IF ?PLIST(FFT)=FALSE THEN LOADFILE(FFT,FASL,DSK,SHARE)$
IF ?PLIST(FILLARRAY)=FALSE THEN LOADFILE(ARRAY,FASL,DSK,SHARE)$
/* set up arrays */	ARRAY([G,H,XA],FLOAT,31)$
			(FILLARRAY(G,[0.0]),FILLARRAY(H,[0.0]),
			FOR I FROM 0 THRU 15 DO G[I]:1.,
			FOR I FROM 0 THRU 31 DO XA[I]:FLOAT(I))$
/* define function to display them */
			P():=GRAPH2(XA,[G,H],[0,1])$
			P()$
/* perform fft */	FFT(G,H)$ 
			P()$
/* put in polar form */	RECTTOPOLAR(G,H)$ 
			P()$
/* undo these operations */
			POLARTORECT(G,H)$ 
			P()$
			IFT(G,H)$
			P()$
/* if you want avoid having the transform done in place,
   copy the arrays first */
			(FILLARRAY(G,[0.0]),FILLARRAY(H,[0.0]),
			FOR I FROM 0 THRU 15 DO G[I]:1.)$
			ARRAY([GT,HT],FLOAT,31)$
			(FILLARRAY(GT,G),FILLARRAY(HT,H))$
			FFT(GT,HT)$
			GRAPH2(XA,[GT,HT],[0,1])$
/* The last part of this demo plots pretty patterns created by FFT.
   They will only look good if your terminal supports high resolution
   plotting.  If it doesn't I suggest you quit out here by typing
   ^G.  This function was pinched out of some magazine put
   out by Tektronix a year or two ago.  */
pl&&
PLINIT(NN):=(BLOCK([I:?RUNTIME()],?SSTATUS(?RANDOM,I)),
	     ARRAY([FR,FI],FLOAT,2**NN-1),N:NN)$
PLINIT(8)$
PL():=BLOCK([XAXIS:FALSE,YAXIS:FALSE,NOPRINT:TRUE,
	     DATEPLOT:FALSE,EQUALSCALE:TRUE],
	    REARRAY(FR,2**N-1),REARRAY(FI,2**N-1),
	    FILLARRAY(FR,[0.0]),FILLARRAY(FI,[0.0]),
	    THRU 2 DO IF RANDOM(2)=0 
			 THEN FR[RANDOM(2**N)]:(-1.0)^RANDOM(2)
			 ELSE FI[RANDOM(2**N)]:(-1.0)^RANDOM(2),
	    FFT(FR,FI),
	    GRAPH2([FR,[FR[0],FR[2**N-1]]],[FI,[FI[0],FI[2**N-1]]]))$
THRU 10 DO PL()$