### Contents

rfftb - compute a periodic sequence from its Fourier coeffi-
cients. The RFFT operations are unnormalized, so a call of
RFFTF followed by a call of RFFTB will multiply the input
sequence by N.

SUBROUTINE RFFTB(N, X, WSAVE)
INTEGER N
REAL X(*), WSAVE(*)
SUBROUTINE RFFTB_64(N, X, WSAVE)
INTEGER*8 N
REAL X(*), WSAVE(*)
**F95 INTERFACE**
SUBROUTINE FFTB([N], X, WSAVE)
INTEGER :: N
REAL, DIMENSION(:) :: X, WSAVE
SUBROUTINE FFTB_64([N], X, WSAVE)
INTEGER(8) :: N
REAL, DIMENSION(:) :: X, WSAVE
**C INTERFACE**
#include <sunperf.h>
void rfftb(int n, float *x, float *wsave);
void rfftb_64(long n, float *x, float *wsave);

N (input) Length of the sequence to be transformed. These
subroutines are most efficient when N is a product
of small primes. N >= 0.
X (input) On entry, an array of length N containing the
sequence to be transformed.
WSAVE (input)
On entry, WSAVE must be an array of dimension (2 *
N + 15) or greater and must have been initialized
by RFFTI.