/src/vzerog.c

https://github.com/mattbornski/spice · C · 193 lines · 16 code · 64 blank · 113 comment · 3 complexity · c3ff68b90ea1e762caf00e75ccf3246a MD5 · raw file 

    

  1. /* vzerog.f -- translated by f2c (version 19980913).
    2. 

  2.    You must link the resulting object file with the libraries:
    3. 

  3. 	-lf2c -lm   (in that order)
    4. 

  4. */
    5. 

  5. 

  6. #include "f2c.h"
    7. 

  7. 

  8. /* $Procedure  VZEROG ( Is a vector the zero vector?---general dim. ) */
    9. 

  9. logical vzerog_(doublereal *v, integer *ndim)
    10. 

  10. {
    11. 

  11.     /* System generated locals */
    12. 

  12.     integer i__1;
    13. 

  13.     logical ret_val;
    14. 

  14. 

  15.     /* Local variables */
    16. 

  16.     integer i__;
    17. 

  17. 

  18. /* $ Abstract */
    19. 

  19. 

  20. /*     Indicate whether a general-dimensional vector is the zero vector. */
    21. 

  21. 

  22. /* $ Disclaimer */
    23. 

  23. 

  24. /*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
    25. 

  25. /*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
    26. 

  26. /*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
    27. 

  27. /*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
    28. 

  28. /*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
    29. 

  29. /*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
    30. 

  30. /*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
    31. 

  31. /*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
    32. 

  32. /*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
    33. 

  33. /*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
    34. 

  34. 

  35. /*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
    36. 

  36. /*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
    37. 

  37. /*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
    38. 

  38. /*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
    39. 

  39. /*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
    40. 

  40. /*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
    41. 

  41. 

  42. /*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
    43. 

  43. /*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
    44. 

  44. /*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
    45. 

  45. /*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
    46. 

  46. 

  47. /* $ Required_Reading */
    48. 

  48. 

  49. /*     None. */
    50. 

  50. 

  51. /* $ Keywords */
    52. 

  52. 

  53. /*     MATH */
    54. 

  54. /*     VECTOR */
    55. 

  55. 

  56. /* $ Declarations */
    57. 

  57. /* $ Brief_I/O */
    58. 

  58. 

  59. /*     Variable  I/O  Description */
    60. 

  60. /*     --------  ---  -------------------------------------------------- */
    61. 

  61. /*     V          I   Vector to be tested. */
    62. 

  62. /*     NDIM       I   Dimension of V. */
    63. 

  63. 

  64. /*     The function returns the value .TRUE. if and only if V is the */
    65. 

  65. /*     zero vector. */
    66. 

  66. 

  67. /* $ Detailed_Input */
    68. 

  68. 

  69. /*     V, */
    70. 

  70. /*     NDIM           are, respectively, a vector and its dimension. */
    71. 

  71. 

  72. /* $ Detailed_Output */
    73. 

  73. 

  74. /*     The function returns the value .TRUE. if and only if V is the */
    75. 

  75. /*     zero vector. */
    76. 

  76. 

  77. /* $ Parameters */
    78. 

  78. 

  79. /*     None. */
    80. 

  80. 

  81. /* $ Exceptions */
    82. 

  82. 

  83. /*     Error free. */
    84. 

  84. 

  85. /*     1)   When NDIM is non-positive, this function returns the value */
    86. 

  86. /*          .FALSE.  (A vector of non-positive dimension cannot be the */
    87. 

  87. /*          zero vector.) */
    88. 

  88. 

  89. /* $ Files */
    90. 

  90. 

  91. /*     None. */
    92. 

  92. 

  93. /* $ Particulars */
    94. 

  94. 

  95. /*     This function has the same truth value as the logical expression */
    96. 

  96. 

  97. /*        VNORMG ( V, NDIM )  .EQ.  0.D0 */
    98. 

  98. 

  99. /*     Replacing the above expression by */
    100. 

  100. 

