vzero_c |
Table of contents
Procedurevzero_c ( Is a vector the zero vector? ) SpiceBoolean vzero_c ( ConstSpiceDouble v[3] ) AbstractIndicate whether a 3-vector is the zero vector. Required_ReadingNone. KeywordsMATH VECTOR Brief_I/OVARIABLE 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_Inputv is a vector in 3-space. Detailed_OutputThe function returns the value SPICETRUE if and only if `v' is the zero vector. ParametersNone. ExceptionsError free. FilesNone. ParticularsThis 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_c, which accepts vectors of arbitrary dimension. Examples1) 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_c: if ( vzero_c ( NORMAL ) ) { [ handle error ] } else { pnv2pl_c ( POINT, NORMAL, PLANE ) . . . } RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) I.M. Underwood (JPL) E.D. Wright (JPL) Version-CSPICE Version 1.1.1, 05-JUL-2021 (JDR) Edited the header to comply with NAIF standard. -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) (IMU) Index_Entriestest whether a 3-dimensional vector is the zero vector |
Fri Dec 31 18:41:15 2021