*
* treverse.F
*
* Ansley Manke
* Sep 15 2004
*
* This function returns the T values of the input variables,
* reversed and on an abstract T axis. Other axes are unchanged.
*
*
* In this subroutine we provide information about
* the function.  The user configurable information
* consists of the following:
*
* descr              Text description of the function
*
* num_args           Required number of arguments
*
* axis_inheritance   Type of axis for the result
*                       ( CUSTOM, IMPLIED_BY_ARGS, NORMAL, ABSTRACT )
*                       CUSTOM          - user defined axis
*                       IMPLIED_BY_ARGS - same axis as the incoming argument
*                       NORMAL          - the result is normal to this axis
*                       ABSTRACT        - an axis which only has index values
*
* piecemeal_ok       For memory optimization:
*                       axes where calculation may be performed piecemeal
*                       ( YES, NO )
*
*
* For each argument we provide the following information:
*
* name               Text name for an argument
*
* unit               Text units for an argument
*
* desc               Text description of an argument
*
* axis_influence     Are this argument''s axes the same as the result grid?
*                       ( YES, NO )
*
* axis_extend       How much does Ferret need to extend arg limits relative to result
*


      SUBROUTINE treverse_init(id)

      IMPLICIT NONE
      INCLUDE 'EF_Util.cmn'

      INTEGER id, arg

* **********************************************************************
*                                            USER CONFIGURABLE PORTION |
*                                                                      |
*                                                                      V

      CALL ef_set_desc(id,
     .  'Returns values reversed in T direction on an abstract T axis')
      CALL ef_set_num_args(id, 1)
      CALL ef_set_axis_inheritance_6d(id,
     .                                IMPLIED_BY_ARGS, IMPLIED_BY_ARGS,
     .                                IMPLIED_BY_ARGS, ABSTRACT,
     .                                IMPLIED_BY_ARGS, IMPLIED_BY_ARGS)
      CALL ef_set_piecemeal_ok_6d(id, NO, NO, NO, NO, NO, NO)

      arg = 1
      CALL ef_set_arg_name(id, arg, 'A')
      CALL ef_set_arg_unit(id, arg, ' ')
      CALL ef_set_arg_desc(id, arg, 'Variable to reverse the T axis')
      CALL ef_set_axis_influence_6d(id, arg,
     .                              YES, YES, YES, NO, YES, YES)

*                                                                      ^
*                                                                      |
*                                            USER CONFIGURABLE PORTION |
* **********************************************************************

      RETURN
      END


      SUBROUTINE treverse_result_limits(id)

      IMPLICIT NONE
      INCLUDE 'EF_Util.cmn'

      INTEGER id

* **********************************************************************
*                                            USER CONFIGURABLE PORTION |
*                                                                      |
*                                                                      V

      INTEGER arg_lo_ss(6,EF_MAX_ARGS),
     .        arg_hi_ss(6,EF_MAX_ARGS),
     .        arg_incr (6,EF_MAX_ARGS)
      INTEGER nt

      CALL ef_get_arg_subscripts_6d(id, arg_lo_ss, arg_hi_ss, arg_incr)

      nt = arg_hi_ss(T_AXIS,ARG1) - arg_lo_ss(T_AXIS,ARG1) + 1

      CALL ef_set_axis_limits(id, T_AXIS, 1, nt)

*                                                                      ^
*                                                                      |
*                                            USER CONFIGURABLE PORTION |
* **********************************************************************

      RETURN
      END


*
* In this subroutine we compute the result
*
      SUBROUTINE treverse_compute(id, arg_1, result)

      IMPLICIT NONE
      INCLUDE 'EF_Util.cmn'
      INCLUDE 'EF_mem_subsc.cmn'

      INTEGER id

      REAL arg_1(mem1lox:mem1hix, mem1loy:mem1hiy, mem1loz:mem1hiz,
     .           mem1lot:mem1hit, mem1loe:mem1hie, mem1lof:mem1hif)

      REAL result(memreslox:memreshix, memresloy:memreshiy,
     .            memresloz:memreshiz, memreslot:memreshit,
     .            memresloe:memreshie, memreslof:memreshif)

* After initialization, the 'res_' arrays contain indexing information
* for the result axes.  The 'arg_' arrays will contain the indexing
* information for each variable''s axes.

      INTEGER res_lo_ss(6),
     .        res_hi_ss(6),
     .        res_incr (6)
      INTEGER arg_lo_ss(6,EF_MAX_ARGS),
     .        arg_hi_ss(6,EF_MAX_ARGS),
     .        arg_incr (6,EF_MAX_ARGS)

      REAL bad_flag(EF_MAX_ARGS), bad_flag_result

* **********************************************************************
*                                            USER CONFIGURABLE PORTION |
*                                                                      |
*                                                                      V

      INTEGER i, j, k, l, m, n
      INTEGER i1, j1, k1, l1, m1, n1

      CALL ef_get_res_subscripts_6d(id, res_lo_ss, res_hi_ss, res_incr)
      CALL ef_get_arg_subscripts_6d(id, arg_lo_ss, arg_hi_ss, arg_incr)
      CALL ef_get_bad_flags(id, bad_flag, bad_flag_result)

      n = res_lo_ss(F_AXIS)
      DO 600 n1 = arg_lo_ss(F_AXIS,ARG1), arg_hi_ss(F_AXIS,ARG1)

      m = res_lo_ss(E_AXIS)
      DO 500 m1 = arg_lo_ss(E_AXIS,ARG1), arg_hi_ss(E_AXIS,ARG1)

      l = res_lo_ss(T_AXIS)
      DO 400 l1 = arg_hi_ss(T_AXIS,ARG1), arg_lo_ss(T_AXIS,ARG1), -1

      k = res_lo_ss(Z_AXIS)
      DO 300 k1 = arg_lo_ss(Z_AXIS,ARG1), arg_hi_ss(Z_AXIS,ARG1)

      j = res_lo_ss(Y_AXIS)
      DO 200 j1 = arg_lo_ss(Y_AXIS,ARG1), arg_hi_ss(Y_AXIS,ARG1)

      i = res_lo_ss(X_AXIS)
      DO 100 i1 = arg_lo_ss(X_AXIS,ARG1), arg_hi_ss(X_AXIS,ARG1)

         IF ( arg_1(i1,j1,k1,l1,m1,n1) .EQ. bad_flag(ARG1) ) THEN
            result(i,j,k,l,m,n) = bad_flag_result
         ELSE
            result(i,j,k,l,m,n) = arg_1(i1,j1,k1,l1,m1,n1)
         ENDIF

         i = i + res_incr(X_AXIS)
 100  CONTINUE

         j = j + res_incr(Y_AXIS)
 200  CONTINUE

         k = k + res_incr(Z_AXIS)
 300  CONTINUE

         l = l + res_incr(T_AXIS)
 400  CONTINUE

         m = m + res_incr(E_AXIS)
 500  CONTINUE

         n = n + res_incr(F_AXIS)
 600  CONTINUE

*                                                                      ^
*                                                                      |
*                                            USER CONFIGURABLE PORTION |
* **********************************************************************

      RETURN
      END