  101. /*        VZEROG ( V, NDIM ) */
    102. 

  102. 

  103. /*     has several advantages:  the latter expresses the test more */
    104. 

  104. /*     clearly, looks better, and doesn't go through the work of scaling, */
    105. 

  105. /*     squaring, taking a square root, and re-scaling (all of which */
    106. 

  106. /*     VNORMG must do) just to find out that a vector is non-zero. */
    107. 

  107. 

  108. /*     A related function is VZERO, which accepts three-dimensional */
    109. 

  109. /*     vectors. */
    110. 

  110. 

  111. /* $ Examples */
    112. 

  112. 

  113. /*     1)  When testing whether a vector is the zero vector, one */
    114. 

  114. /*         normally constructs tests like */
    115. 

  115. 

  116. /*            IF (  VNORMG ( V, NDIM )  .EQ.  0.D0  ) THEN */
    117. 

  117. /*                        . */
    118. 

  118. /*                        . */
    119. 

  119. /*                        . */
    120. 

  120. 

  121. /*         These can be replaced with the code */
    122. 

  122. 

  123. /*            IF (  VZEROG ( V, NDIM )  ) THEN */
    124. 

  124. /*                        . */
    125. 

  125. /*                        . */
    126. 

  126. /*                        . */
    127. 

  127. 

  128. /*     2)  Make sure that a `unit' quaternion is non-zero before */
    129. 

  129. /*         converting it to a rotation matrix. */
    130. 

  130. 

  131. /*            IF (  VZEROG ( Q, 4 )  ) THEN */
    132. 

  132. 

  133. /*               [ handle error ] */
    134. 

  134. 

  135. /*            ELSE */
    136. 

  136. 

  137. /*               CALL VHATG ( Q, 4, Q ) */
    138. 

  138. /*               CALL Q2M   ( Q, M ) */
    139. 

  139. /*                        . */
    140. 

  140. /*                        . */
    141. 

  141. /*                        . */
    142. 

  142. 

  143. /* $ Restrictions */
    144. 

  144. 

  145. /*     None. */
    146. 

  146. 

  147. /* $ Literature_References */
    148. 

  148. 

  149. /*     None. */
    150. 

  150. 

  151. /* $ Author_and_Institution */
    152. 

  152. 

  153. /*     N.J. Bachman   (JPL) */
    154. 

  154. /*     I.M. Underwood (JPL) */
    155. 

  155. 

  156. /* $ Version */
    157. 

  157. 

  158. /* -    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT) */
    159. 

  159. 

  160. /*        Comment section for permuted index source lines was added */
    161. 

  161. /*        following the header. */
    162. 

  162. 

  163. /* -    SPICELIB Version 1.0.0, 18-JUL-1990 (NJB) (IMU) */
    164. 

  164. 

  165. /* -& */
    166. 

  166. /* $ Index_Entries */
    167. 

  167. 

  168. /*     test whether an n-dimensional vector is the zero vector */
    169. 

  169. 

  170. /* -& */
    171. 

  171. 

  172. /*     Local variables */
    173. 

  173. 

  174. 

  175. /*     Leave as soon as we find a non-zero component.  If we get through */
    176. 

  176. /*     the loop, we have a zero vector, as long as the vector's dimension */
    177. 

  177. /*     is valid. */
    178. 

  178. 

  179.     i__1 = *ndim;
    180. 

  180.     for (i__ = 1; i__ <= i__1; ++i__) {
    181. 

  181. 	if (v[i__ - 1] != 0.) {
    182. 

  182. 	    ret_val = FALSE_;
    183. 

  183. 	    return ret_val;
    184. 

  184. 	}
    185. 

  185.     }
    186. 

  186. 

  187. /*     We have a zero vector if and only if the vector's dimension is at */
    188. 

  188. /*     least 1. */
    189. 

  189. 

  190.     ret_val = *ndim >= 1;
    191. 

  191.     return ret_val;
    192. 

  192. } /* vzerog_ */
    193.