To be consistent with the naming scheme for other routines in the AD Library, five routines are available with names formed by replacing AD in the above by one of p0w, a1w, t1w, a1t1w or t2w.

C++ Header Interface

#include <nagad.h>

extern "C" {

void	x10cf_AD_f_ (void *&cb_handle, double &x, Integer &ifail)

}

To be consistent with the naming scheme for other functions in the AD Library, five functions are available with names formed by replacing AD in the above by one of p0w, a1w, t1w, a1t1w or t2w.

3 Description

For routines where it is necessary to perform callback operations via one or more companion callbacks, data must be passed between the procedure argument and any such companion callback via a callback data object as created by x10ba_AD_f. x10cf_AD_f can be used to extract a real value from the callback data object. In this way real values can be communicated between a procedure argument and its companion callbacks.

Note that writing to and reading from a callback data object must be performed in strict order without omission. Reading a data item from the object is equivalent to removing that item from a data stack; reading is, therefore, not passive, but updates the callback data object.

4 References

None.

5 Arguments

1: $cb_handle$ – Pointer to AD Data Input/Output: On entry: will contain a handle to the callback data object.

On exit: will contain a handle to the updated callback data object, with data item removed from data stack.
2: $x$ – Real (Kind=nag_wp) Output: On exit: a real value, $x$ , to be extracted from the callback data object.
3: $ifail$ – Integer Input/Output: On entry: ifail must be set to $0$ , $−1$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $−1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $−1$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $- 1$ or $1$ is used it is essential to test the value of ifail on exit.

On exit: $ifail = 0$ unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry

ifail = 0

−1

, explanatory error messages are output on the current error message unit (as defined by x04aaf).

Errors or warnings detected by the routine:

$ifail = 1$: On entry, cb_handle does not define a valid handle to a NAG AD callback data object. It has not been initialized or has been corrupted.

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.