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/*
 *
 * $Header: fft.c,v 1.2 84/03/25 23:39:22 malcolm Exp $
 *
 * $Log:	fft.c,v $
 * Revision 1.2  84/03/25  23:39:22  malcolm
 * Took out Fortran garbage.
 * 
 *
 */

static char	*RCSid = "$Header: fft.c,v 1.2 84/03/25 23:39:22 malcolm Exp $";

/*
	fft - calculate FFT

	Carl Crawford
	Purdue University
	W. Lafayette, IN. 47907

	Calling Sequence....fft(real,im,m,iopt)
	Where real and im are the real and imaginary
	parts of the input data.  The result is
	returned in place.  M is the log base 2
	of the number of elements in the array.
	Iopt is equal to 0 for the forward
	transform and 1 for the inverse transform.
*/
fft(a,b,m,iopt)
	float	a[];	/* real part of data */
	float	b[];	/* imaginary part of data */
	int	m;	/* size of data = 2**m */
	int	iopt;	/* 0=dft, 1=idft */
{
	int	nv2,nm1,n,le,le1,ip;
	float   pi,pile1,tmp;
	float	ua,ub,wa,wb,ta,tb,*ap,*bp;
	register	i,j,l;
	extern	float	sin(), cos();
	n = 1<>1;
		ua = 1.0;	ub = 0.0;
		pile1 = pi / le1;
		wa = cos(pile1);	wb = -sin(pile1);
		for(j=0;j