1: $x$ – double Input: On entry: the argument $x$ of the function.

Constraint: $x > - 1.0$ .
2: $fail$ – NagError * Input/Output: The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

NE_ALLOC_FAIL: Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
NE_INTERNAL_ERROR: An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
NE_NO_LICENCE: Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.
NE_REAL_ARG_LE: On entry, $x = 〈value〉$ .
Constraint: $x > - 1.0$ .

7 Accuracy

The returned result should be accurate almost to machine precision, with a limit of about

20

significant figures due to the precision of internal constants. Note however, that if

x

lies very close to

- 1.0

and is not exact (for example if

x

is the result of some previous computation and has been rounded), then precision will be lost in the computation of

1 + x

, and hence

\ln (1 + x)

, in s01bac.

s01bac is not threaded in any implementation.

Empirical tests show that the time taken for a call of s01bac usually lies between about

1.25

and

2.5

times the time for a call to the standard logarithm function.

The example program reads values of the argument

x

from a file, evaluates the function at each value of

x

and prints the results.

Interfaces: FL CL AD

s01ba: FL CL AD