SpiceBoolean vzero_c ( ConstSpiceDouble v[3] )
Indicate whether a 3-vector is the zero vector.
None.
MATH
VECTOR
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.
v is a vector in 3-space.
The function returns the value SPICETRUE if and only if v is the
zero vector.
None.
Error free.
None.
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.
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 )
.
.
.
}
None.
None.
N.J. Bachman (JPL)
I.M. Underwood (JPL)
-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)
test whether a 3-dimensional vector is the zero vector
Link to routine vzero_c source file vzero_c.c
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