Table of contents
CSPICE_DIFF takes the difference of two sets of any data type to form a
third set.
Given:
a,
b two SPICE sets, each of the same type, double precision, or
integer.
help, a
STRUCT = cspice_celld(N) or STRUCT = cspice_celli(N)
help, b
STRUCT = cspice_celld(M) or STRUCT = cspice_celli(M)
The user must create `a' and `b' using either
cspice_celld, or cspice_celli.
the call:
cspice_diff, a, b, c
returns:
c a scalar SPICE set, distinct from sets `a' and `b' but with the
same type, containing the difference of `a' and `b' (that is,
all of the elements which are in `a' but NOT in `b').
help, c
STRUCT = cspice_celld(R) or STRUCT = cspice_celli(R)
The user must create `c' using either cspice_celld
or cspice_celli.
None.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
1) Calculate the difference between two SPICE sets of the same
type, and print the result to screen.
Example code begins here.
PRO diff_ex1
;;
;; Create three cells with the necessary size.
;; Set 'c' need not have a larger size than the
;; larger of 'a' or 'b'.
;;
SIZE = 10
a = cspice_celli( SIZE )
b = cspice_celli( SIZE )
c = cspice_celli( SIZE )
;;
;; Create vectors of integers. It is more efficient to
;; load a set from a vector than looping over the
;; call, inserting one 'item' per iteration.
;;
ints1 = [ 0, 1, 1, 2, 3, 5, 8, 13 ]
ints2 = [ 1, 3, 5, 7, 11, 13]
;;
;; Insert the 'ints1' list into set 'a', 'ints2 '
;; into set 'b'.
;;
cspice_insrti, ints1, a
cspice_insrti, ints2, b
;;
;; Calculate the difference between sets 'a' and 'b', return
;; that difference to set 'c'.
;;
cspice_diff, a, b, c
;;
;; Output the contents of set 'c'. Recall
;; set data begins at 'c.base[ c.data + 0 ]'.
;;
print, 'Members of CSPICE set A not in set B:'
for i=0, cspice_card(c)-1 do begin
print, FORMAT='(" ",I2)', c.base[ c.data + i]
endfor
END
When this program was executed on a Mac/Intel/IDL8.x/64-bit
platform, the output was:
Members of CSPICE set A not in set B:
0
2
8
The difference of two sets contains every element which is
in the first set, but NOT in the second.
{a,b} difference {c,d} = {a,b}
{a,b,c} {b,c,d} {a}
{a,b,c,d} {} {a,b,c,d}
{} {a,b,c,d} {}
{} {} {}
The user must create any needed cell structures with cspice_celld,
cspice_celli prior to use regardless of whether the routine
uses the cell as input or returns it as output.
1) If the input set arguments don't have identical data types,
the error SPICE(TYPEMISMATCH) is signaled by a routine in the
call tree of this routine.
2) If the difference of the two sets contains more elements than
can be contained in the output set, the error SPICE(SETEXCESS)
is signaled by a routine in the call tree of this routine.
3) If the set arguments have character type and the length of the
elements of the output set is less than the maximum of the
lengths of the elements of the input sets, the error
SPICE(ELEMENTSTOOSHORT) is signaled by a routine in the call
tree of this routine.
4) If either of the input arguments is unordered or contains
duplicates, the error SPICE(NOTASET) is signaled by a routine
in the call tree of this routine.
5) If any of the input arguments, `a', `b' or `c', is undefined,
an error is signaled by the IDL error handling system.
6) If any of the input arguments, `a', `b' or `c', is not of the
expected type, or it does not have the expected dimensions and
size, an error is signaled by the Icy interface.
None.
1) The output set must be distinct from both of the input sets.
For example, the following calls are invalid.
cspice_diff, current, new, current
cspice_diff, new, current, current
In each of the examples above, whether or not the subroutine
signals an error, the results will almost certainly be wrong.
Nearly the same effect can be achieved, however, by placing the
result into a temporary set, which is immediately copied back
into one of the input sets, as shown below.
cspice_diff, current, new, temp
new = temp
ICY.REQ
CELLS.REQ
SETS.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Icy Version 1.0.2, 24-AUG-2021 (JDR)
Added arguments' type and size information in the -I/O section.
Edited the header to comply with NAIF standard. Added example's
problem statement and reformatted example's output.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections.
Removed reference to the routine's corresponding CSPICE header from
-Abstract section.
-Icy Version 1.0.1, 28-SEP-2006 (EDW)
Corrections to English.
Correct Required Reading citation cell.req to cells.req.
-Icy Version 1.0.0, 21-FEB-2005 (EDW)
difference of two sets
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