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//
// GENERATED FILE
//
use super::*;
use crate::SpiceContext;
use f2rust_std::*;
/// Vector projection, 3 dimensions
///
/// Compute the projection of one 3-dimensional vector onto another
/// 3-dimensional vector.
///
/// # Brief I/O
///
/// ```text
/// VARIABLE I/O DESCRIPTION
/// -------- --- --------------------------------------------------
/// A I The vector to be projected.
/// B I The vector onto which A is to be projected.
/// P O The projection of A onto B.
/// ```
///
/// # Detailed Input
///
/// ```text
/// A is a double precision, 3-dimensional vector. This
/// vector is to be projected onto the vector B.
///
/// B is a double precision, 3-dimensional vector. This
/// vector is the vector which receives the projection.
/// ```
///
/// # Detailed Output
///
/// ```text
/// P is a double precision, 3-dimensional vector containing
/// the projection of A onto B. (P is necessarily parallel
/// to B.) If B is the zero vector then P will be returned
/// as the zero vector.
/// ```
///
/// # Exceptions
///
/// ```text
/// Error free.
/// ```
///
/// # Particulars
///
/// ```text
/// Given any vectors A and B, there is a unique decomposition of
/// A as a sum V + P such that V, the dot product of V and B, is zero,
/// and the dot product of P with B is equal the product of the
/// lengths of P and B. P is called the projection of A onto B. It
/// can be expressed mathematically as
///
/// DOT(A,B)
/// -------- * B
/// DOT(B,B)
///
/// (This is not necessarily the prescription used to compute the
/// projection. It is intended only for descriptive purposes.)
/// ```
///
/// # Examples
///
/// ```text
/// 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 two sets of vectors and compute the projection of
/// each vector of the first set on the corresponding vector of
/// the second set.
///
/// Example code begins here.
///
///
/// PROGRAM VPROJ_EX1
/// IMPLICIT NONE
///
/// C
/// C Local parameters.
/// C
/// INTEGER NDIM
/// PARAMETER ( NDIM = 3 )
///
/// INTEGER SETSIZ
/// PARAMETER ( SETSIZ = 4 )
///
/// C
/// C Local variables.
/// C
/// DOUBLE PRECISION SETA ( NDIM, SETSIZ )
/// DOUBLE PRECISION SETB ( NDIM, SETSIZ )
/// DOUBLE PRECISION PVEC ( NDIM )
///
/// INTEGER I
/// INTEGER J
///
/// C
/// C Define the two vector sets.
/// C
/// DATA SETA / 6.D0, 6.D0, 6.D0,
/// . 6.D0, 6.D0, 6.D0,
/// . 6.D0, 6.D0, 0.D0,
/// . 6.D0, 0.D0, 0.D0 /
///
/// DATA SETB / 2.D0, 0.D0, 0.D0,
/// . -3.D0, 0.D0, 0.D0,
/// . 0.D0, 7.D0, 0.D0,
/// . 0.D0, 0.D0, 9.D0 /
///
/// C
/// C Calculate the projection
/// C
/// DO I=1, SETSIZ
///
/// CALL VPROJ ( SETA(1,I), SETB(1,I), PVEC )
///
/// WRITE(*,'(A,3F5.1)') 'Vector A : ',
/// . ( SETA(J,I), J=1,3 )
/// WRITE(*,'(A,3F5.1)') 'Vector B : ',
/// . ( SETB(J,I), J=1,3 )
/// WRITE(*,'(A,3F5.1)') 'Projection: ', PVEC
/// WRITE(*,*) ' '
///
/// END DO
///
/// END
///
///
/// When this program was executed on a Mac/Intel/gfortran/64-bit
/// platform, the output was:
///
///
/// Vector A : 6.0 6.0 6.0
/// Vector B : 2.0 0.0 0.0
/// Projection: 6.0 0.0 0.0
///
/// Vector A : 6.0 6.0 6.0
/// Vector B : -3.0 0.0 0.0
/// Projection: 6.0 -0.0 -0.0
///
/// Vector A : 6.0 6.0 0.0
/// Vector B : 0.0 7.0 0.0
/// Projection: 0.0 6.0 0.0
///
/// Vector A : 6.0 0.0 0.0
/// Vector B : 0.0 0.0 9.0
/// Projection: 0.0 0.0 0.0
/// ```
///
/// # Restrictions
///
/// ```text
/// 1) An implicit assumption exists that A and B are specified in
/// the same reference frame. If this is not the case, the
/// numerical result has no meaning.
/// ```
///
/// # Literature References
///
/// ```text
/// [1] G. Thomas and R. Finney, "Calculus and Analytic Geometry,"
/// 7th Edition, Addison Wesley, 1988.
/// ```
///
/// # Author and Institution
///
/// ```text
/// N.J. Bachman (JPL)
/// J. Diaz del Rio (ODC Space)
/// W.L. Taber (JPL)
/// ```
///
/// # Version
///
/// ```text
/// - SPICELIB Version 1.1.0, 26-OCT-2021 (JDR)
///
/// Added IMPLICIT NONE statement.
///
/// Edited the header to comply with NAIF standard. Added complete
/// code example. Added entry in $Restrictions section.
///
/// - SPICELIB Version 1.0.2, 23-APR-2010 (NJB)
///
/// Header correction: assertions that the output
/// can overwrite the input have been removed.
///
/// - SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)
///
/// Comment section for permuted index source lines was added
/// following the header.
///
/// - SPICELIB Version 1.0.0, 31-JAN-1990 (WLT)
/// ```
///
/// # Revisions
///
/// ```text
/// - Beta Version 1.1.0, 4-JAN-1989 (WLT)
///
/// Upgrade the routine to work with negative axis indexes. Also
/// take care of the funky way the indices (other than the input)
/// were obtained via the MOD function. It works but isn't as
/// clear (or fast) as just reading the axes from data.
/// ```
pub fn vproj(a: &[f64; 3], b: &[f64; 3], p: &mut [f64; 3]) {
VPROJ(a, b, p);
}
//$Procedure VPROJ ( Vector projection, 3 dimensions )
pub fn VPROJ(A: &[f64], B: &[f64], P: &mut [f64]) {
let A = DummyArray::new(A, 1..=3);
let B = DummyArray::new(B, 1..=3);
let mut P = DummyArrayMut::new(P, 1..=3);
let mut BIGA: f64 = 0.0;
let mut BIGB: f64 = 0.0;
let mut R = StackArray::<f64, 3>::new(1..=3);
let mut T = StackArray::<f64, 3>::new(1..=3);
let mut SCALE: f64 = 0.0;
//
// SPICELIB functions
//
//
// Local variables
//
BIGA = intrinsics::DMAX1(&[f64::abs(A[1]), f64::abs(A[2]), f64::abs(A[3])]);
BIGB = intrinsics::DMAX1(&[f64::abs(B[1]), f64::abs(B[2]), f64::abs(B[3])]);
if (BIGA == 0 as f64) {
P[1] = 0.0;
P[2] = 0.0;
P[3] = 0.0;
return;
}
if (BIGB == 0 as f64) {
P[1] = 0.0;
P[2] = 0.0;
P[3] = 0.0;
return;
}
R[1] = (B[1] / BIGB);
R[2] = (B[2] / BIGB);
R[3] = (B[3] / BIGB);
T[1] = (A[1] / BIGA);
T[2] = (A[2] / BIGA);
T[3] = (A[3] / BIGA);
SCALE = ((VDOT(T.as_slice(), R.as_slice()) * BIGA) / VDOT(R.as_slice(), R.as_slice()));
VSCL(SCALE, R.as_slice(), P.as_slice_mut());
}