Index Page wnreld_c
A B C D E F G H I J K L M N O P Q R S T U V W X
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       SpiceBoolean wnreld_c ( SpiceCell       * a,
                               ConstSpiceChar  * op,
                               SpiceCell       * b   )
#### Abstract
       Compare two double precision windows.
#### Required_Reading
       WINDOWS
#### Keywords
       WINDOWS
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       a          I   First window.
       op         I   Comparison operator.
       b          I   Second window.

       The function returns the result of comparison: a (op) b.
#### Detailed_Input
       a,
       b           are CSPICE windows, each of which contains zero or more
                   intervals.

                   a and b must be declared as double precision SpiceCells.

       op          is a comparison operator, indicating the way in
                   which the input sets are to be compared. op may
                   be any of the following:

                      Operator             Meaning
                      --------  -------------------------------------
                        "="     a = b is SPICETRUE if a and b are equal
                                (contain the same intervals).

                        "<>"    a <> b is SPICETRUE if a and b are not
                                equal.

                        "<="    a <= b is SPICETRUE if a is a subset of b.

                        "<"     a < b is SPICETRUE is a is a proper subset
                                of b.

                        ">="    a >= b is SPICETRUE if b is a subset of a.

                        ">"     a > b is SPICETRUE if b is a proper subset
                                of a.
#### Detailed_Output
       The function returns the result of the comparison.
#### Parameters
       None.
#### Exceptions
       1) If any of the function arguments are SpiceCells of type
          other than double precision, the error SPICE(TYPEMISMATCH)
          is signaled.

       2) If the relational operator is not recognized, the error
          SPICE(INVALIDOPERATION) is signaled.

       3) The error SPICE(EMPTYSTRING) is signaled if the input operator
          string does not contain at least one character, since the
          input string cannot be converted to a Fortran-style string
          in this case.

       4) The error SPICE(NULLPOINTER) is signalled if the input operator
          string pointer is null.
#### Files
       None.
#### Particulars
       This function returns SPICETRUE whenever the specified relationship
       between the input windows a and b is satisfied. For example,
       the expression

          wnreld_c ( &needed, "<=", &avail )

       is SPICETRUE whenever the window needed is a subset of the window
       avail. One window is a subset of another window if each of
       the intervals in the first window is included in one of the
       intervals in the second window. In addition, the first window
       is a proper subset of the second if the second window contains
       at least one point not contained in the first window. (Thus,
       "<" implies "<=", and ">" implies ">=".)

       The following pairs of expressions are equivalent.

          wnreld_c ( &a, ">",  &b );
          wnreld_c ( &b, "<",  &a );

          wnreld_c ( &a, ">=", &b );
          wnreld_c ( &b, "<=", &a );
#### Examples
       Let a contain the intervals

          [ 1, 3 ]  [ 7, 11 ]  [ 23, 27 ]

       Let b and c contain the intervals

          [ 1, 2 ]  [ 9, 9 ]  [ 24, 27 ]

       Let d contain the intervals

          [ 5, 10 ]  [ 15, 25 ]

       Finally, let e and f be empty windows (containing no intervals).

       Because b and c contain the same intervals,

          wnreld_c ( &b, "=",  &c )
          wnreld_c ( &b, "<=", &c )
          wnreld_c ( &b, ">=", &c )

       are all SPICETRUE, while

          wnreld_c ( &b, "<>", &c )

       is SPICEFALSE. Because neither b nor c contains any points not also
       contained by the other, neither is a proper subset of the other.
       Thus,

          wnreld_c ( &b, "<", &c )
          wnreld_c ( &b, ">", &c )

       are both SPICEFALSE.

       Every point contained in b and c is also contained in a. Thus,

          wnreld_c ( &b, "<=", &a )
          wnreld_c ( &a, ">=", &c )

       are both SPICETRUE. In addition, a contains points not contained in
       b and c. (That is, the differences a-b and a-c are not empty.)
       Thus, b and c are peoper subsets of a as well, and

          wnreld_c ( &b, "<", &a )
          wnreld_c ( &a, ">", &b )

       are both SPICETRUE.

       Although a and d have points in common, neither contains the
       other. Thus

          wnreld_c ( &a, "=",  &d )
          wnreld_c ( &a, "<=", &d )
          wnreld_c ( &a, ">=", &d )

       are all SPICEFALSE.

       In addition, any window is equal to itself, a subset of itself,
       and a superset of itself. Thus,

          wnreld_c ( &a, "=",  &a )
          wnreld_c ( &a, "<=", &a )
          wnreld_c ( &a, ">=", &a )

       are always SPICETRUE. However, no window is a proper subset or a
       proper superset of itself. Thus,

          wnreld_c ( &a, "<", &a )
          wnreld_c ( &a, ">", &a )

       are always SPICEFALSE.

       Finally, an empty window is a proper subset of any window
       except another empty window. Thus,

          wnreld_c ( &e, "<", &a )

       is SPICETRUE, but

          wnreld_c ( &e, "<", &f )

       is SPICEFALSE.
#### Restrictions
       None.
#### Literature_References
       None.
#### Author_and_Institution
       N.J. Bachman    (JPL)
       H.A. Neilan     (JPL)
       W.L. Taber      (JPL)
       I.M. Underwood  (JPL)
#### Version
       -CSPICE Version 1.0.0, 27-JUL-2002 (NJB) (HAN) (WLT) (IMU)
#### Index_Entries
       compare two d.p. windows
#### Link to routine wnreld_c source file wnreld_c.c

    Wed Jun  9 13:05:33 2010