void wt1(float a[], unsigned long n, int isign,	void (*wtstep)(float [], unsigned long, int)){	unsigned long nn;	if (n < 4) return;	if (isign >= 0) {		for (nn=n;nn>=4;nn>>=1) (*wtstep)(a,nn,isign);	} else {		for (nn=4;nn<=n;nn<<=1) (*wtstep)(a,nn,isign);	}}