Procedure

     SHELLC ( Shell sort a character array )

     SUBROUTINE SHELLC ( NDIM, ARRAY )

Abstract

     Sort an array of character strings according to the ASCII
     collating sequence using the Shell Sort algorithm.

Required_Reading

     None.

Keywords

     ARRAY
     SORT

Declarations

     IMPLICIT NONE

     INTEGER          NDIM
     CHARACTER*(*)    ARRAY ( * )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     NDIM       I   Dimension of the array.
     ARRAY     I-O  The array.

Detailed_Input

     NDIM     is the number of elements in the array to be sorted.

     ARRAY    on input, is the array to be sorted.

Detailed_Output

     ARRAY    on output, contains the same elements, sorted
              according to the ASCII collating sequence.
              The actual sorting is done in place in ARRAY.

Parameters

     None.

Exceptions

     Error free.

     1)  If NDIM < 2, this routine does not modify the array.

Files

     None.

Particulars

     The Shell Sort Algorithm is well known.

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) Given a list of words, sort it according to the ASCII
        collating sequence using the Shell Sort algorithm.


        Example code begins here.


              PROGRAM SHELLC_EX1
              IMPLICIT NONE

        C
        C     Local parameters.
        C
              INTEGER               NDIM
              PARAMETER           ( NDIM  = 6 )

              INTEGER               WRDSZ
              PARAMETER           ( WRDSZ = 8 )

        C
        C     Local variables.
        C
              CHARACTER*(WRDSZ)     ARRAY  ( NDIM )
              INTEGER               I

        C
        C     Let ARRAY contain the following elements:
        C
              ARRAY(1) = 'FEYNMAN'
              ARRAY(2) = 'NEWTON'
              ARRAY(3) = 'EINSTEIN'
              ARRAY(4) = 'GALILEO'
              ARRAY(5) = 'EUCLID'
              ARRAY(6) = 'Galileo'

        C
        C     Print ARRAY before calling SHELLC.
        C
              WRITE(*,*) 'Array before calling SHELLC:'
              WRITE(*,*)
              DO I = 1, NDIM
                 WRITE(*,*) '   ', ARRAY(I)
              END DO
              WRITE(*,*)

        C
        C     Call SHELLC and print ARRAY again.
        C
              CALL SHELLC ( NDIM, ARRAY )

              WRITE(*,*) 'Array after calling SHELLC:'
              WRITE(*,*)
              DO I = 1, NDIM
                 WRITE(*,*) '   ', ARRAY(I)
              END DO

              END


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


         Array before calling SHELLC:

            FEYNMAN
            NEWTON
            EINSTEIN
            GALILEO
            EUCLID
            Galileo

         Array after calling SHELLC:

            EINSTEIN
            EUCLID
            FEYNMAN
            GALILEO
            Galileo
            NEWTON

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)
     I.M. Underwood     (JPL)

Version

    SPICELIB Version 1.1.0, 06-JUL-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Added complete
        code example based on existing example. Extended $Exceptions
        section to explain what happens if NDIM < 2.

    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)