10 REM INTEGRALE DI EXP(-X*X), SIMPSON A RAFFINAMENTO GLOBALE - FULL
20 REM DATA: ESTREMO A, ESTREMO B, TOLLERANZA ASSOLUTA
30 DATA -2,2,0.00000001
40 LET LOW=0:LET HIGH=0:LET TOL=0
50 READ LOW,HIGH,TOL
60 IF LOW>=HIGH OR TOL<=0 THEN GOTO 460
70 IF LOW<-5 OR HIGH>5 OR TOL<0.000000000001 THEN GOTO 460
80 LET PANELS=8:LET WIDTH=0:LET XVAL=0:LET FX=0
90 LET ACCUM=0:LET RESULT=0:LET PREVIOUS=0:LET ESTERR=1
100 LET WEIGHT=0:LET ITER=0:LET CONVERGE=0:LET SCALED=0
110 GOSUB 320
120 PREVIOUS=RESULT
130 WHILE CONVERGE=0
140 PREVIOUS=RESULT:PANELS=PANELS*2:ITER=ITER+1
150 GOSUB 320
160 ESTERR=ABS(RESULT-PREVIOUS)/15
170 PRINT "REFINE;",PANELS,";",RESULT,";",ESTERR,CRLF
180 IF ESTERR<=TOL THEN CONVERGE=1
190 IF PANELS>=4096 THEN GOTO 300
200 REM STIMA PRECEDENTE CONSERVATA PER RICHARDSON
210 WEND
220 REM CORREZIONE DI RICHARDSON ULTIMA COPPIA DI STIME
230 RESULT=RESULT+(RESULT-PREVIOUS)/15
240 SCALED=INT(RESULT*1000000000+0.5)
250 PRINT "INTEGRAL;",RESULT,";",SCALED,";",PANELS,CRLF
260 PRINT "ESTERR;",ESTERR,";ITER;",ITER,CRLF
270 IF RESULT<=0 OR RESULT>HIGH-LOW+0.00000001 THEN GOTO 470
280 PRINT "SIMPSON TEST OK",CRLF
290 END
300 IF CONVERGE=0 THEN GOTO 470
310 GOTO 220
320 WIDTH=(HIGH-LOW)/PANELS:ACCUM=0
330 FOR I=0 TO PANELS
340 XVAL=LOW+I*WIDTH:GOSUB 440
350 IF I=0 OR I=PANELS THEN GOTO 390
360 IF I-2*INT(I/2)=1 THEN GOTO 380
370 WEIGHT=2:GOTO 400
380 WEIGHT=4:GOTO 400
390 WEIGHT=1
400 ACCUM=ACCUM+WEIGHT*FX
410 NEXT I
420 RESULT=WIDTH*ACCUM/3
430 RETURN
440 FX=EXP(-XVAL*XVAL)
450 RETURN
460 PRINT "ERRORE PARAMETRI SIMPSON",CRLF:END
470 PRINT "ERRORE AUTOVERIFICA O CONVERGENZA SIMPSON",CRLF:END