Procedure

   brcktd_c ( Bracket a d.p. value within an interval ) 

   SpiceDouble brcktd_c ( SpiceDouble  number,
                          SpiceDouble  end1,
                          SpiceDouble  end2   )

Abstract

   Bracket a double precision number. That is, given a number and an
   acceptable interval, make sure that the number is contained in the
   interval. (If the number is already in the interval, leave it
   alone. If not, set it to the nearest endpoint of the interval.)

Required_Reading

   None.

Keywords

   INTERVALS
   NUMBERS
   UTILITY

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   number     I   Number to be bracketed.
   end1       I   One of the bracketing endpoints for `number'.
   end2       I   The other bracketing endpoint for `number'.

   The function returns the bracketed number.

Detailed_Input

   number      is the number to be bracketed. That is, the
               value of `number' is constrained to lie in the
               interval bounded by `end1' and `end2'.

   end1,
   end2        are the lower and upper bounds for `number'. The
               order is not important.

Detailed_Output

   The function returns the bracketed number. That is `number', if it
   was already in the interval provided. Otherwise the returned
   value is the nearest bound of the interval.

Parameters

   None.

Exceptions

   Error free.

Files

   None.

Particulars

   This routine provides a shorthand notation for code fragments
   like the following:

      if ( end1 < end2 )
      {
         if ( number < end1 )
         {
            number = end1;
         }
         else if ( number > end2 )
         {
            number = end2;
         }
      }
      else
      {
         if ( number < end2 )
         {
            number = end2;
         }
         else if ( number > end1 )
         {
            number = end1;
         }
      }

   which occur frequently during the processing of program inputs.

Examples

   The numerical results shown for these examples 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) The following code example illustrates the operation of
      brcktd_c.

      Example code begins here.


      /.
         Program brcktd_ex1
      ./
      #include <stdio.h>
      #include "SpiceUsr.h"

      int main( )
      {

         /.
         Local parameters.
         ./
         #define LISTSZ       4

         /.
         Local variables.
         ./
         SpiceInt             i;

         /.
         Set the values for the example.
         ./
         SpiceDouble          end1   [LISTSZ] = {  1.0,   1.0,  10.0, -10.0 };
         SpiceDouble          end2   [LISTSZ] = { 10.0,  10.0, -10.0,  -1.0 };
         SpiceDouble          number [LISTSZ] = { -1.0,  29.0,  3.0,    3.0 };


         printf( " Number  End1   End2   Bracketed\n" );
         printf( " ------  -----  -----  ---------\n" );

         for ( i = 0; i < LISTSZ; i++ )
         {

            printf( "%7.1f %6.1f %6.1f %10.1f\n",
                    number[i], end1[i], end2[i],
                    brcktd_c ( number[i], end1[i], end2[i] ) );

         }

         return ( 0 );
      }


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


       Number  End1   End2   Bracketed
       ------  -----  -----  ---------
         -1.0    1.0   10.0        1.0
         29.0    1.0   10.0       10.0
          3.0   10.0  -10.0        3.0
          3.0  -10.0   -1.0       -1.0


   2) The following code example illustrates a typical use for
      brcktd_c: force a start magnitude limit to be within a range.
      Note that this code assumes that the user provided value
      is a valid double precision number.


      Example code begins here.


      /.
         Program brcktd_ex2
      ./
      #include <stdio.h>
      #include "SpiceUsr.h"

      int main( )
      {

         /.
         Local parameters.
         ./
         #define KWDSZ        31

         /.
         Local variables.
         ./
         SpiceChar            usrin  [KWDSZ];

         SpiceDouble          maglin;
         SpiceDouble          maglok;

         /.
         Prompt the user for the star magnitude.
         ./
         prompt_c ( "Enter star magnitude: ", KWDSZ, usrin );

         /.
         Convert the user input to double precision.
         ./
         prsdp_c ( usrin, &maglin );

         /.
         Star magnitude must be in the range 0-10.
         ./
         maglok = brcktd_c ( maglin, 0.0, 10.0 );

         /.
         Display confirmation message.
         ./
         if ( maglin != maglok )
         {
            printf( "Provided star magnitude %3.1f is out of range (0-10).\n",
                                                                      maglin );
         }
         else
         {
            printf( "Provided star magnitude %3.1f is in range (0-10).\n",
                                                                     maglin );
         }

         return ( 0 );
      }


      When this program was executed on a Mac/Intel/cc/64-bit
      platform, using "10.1" as user provided input, the output was:


      Enter star magnitude: 10.1
      Provided star magnitude 10.1 is out of range (0-10).

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   B.V. Semenov        (JPL)
   W.L. Taber          (JPL)
   I.M. Underwood      (JPL)
   E.D. Wright         (JPL)

Version

   -CSPICE Version 1.1.0, 08-AUG-2021 (JDR) (BVS)

       BUG FIX: corrected to make the order of endpoints not important
       as stated in the description.

       Edited the header to comply with NAIF standard. Added complete
       code examples based on existing fragments.

       Updated code fragment in -Particulars to show that the
       order of endpoints is not important.

   -CSPICE Version 1.0.1, 11-NOV-2006 (EDW)

      Added "None." text to -Keywords section, required for
      API doc script (cspicehtml.pl) integrity checks.

   -CSPICE Version 1.0.0, 16-AUG-1999 (NJB) (WLT) (IMU)

Index_Entries

   bracket a d.p. value within an interval

Link to routine brcktd_c source file brcktd_c.c