f06cdf (PDF version)
F06 (blas) Chapter Contents
F06 (blas) Chapter Introduction
NAG Library Manual
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NAG Library Routine Document
f06cdf (zcsgs)
▸
▿
Contents
1
Purpose
2
Specification
3
Description
4
References
5
Arguments
6
Error Indicators and Warnings
7
Accuracy
8
Parallelism and Performance
9
Further Comments
10
Example
1
Purpose
f06cdf
reconstructs the parameters
c
(complex) and
s
(real) of a complex plane rotation from the tangent of that rotation.
2
Specification
Fortran Interface
Subroutine f06cdf (
t
,
c
,
s
)
Real (Kind=nag_wp), Intent (Out)
::
s
Complex (Kind=nag_wp), Intent (In)
::
t
Complex (Kind=nag_wp), Intent (Out)
::
c
C Header Interface
#include nagmk26.h
void
f06cdf_ (
const Complex *
t
,
Complex *
c
,
double *
s
)
3
Description
f06cdf
reconstructs the parameters
c
(complex) and
s
(real) of a complex plane rotation, from the value of the tangent
t
, as returned by
f06cbf
:
c
=
sign
Re
t
t
t
1
+
t
2
,
s
=
c
t
.
If
t
<
ε
, where
ε
is the
machine precision
, the routine sets:
c
=
sign
Re
t
t
t
,
s
=
sign
Re
t
t
.
4
References
None.
5
Arguments
1:
t
– Complex (Kind=nag_wp)
Input
On entry
: the value
t
, the tangent of the rotation.
2:
c
– Complex (Kind=nag_wp)
Output
On exit
: the value
c
, the cosine of the rotation.
3:
s
– Real (Kind=nag_wp)
Output
On exit
: the value
s
, the sine of the rotation.
6
Error Indicators and Warnings
None.
7
Accuracy
Not applicable.
8
Parallelism and Performance
f06cdf
is not threaded in any implementation.
9
Further Comments
None.
10
Example
None.
f06cdf (PDF version)
F06 (blas) Chapter Contents
F06 (blas) Chapter Introduction
NAG Library Manual
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017