/lib/libm/src/s_clog.c

https://github.com/avsm/src · C · 85 lines · 22 code · 6 blank · 57 comment · 1 complexity · 95aacec35f66fc1cd6f11e046d5a2327 MD5 · raw file 

    

  1. /*	$OpenBSD: s_clog.c,v 1.2 2011/07/08 19:25:31 martynas Exp $	*/
    2. 

  2. /*
    3. 

  3.  * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
    4. 

  4.  *
    5. 

  5.  * Permission to use, copy, modify, and distribute this software for any
    6. 

  6.  * purpose with or without fee is hereby granted, provided that the above
    7. 

  7.  * copyright notice and this permission notice appear in all copies.
    8. 

  8.  *
    9. 

  9.  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    10. 

  10.  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
    11. 

  11.  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    12. 

  12.  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    13. 

  13.  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
    14. 

  14.  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    15. 

  15.  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
    16. 

  16.  */
    17. 

  17. 

  18. /* LINTLIBRARY */
    19. 

  19. 

  20. /*							clog.c
    21. 

  21.  *
    22. 

  22.  *	Complex natural logarithm
    23. 

  23.  *
    24. 

  24.  *
    25. 

  25.  *
    26. 

  26.  * SYNOPSIS:
    27. 

  27.  *
    28. 

  28.  * double complex clog();
    29. 

  29.  * double complex z, w;
    30. 

  30.  *
    31. 

  31.  * w = clog (z);
    32. 

  32.  *
    33. 

  33.  *
    34. 

  34.  *
    35. 

  35.  * DESCRIPTION:
    36. 

  36.  *
    37. 

  37.  * Returns complex logarithm to the base e (2.718...) of
    38. 

  38.  * the complex argument x.
    39. 

  39.  *
    40. 

  40.  * If z = x + iy, r = sqrt( x**2 + y**2 ),
    41. 

  41.  * then
    42. 

  42.  *       w = log(r) + i arctan(y/x).
    43. 

  43.  * 
    44. 

  44.  * The arctangent ranges from -PI to +PI.
    45. 

  45.  *
    46. 

  46.  *
    47. 

  47.  * ACCURACY:
    48. 

  48.  *
    49. 

  49.  *                      Relative error:
    50. 

  50.  * arithmetic   domain     # trials      peak         rms
    51. 

  51.  *    DEC       -10,+10      7000       8.5e-17     1.9e-17
    52. 

  52.  *    IEEE      -10,+10     30000       5.0e-15     1.1e-16
    53. 

  53.  *
    54. 

  54.  * Larger relative error can be observed for z near 1 +i0.
    55. 

  55.  * In IEEE arithmetic the peak absolute error is 5.2e-16, rms
    56. 

  56.  * absolute error 1.0e-16.
    57. 

  57.  */
    58. 

  58. 

  59. #include <sys/cdefs.h>
    60. 

  60. #include <complex.h>
    61. 

  61. #include <float.h>
    62. 

  62. #include <math.h>
    63. 

  63. 

  64. double complex
    65. 

  65. clog(double complex z)
    66. 

  66. {
    67. 

  67. 	double complex w;
    68. 

  68. 	double p, rr;
    69. 

  69. 

  70. 	/*rr = sqrt( z->r * z->r  +  z->i * z->i );*/
    71. 

  71. 	rr = cabs(z);
    72. 

  72. 	p = log(rr);
    73. 

  73. 	rr = atan2 (cimag (z), creal (z));
    74. 

  74. 	w = p + rr * I;
    75. 

  75. 	return (w);
    76. 

  76. }
    77. 

  77. 

  78. #if	LDBL_MANT_DIG == 53
    79. 

  79. #ifdef	lint
    80. 

  80. /* PROTOLIB1 */
    81. 

  81. long double complex clogl(long double complex);
    82. 

  82. #else	/* lint */
    83. 

  83. __weak_alias(clogl, clog);
    84. 

  84. #endif	/* lint */
    85. 

  85. #endif	/* LDBL_MANT_DIG == 53 */
    86.