Abstract

   CSPICE_PI returns the value of the constant pi.

I/O

   The call:

      [onepi] = cspice_pi

   returns:

      onepi    the value of pi (the ratio of a circle's circumference to its
               diameter), determined by the acos function.

               [1,1] = size(onepi); double = class(onepi)

               That is,

                     onepi = acos ( -1.0 );

Parameters

   None.

Examples

   Any numerical results shown for these examples may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

   1) The following code example returns the double precision value of
      the constant pi and prints it out.

      Example code begins here.


      function pi_ex1()

         %
         % Print the double precision value of Pi
         %
         fprintf( 'Pi: %25.22f\n', cspice_pi )


      When this program was executed on a Mac/Intel/Octave6.x/64-bit
      platform, the output was:


      Pi:  3.1415926535897931159980


      Note that the MATLAB system variable "pi" returns a double
      precision value for PI that equates the value returned by
      cspice_pi, to machine roundoff.

   2) Suppose that you need to compute the vector that results from
      off-pointing an instrument boresight vector by pi/10 radians
      about the Y-axis of the instrument's reference frame.

      Example code begins here.


      function pi_ex2()

         %
         % Let's assume that the instrument boresight is not aligned
         % to the Z-axis of the instrument's reference frame.
         %
         bsight = [ 0.2; 0.04; 1.0 ];

         %
         % A Pi/10 rotation about the Y axis.
         %
         rotmat = cspice_rotate( 0.1*cspice_pi, 2 );

         %
         % Apply the coordinate rotation to the boresight.
         %
         vec = rotmat * bsight;
         fprintf( 'Pointing vector:\n' )
         fprintf( '  %16.12f  %16.12f  %16.12f\n', vec );


      When this program was executed on a Mac/Intel/Octave6.x/64-bit
      platform, the output was:


      Pointing vector:
         -0.118805691116    0.040000000000    1.012859915170

Particulars

   The first time the function is referenced, the value is computed
   as shown above. The value is saved, and returned directly upon
   subsequent reference.

Exceptions

   Error free.

Files

   None.

Restrictions

   None.

Required_Reading

   MICE.REQ

Literature_References

   None.

Author_and_Institution

   J. Diaz del Rio     (ODC Space)
   E.D. Wright         (JPL)

Version

   -Mice Version 1.1.0, 25-AUG-2021 (EDW) (JDR)

       Edited the header to comply with NAIF standard. Added second
       example.

       Added -Parameters, -Particulars, -Exceptions, -Files, -Restrictions,
       -Literature_References and -Author_and_Institution sections.

       Eliminated use of "lasterror" in rethrow.

       Removed reference to the function's corresponding CSPICE header from
       -Required_Reading section.

   -Mice Version 1.0.1, 11-JUN-2013 (EDW)

       -I/O descriptions edits to conform to Mice documentation format.

       Corrected minor typo in header.

   -Mice Version 1.0.0, 22-NOV-2005 (EDW)

Index_Entries

   value of pi