrt (0.5 * fabs (__imag__ x)); + + __real__ res = r; + __imag__ res = __copysign (r, __imag__ x); + } + else + { + double d, r, s; + + d = __ieee754_hypot (__real__ x, __imag__ x); + /* Use the identity 2 Re res Im res = Im x + to avoid cancellation error in d +/- Re x. */ + if (__real__ x > 0) + { + r = __ieee754_sqrt (0.5 * d + 0.5 * __real__ x); + s = (0.5 * __imag__ x) / r; + } + else + { + s = __ieee754_sqrt (0.5 * d - 0.5 * __real__ x); + r = fabs ((0.5 * __imag__ x) / s); + } + + __real__ res = r; + __imag__ res = __copysign (s, __imag__ x); + } + } + + return res; +} +weak_alias (__csqrt, csqrt) +#ifdef NO_LONG_DOUBLE +strong_alias (__csqrt, __csqrtl) +weak_alias (__csqrt, csqrtl) +#endif |