Procedure

     VMINUS ( Negate vector, "-V", 3 dimensions )

     SUBROUTINE VMINUS ( V1, VOUT )

Abstract

     Negate a double precision 3-dimensional vector.

Required_Reading

     None.

Keywords

     VECTOR

Declarations

     IMPLICIT NONE

     DOUBLE PRECISION  V1   ( 3 )
     DOUBLE PRECISION  VOUT ( 3 )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     V1         I   Vector to be negated.
     VOUT       O   Negated vector -V1.

Detailed_Input

     V1       is any double precision 3-dimensional vector.

Detailed_Output

     VOUT     is the negation (additive inverse) of V1. It is a
              double precision 3-dimensional vector.

Parameters

     None.

Exceptions

     Error free.

Files

     None.

Particulars

     For each value of the index I from 1 to 3, VMINUS negates V1
     by the expression:

        VOUT(I) = - V1(I)

     No error checking is performed since overflow can occur ONLY if
     the dynamic range of positive floating point numbers is not the
     same size as the dynamic range of negative floating point numbers
     AND at least one component of V1 falls outside the common range.
     The likelihood of this occurring is so small as to be of no
     concern.

Examples

     The numerical results shown for this example may differ across
     platforms. The results depend on the SPICE kernels used as
     input, the compiler and supporting libraries, and the machine
     specific arithmetic implementation.

     1) Define a set of 3-dimensional vectors and negate each of them.


        Example code begins here.


              PROGRAM VMINUS_EX1
              IMPLICIT NONE

        C
        C     Local parameters.
        C
              INTEGER               SETSIZ
              PARAMETER           ( SETSIZ = 2 )

        C
        C     Local variables.
        C
              DOUBLE PRECISION      V1   ( 3, SETSIZ )
              DOUBLE PRECISION      VOUT ( 3         )

              INTEGER               I
              INTEGER               J

        C
        C     Define a set of 3-dimensional vectors.
        C
              DATA                  V1  /  1.D0, -2.D0, 0.D0,
             .                             0.D0,  0.D0, 0.D0  /

        C
        C     Negate each vector
        C
              DO I=1, SETSIZ

                 CALL VMINUS ( V1(1,I), VOUT )

                 WRITE(*,'(A,3F6.1)') 'Input vector  : ',
             .                        ( V1(J,I), J=1,3 )
                 WRITE(*,'(A,3F6.1)') 'Negated vector: ', VOUT
                 WRITE(*,*)

              END DO

              END


        When this program was executed on a Mac/Intel/gfortran/64-bit
        platform, the output was:


        Input vector  :    1.0  -2.0   0.0
        Negated vector:   -1.0   2.0  -0.0

        Input vector  :    0.0   0.0   0.0
        Negated vector:   -0.0  -0.0  -0.0

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     W.M. Owen          (JPL)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.0.3, 02-OCT-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Added complete
        code example based on existing example.

    SPICELIB Version 1.0.2, 23-APR-2010 (NJB)

        Header correction: assertions that the output
        can overwrite the input have been removed.

    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.0.0, 31-JAN-1990 (WMO)