NAG FL Interface
e01rbf (dim1_​ratnl_​eval)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{m}$ – Integer Input

On entry: $m$, the number of terms in the continued fraction.

Constraint: $\mathbf{m}\ge 1$.

2: $\mathbf{a}\left(\mathbf{m}\right)$ – Real (Kind=nag_wp) array Input

On entry: $\mathbf{a}\left(\mathit{j}\right)$ must be set to the value of the parameter $a_{\mathit{j}}$ in the continued fraction, for $\mathit{j}=1,2,\dots ,m$.

3: $\mathbf{u}\left(\mathbf{m}\right)$ – Real (Kind=nag_wp) array Input

On entry: $\mathbf{u}\left(\mathit{j}\right)$ must be set to the value of the parameter $u_{\mathit{j}}$ in the continued fraction, for $\mathit{j}=1,2,\dots ,m-1$. (The element $\mathbf{u}\left(m\right)$ is not used).

4: $\mathbf{x}$ – Real (Kind=nag_wp) Input

On entry: the value of $x$ at which the continued fraction is to be evaluated.

5: $\mathbf{f}$ – Real (Kind=nag_wp) Output

On exit: the value of the continued fraction corresponding to the value of $x$.

6: $\mathbf{ifail}$ – Integer Input/Output

On entry: ifail must be set to $0$, $\mathrm{-1}$ 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 $\mathrm{-1}$ means that an error message is printed while a value of $1$ means that it is not.

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

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

6 Error Indicators and Warnings

$\mathbf{ifail}=1$

x corresponds to a pole of $R\left(x\right)$, or is very close. $\mathbf{x}=⟨\mathit{\text{value}}⟩$.

$\mathbf{ifail}=-99$

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.

$\mathbf{ifail}=-399$

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.

$\mathbf{ifail}=-999$

Dynamic memory allocation failed.

See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results