HP MLIB User's Guide Vol. 2 7th Ed.

Chapter 5 Fast Fourier Transforms 569
Real-to-complex one-dimensional FFT SRC1FT/DRC1FT
iopt Option flag:
iopt = +1 Compute forward transform.
iopt = −1 Compute scaled inverse transform.
iopt = −2 Compute unscaled inverse transform.
iopt = −3 Initialize work for subsequent
transforms of length l.
Working
Storage
work If iopt = −3, work is initialized for computing
transforms of length l.
If iopt ≠−3, work must have been initialized by a
previous call with this value of l in which iopt was −3.
Output x If iopt ≠−3, the transformed data replaces the input if
ier = 0 is returned.
For a forward real-to-complex transform, the real part
of the i-th complex output point is stored in x(2×i−1)
and the imaginary part of the i-th output point is
stored in x(2×i), i = 1, 2, ..., l/2+1. If needed, the
remaining l/2 − 1 complex output values may be
formed by using the conjugate symmetry condition.
For an inverse complex-to-real transform, the i-th real
output point is stored in x(i), i = 1, 2, ..., l.
Not used as output if iopt = −3.
ier Status response:
ier = 0 Normal return—transform or
initialization successful.
ier = −1 l < 0.
ier = −2 l = 0.
ier = −3 Invalid value of iopt.
ier = −4 Insufficient dynamic memory
available for workspace.