﻿ c06gb Method
c06gb forms the complex conjugate of a Hermitian sequence of $n$ data values.

# Syntax

C#
```public static void c06gb(
double[] x,
int n,
out int ifail
)```
Visual Basic
```Public Shared Sub c06gb ( _
x As Double(), _
n As Integer, _
<OutAttribute> ByRef ifail As Integer _
)```
Visual C++
```public:
static void c06gb(
array<double>^ x,
int n,
[OutAttribute] int% ifail
)```
F#
```static member c06gb :
x : float[] *
n : int *
ifail : int byref -> unit
```

#### Parameters

x
Type: array<System..::..Double>[]()[][]
An array of size [n]
On entry: if the data values ${z}_{j}$ are written as ${x}_{j}+i{y}_{j}$ and if x is declared with bounds $\left(0:{\mathbf{n}}-1\right)$ in the method from which c06gb is called, then for $0\le j\le n/2$, ${\mathbf{x}}\left[j-1\right]$ must contain ${x}_{j}$ ($\text{}={x}_{n-j}$), while for $n/2, ${\mathbf{x}}\left[j-1\right]$ must contain ${-y}_{j}$ ($\text{}={y}_{n-j}$). In other words, x must contain the Hermitian sequence in Hermitian form. (See also [] in the C06 class Chapter Introduction.)
On exit: the imaginary parts ${y}_{j}$ are negated. The real parts ${x}_{j}$ are not referenced.
n
Type: System..::..Int32
On entry: $n$, the number of data values.
Constraint: ${\mathbf{n}}\ge 1$.
ifail
Type: System..::..Int32%
On exit: ${\mathbf{ifail}}={0}$ unless the method detects an error or a warning has been flagged (see [Error Indicators and Warnings]).

# Description

This is a utility method for use in conjunction with c06ea c06eb (C06FAF not in this release) (C06FBF not in this release) to calculate inverse discrete Fourier transforms (see the C06 class).

None.

# Error Indicators and Warnings

Errors or warnings detected by the method:
${\mathbf{ifail}}=1$
 On entry, ${\mathbf{n}}<1$.
${\mathbf{ifail}}=-9000$
An error occured, see message report.
${\mathbf{ifail}}=-8000$
Negative dimension for array $〈\mathit{\text{value}}〉$
${\mathbf{ifail}}=-6000$
Invalid Parameters $〈\mathit{\text{value}}〉$

Exact.

None.