Procedure

   SpiceDouble pi_c ( void )

Abstract

   Return the value of pi (the ratio of the circumference of
   a circle to its diameter).

Required_Reading

   None.

Keywords

   CONSTANTS

Brief_I/O

   The function returns the value of pi.

Detailed_Input

   None.

Detailed_Output

   The function returns the value of pi (the ratio of a circle's
   circumference to its diameter), determined by the ACOS function.
   That is,

         pi_c = acos ( -1.0 );

Parameters

   None.

Exceptions

   Error free.

Files

   None.

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.

Examples

   The code fragment below illustrates the use of pi_c.

      /.
             Compute the polar radius,

                         p
                  ----------------
                  1 + e cos(theta)

             at evenly spaced values of the polar angle, theta.
      ./
            delta = pi_c() / n

            for ( i = 0; i < n, i++ )
               {
               r[i] = p / (1.0 + ecc * cos( i * delta) );
               }

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   E.D. Wright     (JPL)
   W.L. Taber      (JPL)
   I.M. Underwood  (JPL)

Version

   -CSPICE Version 1.0.0, 08-FEB-1998 (EDW)

Index_Entries

   value of pi

Link to routine pi_c source file pi_c.c