Index of Functions: A B C D E F G H I J K L M N O P Q R S T U V W X
Index Page uddc_c

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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

       uddc_c ( Derivative of function less than zero, df(x)/dx < 0 )

       void uddc_c ( void            ( * udfunc ) ( SpiceDouble    x,
                                                    SpiceDouble  * value ),
                     SpiceDouble         x,
                     SpiceDouble         dx,
                     SpiceBoolean      * isdecr )

#### Abstract

       Return SPICETRUE if the derivative of the callback function `udfunc'
       at a given abscissa value is negative.

#### Required_Reading

       GF

#### Keywords

       DERIVATIVE
       GEOMETRY

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       udfunc     I   The routine that computes the scalar value
                      of interest.
       x          I   Independent variable of 'udfunc'.
       dx         I   Interval from 'x' for derivative calculation.
       isdecr     O   Boolean indicating if the derivative is negative.

#### Detailed_Input

       udfunc      is the routine that returns the value of the scalar quantity
                   function of interest at `x'. The calling sequence for `udfunc'
                   is:

                      udfunc ( x, &value );

                   where:

                      x       is the double precision value of the
                              independent variable of the function
                              at which to determine the scalar value.

                      value   is the double precision value returned by
                              `udfunc' at `x'.

                   Functionally:

                      value = udfunc ( x )

       x           is a scalar double precision value at which to determine
                   the derivative of `udfunc'.

                   For many SPICE uses, `x' will represent ephemeris time,
                   expressed as seconds past J2000 TDB.

       dx          is a scalar double precision value representing half the
                   interval in units of `x' separating the evaluation
                   values of `udfunc'; the evaluations occur at (x + dx)
                   and (x - dx).

                   `dx' may be negative but must be non-zero.

#### Detailed_Output

       isdecr      is a scalar boolean indicating if the first derivative
                   of `udfunc' with respect to time at `et' is less than
                   zero.

                   Functionally:

                     d udfunc(x) |
                     ----------- |  <  0
                          dx     |
                                  x

#### Parameters

       None.

#### Exceptions

       1)  If `dx' has a value of zero, an error is signaled by a routine
           in the call tree of this routine.

#### Files

       If the evaluation of 'udfunc' requires SPICE kernel data, the
       appropriate kernels must be loaded before calling this routine.

       -  SPK data: the calling application must load ephemeris data
          for the targets, observer, and any intermediate objects in
          a chain connecting the targets and observer for the time
          used in the evaluation. If aberration corrections are used,
          the states of target and observer relative to the solar system
          barycenter must be calculable from the available ephemeris
          data.

       -  If non-inertial reference frames are used, then PCK
          files, frame kernels, C-kernels, and SCLK kernels may be
          needed.

       Such kernel data are normally loaded once per program run, NOT
       every time this routine is called.

#### Particulars

       None.

#### Examples

       See gfuds_c.

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

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

#### Version

       -CSPICE Version 1.0.1, 01-NOV-2021 (JDR)

           Edited the header to comply with NAIF standard.

       -CSPICE Version 1.0.0, 31-MAR-2010 (EDW) (NJB)

#### Index_Entries

       first derivative less-than zero

#### Link to routine uddc_c source file uddc_c.c

    Fri Dec 31 18:41:14 2021