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