NAG Library Routine Document

C06GCF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     Y(N) – REAL (KIND=nag_wp) arrayInput/Output

On entry: if Y is declared with bounds $\left(0:\mathbf{N}-1\right)$ in the subroutine from which C06GCF is called, then $\mathbf{Y}\left(j\right)$ must contain the imaginary part of the $j$th data value, for $0\le j\le n-1$.

On exit: these values are negated.

2:     N – INTEGERInput

On entry: $n$, the number of data values.

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

3:     IFAIL – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ 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

$\mathbf{IFAIL}=1$

On entry,

$\mathbf{N}<1$.

7  Accuracy

8  Further Comments

9  Example

9.1  Program Text

Program Text (c06gcfe.f90)

9.2  Program Data

Program Data (c06gcfe.d)

9.3  Program Results

Program Results (c06gcfe.r)