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uddc_c

 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.
```

```   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
```
`Fri Dec 31 18:41:14 2021`