1 | /* Return arc hyperbole cosine for __float128 value. |
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2 | Copyright (C) 1997, 1998, 2006 Free Software Foundation, Inc. |

3 | This file is part of the GNU C Library. |

4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. |

5 | |

6 | The GNU C Library is free software; you can redistribute it and/or |

7 | modify it under the terms of the GNU Lesser General Public |

8 | License as published by the Free Software Foundation; either |

9 | version 2.1 of the License, or (at your option) any later version. |

10 | |

11 | The GNU C Library is distributed in the hope that it will be useful, |

12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |

13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |

14 | Lesser General Public License for more details. |

15 | |

16 | You should have received a copy of the GNU Lesser General Public |

17 | License along with the GNU C Library; if not, write to the Free |

18 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |

19 | 02111-1307 USA. */ |

20 | |

21 | #include "quadmath-imp.h" |

22 | |

23 | |

24 | __complex128 |

25 | cacoshq (__complex128 x) |

26 | { |

27 | __complex128 res; |

28 | int rcls = fpclassifyq (__real__ x); |

29 | int icls = fpclassifyq (__imag__ x); |

30 | |

31 | if (rcls <= QUADFP_INFINITE || icls <= QUADFP_INFINITE) |

32 | { |

33 | if (icls == QUADFP_INFINITE) |

34 | { |

35 | __real__ res = HUGE_VALQ; |

36 | |

37 | if (rcls == QUADFP_NAN) |

38 | __imag__ res = nanq (""); |

39 | else |

40 | __imag__ res = copysignq ((rcls == QUADFP_INFINITE |

41 | ? (__real__ x < 0.0 |

42 | ? M_PIq - M_PI_4q : M_PI_4q) |

43 | : M_PI_2q), __imag__ x); |

44 | } |

45 | else if (rcls == QUADFP_INFINITE) |

46 | { |

47 | __real__ res = HUGE_VALQ; |

48 | |

49 | if (icls >= QUADFP_ZERO) |

50 | __imag__ res = copysignq (signbitq (__real__ x) ? M_PIq : 0.0, |

51 | __imag__ x); |

52 | else |

53 | __imag__ res = nanq (""); |

54 | } |

55 | else |

56 | { |

57 | __real__ res = nanq (""); |

58 | __imag__ res = nanq (""); |

59 | } |

60 | } |

61 | else if (rcls == QUADFP_ZERO && icls == QUADFP_ZERO) |

62 | { |

63 | __real__ res = 0.0; |

64 | __imag__ res = copysignq (M_PI_2q, __imag__ x); |

65 | } |

66 | /* The factor 16 is just a guess. */ |

67 | else if (16.0Q * fabsq (__imag__ x) < fabsq (__real__ x)) |

68 | { |

69 | /* Kahan's formula which avoid cancellation through subtraction in |

70 | some cases. */ |

71 | res = 2.0Q * clogq (csqrtq ((x + 1.0Q) / 2.0Q) |

72 | + csqrtq ((x - 1.0Q) / 2.0Q)); |

73 | if (signbitq (__real__ res)) |

74 | __real__ res = 0.0Q; |

75 | } |

76 | else |

77 | { |

78 | __complex128 y; |

79 | |

80 | __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0; |

81 | __imag__ y = 2.0 * __real__ x * __imag__ x; |

82 | |

83 | y = csqrtq (y); |

84 | |

85 | if (signbitq (x)) |

86 | y = -y; |

87 | |

88 | __real__ y += __real__ x; |

89 | __imag__ y += __imag__ x; |

90 | |

91 | res = clogq (y); |

92 | } |

93 | |

94 | return res; |

95 | } |

96 |