Procedure

     SWAPAD ( Swap elements within a DP array )

     SUBROUTINE SWAPAD ( N, LOCN, M, LOCM, ARRAY )

Abstract

     Swap (exchange) two non-intersecting groups of contiguous
     elements of a double precision array.

Required_Reading

     None.

Keywords

     ARRAY

Declarations

     IMPLICIT NONE

     INTEGER               N
     INTEGER               LOCN
     INTEGER               M
     INTEGER               LOCM
     DOUBLE PRECISION      ARRAY  ( * )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     N          I   Number of elements in the first group.
     LOCN       I   Location of the first group.
     M          I   Number of elements in the second group.
     LOCM       I   Location of the second group.
     ARRAY     I-O  The array.

Detailed_Input

     N,
     LOCN     define the first group of elements to be exchanged:
              ARRAY(LOCN) through ARRAY(LOCN+N-1).

     M,
     LOCM     define the second group of elements to be exchanged:
              ARRAY(LOCM) through ARRAY(LOCM+M-1). These must be
              distinct from the first group.

     ARRAY    on input contains both groups of elements in their
              original locations.

Detailed_Output

     ARRAY    on output contains the input array with the indicated
              groups of elements exchanged.

Parameters

     None.

Exceptions

     1)  If the elements to be swapped are not distinct, the error
         SPICE(NOTDISTINCT) is signaled.

     2)  If LOCN or LOCM is less than one, the error
         SPICE(INVALIDINDEX) is signaled.

     3)  If the number of elements to be swapped is less than zero,
         the error SPICE(INVALIDARGUMENT) is signaled.

Files

     None.

Particulars

     If N [M] is zero, the second [first] group is removed from
     its current location and inserted in front of ARRAY(LOCN)
     [ARRAY(LOCM)]. Thus, to move the second [first] group to the
     front of the list, set N [M] and LOCN [LOCM] to zero and one
     respectively. To move the group to the end of the list, set
     N [M] and LOCN [LOCM] to zero and one more than the number of
     elements in the array.

     All of the elements to be swapped must be distinct.

Examples

     Let ARRAY contain the following elements.

           Roosevelt
           Truman
           Eisenhower
           Kennedy
           Johnson
           Nixon
           Ford
           Carter
           Reagan
           Cuomo

     Then the following calls

           CALL SWAPAC (  1,  2,  2,  7,  ARRAY )
           CALL SWAPAC (  3,  1,  3,  8,  ARRAY )
           CALL SWAPAC (  3,  4,  0,  1,  ARRAY )
           CALL SWAPAC (  2,  4,  0,  11, ARRAY )

     yield the following arrays respectively.

           [1]          [2]          [3]          [4]

           Roosevelt    Carter       Kennedy      Roosevelt
           Ford         Reagan       Johnson      Truman
           Carter       Cuomo        Nixon        Eisenhower
           Eisenhower   Kennedy      Roosevelt    Nixon
           Kennedy      Johnson      Truman       Ford
           Johnson      Nixon        Eisenhower   Carter
           Nixon        Ford         Ford         Reagan
           Truman       Roosevelt    Carter       Cuomo
           Reagan       Truman       Reagan       Kennedy
           Cuomo        Eisenhower   Cuomo        Johnson

     The following calls

           CALL SWAPAC ( 3, 2, 4, 5, ARRAY )
           CALL SWAPAC ( 4, 5, 3, 2, ARRAY )

     yield the following arrays. Note that the resulting arrays
     are equivalent.

           [1]          [2]

           Roosevelt    Roosevelt
           Johnson      Johnson
           Nixon        Nixon
           Ford         Ford
           Carter       Carter
           Truman       Truman
           Eisenhower   Eisenhower
           Kennedy      Kennedy
           Reagan       Reagan
           Cuomo        Cuomo


     The calls

           CALL SWAPAC ( 3,  5, 4,  6, ARRAY )
           CALL SWAPAC ( 3, -3, 3, 10, ARRAY )

     signal the errors

           SPICE(NOTDISTINCT)
           SPICE(INVALIDINDEX)

     respectively.

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     H.A. Neilan        (JPL)
     B.V. Semenov       (JPL)
     W.L. Taber         (JPL)
     I.M. Underwood     (JPL)

Version

    SPICELIB Version 1.2.0, 13-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.1.1, 18-MAY-2010 (BVS)

        Removed "C$" markers from text in the header.

    SPICELIB Version 1.1.0, 09-SEP-2005 (NJB)

        Updated to remove non-standard use of duplicate arguments
        in CYCLAD call.

    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 (IMU) (HAN)