/*

-Procedure vzero_c ( Is a vector the zero vector? )

-Abstract
 
   Indicate whether a 3-vector is the zero vector. 
 
-Disclaimer

   THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE
   CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S.
   GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE
   ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE
   PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS"
   TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY
   WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A
   PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC
   SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE
   SOFTWARE AND RELATED MATERIALS, HOWEVER USED.

   IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA
   BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT
   LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND,
   INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS,
   REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE
   REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY.

   RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF
   THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY
   CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE
   ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE.

-Required_Reading
 
   None. 
 
-Keywords
 
   MATH 
   VECTOR 
 
*/

   #include "SpiceUsr.h"
   #undef    vzero_c
   

   SpiceBoolean vzero_c ( ConstSpiceDouble v[3] ) 

/*

-Brief_I/O
 
   Variable  I/O  Description 
   --------  ---  -------------------------------------------------- 
   v          I   Vector to be tested. 
 
   The function returns the value SPICETRUE if and only if v is the 
   zero vector. 
 
-Detailed_Input
 
   v          is a vector in 3-space. 
 
-Detailed_Output
 
   The function returns the value SPICETRUE if and only if v is the 
   zero vector. 
 
-Parameters
 
   None. 
 
-Exceptions
 
   Error free. 
 
-Files
 
   None. 
 
-Particulars
 
   This function has the same truth value as the logical expression 
 
      vnorm_c ( v )  ==  0. 
 
   Replacing the above expression by 
 
      vzero_c ( v );
 
   has several advantages:  the latter expresses the test more 
   clearly, looks better, and doesn't go through the work of scaling, 
   squaring, taking a square root, and re-scaling (all of which 
   vnorm_c must do) just to find out that a vector is non-zero. 
 
   A related function is vzerog_, which accepts vectors of arbitrary 
   dimension. 
 
-Examples
 
   1)  When testing whether a vector is the zero vector, one 
       normally constructs tests like 
 
          if (  vnorm_c ( v ) ==  0.  )
             { 
                      . 
                      . 
                      . 
 
 
       These can be replaced with the code 
 
          if (  vzero_c ( v )  ) 
             {
                      . 
                      . 
                      . 
 
 
    2)  Check that a normal vector is non-zero before creating 
       a plane with PNV2PL: 
 
       if (  vzero_c ( NORMAL )  )
          {
          [ handle error ] 
          }
 
       else
          { 
          pnv2pl_ ( POINT, NORMAL, PLANE ) 
                        . 
                        . 
                        . 
          }

-Restrictions
 
   None. 
 
-Literature_References
 
   None. 
 
-Author_and_Institution
 
   N.J. Bachman   (JPL) 
   I.M. Underwood (JPL) 
 
-Version
 
   -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

      Made input vector const.  Removed #include of SpiceZfc.h.

   -CSPICE Version 1.0.0, 08-FEB-1998 (EDW)

-Index_Entries
 
   test whether a 3-dimensional vector is the zero vector 
 
-&
*/

{ /* Begin vzero_c */

   return  ( SpiceBoolean ) ( v[0] == 0. && v[1] == 0. && v[2] == 0.) ;

} /* End vzero_c */
